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Rush Machinery offers a series of air-bearing end mill grinding fixtures that allow precision sharpening of end mills, reamers, shell mills and various other cutters. The spindle floats on a thin film of air, resulting in a smooth, even, almost frictionless grind, the company says. The fixture mounts on the company’s drill and tool grinders, and it is also available with a universal base to mount on most other tool and cutter or surface grinders, the company says.

The units feature a hard, chrome-plated and ground spindle with a 10″ stroke. Tools are held by 5C or 5-ST collets or by extension bushings for shanks ranging to 2″ (50 mm) in diameter. The fixtures allow for grinding the OD of any number of flutes, and they include a 12-position index plate for end grinding (other index plates are available). The micrometer in feed is graduated in 0.001″ (0.04 mm) of diameter. Use of the fixture allows the operator to customize end mill geometry for optimum performance.

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CINCINNATI, OH - GBI Cincinnati, an industry leader in supplying machine tool technology, has built a reputation on providing customer-driven solutions to a broad array of precision turn/milled-part challenges. The new matec-30 HV/K is yet another step in providing these solutions ever more flexibly. According to Kevin Bevan, president, “These 5-axis traveling column machining centers have torque drives in the swiveling axes (swivel head and rotary table) and are ideal for very precise mold work, as well as mixed volume, short run operations.”

With an X-axis of 1,300 mm, Y-Axis of 600 mm and a Z-axis of 800 mm, the HV/K Series combines high performance milling/turning and large machining capacity within a compact 4,900 mm x 4,355 mm x 3,250 mm space-saving footprint. Table size is 1515 mm x 635 mm. Maximum table load is 1,000 kg and 5 table T slots are standard.

Rapid traverse rates of 30 m/min (48/100 m/min optional) mean accelerated machine cycle times and reduced non-cut time, which increases overall throughput. Also increasing cycle time is an automatic tool-change magazine offering a fast 3.5 sec (vertical) or 6.5 sec (horizontal) tool-to-tool index time. The tool changer holds 36 tools (up to 128 optional) with a maximum tool weight of 3 kg to 10 kg. Maximum tool diameter is 70 mm - 130 mm and length is 360 mm.

The matec-30 HV/K 5-axis machining centers include versatile high-speed linear guide ways in all axes. A high-torque 30 kW AC spindle motor with direct drive permits full horsepower at low spindle speeds. The standard 40-taper spindle delivers 12,000 RPM (42,000 RPM optional) with through-the-spindle coolant at 20 bar (70 bar optional) which helps keep the spindle cool. To assure the rigidity required for heavy-duty cutting, the machine base is manufactured from high-quality mehanite cast iron, ensuring stability for years to come.

The multi-functional machining area is the result of a fixed machine table with integrated rotary table. A 630 mm diameter CNC torque rotary table permits machining on 5 sides, with a speed range of 1,800 RPM. The swing circle of the CNC torque rotary table has a diameter of 1,000 mm. The CNC torque swivel head has a range of ± 105° for horizontal and vertical machining.

An automated lubrication system, a complete coolant system and splashguards with overlapping doors are standard. The electrical cabinet is dust-proof. All wire through-holes are protected by water-resistant fittings to prevent oil moisture from entering. This extends electronic parts service life and assures maximum dependability.

The machining area is completely enclosed with electrically locked sliding doors. Bellows with steel lamellas, chip conveyors and centralized lubrication are all standard, as are glass scales in X-, Y-, and Z-axis.

The matec-30HV/K is equipped with the Heidenhain iTNC 530 control for optimized results in turning, milling and 5-axis machining. Siemens 840 D is optional.

Utilizing only leading edge technology, each matec machine is designed and analyzed using advanced Finite Element Analysis (FEA) for dynamic simulation and structural analysis. All matec machines are laser calibrated and inspected to VDI (German Industrial Standards) to ensure the final product is of the absolute finest quality.
Matec produces a wide range of traveling column machines with X-axis up to 12 m. Using a modular design approach, machines can be customized to suit the end-user’s specific application.

Master distributor GBI in Cincinnati, Ohio is the exclusive United States distributor for the matec Maschinenbau GmbH line of machine tools and provides an unparalleled degree of training, service and support for all matec machine tool products in the USA.

For more information, contact GBI Cincinnati, Inc, 6899 Steger Drive, Cincinnati, OH 45237. Tel: 513/841-8684. Fax: 513/841-7381. Web: www.gbicincinnati.com. E-mail: info@gbicincinnati.com

According to Kevin Bevan, president, “These matec 5-axis machining centers are ideal for ultra-close tolerance precision mold work, as well as mixed volume, short run operations.”

Contacts:

Marketing:
Robin Bergstrom
USA
Phone: 859-689-9551

General Information:
Kevin Bevan
USA
Phone: 513-841-8684
Company Information:
Name: GBI Cincinnati, Inc.
Address: 6899 Steger Dr.
City: Cincinnati
State: OH
ZIP: 45237
Country: USA
Phone: 513-841-8684
FAX: 513-841-7326
http://www.gbicincinnati.com

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CAM developer DP Technology recently performed a successful test cut of a new cutting tool for turning applications that is designed to reduce vibration and heat buildup. The company’s CAM software package, Esprit, now contains an add-on for programming the new tool.

Developed jointly by machine tool builder Mori Seiki and cutting tool manufacturer Kennametal, the turning spinning tool is designed to distribute heat and wear more effectively than a single-point lathe cutter. It employs a specialized insert, which is similar in design to a round, or full-radius, insert, and it is mounted at the bottom of a cylindrical tool shank held in a rotary spindle.

Olivier Thenoz, mill-turn product manager at DP Technology, teamed up with Nitin Chaphalker, engineering team leader for Mori Seiki’s Machining Technology Laboratory, (MTL), to perform the test cut. Performed on steel workpiece mounted on a Mori Seiki NT4200, the test included roughing and finishing operations with OD passes on straights, tapers and arcs without the use of coolant.

“The advantage of the spinning tool is that there is no single point that is in contact with the workpiece all the time, and this is very good for heat dissipation and tool wear,” Mr. Thenoz says. “Cutting conditions are no longer limited by the heat generated in the process, but by the power available in the machine.”

Mr. Chaphalker adds that axially loaded tools such as the spinning tool direct most of the cutting forces axially into the spindle, reducing vibration and chatter. In contrast, cutting forces generated by single-point cutters impart a bending movement on the tool and cause vibration.

For the initial OD rough cut, the spinning tool was inclined at a 20-degree angle to allow effective heat evacuation. The turning spinning was also said to perform admirably when tested on taper and arc moves that required back-and-forth motion. It remained close to the material throughout the cut without requiring the repositioning moves necessary when using single-point tools cutting in a single direction.
http://www.mmsonline.com/articles/spinning-turning-tool-offers-alternative-to-single-point-cutters.aspx

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Choosing the right machine for the right application is a significant challenge. Choosing a machine that will also be able to produce the more complex parts that may present themselves down the road is an important part of the process. The buyer also must consider a “standard,” “performance” or “high-performance” machine level (or platform) that pushes the envelope of capability and functionality. Many machine tool builders offer machines in two levels or all three levels, and typically, as capability and functionality increase, the levels of performance expand as well. But along with the increased capability and functionality found with high-performance machines comes a higher price tag. To get the most from a machine tool purchase, the buyers must zero in on the many variables, including budget, workflow, manpower availability and their machining expertise.

Machines at the standard level include features for doing prototype work or small to medium-sized production—primarily basic two-axis lathe parts. At the performance level, machines take on increased capability and functionality engineered for medium- to full-scale production environments. These machines typically include live tooling, C-axis capability, subspindle, and more. Material hardness, surface finish and possibly part quantity are more critical considerations. The high-performance level is necessary when additional axes (Y axis), twin spindles, automation, material hardness, quantity and possibly grinding quality tolerances and finishes are required. Machines in this category can be distinguished by the components that are engineered into the machine structure.

This article focuses on categorization of turning centers, but conceptually the principles apply to other machine tool types (VMCs, grinding machines, and others) as well.
Capability

Machine capability relates to the machine’s ability to achieve a desired level of performance based on accuracy, productivity and reliability:

•  Accuracy—dimensional, shape (form) and surface finish

•  Productivity—Output (metal removal rate) and ability to cut different materials and irregular shapes with different types of stationary and live tools

•  Reliability—mean time between failure, mean time to repair and durability (ability to keep initial level of productivity and accuracy)

With Ra being the most common measure of surface finish, the level of finish machined on a specific product is based on material Rc hardness, desired throughput and machine stiffness. If the manufacturer only needs to produce a few parts and the material is not exotic, a low Ra is possible even with standard level machines. However, more commonly, a low Ra will require a higher level of capability in order to machine consistent parts in small, medium or large quantities.

Any machine may be capable of producing accurate parts to a tight tolerance with enough human intervention. But once the quantity goes up and the demand for accuracy and repeatability remains tight, the move to more capability with reduced human intervention will attain a higher level of accuracy. Key factors with part tolerance include accuracy and repeatability, CPK/PPK requirements and throughput level. Note that when it comes to accuracy, all standards are not the same. It is very important to confirm what standard or guideline is being used for fair comparison with different manufacturers. For example, are machine builders using ISO standards, European (VDI) guidelines, Japanese Industrial Standards (JIS) or National Machine Tool Builders Association (NMTBA) definition? This is essential data when developing a comparative spreadsheet.

All three levels of machine performance are capable of being in a production environment. The key factors of throughput, beyond the quantity of parts, are the level of part complexity, overall part tolerance and surface finish (cylindricity may also be a factor), and type and hardness of material. If the part is basic and the tolerance is wide open, then a volume of parts on a standard level machine may be possible. If the quantity is high and the tolerance tight, then a higher performance machine is likely the better choice.

Functionality

This term relates to the multitude of operations that can be performed at one machine level on any part in a single setup. Functionality drivers include part complexity and manufacturing strategy. Factors include number of axes, additional process functions, automation and in-process controls. If a complex part with various feature orientations requiring close geometric tolerances needs to be produced in one setup, then the machine needs to be configured with multitasking capabilities.

Once the machine capability and functionality needs are determined, the next area of concern is machine selection based on performance (material hardness, surface finish requirements or quantity).

Material Selection

General guidelines can be helpful in choosing materials for typical machining scenarios.

Standard level, in the 0 to 35 Rc range: Cast iron, cast steel, brass bronze, aluminum and coppers

Performance level, typically up to 45 Rc range: All the above plus stainless steels

High-performance level, typically up to 70 Rc range: All the above plus titanium alloys, magnesium alloys, exotic alloys and heat-resistant (super) alloys such as Hastelloy, Inconel, Nimonic and Waspaloy

Metals listed at the high-performance level may be run on standard level machines with less complex part configuration requirements, but having the best match-up of machine performance properties (such as speeds, feeds, spindle and axis drive and motor power ratings) will determine if the part can be produced effectively.

Machine Construction

Each machine level has distinct design elements for its machine components to achieve desired results. These characteristics include machine stiffness, damping features, base type and weight, castings and materials, ballscrews (diameter size, type and classification), linear guides (size, type and classification), motors and drives (size, type and classification), overall system compliance and control features (functions and type).

Design life of these components is equally important to consider. A new machine that holds very good accuracies for the first few years of operation can deteriorate relatively quickly, based on the level of components used. On the other hand, a machine designed and built with consideration of the size, type and classification of all critical components can maintain a high level of accuracy much longer.

Thermal Considerations

Thermal design considerations vary between machine levels. In the case of the high-precision Hardinge RS-series turning center, continuous airflow in and around the thermally symmetrical headstock frame affords optimum thermal stability for increased part accuracy. The symmetrical dissipation of heat minimizes the transfer of heat generated by the spindle bearings into the cast iron machine structure. This design allows the spindle centerline to remain in a fixed location, unlike standard- and performance-level machine spindles that may migrate vertically as a result of thermal growth.

Other key areas of heat generation are in the axis way systems. Standard-level way systems can experience heat buildup, especially under heavy load conditions. Heavy-duty, high-accuracy linear guideways and ballscrews not only allow large load ratings, but also greater positioning accuracy and less thermal growth. And to compensate for ballscrew growth, high-performance machines typically incorporate linear glass scales. Thermal considerations are also important as they relate to turrets, carriage design, material selection, and so on for each level. The machine environment can also be a factor. Temperature swings can adversely affect part accuracy. Coolant temperature, for example, can be maintained when using a coolant chiller, thus minimizing the impact heat can have on maintaining a high level of part accuracy.

Moving Up To High Performance

A host of other factors can come into play when considering the move to a high-performance turning center, including machinist availability (reduced number of machinists running multiple machines), expectations of machining complex parts having tight feature orientations, staying ahead in the technology curve for competitive quoting and materials to be machined. The higher the technological features a machine has to offer, the longer the competitive timeline. Faster spindle speeds, faster traverse rates, higher quality ballscrews and environmentally friendly lubrications all allow the user to stay ahead of the curve rather than using standard-level machines built with less stringent standards, components, capability and functionality.

Even if a high-performance machine seems precisely what the business needs to be truly competitive, the higher cost may still make the buyer hesitant to move forward with the purchase. A machine with just the right capabilities and functionality may still seem like it will create too many financial issues to be practical. In such a case, the 5-year/2-percent rule can be used to help turn problems into opportunities.

The total cost of the machine leased throughout a 5-year term can be calculated using the following formula: $205,000 (total machine price) times 2 percent equals $4,100 (monthly payment); divided by 20 working days equals $205 per day; divided by 8 hours equals $26 per hour.

Another way to see the affordability with some compromise would be to formulate starting with the machine base price and add the option costs one at a time. For example: $120,000 for the base machine times 2 percent equals $2,400 monthly payment; divided by 20 days equals $120 per day or $15 per hour. The same formula is then applied to the options (using live tooling and C axis as an example): $17,000 times 2 percent equals $340 monthly payment, $17 per day, $2.13 per hour. The total cost is then $17.13 per hour. Further options can be added until the price comfort zone and needed capability and functionality are in tune. Of course, actual costs and rates will vary, but this is a good rule-of-thumb calculator. Down payments on the lease can also help to ease the extended price burden. 

http://www.mmsonline.com/articles/turning-center-categorization.aspx

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“Our machinists are excited about the prospects of bringing in a new machine now.”

That’s not always the sentiment when a shop’s management starts making significant changes to the equipment on the floor. Often machine operators can be quite apprehensive when they learn that the machines they’ve become experts on and the processes under which they’ve been operating will soon be replaced. But at Norriseal (Houston, Texas), such changes have brought excitement to the job, with increased capacity, significant productivity gains, more efficient workflow and a positive effect on the company’s bottom line that every member of the organization can benefit from.

Patricia Lewis, operations director, goes on to explain that although the company has an aggressive executive staff that tries to move forward with processes in the factory, shop personnel were not always so flexible. “We are very engaged with our customers; we frequently bring them to our facility so they can learn about our company and its capabilities. But we sometimes lacked in capitalizing on our biggest asset—our people. We had a machinist at each machine. It wasn’t until we brought in a new manufacturing engineer, who had a fresh perspective and started to question the procedures, that we revitalized our approach to improving efficiencies of our people, processes and equipment.”
Roots In Oil And Gas

Founded in 1955, Norriseal is a manufacturer of valves and controls, serving predominantly the oil and gas industry, but also a range of other industrial markets. The company was acquired in 1962 by Dover Corporation, operating in the Energy Products Group in the Fluid Management segment. Bob Funk, company president, notes that being part of Dover, with its understanding of manufacturing companies and financial resources, enables the company to move forward with its strategic plans. Norriseal operates out of the 75,000-square-foot headquarters, with about 100 employees working in engineering, manufacturing, customer service and technical support. This facility takes raw material to finished product, including all manufacturing, assembly and testing. Sales and support services are also available through a global network of representatives.

A great deal of machining takes place at Norriseal, including turning, milling and grinding work. Material is primarily 17-4 and 316 stainless, in barstock and castings. In recent years, the company has begun to take a good, hard look at which machines are pulling their weight and which ones should be replaced with newer technology; which tooling solutions are most effective and which are leftovers from days long ago; and generally, what operational methods can be applied to maximize resources.
Changing Philosophy

In 2006, the investments in machining began with the purchase of a 600-mm horizontal machining center and a CNC lathe. The success of the first two machines also highlighted the need for a new manufacturing engineer. In July 2007, Norriseal hired David Bickerdyke as senior manufacturing engineer and charged him with refining the manufacturing process within the organization. Mr. Bickerdyke was aggressive in applying his experience to eliminate the less productive equipment, implement lean manufacturing strategies and motivate the employees by engaging them in production decisions. Within 14 months, the company had retired 11 machines from the shop floor, including mills, engine lathes and screw machines that were each more than 20 years old. In their place came three Mori Seiki machines—a dual-process CNC turning center, another CNC lathe, and most recently, an integrated turn/mill center. This latest machine has created the most excitement throughout the factory.

The turn/mill was brought in as a direct replacement for two other machines. As such, as many as 1,600 existing parts are currently being run on or programmed for that machine. The programs are written mostly as they are needed, but a spreadsheet tracking the part usage for the previous 2 years also gives Mr. Bickerdyke an idea of the highest-volume parts that are most likely to be needed next. “We’ll work on parts that are in immediate need first,” he explains. “When those are complete, we’ll go back to the spreadsheet to determine which parts we can work ahead on. So we’re always programming, but we’re finding huge savings with that machine.”

The savings can be clearly seen with a typical part—a butt plug machined from 17-4. This part was previously run in five operations—two on a lathe and three on a vertical mill. The setup time for those two machines was a total of 6 hours, and cutting time was about an hour and a half. Worse still was the time the parts would sit lined up in front of machines, between operations, awaiting the next step. Running one of these parts often took more than a week. On the turn/mill, setup is 45 minutes and machining is 45 minutes.

“One reason this machine works so well for us is the 40-tool magazine,” Mr. Bickerdyke says. “An OD turning tool, which is turning on the main spindle, can also be rotated 180 degrees to cut on the subspindle. You can rotate it 90 degrees so it can bore as well. So on this part, we face, bore, spin it around, finish, spin it around again and go the other way, all with one tool.” Also on the turn/mill are two 12-inch Schunk quick-change jaw chucks—a hardened base jaw and a soft jaw on the top. On the main spindle are three sets of hard jaws that provide a 12-inch range. They repeat within about a half a thousandth.
It’s In The Programming

Another reason Norriseal has had such success with its turn/mill center, as well as its other machines, is the programming process it uses. The company uses Edgecam software from Planit Solutions. Mr. Bickerdyke first explains the general reasoning behind using the software offline. “There’s no way we’d spend that kind of money on a machine only to offload it to a guy on the floor to spend time programming. While he’s programming, the machine’s not productive. Besides that, he’s trying to catch interference on the fly, and that’s just asking for trouble.”

Instead, while the machine is running one part, other parts are being preprogrammed in an office. Simulations are run on the computer screen to catch potential crashes before they can cause real problems.

Norriseal has been using Edgecam for several years, but recently upgraded to Solid Machinist, a module of the CAM system for generating milling and turning machining strategies and NC code from solid models. This version uses automatic feature recognition to interrogate the solid model and quickly identify machineable features. The software then offers the user the most appropriate tooling and machining strategy to generate accurate tool paths.

“We’ve been doing a lot of these jobs for years, so solid models did not exist for them before,” says Mr. Bickerdyke. “We didn’t need them before we had the turn/mill center because it was basically 2D machining. With multi-axis machining, though, we need a model. We import mostly from SolidWorks, but files from any major CAD system can be used.”

Mr. Bickerdyke makes extensive use of the PCI (parametric command interface) feature as well. The PCI is a quick script like a macro file that he is able to write for certain processes that he needs to program on a regular basis. “These can bring programming time from 45 minutes down to about 10,” he comments. “It quickly grabs your tool, all your comments, your rapid moves. We take a program and specify what we want by highlighting how we want to face and rough turn and that sort of thing. It works similar to a Microsoft Wizard or a template for our operations. It makes the process more predictable.” This predictability is particularly beneficial when more than one programmer is involved. “Even if a new person comes in who’s used to programming a certain way, the PCI forces him to do it our way. We have a template to work with that is consistent from one part to the next and one person to the next.”

Also contributing to fast and effective code generation is the Edgecam Code Wizard application. This feature allows programmers to configure code generators using a simple template that provides the basic structure of the CNC control. It then prompts the programmer to make minor adjustments to the code to get the exact output required. “The Code Wizard is great for troubleshooting,” Mr. Bickerdyke points out. “You can use a code constructor trace, and it will break your code down into separate sequences, allowing you to see exactly where the problem is. Then it steps you through the changes and, when complete, it updates the post processor.”
Involving Everyone

Part of the changing philosophy at Norriseal has been to engage everyone in the company in the process improvements. On a programming level, this has meant providing the machinists with a new perspective—they now have Edgecam right at the machine. A PC with a student edition of the software is installed at each machine. This version is fully functional except for posting permissions. When the operator gets a job, he takes the appropriate folder to the machine, scans a barcode, and the program is downloaded directly to that PC via a wireless network. If the operator is not familiar with the job, rather than studying drawings, he can simulate it right there to see exactly what the tool is going to do. “This gives the operator a lot more confidence,” says Mr. Bickerdyke. “He can see right there what the programmer did.” The company plans to eventually have a PC at every machine.

This connectivity has also allowed the company to implement a shopfloor monitoring system from Predator Software Inc. that keeps all personnel in tune with the production process. Separate from the CAM software, Predator MDC (machine data collection) collects, reports, charts and processes shopfloor manufacturing data in real-time. Machine data collection improves manufacturing by supplying accurate shopfloor productivity metrics to improve operations and to make better decisions.

Norriseal has a monitor mounted on the wall in the middle of the shop floor that displays the status of all of the machines, which parts are running and the number of good parts and bad parts. This display, which is customizable with almost 240 different reports, can be viewed from any PC throughout the shop. Other data relating to each machine, operator, part number, downtime and efficiencies can also be accessed. Larry Williams, vice president of finance, explains the system’s potential: “Some could view this as a way to monitor machinists. I see it as an opportunity to integrate a business system and have real-time understanding of exactly what it takes to produce parts, for costing, quotation and process planning. If I ran a job shop, I’d have this in an instant. For us, doing a lot of standard products, it helps us to prove out old standards and verify our projections for shopfloor productivity.”

Innovative approaches such as these have been fundamental to Norriseal’s accelerated business plan. Since Mr. Bickerdyke’s arrival less than 2 years ago, manufacturing throughput has increased by more than 10 percent, already surpassing the company’s long-term goals. On-time shipments and leadtimes have also improved significantly. Ms. Lewis comments, “As an executive staff, we attribute many of our shopfloor improvements to the contributions of David and the equipment and programs that he has brought to the company.”

Although the effects are clearly linked, Mr. Bickerdyke describes the improvements as more of a shift in company-wide ideology. “It’s nice when you can be with a company that is interested in change that makes sense, and not just for the sake of change. We’ll continue to replace the remainder of our older equipment with new, more efficient machines over the coming months and years. And as we do it, our machinists continue to get more excited about the prospects. We’ve managed to bring back in-house a good deal of our work that previously was being farmed out, and our people realize the benefits of this.” But Norriseal won’t bring in-house all of its machining requirements—only what it’s good at. And something the company is clearly good at is getting the most out of its machines and personnel—more with less.
http://www.mmsonline.com/articles/cam-and-turnmill-making-more-with-less.aspx

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What can a high speed control do for you? In simple terms, it gives you the ability to finish one task faster and move along to the next sooner. In drilling and tapping, this can result in faster hole-to-hole times, quicker spindle reversals for tapping, and substantial cycle-time reductions. The most dramatic benefits, though, come in 3D contouring. Few, if any, drilling and tapping jobs require a million lines of machine codes. In molds, dies, patterns, and prototypes, complex surfaces comprising a million or more line segments are not at all uncommon. Saving just a fraction of a second per move can result in substantial cycle-time improvements.

As an example, the part that formerly took 3 hours and 43 minutes to mill accurately on a machining center. The part is being cut in wax, but is actually commonly milled in carbon as an electrode to burn cashew-shaped gates for plastic injection molds. A control retrofit enabled that same machine to mill a more accurate part in just 17 minutes. The user enjoys greater productivity from his people and machinery. He also enjoys a distinct competitive advantage when selling his work, because he can deliver an equally good or better job for less money, in less time.

In a broader sense, high speed creates many other benefits. Improved accuracy, fit, finish and cutter life are the most commonly reported peripheral benefits. Customers share the benefits of high speed through the entire manufacturing process, not just to produce more work in less time, but also improving the accuracy and finish and reducing polishing and fitting time. They do this by using the high speed to reduce the stepovers and the tolerances. Tools simply last longer because their chip load is much more consistent.
Relativity

“High speed machining” lured us with a promise of going faster. But faster than what? Each of us has a different perspective on what truly constitutes high speed machining, depending on our experience, applications and our needs.

The relative connotation of high speed is evidenced by talking with different people who utilize high speed milling on a daily basis. Going from 10 ipm roughing pre-hardened tool steel to 30 ipm, or from 30 ipm to 180 ipm, can be high speed in the mold business. Still, if your application is the milling of foam patterns for automotive stamping dies, 800 ipm may not be fast enough.

There is no clear threshold where plain old milling becomes high speed milling. High speed is relative, based on your perspective, your materials and your needs.
Surfaces To Points To Surfaces

The evolution of CAD/CAM into a powerful tool for 3D surface creation is the main reason we talk about high speed milling for molds and dies. CAD works with entities and surfaces. Points, lines, arcs, cylinders, spheres, planes, and so on, all join in CAD to create surfaces. CAM then translates those surfaces into point meshes of data for machines. Once that data is passed to the CNC, it executes one point at a time to reconstruct the surface. In order to do this efficiently, points are not milled at random, but rather organized into a data flow along slices or flow lines. These may be along any axis or across a combination of axes, or even along a constantly changing detail on a surface. In any case, the flow of data is from one point to another along the flow line or slice, then typically to step over and repeat that slice either in a single direction box-type cycle or in a zigzag of back and forth movements along the flow.

Point-to-point then is the process of creating surfaces by milling from one point to another in succession. As we apply point-to-point to high speed milling, that succession from one point to another should ideally be quite fast.
Chordal Deviation

CAM typically creates points with various distances between them. Why? If we step back a moment and just consider milling an arc by single point moves, we see that the arc really becomes a series of line segments. Those line segments deviate from the arc by a value commonly called chordal deviation. This value is set in your CAM system to define what the acceptable deviation from the surface will be, based on the accuracy required for the application. The natural desire is to be as accurate as possible, but stating a deviation value that is too tight can result in enormous file sizes and high data density that can be difficult to handle. Chordal deviation must be properly set to lend balance to productivity and required job accuracy.

The result of chordal deviation from CAM is a series of chord segments that are now becoming commonly referred to as “point departures.” This term simply means the distances between successive point-to-point moves.
Look-Ahead

In 3D contouring the cutter must flow through the points without dwelling, but also must not inadvertently overshoot its intended path and consequently gouge the workpiece. Most numerically controlled milling machines take from 0.100 to 0.200 inch to stop from a move at 100 ipm. If a CNC and machine are instructed to flow through data at high feed rates, yet point departures are short, gouges can result at points of abrupt changes in the contour. Look again at the shape shown earlier. There are several close data segments at the bottom of the contour. This is an area of great danger for gouging. The longer line segments going from left to right might easily permit high feed rates. Without look-ahead, the CNC might be surprised by the abrupt change in direction over a short move of only 0.010 inch. If the feed rate is too high to stop in that distance, the result will be an overshoot.

Look-ahead must evaluate data many blocks ahead to prevent such gouges. In most applications one or two, or even ten or 20-block look-ahead is not enough. The amount of look-ahead needed varies based on contours, feed rates and machine performance. In general, look-ahead cannot be limited to any arbitrary value, because conditions are constantly changing. Ideally, look-ahead should be dynamic, varying the distance and number of program blocks based on the part profile and the desired milling feed rate.

Look-ahead is now offered by some companies either as a preprocessing step or as a part of a DNC system. To achieve the effect of look-ahead, the system must add data segments at varying slower feed rates. In this way, gouging and overshoots can be prevented. The drawback is that by adding program lines, the data throughput problem is exacerbated, greatly reducing productivity.
High Feed Rates

How accurate can a CNC really be at high feed rates? We can answer this by analyzing the entire machine system, starting at the CAD/CAM system and ending with the machine iron. Because we are talking specifically about the controls here, let’s assume that everything else is in order, and that the control is the only issue.

Servo cycle time is the amount of time a CNC takes for each measuring and command cycle. In other words, if the control’s servo cycle time is 20 ms (milliseconds, or thousandths of a second), then the axis positions are measured and a new direction commanded by the control 50 times a second. Though 20-ms servo cycles were thought to be good just 10 years ago, servo cycle times over 4 ms are now considered inadequate. At a fairly common 3-ms servo cycle time, positions are being measured and corrected 333 times per second. A machine moving at 100 ipm is moving 1.66 inches per second, so each time the axes are measured, the machine should be moving 0.005 inch.

This might be alarming to you if you are trying to hold tolerances to 0.0001 inch or so, because your machine is basically out of control for 0.005-inch increments at a time. The accuracy problem gets worse when attempting to mill at 400 ipm, where a 3-ms servo cycle results in 0.020-inch moves between measurement and correction commands from the control.

Chart 1 shows a few sample servo cycle times, measuring speeds and distances at feed rates. This chart demonstrates that to mill as accurately at 1200 ipm as at 100 ipm, the control must indeed be very fast.

Feed rates will continue to increase, and the need for faster servo cycle speeds will continue to grow. Cutter technologies are proving capable of supporting amazing speeds and feeds. The other supporting technologies like high speed spindles, end mill holders, and so on are all enabling amazing speeds and feeds. Machines with linear motors are now available with traverse rates to 3,000 ipm and more. They can accelerate to 3,000 ipm faster than most machines today can get to 300.

Block transfer timethat is, the number of blocks-per-second the control executesshould not be confused with the servo cycle time. Ideally, the servo cycle time should be faster than the block transfer time. Still, it is possible for controls that execute a high number of blocks-per-second to execute at slower servo cycle times. In these cases, the number of blocks-per-second is misleading, indicating a higher speed than can really be achieved if each block is an actual discrete motion block. The combination of fast block transfer time with a still faster servo cycle time ensures high data throughput, with optimal accuracy.
The DNC Bottleneck

Now that we’ve looked at the control’s ability to mill accurately at high speeds, we have a new dilemma: how to get the program information to the CNC fast enough to avoid data starvation. Anyone who has milled 3D contours has watched as the CNC has stopped and waited to fill the buffers again to continue program execution. Loading the program into the control helps it run faster, yet that can often be impractical with the small CNC memories or slow communications speeds.

First, let’s consider DNC, the most common communications in use for CNCs today. DNC stands for distributed numerical control, the distribution of numeric cutter path data to CNC machinery, or direct numerical control, the “drip feeding” or dynamic downloading of numeric cutter path data “on-the-fly” as the CNC executes it.

DNC is typically performed through a serial communications link at data rates of 110 to 38,400 baud or bits per second. Most common is 9600 baud, resulting in potential throughput of up to 960 characters per second.

Program information for the CNC usually is in blocks or lines of program data averaging approximately 20 characters per line. For example:

G1 X123.456 Z234.567

Even spaces and invisible “control” characters like the carriage return and the linefeed take time for transmission. The addition of 3-, 4- or 5-axis definitions, line numbers and feed rates simply add to the overhead in data transmission. Given a communications rate of just 960 characters per second, the CNC is then limited by DNC to just 48 blocks per second. In reality, DNC overhead commonly results in still lower performance, generally about half the theoretical potential. At this rate of 24 blocks per second with 0.010-inch point departures, the resulting DNC speed limit is just 14.4 ipm. That is too slow for high speed milling no matter where the observer’s relativity is based.

There are several techniques used to speed DNC performance:

* Use incremental data where points are measured from the last location, rather than absolute where all points are measured from one fixed location.
* Use integer data, where a dimension like 0.012 is instead shown as 120, eliminating the decimal point, but adding trailing zeros.
* Data compression, using mathematical algorithms to make data, takes less space.
* Preprocessing, to reduce data tolerances and eliminate unneeded data.
* Don’t use cutter compensation or fixture offsets, mirror imaging or scale factors.

These techniques increase the operator workload, increase the opportunities for errors, and reduce the operator’s flexibility with the machine. Networking your DNC computer may help work flow, but does not solve the data flow problem. Many DNC computers are networked to get the data from the CAD/CAM to the DNC system fast, but the data flow is still restricted between the DNC PC and the CNC control by the limited bandwidth of RS-232 communications.
Direct CNC Networking

Direct CNC networking, or DCN, offers a better solution to the data flow problems in high speed milling. DCN uses existing networking architectures to provide a direct network link from the CAD/CAM to the CNC, eliminating the DNC system entirely. DCN is normally 1,000 times faster than DNC. This can be illustrated by the fact that a 10-MB file, which takes 3 hours to transfer by DNC at 9600 baud, takes less than a minute by DCN.

While Ethernet is the most common network architecture in use today, Arcnet, Token Ring and Fast Ethernet are examples of other common networks in use. Software protocols used include Novell’s IPX/SPX specification, TCP/IP and NFS as found in most UNIX systems, Netbeui as used by Microsoft’s LAN Manager, and more.

Networking architectures are already commonly available with data rates of 100 megabits per second or more, even ten times faster than standard Ethernet. Direct CNC networking eliminates any data bottlenecks.

DCN also provides infrastructure for growth, a foundation for expansion into the future. On PC-based (personal computer) controls, interesting possibilities include running CAD/CAM, job control and quality control software right in the controller.
Digital Signal Processing

The technology that allows “plain old PCs” to act as high performance CNC controls is known as digital signal processing, or DSP. Digital signal processing uses special dedicated processors to convert and interpret digital signals at very high speeds. Using DSP, a single board can control up to eight axes at the fastest servo cycles discussed earlier. Not so long ago, a much larger board would have been required for a single axis, operating at speeds 200 times slower.

The incredible power of DSP for specific tasks is illustrated by the fact that a DSP chip can execute a multiply-accumulate (MAC) instruction, a fundamental operation, in a single clock cycle. This same operation on a current Pentium processor chip takes 11 clock cycles. Obviously a 120-MHz Pentium will still take nearly four times as long as a 40-MHz DSP processor.

Earlier, we saw how dramatically the control’s servo cycle time can impact the accuracy of the control. DSP is the key to fast servo cycles. DSP also influences the acceleration and deceleration “ramps” of the CNC control. Traditional CNCs simply set up a ramp rate for accelerations. Because of machine dynamics and drive systems, the machine suffered “following error”. With so much power, DSP systems allow tuning the acceleration for real conditions and specific machine characteristics. Acceleration is no longer simply a straight-line ramp, but rather is tuned as a sort of “bell” shape. This optimization minimizes following error, reduces strains on the machine, yet provides greater acceleration overall. DSP’s speed allows better accuracy and speed, yet is gentler on the machines it controls.

There are many varieties of DSPs, and those choices give control builders choices in their priorities for control functions. The variety of DSPs available means that you as a user can obtain different control performance, functions and capabilities to meet your specific needs.

DSP also has the ability to handle a variety of servo amplifier and measuring scenarios. While most traditional CNCs are limited to interfacing with one specific drive type, many DSP boards allow the integrator the flexibility to work with several, or most available interfaces. Given the concept that technology will change over the life of a machine, this flexibility is reassuring.

One of the other great benefits of DSP is that the main CPU (central processing unit) in the PC is still free to perform other tasks. In reality, a PC equipped with a DSP for machine control is using multiple processors, gaining a tremendous performance advantage. The DSP can be measuring and commanding axis positions while the main CPU is handling the receipt of network data and preprocessing that data for look-ahead to optimize milling speeds and part accuracies at the same time.
Open Systems Architectures

The use of an Intel x86 series processor in itself does not mean that a control is open architecture. Even using a PC-based design does not always mean that the architecture is really open. Open architecture can have many interpretations, none necessarily more right or wrong than another.

To me, open architecture implies two key components: an ability to be serviced and an ability to be changed without proprietary parts and/or knowledge. This means that open architecture should empower the owner to have choices in service and in expansion and updates.

There is a general convergence in the industry toward PC-based controls. This gives everyone the widest possible choice of design options and expansion flexibility. Personal computers, serviced by virtually anyone, in a variety of environments, have arguably proven to be as reliable or more reliable than the best of “hardened” CNC controls. The amazing development of PC features and performance has left the industrial CNC control market reeling to stay remotely in step with developments.

For use as a CNC, the PC may be used in a “shop hardened” configuration, available from a limited number of specialty PC suppliers. Alternately, virtually any common PC may be implemented within a variety of shop enclosures, providing protection from the contaminants in the shop atmosphere. If the air we breathe in a shop is worthy of our health risks, though, perhaps a PC need not even be protected from the shop atmosphere to be reliable. Many users of PCs for DNC would argue that plain old office-type PCs are perfectly fine for shop use.

One advantage which some industrial PCs offer is a “watchdog timer.” This is an output that may be incorporated in the Emergency Stop circuit for a machine to add to the CNC’s safety. A dedicated circuit in the computer constantly checks the integrity of the computer processes at very high speeds to ensure that the system is operating normally. If the system does not check out, the output can disable the machine motion by shutting off the drives as an Emergency Stop. This PC watchdog timer does not replace the DSP’s watchdog timer, but rather complements it with additional security.
Multiprocessor Strategies

Earlier we talked about the fact that a PC teamed with DSP is actually a multiprocessing computer. This concept can be carried further in several ways.

Multiprocessors can give the CNC operator the ability to multitask. He may simply edit programs that are about to be run, or carry that further with graphical verification of programs submitted by the CAD/CAM department for operation. The operator may even use shopfloor programming to prepare cutter paths from IGES surface data right in the CNC control.

Within the PC marketplace, there now exists a number of computers that are equipped with or can be updated with multiple processors. For controls operating under Windows NT or UNIX, the multiple processors may offer performance benefits and the opportunity to use other programs effectively within the control while cutting.

An alternative is the use of entirely separate computers, controlled by the same keyboard and monitor. There are several CNCs in the marketplace today using this concept to maintain a high level of CNC control integrity and security while still performing other tasks. Multiple computers may be implemented in a number of different ways. Several companies have long offered dual-processor options, using a physical switch to select the “MS-DOS” mode or the CNC. Others use keyboard commands to select between the computers. Still others obscure the second computer, using one computer with multitasking as the user interface, and having it pass commands to the machine control computer.

The multiple computer strategy can be very simple to implement, gives the operator multitasking capabilities, and offers security for the CNC process. Moreover, multiprocessors offer another level of performance for high speed milling, allowing the operators to perform multiple tasks quickly and efficiently at their machine control station.
A Look At The Future

As we consider the future, the certainty is that CNC will continue to change. CNC will have to be able to accommodate the evolutionary changes in the industry without requiring the complete replacement of those controls as has been the norm with traditional CNC designs.

The example that I like to use to illustrate this is the word processor. When first introduced, it was an impressive contraption, consisting of a large workcenter with a green display screen, keyboard, printer, and built-in logic, the firmware. When new features were introduced, the entire word processor required replacement at a cost of tens of thousands of dollars, and the old system was traded in for pennies on the dollar. Through evolution, today’s word processor is now a shrink-wrapped piece of software that may be used on virtually any personal computer. Costs run in the tens or hundreds of dollars, and updates for new features are less than that. Installation of the update is performed by the user, generally in just minutes. Again, the evolution of the word processor parallels developments in many other computer industries, and is a good example of where CNC is likely to go.

Shrink-wrapped CNC? Is it possible? Imagine buying a fancy new CNC machine, and selecting your CNC as a software package for it, not an entire custom interface.

Think about new features evolving. They have historically made your CNC machine obsolete. Now imagine again getting updates at low cost, as with the word processor, or with your CAD/CAM system. We call these incremental advances in the technology. Simple, low cost changes will keep your present equipment and entire company competitive.

All this is not just a pipe dream, but the developments are taking place right now to make it a reality. Change is the one thing we can count on in the future. CNC must be able to accommodate that change.

Chart 1–Distances Moved At Given Feed Rates And Servo Cycles
Time
ms Cycles/
Second Distance Traveled
100 ipm 400 ipm 1200 ipm
20 50 0.0333″ 0.1333″ 0.4000″
10 100 0.0166″ 0.0667″ 0.2000″
3 333 0.0050″ 0.0200″ 0.0601″
1 1,000 0.0016″ 0.0066″ 0.0200″
0.4 2500 0.0007″ 0.0026″ 0.0080″
0.1 10,000 0.0002″ 0.0007″ 0.0020″
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Multitasking machines offer a number of advantages, including reducing multiple setups that require manual material handling and refixturing. However, many fabricators still use multiple operations on separate machines to process tube and pipe components. Secondary operations such as tapping are especially problematic for large workpieces that are difficult to move and refixture. Thus, adding tapping capability to Mazak Optonics’ Fabrigear series of laser cutters is “the next logical step” for a machine that can already perform many large tube and pipe operations common in a single setup, says Bob St. Aubin, vice president of sales and marketing.

Tapping can be performed on virtually any type of tube or pipe that the Fabrigear can handle. These include not only square, round and rectangular components, but also a range of structurals, including I-beam, U-channel, C-channel and L-channel shapes. The tapping unit can hold six different taps ranging in size from No. 5 to ½ inch and metric sizes ranging from M3 to M12. The drive system uses a servo motor for tap rotation and Z-axis travel to provide “rigid” tapping characteristics, the company says. Other standard features contribute to unattended operation, including automatic tap breakage detection, an automatic tap-paste applicator and air-blast removal of dust and chips that accumulate on the tap.

Designed for large-part applications, the Fabrigear is available in two models. The FG-150 can accomomodate workpieces as long as 26 feet that weigh as much as 727 pounds, while the FG-300 can accommodate 40-foot-long materials as heavy as 1,058 pounds. To process complex 3D shapes such as I-beams, C-channels and others, the machine’s 64-bit CNC controls six axes of motion and four programmable rotary chucks. The multiple axes allow the cutting head to tilt and rotate around spinning workpieces, while the chucks are designed to grip and center tube and pipe of virtually any shape.

The chucks are part of an automatic loading/unloading system designed to limit operator involvement and simplify setup. The four chucks are divided into two sets, one on the infeed side of the machine and one on the outfeed side. Feeding arms move the workpieces from a five-position, V-support conveyor to the first set. The rear chuck grasps the tube or pipe, while the front chuck uses roller bearings to center it. The workpiece can then be handed off to the other set of chucks, either for back-end operations or for unloading via another set of V-conveyors.
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For energy industry manufacturers, enlarging pre-drilled or cast holes to diameters as large as 7 or 8 inches is not uncommon. Bringing such holes to size often requires multiple, incremental boring passes, with operators readjusting boring bar cartridges to the proper diameter between each pass and changing tools when stroke runs out. This can lead to lengthy cycle times that negatively impact efficiency and throughput.

Van Currie, a manufacturing engineer at oil and gas industry manufacturer Wellhead, Inc., is all too familiar with this problem. To produce one valve body, the company had to machine two blind holes measuring nearly 21 inches deep and 8 inches in diameter—an application that took more than 8 hours to complete. Unsatisfied with this production process, the company turned to Allied Machine and Engineering for a solution that would reduce cycle time. The drilling system manufacturer responded with a tool that could nearly finish the bore in a single pass and cut cycle time to less than 1 hour. The key is a phased insert arrangement that allows high material-removal rates even on low-horsepower machines.

“We went from having to continually adjust and change out our old boring head to this one hole-opening drill,” Mr. Currie says. “It paid for itself after the first couple of parts.”

Founded in 1947 and recently acquired by Seaboard International, Wellhead produces oil-industry parts such as valves, drilling flanges, coiled tubing heads, ring seal packers and more. The Bakersfield, California-based manufacturer services and supplies customers worldwide in locations including Texas, Wyoming and Colorado as well as Canada and even Kuwait. More than 100 employees work in shifts round-the-clock to produce primarily large parts weighing as much as 4,000 pounds, some that take as long as 8 hours to machine.

The valve body in question was machined out of forged 4340 alloy steel using a 15-hp Toshiba Shibaura horizontal boring mill running with flood coolant. Each part required two holes, which were cut from stock on the manual machine with a two-flute insert drill at 56 rpm and 0.006 ipr. A small carbide point created a pilot hole and centered the tool, while inserts arranged along the body enlarged the hole to a 5.9-inch diameter in a single pass.

The problem arose in the subsequent boring operation used to enlarge the 21-inch-deep hole to the final diameter of 8 inches. The shop ran an adjustable boring bar at 125 rpm and 0.75 ipm. Bringing the hole to size took 7 passes with this tool. Between each pass, operators had to adjust the set screw or install another boring bar when the first reached the limit of its stroke. This led to a total cycle time of more than 8 hours per part.

“We were able to open up the 5.91-inch hole really quick with the two-flute drill. But going from 6 to 8 inches with a rotating boring bar that could only take a 0.2- or 0.3-inch depth of cut per pass—this was really time consuming,” Mr. Currie says.

The shop had successfully used tools from Allied Machine and Engineering in past operations, so it turned to that company for advice on how to reduce cycle time on the valve body. A representative from Allied distributor Praxair recommended the Opening Drill adjustable boring tool. Off the shelf, the tool is available in a maximum diameter range of 2 to 5.62 inches, so the company built a custom 8-inch model specifically for Wellhead.

The Opening Drill features two diametrically opposed insert cartridges that are phased to create an overlapping cut. The cartridges are identical; the user simply selects one to cut the finish diameter, and the other becomes the inboard cartridge. After the outboard cartridge is adjusted to the finish diameter, the inboard cartridge is set to a smaller radius (the phase difference is always considered as radius, not diameter). Thus, when the tool spins, the cartridges overlap, with each removing only a portion of the total material needed to reach finish diameter. This configuration distributes cutting forces between the two insert cartridges, reducing the overall load on the spindle to allow higher metal-removal rates.

“The inserts lasted for an entire pass, so we weren’t breaking or having to change inserts at all,” Mr. Currie says.

According to the manufacturer, the tool is especially useful for low-horsepower machines such as Wellhead’s 15-hp boring mill. That’s because with high enough rpm, its multiple inserts can remove a substantial amount of material, even at low feed rates.

Mr. Currie adds that the tool solved Wellhead’s hole-straightness issues as well. The two-flute drill used to cut the hole from the raw material had a slight “walk”—that is, a tendency wobble off center and create an angled hole. However, while other tools might have a tendency to follow the angle of the hole during boring operations, the Opening Drill has no pilot mechanism for finding a center on the material. This allowed the overlapping inserts to bore straight into the material and bring the pre-drilled hole into alignment.

It took a few trial runs to find the Opening Drill’s “sweet spot.” After about a half hour of playing with speeds and feeds, however, its benefits became readily apparent. Running the tool at 125 rpm and 0.46 ipm, Wellhead could open the hole to 7.9 inches in a single pass (the company removed the remaining 0.1 inch in a separate operation to achieve desired surface finish). Cycle time was reduced to 46 minutes, saving 3.5 hours per hole and about 7 hours per part. After 10 holes, Wellhead generated a total cost savings of more than $1,500.

“It really knocked out that material in a hurry,” Mr. Currie says. “There was nothing else out there to go this big. You had to adjust boring bars or swap out the tool for each cut.
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Peering at the shiny NT4250 DCG situated on Mori Seiki distributor J&H Machine Tools, Inc.’s shop floor, Imo Pump realized that it would need to make some savvy toolholding choices to assume ownership of the nicely equipped mill-turn center. The pump manufacturer had reached a pivotal point in production of a certain screw. In fact, what was called for was a complete overhaul of the current machining process. Capable of turning and milling in one setup, the mill-turn machine could consolidate multiple setups and thus enable the company to streamline screw production. However, implementing the revamped process would hinge on identifying the proper tooling to complement the machine’s ample capabilities.

The Monroe, North Carolina-based shop says its first order of business was to identify a way to hold the tool securely enough during a rough slotting operation, an integral part of the machining sequence. Otherwise, it would not have adequate means to abate vibration and decrease cycle time. Thus, it would not have a way to justify the expense of acquiring the NT machine.

“Initially, we were rough milling these screws using a totally different method,” explains Jonathan Hunter, manufacturing engineer at Imo Pump. “We were using numerous machines to carry out what we can now accomplish with one. Between turning operations, milling keyways and milling threads, I suppose that we’ve been able to eliminate five different setups.”

Ultimately, the shop chose to apply a milling chuck to a distinct spindle interface, a Capto C6 to be exact, to reach higher cutting efficiencies, accelerating cycle times by between 15 to 20 percent.

The particular component is a power rotor screw to be implanted in one of the many screw-type pumps of varying shapes and sizes conceived and manufactured at Imo Pump. Predicated on engineering principles set in place by founders Carl Montelius and Bengt Ingestrom in 1931, Imo Pump is now a division of Colfax Corporation. Credited with the design of the first multiple-screw pump, the company says its rich history of invention continues today, as it produces pumps that operate quietly at high speeds and high pressures in thousands of applications. The manufacturer attributes the widespread use of its pumps to the simplicity of the design. Its products can be found in barges and ships and in engine rooms on commercial marine vessels and combat ships, to name a few.

Commonly made of 4140 steel, the power rotor screw is turned by the motor and drives two idler screws in the low-pulsation pump. Because this screw ensures the smooth operation of the three-screw pump, it is imperative that the shop machine it accurately on a consistent basis. In order to do that, Imo Pump would need to remedy a vexing process segment—a rough slotting operation. The operation involved rough milling the screw threads using a 3/4-inch, four-flute carbide end mill.

“This roughing of the slot, which is a key area of the part itself, was really the driver to make or break the entire process,” comments Jack Burley, VP at Big Kaiser.
The Matter With Chatter

Thus far, the company had not been able to hold the carbide end mill rigidly enough to make the required depth of cut (DOC) and achieve the high speeds necessary to rough mill the threads expeditiously. Realizing that inadequate clamping forces could potentially cause rough finishes, frequent tool breakage and workpiece marring, Imo Pump began a series of trials.

J&H Machine Tools, Inc. performed all of the testing at its Charlotte, North Carolina facility. Over the course of the trials, various seemingly plausible options proved impractical, given the cycle time and concentricity constraints.

For instance, both an end mill holder and an ER collet chuck posed limitations. For this applicaiton, both lacked the characteristics needed to provide the necessary rigidity, which meant running the part slower.

“During roughing, the ER collet chuck was actually pulling the tool out of the holder, making it cut undersize,” Mr. Hunter explains. “The standard end mill holder imposed extra forces on the tool itself. I noticed extra wear on tool while holding in that style. The excessive vibration caused stresses that receded the end mill.

“With this collet style, we could only achieve about half the depth of cut,” he adds. “In addition, we were running slower, and the collet seemed to be marring the workpiece.”
The Right Connection

After weeks of trial runs that failed to meet the predefined operating parameters, the team was open to suggestions. It consulted Richard Bevers, regional manager for Big Kaiser. One facet of the shop’s selection criteria was compatibility with the Capto C6 spindle interface.

As Mr. Burley explains, the Capto C6 interface already provides a foundation for rigidity, which can be enhanced with the appropriate application-specific toolholding.

“This spindle interface consists of a tri-lobed tapered male connection so that when you put it into a receiver there is no drive key per se,” Mr. Burley explains. “The polygon shape is the drive system. Because it is on a slight taper, it precisely locates into a spindle.”

As a licensed manufacturer of Coromant Capto tooling systems, Big Kaiser offers numerous toolholding systems that are compatible with spindles equipped with a Capto interface. After reviewing the application, Mr. Bevers determined that the Mega Double Power milling chuck could potentially rectify chatter issues associated with the other two holders. Supplied from stock, the tool was placed into operation immediately. With the vibration issues remedied, Imo Pump was consequently able to increase the DOC as well as the feeds and speeds.
Better Concentricity

According to the manufacturer, the rigidity of the holder itself and how it clamps on the tool eliminates the vibration. Its locking nut configuration enables the chuck to offer accuracy of 0.0002 inch at four times the diameter, which translates to constant cutting for all flutes engaged in the workpiece.

Rigid clamping begins with the outer diameter of the toolholder, which is said to be completely symmetrical. To tighten the tool in place, the operator need only turn this nut in a clockwise direction with a custom wrench, dubbed the Mega wrench. This wrench fits over the diameter and works as a one-way clutch. It grips the smooth OD without marring or causing indentations on the clamping nut. When the nut is fully tightened, there is double contact between the toolholder body and the nut itself.

“This milling chuck has high gripping force, probably in the order of seven to ten times more than what one might find with a collet chuck,” Mr. Burley says. “It offers excellent runout and higher mass and damping capability when compared to an end mill holder.”

These capabilities, Mr. Burley says, can be attributed to larger mass at the cut (where the tool goes into it) and the construction of how the tool is clamped is so much more rigid, the damping capability of the tool results in smoother cutting.

Mr. Burley approximates that Imo Pump has realized three times more DOC and three times faster feed rate with this tooling solution, compared with the ER collet and the standard end mill holder.

Big Kaiser’s Double Shot (DS) configuration also contributes to noticeable gains in cutting efficiencies at Imo. A standard feature of all Big Kaiser toolholders, this peripheral cooling system propels coolant through the holder, right along the edge of the end mill.

“The body of the toolholder contains holes to allow coolant to pass through,” Mr. Burley explains. “This not only flushes chips but also cools the cutting edge.”

Since May 2007, the mill-turn has resided at Imo Pump’s Monroe facility. Coupling its capabilities with the attributes of the new milling chuck has been instrumental in streamlining screw production. The company cites a setup reduction of 35 percent (on average), in addition to favorable tooling life and discernable leaps in productivity.

“We’ve noticed better life on that particular tool, and we just added another chuck,” Mr. Hunter concludes.

By all accounts, the toolholding itself, though initially more expensive than other options, is earning its keep.

“The tooling has been crucial in delivering a marked improvement in productivity,” Mr. Bevers concludes. “In the long run, those kinds of results are more valuable than saving a few bucks on a toolholder.”

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