An arthroscopic shaver from Pro-Dex has very tight tolerances.
Pro-Dex Inc. (Santa Ana, CA; www.pro-dex.com) specializes in quickly developing and manufacturing technology-based products that incorporate embedded motion control and miniature rotary-drive systems.
The parts the company makes must be very precise. For example, its arthroscopic shaver 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 throughhole is machined off centerline along the entire top 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 throughhole becomes off-center in the finished instrument, and it has a triangular tear-drop shape that is easy for the user 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 aesthetics are also very critical to all of Pro-Dex’s instruments,” says Vic McBenttes, manufacturing supervisor. 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, quality could suffer and parts may have to be scrapped.
“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 Pro-Dex consistently checks parts and tooling. It developed tooling cycles to either change them out or resharpen as needed.
In order to facilitate some new instruments the company was going to be producing, it turned to Hardinge (Elmira, NY; www.hardinge.com). Hardinge makes the Elite 8/51 turning center with live tooling that can turn up to a 2-in. diameter using a bar feeder and collet setup, or up to 10 in. diameter using a jawed chuck.
McBenttes says, “The reason we purchased this machine was to manufacture larger instruments. Most of our dental products and the parts that go inside them are generally from 0.050 to 1.0 in. diameter. The newer instruments we’re making can be almost triple these diameters.”
“This turning center has allowed us to produce the larger-diameter parts for our products,” he continues. “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 2 in. through the spindle with the attached bar feeder. But we can add a jawed chuck to the spindle and machine all the way to an 8-in. diameter. Right now, we’re using an air collet, and the biggest part we’re producing is about 1 to 1.5 in. in diameter.”
Another important advantage 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. For programming, they use Mastercam CAD/CAM software version 9, made by CNC Software Inc. (Tolland, CT; www.mastercam.com).
Tom Mullin, vice president of operations, says that all of Pro-Dex’s programming is primarily done by in-house programmers who also operate the machine tools. Training is important for the programmers, he says, and the company’s operators took a local course consisting of two classes a week for four months.
Mastercam was chosen because, as McBenttes says, “It is the most user-friendly toolpath software there is, in my opinion.”
When asked if programming the machine using its CNC programming software would be just as easy, McBenttes says, “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.