Software and Advanced Machine Tools Fill a Need for Better Cycle Times and Quality

With micro-motors spinning at speeds from 5,000 to 200,000 RPM and part tolerances that would make most machinists sweat, Pro-Dex medical instruments can help a skilled doctor relieve a patient’s pain and suffering.

Founded in 1971, Pro-Dex Inc. pioneered the first miniature air motors for surgical procedures, later expanding on that technology to develop a broad base of products.

The company's strategic focus is to get products to market faster, at a lower cost, and with high quality. Today, the company specializes in quickly developing and manufacturing technology-based products that incorporate embedded motion control and miniature rotary-drive systems. With operations in Santa Ana, California and Beaverton, Oregon, Pro-Dex designs and produces products to sell directly to distributors or builds products for other companies. These products are found in hospitals, dental offices, medical engineering labs, scientific research facilities, and high tech manufacturing operations around the world.

The Pro-Dex Micro Motors' 19,000 sq. ft. facility in Santa Ana, California houses both staff and equipment that is capable of designing and manufacturing a finished product. With 100 people, the company runs three shifts per week: day, afternoon, and one for weekends from Thursday through Sunday.

With ever increasing sales, the company realized that they were limited in product manufacturing because of the size capabilities of their machining equipment, most of which are Hardinge turning centers or Bridgeport VMCs. To expand their product line, Vic McBenttes, Jr., manufacturing supervisor, decided to purchase a new machine. It was a Hardinge Elite 8/51 turning center with live tooling that would give them the capability of turning up to a 2” diameter using a bar feeder and collet setup or going up to a 10” diameter part by using a jawed chuck.

He says, “The reason we purchased this machine was to manufacture larger instruments. Most of our dental products and the parts that go inside of them are generally from 0.050’’ to 1.0” diameters. The newer instruments we’re making can be almost triple these diameters.”

Some of these products are arthroscopic shaver handpieces that allow surgeons to cut or scrape tissue, bone, or cartilage through a small incision. These allow a much less invasive type of surgery that is easier on the patient.

“This turning center has allowed us to produce the larger diameter parts for our products. It also has live tooling capabilities like a milling machine, so we’re able to machine parts more completely in one setup. The largest diameter we can machine is two inches through the spindle with the attached bar feeder. But we can add a jawed chuck to the spindle and machine all the way up to an 8” diameter. Right now, we’re using an air collet and the biggest part we’re producing is about 1-1/2” in diameter.”

Another important component to using the Hardinge turning center is the ability to program it quickly, which is not easy with the machine’s fourth axis for live tooling. In fact, with this option McBenttes says that it’s much better to program off-line and use the company’s Ethernet system to download the programs right to the machine. For programming, they use Mastercam (CNC Software, Inc., Tolland, CT) CAD/CAM software Version 9 for both their turning and milling centers.
Parts at Pro-Dex must be very precise. For the arthroscopic shaver the company produces, it starts out as round aluminum bar stock. A hole is drilled all the way through the instrument’s centerline and then a number of different bore diameters are produced in this hole. Other features are also machined on the shaver’s centerline and along the length perpendicular to the lengthwise hole.
Next, another through hole is machined off centerline along the entire length on top of the shaver. This hole is used for suction of water from the cutting end of the handpiece. The entire part is milled to a final contour so that the large centerline through hole becomes off center in the finished instrument, and it has a triangular tear-drop shape that’s easy for a doctor to hold. At the back of the shaver, cables and a tube are attached and another end piece connects all the electrical components. The front of the instrument has a collet that holds a surgical cutting tool.
“Part tolerances and esthetics are also very critical to all of Pro-Dex’s instruments,” says McBenttes. Tolerances for some of the components, including the shaver, are within two tenths of a thousand. Programming is very critical for these parts. Without the ability to verify the toolpaths, which Mastercam offers, quality could suffer and scrapped parts could be produced. “We have a tolerance range anywhere from plus or minus two thousandths for some components, while others go all the way down to plus or minus a couple of tenths. For us, being in the medical device industry, every machining center has to have super precision capability. What’s really important is the machine’s capability, being able to hold within tenths of a thousand, and part-after-part repeatability. The machine must repeat and hold a tolerance.”

McBenttes says they consistently check parts and tooling. They’ve developed tooling cycles to either change them out or resharpen them as needed. He adds, “Medical parts require special attention. Even though the machine is very accurate and repeatable, we inspect every critical tolerance to insure its quality. I have an operator checking parts all the time.”

Finding a better way to machine
Pro-Dex’s Hardinge Elite was purchased with a live tooling option. This allows them to mill and drill both on a part’s centerline and off the centerline, up to an inch in two axes. What’s important for using the live milling tools on the machine, McBenttes says, is having a good CNC programmer and the right software for toolpaths.

He notes, “Having live milling helps us eliminate processes on our milling machines. We’re able to machine the part complete by doing off-center or on-center operations. It also allows us to eliminate additional part handling and setups, and extra steps where you can get tolerance stackup. It also eliminates additional tooling and operators. It all stays on one machine and we’re able to machine a part more efficiently.”

Efficient Programming
Tom Mullin, VP of Operations, says that all their programming is primarily done by in-house programmers who also operate the machine tools, but McBenttes also does some of the programming. Training is important for the programmers, adds Mullins. Their operators took a local course that had two classes a week for four months.

McBenttes says the reason they choose Mastercam was because, “It is the most user-friendly toolpath software that there is, in my opinion.”

Mullins adds, “A lot of it had to do with availability of training and support, and its ability to integrate with CAM packages that we use.”

When asked if programming at the machine using its CNC programming software would be just as easy, McBenttes states, “With manual programming, there is a lot of operator error. We can avoid this with Mastercam, and it’s designed to give you the right feeds and speeds for every operation.”
With the types of parts that Pro-Dex produces, many so tiny that they can easily fit on a dime, toolpath verification is a very important feature to prevent tool crashes and keep quality high. McBenttes mentions, “We verify our toolpath before programming the machine. It eliminates errors, and it’s a great feature to have. I like the fact that I’m able to see the cut and the capabilities of the machine that we’re using. By feeding the information into Mastercam on our tooling and machine capabilities, it gives us a more productive and efficient program. I like to be able to see the toolpath before I cut the part - that’s the bottom line.”

Mastercam has also helped with their fourth axis programming. McBenttes says, “It does help a lot, because the fourth-axis manual programming is really intensive. It takes a long time to do. With Mastercam, you use the geometry given by the engineers, you follow the toolpath, and it’s done.”

Make it Look Great
Another important feature of medical equipment is its cosmetic appearance says McBenttes. “This plays a huge role with these parts. Cosmetics are important to the customer, it demands a high level of quality and workmanship from us. So we pay attention to detail. And by doing that, and emphasizing truer precision and cosmetics, the quality of the parts is better.

“If you go into a dental office or a surgical suite, and you pick up a hand drill that costs several thousand dollars it needs to look nice. We can’t afford to have any cosmetic flaws. Maintaining a cosmetic finish is critical for secondary finishes like anodizing and plating“ he explains.

“The finishes on our instruments after machining are anywhere from 16 to 32 micro inches, a mirror finish,” McBenttes states. “To us, it’s a really good machine finish. We do use the machine tools to control the finish, because it makes any secondary process more predictable.”

Consistent Quality
McBenttes adds, “We have a system here to maintain quality parts. Once all the first article dimensions are approved, and the setup is accepted, we start machining. After the first article the operator inspects 100% on tight tolerances. Then for every 20th part, he inspects 100% of the dimensions.

Product volumes at Pro-Dex vary immensely. The parts that they make vary from thousands a month, down to only a handful. Types of materials the company cuts include 60 or 61 aluminum and 416, 303, 440, 17-4 stainless steels, and brass for bushings and internal part components, but no exotic metals like titanium.

Currently McBenttes says the company to produces its products on a just-in-time basis and programming efficiency using Mastercam helps. He mentions, “That’s the focus of the company; we try to do everything just-in-time, try to get it quickly to the customer and Mastercam helps us achieve that.”