Shop Solutions: Medical Devices Depend On Software
With micromotors spinning at speeds from 5000 to 200,000 rpm, and part tolerances that would make most machinists sweat, Pro-Dex Inc. (Santa Ana, CA) is producing medical instruments that help doctors relieve patient pain and suffering.
Founded in 1971, Pro-Dex pioneered the use of miniature air motors for surgical procedures, later expanding that technology to develop a broad base of products. The company specializes in developing and manufacturing technology-based products that incorporate embedded motion control and miniature rotarydrive systems. These products are found in hospitals, dental offices, medical engineering labs, scientific research facilities, and high-tech manufacturing operations around the world.
Pro-Dex designs and produces products to sell directly to distributors, and builds products for other companies at its facilities in Santa Ana, CA, and Beaverton, OR. The company runs three shifts per week with 100 personnel: day, afternoon, and one shift for weekends from Thursday through Sunday at the Pro-Dex Micro Motors 19,000 ft2 (1765-m2) facility in Santa Ana.
With sales increasing, the company realized that it was limited in manufacturing capacity, most of which was supplied by Hardinge turning centers or Bridgeport VMCs. To expand machining capabilities, Vic McBenttes Jr., manufacturing supervisor, purchased a Hardinge Elite 8/51 turning center with live tooling that would provide the capability of turning to 2" (50.8-mm) diam using a bar feeder and collet setup or going to a 10" (254-mm) diam part by using a jawed chuck.
"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" [1.27-25.4-mm] diam. The newer instruments we are making can be almost triple these diameters," McBenttes explains.
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," McBenttes explains. "The largest diameter we can machine is 2" [50.8 mm] 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" [203.2-mm] diam. Right now, we're using an air collet, and the biggest part we're producing is about 1 1/2" [38.1-mm] diam."
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, Pro-Dex uses Mastercam CAD/CAM software Version 9 from CNC Software Inc. (Tolland, CT) for both its turning and milling centers.
Parts at Pro-Dex must be very precise. The 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 diam 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. 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 0.0002" (0.005 mm).
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 thousandth, and part-after-part repeatability," McBenttes says.
Pro-Dex consistently checks parts and tooling and has developed tooling cycles to either change them out or resharpen them as needed. "Medical parts require special attention. Even though the machine is very accurate and repeatable, we inspect every critical tolerance to ensure its quality. I have an operator checking parts all the time," he says.
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.
"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."
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 chose 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. "We verify our toolpath before programming the machine. It eliminates errors, and it's a great feature to have," says McBenttes.
"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."
Another important feature of medical equipment is its cosmetic appearance, says McBenttes. "The finishes on our instruments after machining are anywhere from 16 to 32µin. [0.0004 mm], a mirror finish," McBenttes states. "To us, it's a really good machine finish. We use the machine tools to control the finish, because it makes any secondary process more predictable."
Pro-Dex has 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," McBenttes explains.
Product volumes at Pro-Dex vary greatly. 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.
Inspection Software Tracks Tank Repair Data
Refurbishing any modern vehicle can be a daunting task. When that vehicle is a Bradley Fighting Vehicle, the process is, as it is described by the Department of Defense (DOD), mission-critical.
DRS Laurel Technologies (Johnstown, PA), a division of DRS Technologies Inc., is a partner with a major defense contractor in the DOD Bradley RESET program. RESET's mission is to refurbish and return Bradley Fighting Vehicles to active service in Iraq and Afghanistan.
DRS Laurel Technologies is responsible for inspecting, repairing, and certifying more than 100 different cables (wiring harnesses) located throughout the hull and turret of each vehicle. These wiring harnesses support a host of systems including engine and vehicle controls, vision enhancement, target acquisition, battlefield position, and tactical information.
Challenges in the refurbishing process range from accurately identifying parts that need repair to providing effective communications with the factory floor about when repairs were made, by whom, and where. In addition, the customer requires that cables be packed in a specific order, in specific boxes so they can be readily located.
To meet the data-intensive challenges required by the RESET program, DRS Laurel chose ASI Data-Myte Inc.'s (Plymouth, MN) Inspect visual-inspection software. At the heart of the Inspect system is a visual record for each cable processed.
"The system provides a major improvement in communication," says Bob Sewalish, DRS Laurel Technologies' quality engineer. "There is no question about what needs to be done. It's not like somebody putting a tag on a cable that says, 'Do this list of things,' then having the tagged cable go down to the repair area, only to have the repair person ask, 'What did you mean by this? Where is that? I can't find this!' That doesn't happen," Sewalish says.
DRS Laurel Technologies put together an entire quality document for the program with work instructions on how it will make repairs, taking into account that different areas require special considerations. With ASI DataMyte Inspect visual-inspection software, special work instructions are embedded right on the screen. "It's very visual and it's very simple. It tells you exactly what to do," Sewalish explains.
Cable prep begins with the initial vehicle teardown at DRS Laurel Technologies' business partner's location. Cables are removed from a vehicle and crated, with that vehicle's serial number assigned to each crate, and then delivered to the work area. The team member prints out a complete set of labels based on the vehicle's serial number. Then the process of cleaning the harness and attaching the appropriate label to each cable begins. The cables are scanned to record the vehicle's serial and cable numbers, initiating the visual record for that specific part.
Data are transmitted to the DRS Laurel Technologies' Johnstown facility server. The scanning process is repeated by recording the receipt, cleaning, and shipping information for each cable. Any remaining unused labels are then scanned and recorded as not received.
Prior to shipment, there is a complete reconciliation of all the cables for that specific vehicle. "If our partner says they delivered 98 cables to the DRS Laurel Technologies workstation, but we are only shipping 95, we need to account for those missing cables. The Inspect transactions record, coupled with status and shipping reports, helps us do just that," says Sewalish.
Incoming receiving and inspection at Johnstown involves opening the incoming container and scanning each cable to display the visual record for the cable. The inspector uses this visual record to identify locations of needed repairs, which are indicated by red markup flags.
Once the inspection is complete and the visual image marked up, the inspector places the cable in a tote for routing. Cables requiring no repair move to the electrical test area. Cables to be repaired or scrapped are routed accordingly.
Scanning each cable confirms receipt and alerts the inspector if any unscheduled items are received. The inspector can also retrieve numerous reports to aid the reconciliation of the shipments between the partner's location and DRS Laurel Technologies' facilities.
Totes of inspected cables are routed to the desired station for repair. Each cable is pulled from its tote and scanned to display the visual record. The team member makes the needed repair and notes the completion of the repair. Each green flag indicates a completed repair at that location.
"With the visual image everything is highlighted that needs repair," Sewalish explains. "It's all pictorial. Team members can look at the picture and compare it to the physical cable in their hand, and know what to do with it. When the repair is complete, they click on it and mark it repaired. Now we know who required it, and when it was repaired. It's all recorded."
A functional electrical test is performed when the team member takes a cable from a tote and scans the cable to pull up the visual record for that specific unit. The cable is tested and results noted. Cables are then routed to final inspection.
The inspector scans the cable, reviews both the visual record and the physical cable, and completes the inspection. If the item passes, it moves to the shipment prep area. If the cable fails, it is either scrapped or additional repairs are noted on the visual record. Again, cables to be repaired or scrapped are routed accordingly.
Once the cable passes final inspection, it goes on to a holding rack, so it can be packed with other cables that make up a complete kit. The customer requires that the cables be packed in a specific order in specific boxes. Once delivered, each box will make its way to a set location on the customer's production floor and the cable will be used in a specific order.
"When we go to pack the boxes again, we scan the cables for serial and part number information and also wand the box number into the system. If the customer has a question about a cable, we can tell them the exact box we placed the cable in," Sewalish explains.
ASI DataMyte's Inspect software has proven its value in tracking cables through multiple revisions resulting from variation from vehicle to vehicle. For example, a cable could be from a one-year-old vehicle or it could be from a 10-year-old vehicle. DRS has to make repairs as needed and verify the cables are as good as new and at the same revision level as new ones. In special cases, the old cable is moved up to the revision level. Those instructions are simply embedded in the pictorial for those specific cables.
Cables that are considered mission- critical are identified with a message in red: "Other than cleaning and testing, if any problem DO NOT REPAIR-Mission-Critical—scrap." A similar message appears for another class of cables that are inexpensive to purchase so that you can't afford to repair them.
Inspect software gives DRS Laurel Technologies the ability to reconcile shipments and product movement for each specific vehicle, and audit scrapped cables on a periodic basis. The system produces more than 70 reports that are viewable via any standard web browser."
Reverse Engineering Steam-Turbine Repair
Repairing steam turbines is all about efficiency, quality, and precision for the petrochemical, oil and gas, and power-generation industry.
Failure to make repairs in a timely manner can result in the loss of hundreds of thousands of dollars a day if a key piece of machinery is kept out of action. The challenge of repair is complicated by the fact that there are almost never any original drawings to go by. Typically, the drawings have been lost. Even when they are available, they may not be very helpful anyway, because of modifications, wear, and corrosion of components over the years.
Hickham Industries Inc. (La Porte, TX) uses a Romer/CimCore arm and Delcam's PowerInspect inspection software as a critical part of its steam turbine repair manufacturing process. Established in 1974 and a Sulzer Turbomachinery Services Co. since 1985, the company offers full-service repair, remanufacturing, and reconditioning of steam and gas turbines, as well as for general rotating and reciprocating equipment.
"We have to get the measurements right. The margin for any type of error is very small, and the price of an error is extremely high," explains Dave Dixon, project manager for Hickham's hot-gas expander business. "Data from our reverse engineering efforts support all the key decisions on what repairs are needed, how they will be done, how long it will take, and which parts must be replaced," he explains.
Project Engineer Jaime Valdez adds that the likelihood of errors is reduced by using PowerInspect. "By giving us dimensions that are reliable, the Romer/CimCore arm and Power-Inspect help ensure that we are making the right decisions," Valdez says.
Internal diameters of casing seals are the largest and most awkward surfaces to measure and among the most critical. The ends of the blades of the rotating parts run with tight clearances to the casing. If these dimensions are exceeded, the turbine's efficiency plummets.
In rebuilding casings, often the diaphragm, seal, and bearing housing fits on a case are eroded. To repair them, damaged sections must be removed and remachined in preparation for being built up again with welded metal. The weld is then machined to the final dimensions.
"PowerInspect helps us establish dimensions to an existing reference point so that we can accurately return the weld repair to as-new dimensions," Valdez says.
"Our machinists then cut these parts to our numbers," operator Jesse Haver explains. "The accurate measurements mean they no longer have to do trial-and-error machining. All the time-consuming maneuvering that goes with cut-and-fit machining has been eliminated. We can now do in two days what sometimes took weeks," Haver says.
"Another nice thing about Power-Inspect is that it works well with the plant's new wireless network," Haver adds. "After a measuring job, in the time it takes to pack up the Romer/CimCore arm and bring it back to the office, the network has sent the data back to the laptop in the office, and formatted the measurements into a formal report. We can see it immediately."
Dual-Pressure Valves Reduce Waterjet Downtime
Creative Edge Master Shop (Fairfield, IA) runs its nine waterjet systems more than 80 hr a week, cutting intricate pieces of mostly stone and tile for custom flooring designs that can be seen in fine homes, commercial buildings, and civic institutions around the world.
Creative Edge has contributed to numerous landmark architectural projects, including O'Hare International Airport, the Astronauts' Memorial at Kennedy Space Center, and the Federal Reserve Bank of Minneapolis.
The nature of such delicate cutting requires Creative Edge's waterjet operators to alter high-low waterpressure settings as many as 200 times a day, a process that can take 10 sec per cycle, and put tremendous strain on the intensifier pump that powers the waterjet, as well as the connecting high-pressure hoses.
"Ten seconds times 200 cycles per shift add up to significant production gains, especially when you consider that we cut many small parts that may only take 30 seconds in actual profile cut time," explains Mark McCabe, Creative Edge engineer. "If you're doing lots of highlow cycles, you are stressing every component. On one machine, I was replacing blown lines every week. Every week, I would have a leak somewhere and would have to spend $200/hr for maintenance."
Wary of this time-consuming and costly downtime, McCabe decided to buy a Dual Pressure Valve from Jet Edge Inc. (St. Michael, MN) for his overworked intensifier pump. He had determined that Jet Edge Dual Pressure Valves had already resulted in reduced maintenance on two other intensifier pumps in his shop.
"I believe that we purchased the very first Dual Pressure Valve ever produced by Jet Edge, and have had only routine seal changes for over five years," he says.
The Jet Edge Dual Pressure Valve is a remotely mounted valve that allows waterjet operators to control water pressure independently of the intensifier pump. This enables operators to run a number of tables or cutting stations at various pressures. In low-pressure piercing applications, the Dual Pressure Valve can increase productivity by allowing operators to reduce and raise water pressure instantly.
The Jet Edge Dual Pressure Valve will operate with any manufacturer's pump, cutting head, or cutting system, and is fully configurable for pressure change ratios. Connection points are standard 60,000 psi (413-MPa) type. The Dual Pressure Valve is pneumatically operated and must be used in conjunction with another normally closed on/off valve or cutting head.
"We have also found that materials that require lower pierce pressure also cut well at lower overall pressure, so that a simple reduction of the intensifier's high-pressure setting sets both pressures appropriately without loss of cutting speed, but increases component life at the reduced pressures," McCabe says.
Since installing the Jet Edge Dual Pressure Valve, McCabe has not had to service the offending intensifier pump, and has increased productivity by eliminating downtime between high-low cycles.
In addition to the Dual Pressure Valve, Creative Edge also had a new Jet Edge attenuator installed in the intensifier pump despite the fact that pump was made by a different manufacturer. The pump's previous attenuator had failed due to the stress of fluctuating from high to low pressure prior to the installation of the Dual Pressure Valve. Jet Edge was willing to rebuild the attenuator until it was no longer serviceable, while the pump's manufacturer was willing to rebuild it only once, McCabe says.
Creative Edge also has switched to Jet Edge Omnijet cutting head valves. In addition, the company installed Jet Edge high-pressure orifice mounts on its cutting heads, and has determined that they are getting twice the jewel life as competitor models.
"We have used everybody's products. If the product isn't good, I don't buy it. We are in production all the time, so the significance of reliability is really big to me," McCabe says.
Customer service also is very important to McCabe. "If I call Jet Edge and tell them I need an Omnijet valve, it's here tomorrow," says McCabe.
"When you pick up the phone and you're in trouble, you want someone on the phone who cares," he says. "Jet Edge is always there and they get to the bottom of it."
This article was first published in the July 2006 edition of Manufacturing Engineering magazine.