Zooming in on Micro Tooling

Medical parts manufacturer uses advanced CAM system to carve out silicone micro molding tooling and part prototyping niche

Roshan Bhakta, Project Engineer for Albright Technologies, dutifully attends silicone micro part injection mold runoffs about two to three times a week inside the company's class 100,000 clean room. He is there to make sure that their unique products—stents, strain reliefs, and embeddable drug delivery systems (sometimes no bigger than a flea) — have no unacceptable flash, surface imperfections, or dimensional variations.

This is almost never the case. He and his toolmaking and injection molding counterparts have been working for more than a year to develop a process that results in on-spec micro-molded prototype parts the first time through. If a prototype part were to fail inspection, Bhakta would drop whatever he is working on and begin refining the CAM toolpaths used in making the errant mold so that a new one could be manufactured the same day. On the vast majority of days, he heads back to his Mastercam seat (CAD/CAM software from CNC Software, Inc., Tolland, CT) and continues working on the toolpaths for the next mold run-off in a day or so.

The ability to keep tight delivery schedules, sometimes with only a couple days lead time, has been critical to meeting the needs of medical device manufacturers that may be located anywhere in the continental United States. Shipping costs and delivery times are not a problem. With parts so small, FedEx can deliver even complete production runs overnight. However, virtual proximity to the customer is a requirement in terms of being able to work closely with an OEM to understand design requirements and to be able to quickly convert their CAD models into effective tooling.

Second Time Around

Bhakta is a design engineer by training, priding himself on his proficiency with Pro/E and SolidWorks. He briefly held an entry-level position at Albright Technologies shortly after graduating from college. Then he took a position with another company. When Albright decided it needed to upgrade its CAM capabilities with a product that seamlessly integrates with SolidWorks, Albright's management immediately thought of Bhakta as a person well qualified to manage and refine the prototype tool manufacturing process.

In 2008, after many years of working with a basic CAM programming package, Albright Technologies upgraded to Mastercam X3 Mill because of its true CAD interface and the exceptionally broad range of toolpath options. The breadth of capabilities and refinement options were particularly important because Albright is frequently called upon to break into new territory when developing tooling for molding its customers' new medical micro part designs.

Bhakta said he had no previous experience with Mastercam, but this was not a problem. He thought the interface was very much like the CAD programs he was familiar with. "It was just a matter of practice, just learning what all the buttons meant," he said. Relying on his previous experience with CAD software, another CAM package, as well as support and training from his local dealer (Services Four Automation, Sterling, MA), he cut his first parts for a mold in about a week. It took him only a few months to become very comfortable using the software. Now CAM software plays a pivotal role in the performance of his job.

Assembling the Pieces

Albright had collected all the pieces requisite for creating a responsive micromolding tooling and prototyping facility. It includes the clean room with microinjection molding presses, quality lab, two three-axis mills, and finally Mastercam. It was Bhakta's responsibility to get these pieces working together as a highly responsive and seamless tool manufacturing operation. There were a number of issues he needed to address:

Postprocessors: One of the first concerns was to get postprocessors that would work cleanly with the company's two CNC mills, a Mori Seiki Cyclone and a Topper with a Fanuc controller. Each would require its own postprocessor, and these were produced expeditiously by Services Four Automation. The posts use entirely different code, and Mastercam knows which to use based on the machine definition in the program. Usually Bhakta knows which machine he will be making the part on, but things can change.

He said, "Say I have already made 10 toolpaths. I don't have to blow those all away. I can go to the properties in the program and say I want to switch to this machine now. When it generates the code for those 10 toolpaths, it knows not to use the machine for the first one, but now it goes to the second one because I have changed it." This gives Bhakta the flexibility to use his equipment interchangeably to best meet the contingencies of his production schedule.

Toolpath Selection: One of the reasons Albright selected Mastercam was because it provided a large number of toolpath options, each with their own user-configurable variations. So no matter what operation is required, he knows that there will be a toolpath selection to get the job done quickly, without jeopardizing tool life.

For example, Albright routinely uses the surface rough rest mill to finish leftover toolpaths. It allows him to use larger tools to quickly machine broad sections of the part. Mastercam automatically calculates which areas of the part the larger tool missed, and it sends in a smaller tool directly to those areas to clean them up. Bhakta said that finding the remaining material requires a very powerful calculation. Other CAM software he has used can't do this. Instead, they send the smaller tool to the general area of the uncut material and then bring the tool in slowly as it "cuts air" until it eventually engages.

The tool Bhakta uses most frequently is a 0.005-inch flat end ball mill. It's about the size of a sewing needle. Stepovers are sometimes as small as 0.0005 to protect the tool and provide high finishes that require very little in the way of manual finishing operations. He said, "Since the end mills we use are extremely small, we have to feed them slowly. To cut one inch of air is going to take us 15 minutes and that may be on just one pass. To complete the machining, this tiny mill is going to move back and forth a couple hundred times. Eliminating almost the entire air cutting shaves numerous hours from the manufacturing cycle, and we get our molds completed, proven, and prototype parts shipped to the customer a lot faster."

Toolpath Verification: When Bhakta transfers the program for manufacturing a mold component over to his machinist, he has a lot of confidence in it. This is because he relies on Mastercam's computer simulation capabilities to determine if the tools and movements he has chosen actually do what he imagined they would. From experience, they know that verification eliminates unexpected problems, so they can run the program without continually hovering over it to see what's going to happen.

Making the Process Visible

Albright's customers have bought into their manufacturing process, and Bhakta has been producing from one to three micro molds for silicone parts just about every week for the past year. To grow the business, they would love to be able to show this handiwork to prospective customers, but there's a catch. The work is subject to confidentiality agreements that prohibit Albright from showing either the parts or the tooling.

So Bhakta has been asked to design and manufacture tooling for parts demonstrating the company's unique capabilities. His first design was a barely visible part that has features resembling those Albright has created in prototypes for actual customers. It has a body about the size of a dull pencil point with a 0.010 hole running though the entire length. There are also two support arms that were machined in the cavities using a 0.005-inch diameter ball mill. Each arm has a 0.003 hole in the middle, ostensibly to accommodate some sort of fastener. A slight undercut in the top of the part required the use of a third (top) block in the design of the mold.

Bhakta said, "Our manufacturing process generated parts that were reproduced exactly as drawn. This tells me that the code generated by Mastercam is delivering ultra-precise control over the head of the machine, allowing us to make something this small."

Bhakta went from art to part in just four days, demonstrating the type of turnaround time that is possible, even for tooling that is quite complex. This is very important in the medical design world where proof-of-concept prototypes must frequently be delivered in time frames dictated by the schedules of nervous investors and other approval sources.

He is hoping that such micro demo parts will fulfill their design intent, attracting a lot of attention to capabilities that are otherwise barely visible.