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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. 

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Growing worldwide demand for natural gas and oil has pushed up prices. Gasoline and diesel fuel are hitting record prices at the local station, much to the chagrin of car and truck drivers. Of course, increased demand and higher prices encourage energy companies to find new sources in the ground. This means more well drilling wherever oil and gas deposits are likely to be reached.

That’s good news for companies that make supplies for the oilfield industry, companies such as EWECO in Magnolia, Texas. EWECO is a major manufacturer of mud pumps and related components. “We’ve seen more growth in this market lately than we’ve seen in 30 years. Our backlog is bigger than it’s ever been,” says Michael Williams, president of the company.

Every oil or gas well drilling site needs at least one mud pump; some sites may have two or three. Mud pumps are large pieces of equipment that force “mud” down a well hole so that small pieces of drilled rock can be carried up with the mud as it is sucked back out of the hole. Successful, economical well drilling can’t happen without a mud pump, and if a mud pump fails, drilling stops. According to Mr. Williams, EWECO pumps have a reputation for durability and long life in the field, so his company’s pumps are in great demand right now. He attributes the quality of these pumps to highly efficient designs, high-quality materials and accurate machining of critical components. Moreover, he likes to say that EWECO wrote the book on mud pumps, but some of the best chapters are still being written.

Keeping up with the current rush of orders while maintaining its manufacturing standards is a challenge for EWECO. “Our customers expect to have their pumps delivered when promised; issues with our machinery can’t be offered as excuses,” Mr. Williams says.

Recently the company underwent an expansion to their manufacturing facilities by adding two new HBMs and 50,000 square feet of floor space. The new expansion is served by a pair of 40-ton cranes to meet the need for newer, larger units. If the necessary capacity to satisfy the market demand could not be found under its own roof, then outsourcing would be the only alternative. However, EWECO is both a pioneer and a leader in the mud pump market, and they would rather keep this technology in-house, if possible. EWECO faces pressures from low-cost regions of the world that seek to copy components. Mr. Williams says that copies are typically not made of the same durable materials that EWECO uses and the life of the components is far lower.

Mud pumps can be many feet long and are designed to be delivered on flatbed trucks. Many units are being packaged for sale to companies in the North Sea and provinces in the former Soviet Union. One key feature of EWECO pumps is the large, rigid rectangular frame that gives an assembled pump its stability and durability in the field. Other large components include valve bodies and manifolds. The size and shape of these workpieces call for horizontal machining. Indeed, EWECO relies on HBMs in its shop. The shop has 14 HBMs, all from Nomura (distributed in the United States by SB Machine Tools, Schaumburg, Illinois).

The newest machine is a Nomura HBA-135. This machine has an extra meter of Z-axis travel compared to other models considered for the application. Not only does this extra travel allow several operations to be combined in one setup, but the accuracy of this travel establishes the foundation for the precise, efficient operation of the pumps when assembled and tested. In fact, the ability to machine large, complex components accurately helped make it possible for the company to introduce its new five-piston series of mud pumps last February. These new pumps achieve much more efficient operation than the company’s popular three-piston models.

Although the five-piston designs have more components and a more complex mechanical operation, they have an uptime record as good as the simpler three-piston versions.

“Without the capability of our horizontal machines, EWECO could not have launched this new product line,” Mr. Williams says. “As it is, the new pumps are expected to add double-digit growth to our sales in 2008. We’ve been able to reach new markets and hit our sales targets because of the efficiency and accuracy of our HBMs,” he says.

Reaching Growth Goals
Mr. Williams’ father, Ellis, gave the company both its name and its spirit. EWECO stands for Ellis Williams Engineering Company. The elder Mr. Williams was a pioneer in the oilfield business who highly valued efficiency and innovation. These are two characteristics that his son says he now pursues with the same drive. The father’s legacy reaches back to the 1940s, when he began his career with Continental-Emsco. At that time, the industry still used steam-powered pumps. However, the demand for more power and greater portability eventually made the steam versions obsolete, ushering in the age of the twin-cylinder pump powered by electric motors. The twin-cylinder model D-175, designed by Mr. Williams, became a mainstay of the industry. The need for still more power brought about models such as the D-225 and the D-550. Eventually, a 1,600-hp version, the D-1600 was developed. In 1967, the elder Mr. Williams’ development efforts prompted a change from the Duplex series to what he called the Triplex series. The Triplex used three cylinders instead of two, thus distributing loads more evenly among components and increasing both pump life and performance. At the time, the idea was considered revolutionary. It was well-received in the market, making the Triplex the industry staple that it is to this day, the younger Mr. Williams says.

Years ago, industry needs encouraged changes to pump design, and today, needs are again testing the limits of current technology. Much of the current oil supply is found under shallow sands, and it is being consumed at record paces. Any newly found deposits of oil are deeper and under more layers of rock. Reaching those deposits would be impossible if it were not for an engineered fluid that drillers simply call “mud.” This slurry of dissolved clay and polymers is aptly named—it has the consistency and density of wet cement.

Mud, according to Mr. Williams, has about a dozen functions in an oil well. Perhaps its most important functions are to carry bits of drilled rock back to the surface and to keep the cutting tip cool. A more advanced drilling method allows drilling mud to act as a hydraulic power supply. Instead of turning the whole drill string (the entire length of pipe down the well hole), the hydraulic energy carried by the mud is used to turn just the cutting tip, making it possible to drill deeper and through more rock than previous technology allowed. Using this technique, drilling can penetrate at an angle (directional drilling), avoid difficult layers of rock and hit deposits previously considered too costly to reach. To perform directional drilling successfully, acoustic data must be retrieved from the mud being pumped into the hole. This data is referred to as MWD (measurement while drilling) and LWD (logging while drilling). Acoustic reflections from the hole and surrounding rock layers indicate the depth and direction of the cutting tip. They also reveal information about rock layers surrounding the tip. However, a major source of interference to this technique is the mud pump itself. As the pistons move in and out, forcing material down the hole, resulting pressure variations cause acoustic pulses that must be filtered from the MWD/LWD systems.

In February 2008, EWECO released the Quintiplex series mud pump. The Quintiplex has five cylinders instead of three. Using five cylinders reduces pressure variations by more than 70 percent, thus reducing mud “noise” on the drill string and, in turn, allowing more accurate MWD/LWD readings. Increasing the number of cylinders decreases the load each component is required to carry by more than 40 percent, compared to Triplex pumps of the same horsepower. Although this new design increases the working life of each component, it multiplies their number. Every component, no matter how well designed or well built, will eventually wear out or need to be replaced, so the complex Quintiplex design heightened the importance of precise manufacturing to extend the useful life on critical components. The company’s HBMs have to support this mandate.

Reaching Between Two Extremes
While many configurations exist for HBMs, EWECO has found a size and arrangement that works well for them. “I’ve had floor models, but I prefer the table type. The accuracy of every machining operation downstream is controlled at the HBM. It took me a long time to understand that,” Mr. Michaels explains. Some HBMs provide Z-axis travel by moving a saddle, which has a rotary table mounted to it, to and from a fixed column. Other HBM configurations have a flexible traveling column. In this design, the table is mounted to a saddle that only moves in the X axis. It cannot move to or away from the spindle. For this type of machine, Z-axis motion is accomplished by moving the column to and from the fixed table. At EWECO, the traveling-column design is critical to the overall mud pump accuracy because it allows both sides of the frame to be machined in the same setup without moving the part. With the traveling column, the Z axis can be fully retracted from the table to allow the large rectangular frame to rotate about B axis. When the rotation is complete, the second side can be milled to complete the part. According to Mr. Williams, the B axis of the Nomura HBA-135 can be positioned accurately within 3 arc seconds, thus making the bore-to-bore alignment of the crank bores very good. While fully retracting the Z axis represents one extreme of travel, being able to reach the table requires another extreme—that of the Z-axis stroke. This why the extra meter of travel in this axis is essential.

Rigid Frames Help EWECO Reach Long Life
The frame of the mud pump influences the overall life of the pump because it holds the crank (also called the eccentric), the input shafts and the idler shafts in alignment. The Quintiplex, according to EWECO, is the first pump to have a balanced eccentric crankshaft. It is important to be able to get close to the crankshaft when doing layout work so components fit as they should during assembly. When asked about the traveling-column feature and how important it is to manufacturing the pump successfully, Mr. Williams replied, “If we couldn’t back the column out of the way and machine the frame in one setup, we’d have to redesign the whole product.”

However, the extra-long Z axis isn’t the only must-have feature of EWECO’s HBMs. The quill design produces and transmits a great deal of torque and thrust for heavy machining.

Spade Drilling Works The Quill
According to Mr. Williams, the balanced crankshaft and rigid, accurate frame allow precise alignment of gears, pinions and shafts. Yet, the real workhorses of the pump are its pistons, cylinders, valves and manifolds. Mud is a thick and abrasive material, so it naturally causes wear on cylinders and pistons. However, these components can be serviced in the field, whereas the valves and manifolds are not designed to be replaced on a regular basis. For this reason, they are made of either 4130 or 4340 steel, which resist wear. Manifolds can be as long as 48 inches and can have drilled holes as wide as 5 inches in diameter.

EWECO uses a spade-drilling process to make holes in these parts. Spade drilling requires substantial torque, and EWECO depends on its HBMs to deliver this high drilling force. For example, the three-speed gearbox on the HBA-135 is capable of generating nearly 3,000 foot pounds of torque. The lowest programmable spindle speed is 5 rpm. Using the higher gears yields a maximum 2,500 rpm. According to builder, the gearbox design allows the spindle to reach maximum torque throughout its speed range. The HBM’s 5.3-inch diameter quill is nitride hardened and ground to a mirror finish. This finish increases the amount of surface area in contact with the quill sleeve for greater rigidity.

The spindle quill can feed with a maximum of 7,000 pounds of force and reach a maximum depth of 27.5 inches. For holes too deep to complete from one side, the hole is drilled on the first side, then rotated and drilled on the second side. At EWECO, a mismatch where the holes meet is unacceptable, so the HBM must be accurate and precisely aligned. Mr. Williams reports that the HBMs meet this requirement, even under heavy machining loads.

The combination of the traveling-column configuration, extra Z-axis travel and high-torque/low-rpm capability makes the HBM a very flexible machine tool for EWECO. The company’s success with its new five-cylinder mud pump product line reflects the importance of this flexibility in today’s market. Flexibility is also the key to thriving in the future if and when market conditions change. As Mr. Williams points out, past experience has been a good teacher.

Being Flexible Helps Reach New Markets
The search for new sources of oil and gas hasn’t always been as intense as it is today. As recently as 10 years ago, the price of a barrel of oil was $11. During that time, no one was paying to explore for new oil because the market seemed to be flooded. When well drilling slowed dramatically as a result, EWECO relied on its flexible approach to manufacturing to reach markets that were not energy-related to support the business. In addition to oil well drilling, mud pumps can be used to dispose of saltwater and to remove flood water. Pumping cement is also a significant market for mud pumps because they are more reliable than equipment in use for this application. Also during this last drilling slump, EWECO expanded into industrial water blasting. Perhaps the most innovative application of the mud pump was in the field of horizontal directional drilling. This method is used to drill under rivers, highways or subways. It helps in laying pipelines and adding to communications networks when excavating the site would be undesirable.

Mr. Williams believes that keeping flexible machinery such as the HBM in his manufacturing base means EWECO can respond to similar opportunities as they emerge in the future, without having to outsource production of components.

Reaching Toward the Future
Markets expand and contract as a part of usual business cycles. The oil market is no exception. In 1979, a shortage of oil hit the pocketbooks of car and truck drivers. In 1999, a surplus of oil hit the pocketbooks of oil producers. No one is sure what lies ahead for oil and gas prices. No one doubts that a supply of oil that is easy to find as well as easy to extract is limited. Mr. Williams’ father, Ellis, predicts that the oil market will undergo a correction as it did after the shortage in 1979, bringing prices back to palatable levels. In whatever direction the oil market swings, it is clear that EWECO mud pumps will be pushing cutting tips deeper and in new directions, and that EWECO will be pushing its product lines deeper into other industries and into new applications.

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Shops commonly outsource non-machining operations because the envisioned cost and learning curve make it seemingly impractical to bring those processes in-house. They’d rather leave heat treating, laser welding and other such processes to vendors with the expertise and the right equipment, and concentrate on their core compentency—machining good parts.

Anodizing is a process that shops often outsource because of these reasons. In addition, it is likely that they are unsure about the anodizing process itself as well as regulatory, safety and environmental issues (some of which vary from state to state). That said, shops can realize considerable cost savings by bringing anodizing in-house. In doing so, they will gain direct control over quality and delivery time while alleviating logistics headaches, too.

So, how do shops know if adding anodizing is right for their situation? One way to determine this is to contact designers and builders of anodizing systems. IPEC Global (Ontario, California) is one such company. Ken Emilio, company president and CEO, has owned and operated machine shops for years and has created a number of anodizing lines for shops. The information he provides in this article offers an overview of anodizing fundamentals along with practical information for shops that may be at the very early stages of anodizing investigation. Although this article isn’t meant to be a “how-to” piece, it does answer initial questions shops often have about the feasibility of adding anodizing to their list of manufacturing capabilities.

What Is Anodizing?
Anodizing is an an electrochemical process that speeds the natural oxidation of select non-ferrous materials. It improves material surface hardness and wear resistance, and it allows users to manipulate oxidation thickness. Aluminum and titanium are the two most common materials shops are likely to encounter that require anodizing. Anodized components are used for a variety of military, medical, commercial and automotive aftermarket applications.

Anodizing also enables users to change a part’s color using dyes (in the case of aluminum) or manipulating electrochemical parameters (for titanium). For some applications, this color may be simply for aesthetics. For others, such as medical devices, specific colors are chosen for identification purposes. The color of a medical screw, as an example, may dictate the screw’s thread dimension and diameter. This color coding also helps with inventory control, making it unneccessary for hospital employees to be familiar with fastener nomenclature or dimensional identification.

There are three types of aluminum anodizing. Type I anodizing, which uses a chromic-acid-based chemical bath, is commonly used for applications that require a thin, protective coating and a high level of corrosion resistance. It also serves as an effective primer prior to painting or other coating operations.

Type II anodizing is the most common and often the most affordable aluminum anodizing process to bring in-house. It is used on a wide variety of applications and enables parts to be dyed in virtually any color. It is based on a sulfuric-acid chemical bath.

Type III anodizing is known as hard-coat anodizing. It is used when a very hard surface is needed, such as for weapons, sporting goods and bearing surfaces. Type III anodized parts typically aren’t dyed. Rather, shades of gray are achieved by altering temperature, voltage and bath compositions.

Should Shops Anodize?
To gage the appropriateness of adding anodizing, a shop should first calculate the amount it currently spends outsourcing anodizing. If that cost is less than $10,000 per year, then it’s generally a good idea to continue using the vendor as long as that vendor is dependable.

If anodizing costs as much as $50,000 per year, then installing a small, modular anodizing line makes sense. These prefabricated systems look like a series of in-line washing machines, and have all necessary tanks, ventilation and closed-loop, rinse-water recycling systems. These units range in price from $30,000 to $75,000. Securing requisite permits for these units typically is not a challenge because the chemical volumes are relatively low and spill containment and fume control are often built into the unit. Such modular anodizing lines are suited for small quantities of parts as large as 2 cubic feet, and typically have a footprint of approximately 20 feet by 8 feet. Part racks are moved manually from tank to tank with these small modular systems.

If anodizing costs $150,000 or more, then a medium- or large-scale modular anodizing line may be appropriate. These systems sometimes use a hoist to move part racks from tank to tank. Prices range from $100,000 to $150,000, and it’s recommended that shops contact an anodizing consultant to help plan line design and develop operation manuals.

Modular anodizing systems generally aren’t recommended if a shop’s annual anodizing cost exceeds $250,000. The tanks, pollution control and other related equipment will be significantly larger. Although lines of this type might cost between $250,000 to $500,000, an anodizing cost savings of 50 to 60 percent is possible. In this case, an anodizing expert should certainly be used to develop a preliminary line design before a shop solicits estimates from equipment suppliers.

Steps In Anodizing Aluminum
Parts must be immersed in a number of baths before and after the actual anodizing process. Each bath has a specific temperature, chemical concentration and immersion time that must be monitored and maintained. Proper rinsing after every support bath is essential. What follows are the typical steps for Type II anodizing of aluminum alloys. (See page 104 for a detailed list of operations for Type II anodizing of 6061-T6 aluminum.)

* Alkaline clean—Alkaline cleaning is often the first anodizing step. This bath is designed to remove grease and oils from parts without etching the parts or removing material. Alkaline cleaning is typically followed by a rinsing bath.
* Alkaline etch—This bath removes oxides and gives the parts a smooth, matte finish. An etch bath is not required when a brilliant shine is desired at the end of the process. Etch baths should be followed by vigorous rinsing.
* De-smut—The de-smut/de-oxidizer bath removes the dark smut created by the etch bath and is a critical step prior to anodizing. De-smut stations usually use nitric-acid or ferrous-sulfate baths.
* Bright dip—The bright anodizing bath, typically of concentrated nitric acid, ultimately shines and protects the part surface. This bath does emit large volumes of nitrogen oxide fumes, however, so proper ventilation is essential. Anodizing in high volumes can require scrubbers to clean these fumes before they are released into the atmosphere.
* Color—A wide variety of different colors and color patterns are possible in a dye bath.
* Seal—Anodized aluminum surfaces require sealing to eliminate color fading or running. Some sealers include sodium dichromate for added corrosion resistance.

Safety

Operating an anodizing line is similar to operating aqueous cleaning, deburring and vibratory finishing tools. That said, anodizing uses hazardous chemicals so worker safety is paramount. The types of hazardous materials shops will need to purchase, use and store include sodium hydroxide, chromic acid (for Type I anodizing), sulfuric acid (for Type II and III anodizing), nitric acid, ferrous sulfate, nickel acetate and organic dyestuffs. Obviously employees should be outfitted with the proper protective gear. For information about handling these materials, shops should contact their state’s department of environmental quality.

In addition to hazardous chemicals, anodizing also generates hazardous waste. This includes diluted wastes such as rinse water and concentrated wastes from cleaner tanks that need to be removed.

Two other areas of concern are wastewater discharge and air-pollution control. The wastewater from rinsing can be recycled or sent to the sewer if local regulations are met. Adequate ventilation is also necessary. Most modular anodizing units have integral ventilation hoods. Anodizing fumes must be exhausted outside the facility, so a corrosion-resistant exhaust fan and ducting are needed. Type I anodizing emits chromic-acid fumes and most government agencies will require a fume scrubber. Scrubbers may not be required for Type II or III anodizing.

Regulatory And Environmental Issues
Many times the regulation process depends upon the number and size of the anodizing lines. Modular, self-contained lines are generally easier to permit than large lines. Shops considering a large line should plan on spending more time and money on engineering and permits.

In many cities permits are submitted to the local fire department for final approval. Fire codes tend to focus on chemical containment and storage in addition to fume exhaust, ventilation and fire sprinkler systems. In cases of large anodizing lines, some fire departments require an extensive ventilation system with emergency generators and fire sprinklers installed within the duct work. This most likely will not be required for small anodizing systems.

Expect Some Frustration
Shops should expect problems during the learning, installation and start-up phases. For instance, it may be difficult to locate a chemical supplier in the area. Shops may also need to purchase anodizing racks or masking materials outside of their state. Simply put, anodizing lines, even small ones, are not “plug-and-play.” However, investing time and effort early in the planning stage will result in an anodizing process that is as effective as it is easy to maintain and operate.
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Cutting tool manufacturers often perform post-grinding operations such as honing and polishing to improve tool surface finish and generate precisely rounded cutting edges. These operations lead to better chip flow, longer tool life and improved adhesion prior to coating processes. They also reduce the coefficient of friction of coated tools by removing droplets and other imperfections left behind after CVD or PVD.

Schütte TGM offers an alternate surface finishing method on its WU-305 tool grinding machines. The process uses magnetism to swirl abrasive powder across the surface of a cutting tool to smooth and improve its finish. The technology was originally designed for use on stand-alone equipment, but a magnetic finishing module has been engineered to be compatible with the wheel-changing mechanism used on the WU-305 machines. This enables the machines to both grind cutting tools and to treat them via magnetic finishing in one setup.

The primary components of the finishing module are two revolving magnetic discs located on either side of an enclosure containing the abrasive powder. Each powder grain contains both abrasive and magnetic material. Once a tool is inserted into the enclosure, magnetism causes the powder to swirl around the tool and smooth its surface. This magnetic finishing technology is also being applied in aerospace and automotive applications to reduce friction between mating components such as gears and engine parts.

Schütte currently offers four powder grit sizes—400, 600, 1,000 and 1,500—which users choose based on their finish requirements. The company says the magnetic finishing process can deliver 0.02-µm Ra and 0.08-µm Rz. In addition, it is said to generate a reproducible radius of cutting tool outside edges and chipping edges between 3 µm and 50 µm.

The WU-305 machines can grind, mill, belt-sand and polish, so their coolant system has been designed to accommodate machining chips, grinding swarf and the powder used in the magnetic finishing operation.
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Manually controlled, horizontal honing machines will probably be on shop floors for many more years, but a new generation of vertical CNC, multi-spindle machines has emerged in the last few years that is transforming “honing” into high-volume precision bore machining. Equipped with in-line air gaging for process and tool feed control, these machines are being rapidly adopted because of their exceptional precision, process capability, output and ease of automation. Individual machines—configured as automated cells—are now producing more than 15 million parts per year, with high process capability and accuracies of 0.25 to 1.25 micrometers (0.00001 to 0.000050 inch).
Why Multi-Spindle?

Makers of small engines, hydraulic valves, gears, compressors and pumps, to name a few, are driving a renaissance in honing as they strive to make their end systems reach a higher performance level. The key issue is producing tight component tolerances with high process capability (Cpk).
Whenever a part rotates on a shaft or a piston slides inside a bore, performance-oriented manufacturers are adopting honing to improve their products by tightening tolerances. The goal is gearboxes and transmissions that run quieter, smoother and longer. It includes hydraulic systems that are more precise, responsive, efficient and leak-resistant as well as small engines that deliver higher power densities and produce less pollution. To produce these parts in high volumes, automation is the key.

Multi-spindle vertical honing machines are not completely new. Hydraulic versions of this platform have been around for years, but carry with them all the disadvantages that drove hydraulics out of other machine tools many years ago—cost, larger footprint, noise, heat, maintenance and performance drift. Single-pass honing machines are usually multi-spindle verticals, too, but lack the capabilities of a conventional hone for correcting geometric error in long bores and producing a true crosshatch finish.

A number of factors prompted the development of the new breed of all-electric, multi-spindle, vertical honing systems. By its nature, honing often requires two steps: a roughing step to produce the precise geometry and size of the part, and a finishing step to produce the surface spec. When a part has a blind bore or other features that might cause the abrasive tool to wear unevenly, stock removal and finishing steps are often separated. The need to hone increasingly complex parts with keyways, ports, blind bores, and so on in several steps makes an automated, multi-spindle machine a cost-effective solution.

New issues with part quality also make a multi-spindle system a cost-effective approach. A honing operation is most efficient when the arriving parts are high quality, with little stock removal needed. Despite this, upstream processes today, which may be fast and effective, often produce a spread of tolerances on parts that require more stock removal in honing to hit the size, straightness, cylindricity and roundness specs.

A changing workforce in the U.S. and Europe—focusing attention on labor and factory-floor efficiency—influenced the development, too. In the U.S., a generation of craftspeople who have honed parts on manual machines is now retiring. Today’s automated, multi-spindle machines have all the skills of these retiring craftspeople built into the control systems. In terms of floor space, the multi-spindle machine can reduce the requirement to one-third or less. Cycle times, likewise, are often halved.
Product Performance Drives Tolerance Reduction

It’s important to note that honing is a process of choice for makers of performance-oriented products because it precisely creates three key characteristics in parts in a way that no other process can: final size, geometry and surface finish.

Manufacturers have tightened the dimensional requirements for parts to achieve greater performance from end products—tighter sealing and less hysteresis, noise and vibration. Diesel fuel injectors offer a good example. Typical print tolerances are 0.0013-mm (0.000051-inch) straightness per side on the bore, 0.001-mm (0.00004-inch) taper in the bore, and 0.0013-mm (0.000051-inch) roundness. Manufacturers in production mode strive for less than 0.001 mm (0.00004 inch) on total measured bore variation when using scanning air gages, with roundness less than 0.0005 mm (0.00002 inch). They match fit plungers with 0.006- to 0.007-mm (0.00024 to 0.00028 inch) clearance, with a 0.001-mm (0.00004-inch) total tolerance on the fit. As the match clearance gets smaller, surface tribology and retention of a lubricating film become more critical.

This requires a much higher level of precision in component parts, increasing the likelihood that several steps will be required for honing. Overlaying the need for greater precision is the requirement for high-process capability, an area where servo-controlled honing shines.

When holes produced satisfactorily on lathes suddenly have to meet a process capability of 1.67 or 2.0 Cpk, turning operations may fall short. That kind of capability requires a process that’s easy to “dial-in” with high precision, and very stable once it’s established. For example, a lathe may get to a certain value, but if tweaked, a little will jump to a value out of spec and throw the process off. A computer-controlled hone can easily get within 0.00025 mm (0.000010 inch) of a specified size, and with the resolution on the tool-feed systems of today’s machines, the variability is small.

Conventional honing is inherently able to correct bore geometry (cylindricity, roundness, taper, size, straightness) with a reciprocating abrasive that contacts a large percent of the bore’s length. ID grinding can correct geometry, too, but works best for parts with larger (> 0.75 inch) bores and low length-to-dimater ratios (0.5-to-1). At a length-to-diameter ratio of 2-to-1, honing has a an advantage in speed of material removal, and more than a 5-to-1 length-to-diameter spindle deflection on an ID grinder might cause taper issues.

Neither grinding nor turning can produce honing’s characteristic crosshatch pattern on the bore surface. Conventional honing leaves a desirable crosshatch pattern on the bore, while finishing the surface to a given spec. The crosshatch can be thought of as two opposing helical patterns.
A bore finished with a single-point tool has one telltale helical pattern. The resulting “threaded” finish can lead to lubricating films being pushed out of the bore. If the bore serves as the outer race of a bearing, the finish from turning may lead to the needles in the bearing being pushed toward one end, causing premature wear and binding.

This crosshatch pattern can be controlled to produce a specific angle and depth (with plateau honing), which manufacturers use to manage the retention and distribution of lubricating oil films. Performance-oriented manufacturers are also paying greater attention to cylindricity and the surface parameters Rk, Rpk and Rvk (see box). Makers of hydraulic cartridge valves and similar components fine-tune these parameters based on the characteristics of the mating/sliding parts.
A 90-Degree Turn For Honing

Traditional honing is often a horizontal process where the part reciprocates. A horizontal process is fine for lighter parts, and the fixtures are inexpensive, but a vertical arrangement has a slight advantage because there is no potential for bending forces on the tool. Theoretically, there is an accuracy advantage to a reciprocating spindle and stationary part, particularly as part weights increase and tolerances are reduced.
A multi-spindle vertical hone is also easier to automate. Untended vertical honing cells may integrate capability to measure a feature on incoming parts, such as bore size, then orient them, place them into a fixture, air gage them after each step, sort them by size after processing, orient them and sometimes perform secondary operations. Even in a basic single-spindle, manually loaded operation, a vertical machine can have multiple workholding positions to maximize spindle productivity.

The major engineering requirements for three machine platforms recently developed was the flexibility to use servo control in any axis of motion, including the stroking system, spindle rotation, tool feed system, machine movements and part indexing systems, depending on the model.

Servo stroking in a vertical platform is a significant issue. In a horizontal machine, this system is less expensive, the stresses on it are low, and it takes less power to drive it. Vertical designs have traditionally used a hydraulic drive or a four-bar linkage. In a vertical arrangement, the spindle mass has to be accelerated/decelerated at each reversal point, at rates to 400 strokes per minute. A new servo-driven ballscrew proved to be the only technology capable of withstanding this duty. This drive system was installed in a beta machine, which processed several hundred thousand parts per year during an extended test. Currently this stroking system is extremely robust, and far more precise and controllable than a hydraulic drive—approximately 400 percent more accurate.

Sunnen wrote the motion profiles for the stroking system, which is closed-loop controlled. This high-precision motion control allows the user to tailor the spindle action to optimize the honing process—not unlike what a craftsman would do in a manual
process.
Three Modular Platforms For Bores
To 300 mm (12 inches)

The new Sunnen SV-1000, SV-310 and SV-500 vertical CNC honing machine series represent the basic platforms on which honing is being transformed into automated precision bore machining. All are modular, engineered to scale up from a single-spindle job-shop machine to fully automated multi-spindle cells. Easily configurable, they are available with post-process inspection, along with special tooling, robotic integration, part orientation, gaging and other options needed for purpose-designed systems. The SV-310 and SV-500 also accommodate the hone head, which can be equipped for in-process air gaging. The SV-500 combines servo control of spindle rotation, stroke and tool feed. The servo spindle enables the machine to produce a constant crosshatch angle, end-to-end in the bore, responding to the technology needs of manufacturers in the diesel cylinder liner market.

SV-1000 series machines can size bores to accuracies of 0.001 mm (0.00001 inch). This machine is designed for part diameters of 3 to 65 mm (0.120 to 2.56 inches) while the SV-310 handles parts to 200 mm (8 inches) and SV-500 to 300 mm (12 inches). Any of the machines may be able to handle larger bores, depending on the part material and bore length. All are designed for lean production environments to permit rapid change-overs and reconfigurations from manual to rotary or linear part handling. From an operator’s perspective, all three machines have an identical look and feel.

The basic single-spindle SV-1000 module, for example, starts with a fixed tooling plate or servo rotary table. A cast-polymer base provides excellent vibration damping and structural rigidity, while removable guarding facilitates different processing options and future repurposing of the machine.

For unmanned cellular processing, the SV-1000 can be integrated with an Etamic CNC servo air gaging system. It provides post-process air gaging for closed-loop control of bore size and geometry, along with downloadable SPC data and feedback control. Matched with diamond-plated CGT Krossgrinding tools or MMT multi-stone mandrels, the air-gage-equipped machine can automatically control hole size to accuracies of 0.001 mm (0.00001 inch), eliminating the need for craft skills. A load-sensing tool feed system minimizes processing time by sensing where and how much to hone the bore.
The Right Tool For The Job

Sunnen’s MMT tool is a more traditional metal-bond super abrasive tool design. It is used most commonly with the SV-1000 machines. It uses a metal-bond abrasive, so cutting force is low, the abrasive is self-sharpening, and it produces a consistent surface finish from new to worn. The ability to manipulate the mix of the abrasive and bond gives the MMT tool a wide application range.

The Krossgrinding tool has an expandable diamond-plated sleeve that surrounds the tool. The sleeve design of the abrasive is well applied for parts with ports and keyways, because it resists the tendency to wash out the edges of these interruptions. Though it lasts many times longer than a metal-bond abrasive, diamond-plated honing tools work with a smaller window of suitable part materials and work best with very rigid parts. As the diamond begins to dull, this type of abrasive tends to push and plow metal, rather than cut it, requiring higher cutting forces, so it is important to consider part distortion during processing.

The new stroking drive provides the highest level of flexibility and consistency in spindle reciprocation to allow a new level of process optimization. Unique in the industry, it enables the SV-1000 to do both conventional honing and single-pass honing, using available adapters, to give the machine job shop versatility and return on investment.

A recent typical application for the SV-1000 involved production of spool valve parts for fluid power equipment. The hardened steel part (56-59 Rc) requires stock removal of 0.1 mm (0.0035 inch), with final part specs of 0.0008-mm (0.00003-inch) straightness, 0.0005-mm (0.00002-inch) roundness and a surface quality of 0.0125-micrometer (5-microinch) Ra. Varying wall thicknesses throughout the length of the bore make this a challenging part. The fully automated honing cell for these parts includes a six-axis robot, which takes parts from a bowl feeder, inspects the incoming bore, aligns the parts for proper fixture loading, and places them in the honing fixture. The three-spindle hone is tooled to remove different amounts of stock and produce the required finish in steps. At each station, the part is air-gaged and the honing process automatically compensated. The honing system sorts the parts into five classes, each separated by 0.0006 mm (0.000025 inch), corresponding to the size classes achieved in the production of the mating parts. Ninety-five percent of the parts coming off the honing system fall within one 0.0006-mm (0.000025-inch) class size.

As manufacturers continue to raise the bar for part tolerances to these levels, precision multi-spindle bore machining systems are winning a prominent place on the production floor.

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