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Producing parts with complex, intricate geometries can be a challenge for any shop, but in the medical field, this is routine. With little room for error, medical manufacturers machining high-precision components that require tight tolerances need reliable quality control systems to ensure their products meet specification. However, without an efficient means of collecting and storing measurement data, quality control can become a vexing bottleneck that adversely affects the entire operation.

Quality control inspectors at surgical tool manufacturer T&L Sharpening can attest to that fact. The company’s manual, paper-and-pencil data entry process had slowed data collection to a painstaking crawl and left ample room for human error. In addition, the use of hardwired measurement devices at the shop’s single inspection station limited inspectors’ mobility and created unnecessary clutter. To address these issues, the shop invested in L.S. Starrett’s DataSure Wireless Data Collection System. The new system not only eliminated a troublesome safety hazard caused by tangled wires, but also increased the flexibility, productivity and accuracy of the measurement process.

Located outside of Warsaw, Indiana, T&L was founded 30 years ago and made a name for itself as a manufacturer of hand-ground bone rasps. Today, the company provides manufacturing, sharpening, reconditioning and modification services primarily to the orthopedic industry. On the 7,000-square-foot shop floor, operators run surgical tools such as rasps, twist drills, reamers, end mills, taps and more in batch sizes ranging from one piece to thousands. More than 90 percent of the work is done in stainless steel via CNC machining, Swiss turning and grinding and quality checked with calipers, micrometers and scopes.

T&L’s products are not implants that remain in the body after surgery, so the company does not need to conform to the myriad FDA requirements that typically affect OEMs. Thus, many of the shop’s customers don’t demand full statistical process control (SPC) for the surgical cutting tools. Nonetheless, the shop still strives to provide SPC, according to company president Thomas All.

“Although the industry is not currently requesting full SPC from surgical tool manufacturers, it may move that way. Regardless, our goal is to attain this anyway because SPC inevitably promotes better quality and productivity and fewer errors,” Mr. All says.

With this goal in mind, the company implemented a stringent quality-control program involving an inspection station where multiple operators measured parts with hardwired measurement devices. However, the wires of the measurement devices would constantly become tangled, hampering productivity and creating a safety hazard. Moreover, the manual data-recording process often relied on an inspector’s memory or handwritten notes. Especially for larger jobs, this made quality control a daunting task, whether it involved providing low and high readings or 100-percent inspection of a lot. Entering data in Excel spreadsheets to compile Cpk range, X-bar and R data provided a partial solution to this issue. However, using a wired system meant workers still had to bring parts to the measurement area for inspection.

To remove the wires and increase mobility for quality control inspectors, the company began to investigate available data collection options. When Starrett presented its DataSure Wireless Collection System, T&L was sold on the concept from the start, says Tom Herr, quality manager.

“It wasn’t a matter of if we were going to go with the system; instead, it was a question of how quickly we could get it up and running,” Mr. Herr says.

In fact, the radio-based system proved to be relatively easy to set up. First, six miniature radios (called end nodes) were connected to the data output ports of the shop’s electronic tools. Although T&L’s calipers and micrometers are not Starrett tools, they are fully compatible with the DataSure system, as are most other major brands of electronic tools. The next step was the installation of a wireless signal router, which extended the system’s range by 100 feet. Finally, the company set up a gateway that connects to a PC and acts as the central point for data collection and tool management.

“Once we had things set up and ready to go, there was very little time spent adjusting to the new system,” Mr. Herr says. “We were up to speed in an hour or two with very little training.”

Now, T&L inspectors can move about freely with their measuring devices, allowing several people to work in the same area simultaneously. Additionally, workers can conduct inspections from different points in the shop rather than bringing all parts back to a common area. According to Mr. Herr, the result is a 25-percent reduction in average inspection, collection and documentation time, considerably improving throughput and reliability. Also, the elimination of wires has increased safety by reducing accidents and injuries. Perhaps most importantly, data collection is not only accurate, but in real time.

“DataSure has proven to be a very handy and convenient system for us,” Mr. All says. “When the industry comes knocking, demanding full SPC for surgical instruments, we’ll be ready.”

The R.O.I. on implementing the DataSure system was fast. T&L Sharpening estimates their annual savings at $50,000—and that’s without utilizing the system to its fullest. The company still does some hand documentation because they’ve been too busy to fully implement SPC. But because some customers will not require 100-percent inspection if a shop can provide SPC documentation, T&L is quickly heading that way.
http://www.mmsonline.com/articles/wireless-data-collection-readies-surgical-toolmaker-for-full-spc.aspx

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Shops consider a number of factors when justifying automated parts storage systems, including cost, required floor space and machining application. A clever use of configurable storage racks in place of rotating magazines keeps the design of Erowa’s Robot Compact handling facility simple and affordable for shops of all sizes. The racks are internal to the robot, so the system occupies little space on the shop floor and can get very close to the machine tools it serves. The robot is designed especially for manufacturers of small parts such as medical components and EDM electrodes.

The robot is most useful for shops that need immediate productivity improvements but can’t afford to spend time and money implementing larger, more complicated solutions, says Bob Byers, vice president of sales and marketing at Erowa. Increased customer demand, more exacting tolerances, new jobs involving geometrically complex parts—all these factors can drive shops to seek technological solutions for improving productivity. Often, however, purchasing the latest machine tools and other equipment isn’t always possible or even necessary, Mr. Byers explains. A more economical solution is to find a way to increase the productivity of existing equipment.

“In the era of ‘bigger, faster, stronger,’ we’re going back to a very simplistic approach with the Robot Compact,” Mr. Byers says. “Most people think they need a wholesale change in their shop, but sometimes tweaking one little area can increase profits. Starting out small with something very simple that can increase the productivity of the machine tool is huge.”

With that in mind, the robot is designed to be easy to install and operate. The racks used to store workpiece pallets are easier to change out than a rotary magazine system, Mr. Byers says. This allows shops to easily reconfigure the system for different applications. Moreover, with the racks mounted inside the system to the left and right of a small gripping arm, all movement is internal to the robot. This configuration keeps the robot’s footprint to 2 square meters and allows installation right next to machines with virtually no gap. Despite its small size, the Robot Compact features 160 pallet positions. It can supply one or two machines with pallets weighing 30 kilograms or less.

“This is something a shop can implement, make money from and see immediate benefits without a lot of investment in time and money,” Mr. Byers concludes.
http://www.mmsonline.com/articles/compact-handling-facility-sticks-to-basics.aspx

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Since 1995, Pointe Precision, a one-stop machine shop in Plover, Wisconsin, has specialized in producing critical-tolerance parts for the medical and aerospace industries—parts that could endanger lives if they fail. “Our components are what we call ‘life-critical,’” observes company President Joe Kinsella. “Consequently, we take inspection very seriously.” For this reason, Mr. Kinsella likes to point out that “quality” is not a department, but an integral part of the shop’s overall process. In fact, shopfloor inspection is an essential part of its strategy.

Thus, every workcenter is equipped with surface plates and the inspection equipment necessary to allow operators to perform consistent and reliable in-process inspection. One of the busiest pieces of inspection equipment is a Starrett HD400 horizontal benchtop, dual-lens measuring projector, also referred to as an optical comparator. Since purchasing the device, the shop has gained an edge by trimming time from the production cycle without compromising quality.

ISO-certified since 2000, Pointe Precision employs 110 people, 70 of whom are engineers and technicians pursuing a Six Sigma methodology aimed at zero-defects quality output in less time and at a lower cost than the competition. The company operates on a 5-day, two- and three-shift schedule with some lights-out production. The 60,000-square-foot production facility turns out 3,500 different types of products per year. It’s a mid- to low-volume contract manufacturing operation focused on parts with a high degree of precision and variation.

“Our customers’ tolerancing is becoming very stringent,” Mr. Kinsella says. “Right out of the chute, you have to deliver perfect parts.”

With such strict tolerances, the shop needed an inspection system that could repeatedly ensure that critical dimensions and features on machined parts were within customers’ specifications. The Starrett HD-400 not only met the shop’s expectations in terms of accuracy, but also reduced both in-process inspection times and change-over time between work orders.

The horizontal measuring projector provides a 16-inch by 6-inch measuring range using an indexing dual-lens slide and triple-bundle, fiber-optic surface illumination with dual-intensity tungsten halogen profile illumination. The device profiles parts on a 16-inch-diameter screen with 10 to 100 times magnification. Generally, the horizontal-type optical comparator works best with parts that need to be fixtured, held in a vise or held on centers, according to manufacturer L.S. Starrett.

In addition, the comparator is equipped with a Metronics QC200 digital readout device for geometric dimensioning and tolerancing (GD&T) calculations. “The Starrett HD400 allows us to verify a wide variety of product characteristics very quickly,” explains Chris Spranger, quality assurance manager. “We measure many features, including angles, outside diameters, runout, hole sizes, corner breaks, threads, radii and shaft lengths on parts measuring 2 inches or less.”

According to Mr. Spranger, minimizing setup time is a critical factor in keeping the company competitive. Some runs involve as few as 50 pieces. Others may involve a thousand. As any manager knows, setup time does not pay the bills. While the plant depends on a state-of-the-art, climate-controlled metrology lab for some measurements, placing the Starrett comparator in the turning area for visual verification has eliminated many time-consuming trips to the inspection room.

This is possible because the device can be used for some measurements that previously required a CMM, says Randy Grezenski, Pointe Precision manufacturing engineer. “We can take three hits of an arc, for example, on a half-spherical radius measuring 1/2 inch in diameter and take three points, make a circle and establish a centerline on the part,” he says.

Now, Mr. Spranger says, most inspection is done at the machine. He points out that in addition to the optical comparator, the turning department has installed Starrett surface plates and other gages for use with each lathe. Each of the shop’s 12 turning centers is set up for new jobs anywhere between two and seven times in a 24-hour period, with each setup taking between 30 minutes and 3 hours. Mr. Spranger says 10 to 25 percent of setup time is absorbed by the first-article verification process—a procedure now performed on the shop floor rather than the CMM/inspection room.

Additionally, if operators had to inspect precise parts using only micrometers, indicators and other conventional gages, inspections would take much longer than they do with the optical system. That’s because the non-contact technique can graphically display and measure parts with dimensions and shapes that would be hard to measure with regular gages. In fact, using conventional gages rather than the optical comparator would make inspection times two to four times longer, depending on the product, Mr. Spranger notes.

“You can easily see the impact of an inspection process that could take three or four times longer to complete,” Mr. Spranger says. “The Starrett HD400 helps us minimize setup time and get into production mode quickly.”

Unlike the shop’s previous system, the Starrett device enables operators to check distances and concentricity. Additionally, it has sharper, clearer optics that detect edges better, says operator Marty Cattanach. “Before the HD400, features were very fuzzy and shadowed,” he explains. “The Starrett comparator allows you to see much greater detail. It’s just more accurate and much faster.” Mr. Cattanach adds that the device’s quick-release fixture saves time compared with a manual crank handle, and the screen rotates easily for checking different angles.

Mr. Spranger estimates that the Starrett optical measuring system has reduced overall inspection time by as much as 75 percent, depending on the complexity of the part. “We have found optical, non-contact measurement to be an integral part of our turning work,” he concludes. “The Starrett HD400 provides a more reliable, repeatable and far faster method for inspecting parts, including setup and the all-important first-article inspections.”
http://www.mmsonline.com/articles/optical-measurement-keeps-pointe-precision-sharp.aspx

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PROBLEM: Segmented tire molds required complex, time-consuming programming

SOLUTION: HyperMill CAD software from Open Mind

RESULTS: Improved delivery time, part quality

Chris Sipe, owner of Northeast Tire Molds in Akron, Ohio, likens machining tire molds to evolutionary theory—while some firms go out on a branch and never go any higher, others can look a little further down the road and adapt to changing conditions. Mr. Sipe says his company is one of the latter. Having machined tire molds for more than 30 years, Northeast has moved from the traditional model of machining two-piece tire shell molds from castings to machining segmented molds directly from aluminum stock. Business has doubled during the past 2 years as a result.
A key component of this transition was hyperMill, a CAM package developed by Open Mind Technologies. Tire molds are extremely complex, with numerous 3D contours and cavities, and this creates a significant programming challenge. In his evaluation of the software, Mr. Sipe found that one programmer using hyperMill required only 3 months to accomplish the same amount of work that took a year with the company’s previous system. Along with an investment in the simultaneous five-axis machine tools and associated tooling needed for such work, the software has enabled Northeast to provide higher-quality products and faster delivery.

For many years, the standard in tire manufacturing has been two-piece shell molds. Uncured (or “green”) tires consist of layers of inner liners, tire cord fabrics, steel, Kevlar and extruded rubber. The green tires are placed into a press where the upper and lower mold sections meet. Heat energy creates chemical reactions to cure and bind the rubber, steel and fabric layers. Meanwhile, pneumatic bladders inflate to expand the tire against the mold and impart the tread design and required sidewall engraving. Post-press requirements can include dimension checks, X-ray inspections and other section analysis.

However, deforming and shaping a green tire within the contour of a two-piece mold can cause the rubber to move, affecting thickness conformity throughout the tread. On the other hand, segmented molds consisting of 7 to 10 sections with separate sidewall plates can decrease this movement and improve overall tire performance. The downside is that segmented molds take longer to cast, machine and finish, significantly increasing costs.

Although direct-machining techniques debuted in the 1960s, the process was complex, time-consuming and expensive. The advent of five-axis machine tools and 3D CAD models excited many mold builders, but significantly attacking lead time remained a struggle. “Tire molds require a very high standard of five-axis simultaneous methods,” says Mike Christie, Northeast Tire Molds vice president and a 15-year veteran of the company. “We believed in the idea of eliminating castings and direct-machining tire molds from stock, but unfortunately, the programming efforts were immense. And with segmented molds, the same problems repeated themselves in many locations.”

To eliminate castings, Northeast needed simultaneous five-axis machine tools, tooling and programming capabilities that would allow it to machine the molds directly from stock. Procuring such a package, however, took years of education and experience. “We wanted to be self-sufficient,” Mr. Sipe says. “We didn’t have a foundry, and we couldn’t control our costs with outside vendors, so we sought capital equipment where the model didn’t matter.”

Mr. Sipe found one piece of the package at the 2001 EMO show in Hannover, Germany: a five-axis Alzmetall milling machine. “You could purchase three other five-axis machines for the price of one Alzmetall, but you’re not getting three times more capacity,” he says. By 2005, he was ready to take delivery, but not without the programming wherewithal.
One advantage of segmented molds often touted by tire makers is that if a particular tread problem exists, they can correct one segment without recasting the entire mold. However, Northeast found itself writing its own lengthy routines to repeat programs in various mold locations. The company tried to use the same five-axis CAM software used by one of its major customers, but the results were a “nightmare,” Mr. Christie says. All data, including intermediate results, went into one big file, which frequently became too large to handle correctly. Programmers often found themselves waiting a half-hour or longer just to open files.

Believing it had a state-of-the-art system, Northeast gave itself 9 months to learn the programming before taking delivery on the new five-axis machine. Still, the company made little progress. “We were told by experienced people what we could and couldn’t do,” Mr. Christie says. “The amount of time invested to get the end result was astronomical.”

Faced with these difficulties, Mr. Sipe recalled talking to Open Mind Technologies at EMO 2005 about tire mold programming. When he decided to evaluate hyperMill, Open Mind’s CAM system, he found it had a number of advantages over the company’s current system and decided to implement the software in the shop. “We had automatic indexing and collision checking, which we didn’t have before,” Mr. Christie says. “We were able to model the entire machine in hyperMill, and everything is interrelated. Our old package wouldn’t let us check back.”
The software also can quickly handle the large amount of data, and it enables parametric modeling through CAD interfaces. Other features include global swarf machining; stock trimming and stop surfaces in five-axis strategies; associative programming; automation through macros from 2D to five-axis in the same package; and 2D through five-axis program generation via the same postprocessor.

In addition, the software offers a tire-specific package in which all 2D, 3D and five-axis strategies are expanded by a parameter that allows the user to assign a pitch to each machining strategy. This makes segments composed of a specified pattern of pitches easier to produce. Automated segment generation not only assigns NC tool paths to the corresponding mold segments, but also adjusts tool paths that go beyond segment boundaries.

With the right machine tools, tooling and programming support, Northeast Tire Molds is now reaping the rewards of multitasking. The shop has moved from performing as many as eight operations on various machines to loading raw material and proceeding to the finished part on a single machine with no subsequent benchwork. For an average tread, the company can deliver a mold in the time it used to take to get the casting. Mold quality has also proved. “Customers find their molds are lasting longer, and the quicker delivery time means we have more time for testing new things,” Mr. Sipe says. “Business has doubled in the last 2 years, and the amount we’ve advanced in the last 6 months makes it very exciting to envision next year.”
http://www.mmsonline.com/articles/cam-system-simplifies-tire-mold-programming.aspx

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Part I, Utilizing an off the shelf PC as a CNC Controller

There are two main groups that can take advantage of today’s low cost PCs as an effective and inexpensive CNC controller.

• Retrofits to existing CNC machines with outdated or proprietary controls in need of service.

• Shop built and home built CNC machines.

Inexpensive PCs can cost as little as $150.00 and yet provide a dependable and effective CNC machine controller. Some sources to consider for obtaining such a system are outpost.com and dell.com. Oupost.com is an outlet for Fry’s electronics. They have one PC on sale ranging from $150.00 to $199.00. Several have successfully used this PC in conjunction with MACH2 CNC controller software.

Tradeoffs: Price vs. Quality. With the lowest cost PCs there a tradeoff in performance, quality, and reliability. The manufacturers of these machines use low cost hardware in their manufacture and they make compromises in the design of the systems to keep their costs down. Inexpensive hardware translates directly to a higher failure rate and more difficult to obtain manufacturer support. This can be a deciding factor by itself if you rely on this machine for production.

Design compromises which are common in low cost PC have an impact on performance. The primary concerns are: insufficient memory, the use of shared memory, and on-board graphics devices. The primary hardware requirements for a PC based CNC controller are sufficient memory, and sufficient processor speed. You can see that the compromises present in these systems are in direct opposition to the requirements for CNC controller.

At the bottom end of the Inexpensive PC market there are off the self solutions that will function well as a PC based CNC controller. As with all things, you tend to get what you pay for, so the buyer is advised to be aware of the requirements and limitations that are in play.

Part II in this series of articles will examine an alternative to buying an off the shelf solution and explore building a PC to meet your specifications.

Dan Staber a Mechanical Engineer offering design, analysis, consultation, and project management services. Dan is also a licensed professional engineer is the states of South Dakota and Washington. For more information please vist - http://www.qacad.com

dcstaber@qacad.com

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Since we are dealing with machines that do work for us, we need to control those machines somehow. We need to control them for safety reasons as well. If you give a machine improper commands it can easily get out of control and cause harm to you or the part you are machining. We want to give appropriate commands to our machines, at appropriate times so they are not “out of control”.

The language that these machines use is called G-code. G-code has been around since the early 60’s. There are a number of variations of G-code, but most are very similar to one another. See the previous section for a sample of G-Code. We will need to use a computer to talk with our CNC machine. Our computer will send signals to our CNC machine. In-between our computer and our CNC machine sits a controller. A controller converts commands into signals that are used to control the motion of our machine.

As these signals are sent out of the controller, they go to either stepper or servo motors. This is how we create motion. These motors drive our various axis on our CNC machine. While we are moving our axis, there is generally a cutting tool of some sort removing material. This is the machining process coupled with CNC.

Here is a brief description of the two types of motors generally used in CNC:

Stepper motors:

Simple design

Easy to use

Generate torque at low rpm

Do not know their position in relation to the program

Servo Motors:

Generate torque at high RPMs

Generally need gearing of some sort to be effective

More sophisticated

Can maintain their relative position, thus, they can be more accurate

Machine Controllers

Controllers generally stand alone near the CNC machine. They act as a translator between your control computer and your CNC machine. Generally, they add quite a bit of cost to a CNC machine as well. Controllers can cost anywhere from $1000-$20,000 or more depending on their sophistication.

Don is active in G Code and CNC Milling.
CNC Machine is part of his expertise.

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