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MTD Micro Molding

Massachusetts Company Has Singular Focus on Medical Micro Molding

MTD Micro Molding is one of the rare specialists in micro molding of advanced medical products.

MTD Micro Molding is a micro medical device manufacturer that focuses its efforts in one area: the micro molding of advanced medical products. Located in Charlton, Massachusetts, MTD Micro Molding is an ISO 9001:2008 certified manufacturer of micro-molded parts that have microscopic features or are microscopic in overall size.

“Medical micro molding is what we do,” said Lindsay Mann, MTD Micro Molding’s director of marketing, in an email interview, “and all we do. Our operation isn’t a small corner of a bigger plant; it’s our entire plant.”

About 80 percent of the components produced by MTD are implantable devices, with 75 percent of those targeted for bioresorbable applications, according to Mann. The micro medical devices produced by MTD Micro Molding support a variety of medical categories, ranging from cardiac to neurosurgical, gastrointestinal, bronchoscopy, oncology, urology, orthopedic, endoscopy, and drug delivery, among others. Examples of thermoplastic products manufactured by the company include permanent screws, micro links, and ejector rings; bioresorbable examples include absorbable stents, staples, and screws.

A successful micro part starts with a very exact mold, an area of capability in which MTD takes a great deal of pride. Having the tooling and molding department under one roof is a huge differentiator for the company, according to Mann, who said that MTD doesn’t outsource any of its work.

“We build and mold everything ourselves,” she said. “The MTD team, with 400-plus years of plastics experience, includes the tool builder and the molding technician, and they work very closely together with the goal of producing the best part possible. This means instantaneous feedback and excellent internal communication and documentation, which allows for first shot quality.”

The company often recommends micro molding design refinements and alternative materials to enhance manufacturability. Material selection is critical, Mann said, because it can affect critical features and everything from tolerances and dimensions to strength, usability, design, speed-to-market, and cost.

“Our material database also lets us predict how a specific material will flow in an application,” she said. “We’re here to help our customers get it right from design through production so they can produce a high quality device, and get it to market quickly.”

Mann and other members of MTD Micro Molding’s team recently participated in an email interview with Design-2-Part Magazine to discuss some of the factors that make the company unique. Team members who participated were Dennis P. Tully, president; Peter Wojtas, process engineer; Brian Matachun, director of sales; Lynzie Nebel, project engineer; Gary Hulecki, executive vice president; and John Clark, tooling supervisor.

Following are edited excerpts of the interview:

D2P: One of MTD Micro Molding's strengths is its expertise in material selection, which it calls "a crucial step in product manufacturability." What are some of the material properties that are important to customers looking for micro molded parts, like bioabsorbable stents and implantable staples, as well as for tiny parts like fixation screws and thin-walled micro components?

Dennis P. Tully (DPT): MTD uses material characterization tools to help predict the risk of material choice in the early stage discussions with customers. Being able to review our material database in early discussions gives our customers a larger list of material options to consider without having the expense of a full mold flow analysis.

Peter Wojtas (PW): When researching the characteristics of a new resin, we blend the high technology techniques (DSC testing) with old school observation (pellets on a hot plate).

Lynzie Nebel (LN): The functionality of a customer’s specific part design will dictate what material properties they need. If a customer needs a flexible material with very strict tolerances, we explore what dimensional aspects they can compromise on in order to build the part with that material in our design review. The material requirements need to be understood so we can have the option of helping a customer choose an alternate material that is acceptable to their design’s function, drawing tolerances, and is also manufacturable.

Brian Matachun (BM): MTD’s 43 years of experience in polymeric micro-injection rheology allows us to tell clients with a very high degree of confidence that the material they selected is suitable to fill their particular geometry, whether it be a thin wall, small core pin, ultra-high precision features, or high aspect ratios. MTD has invested millions of dollars into characterization techniques for materials on a micro level that simulate real world molding conditions. These methods, which are highly unique and closely guarded by MTD, allow our engineering staff to create and build upon our experienced “Material Database,” which comprises about 100 materials in both the thermoplastic and bioabsorbable molding space. Not only does this give us real world data, but some of the material outputs are simply empirical and allow us to cross over between families of polymers. Just imagine the capability of leveraging polypropylene data to PLLA or PEEK resins to allow clients the option of trying other materials in the event the initial material choice did not meet their design’s functional requirements.

D2P: MTD Micro Molding claims to be the best at providing the key to a successful micro part --- an exact mold. What does it take to provide an exact mold: What work is involved, and why is close interaction between the tool builder and the molding technician important?

John Clark (JC): To build an “exact mold” takes highly skilled toolmakers that know the machines they are using in an out. It is one thing to say you can make a tight tolerance piece of steel using one piece of equipment, but to transfer that workpiece from machine to machine and be able to accommodate for the minor level of error every machine tool on the market has is the key to success. That is something our tool makers do extremely well, using practices we have developed over time.

Another big advantage MTD has is that our tooling and molding engineers work together closely during the tool design. Once the tool is built at MTD, it gets turned over to our molding group, so it makes the most sense to have them involved in the design from the start. This way, any potential problems in molding can be considered and corrected early on. It can be as simple as runner sizing, or as complex as part spacing to allow for robot interface. These are things that are crucial to point out and correct before it becomes an issue at the press, and that ensure first shot success for the process engineers.

PW: Micromolding is a much different beast than macro. General industry data, guidelines, and practices do not apply to micro molding, in many instances. Advertised material shrink data, even pertaining to widely utilized resins, is not always applicable. MTD uses a proactive approach by utilizing standardized sampling molds to predict shrinkage with great accuracy in thin-wall and micro parts.

The best ideas often come from the least likely source. Micro parts definitely create macro problems. During mold design reviews, aspects of the entire process to manufacture the part are taken into consideration. Each department questions and recommends changes to improve the chances of success. The inquiry alters the thought process to justify the approach to the tool build to accommodate processing and automation.

BM: Every project we take on starts with the same four questions: “How can we solve the problem, build the mold, scale it up, and remove cost?” If these four rudimentary questions cannot be answered and collectively agreed upon, we need to engage the client and temper the expectations or, at the very least, ensure that the clients’ expectations are properly aligned. Having the tool builder, process engineer, metrologist, and automation group all under one roof allows us to mitigate failure and identify challenges as a team and put together a plan that will ultimately meet or exceed our clients’ needs.

MTD provides a complete micro molding process, which the mold is a portion of, and certainly part of the solution. When MTD looks to create a parting line mismatch of less than 0.0002 inch or a part that has a 0.0008-inch wall, or a tip radius of 5 microns with a 0.0018-inch through hole, it is the whole team that is engaged. This is how MTD has become known as one of the world’s expert precision-mold fabricators. MTD’s execution of its proven process and strategy is exact, and this is understood and practiced company-wide. When you see it unfold in front of you, it is certainly a thing of beauty, just like the perfectly hit golf ball.

Gary Hulecki (GH): Manipulating the machine tools to achieve accuracy that is normally not achievable is the key. And unconventional machining methods are tested and proven every day at MTD to achieve desired results. This success is primarily attributable to our highly skilled toolmakers that have honed their craft over time. What used to be considered a challenge at MTD is now part of our every day, and we are always reaching for what’s next and taking the necessary steps to get there. Instead of viewing it as arriving at a finish line, we look at it as leveling up.

D2P: How does the Sarix micro EDM technology work, and what are the advantages that it provides in making tiny medical micro molds?

JC: Sarix micro EDM technology combines conventional 3-axis CNC milling with micro technology. The machine works by rotating a spindle that is loaded with a customized, 300mm long solid carbide electrode diameter, which is based upon the spindle collet size. For MTD, that diameter is 0.4mm. The machine is outfitted with a horizontal 0.2mm brass wire that is used for creating custom sized and shaped electrodes. With that brass wire, you can take the 0.4mm diameter all the way down to 0.005mm and use it as the cutting tool.

The beauty of the machine is once the program is proven out, a workpiece can be set up and operate unattended. The algorithms that run in the background during operation constantly check the electrode for wear, and, once worn too far, the machine signals to leave the workpiece to return to the brass wire to regenerate a new electrode. Once completed, it goes back to the workpiece and picks up where it left off.

The most significant advantage of using the Sarix machine lies in the Micropulse power generator, which creates such fine arcs that result in essentially zero overcut. This means that if you are using a 0.05mm electrode, you will be able to achieve 0.025mm inside corner radii, which is nearly impossible with a conventional sinker EDM. In many cases, polishing cores and cavities is no longer necessary due to the ultra-smooth finish that can be achieved with the machine’s standard machining operations.

D2P: MTD Micro Molding is said to produce acceptable product on the first mold sampling 90 percent of the time, while surveys indicate a 20 percent success rate, on average, for the industry. That means MTD needs to make adjustments only 10 percent of the time after the first sampling, versus an industry average of 80 percent of the time.

DPT: First and foremost, all MTD employees share the vision “Be the First, Be the Best.” That desire creates the right atmosphere to accomplish great things together. Obtaining first shot quality requires control of many variables from all team members.

The important requirements are: 
D2P: What is it about the company's capabilities that allows MTD to have such a high success rate on the first mold sampling?

PW: There are multiple steps involved in achieving the success we have experienced. The key factors include learning from our history, distrust of general industry data, and open and frank communication.

We learn and retain from past mistakes. At MTD, mistakes are a critical part of learning and, in unknown circumstances, they can be the expected initial outcome. However, mistakes are company (not individually) owned. The cause and outcome of a mistake must be fully recognized and understood to pave the way to finding the eventual solution. For example, early struggles in processing some very low Tg bioabsorbable resins initially created some frustration and disappointment. However, once the process was developed, the material preparation and temperature profiles for metering very low Tg materials were universally applied to many similar grades of polymers.

The same approach applies to tooling; limits need to be pushed and failure accepted as long as that knowledge is retained and leads to the solution. As Einstein said, “we cannot solve our problems with the same thinking we used when we created them.”

BM: MTD’s abilities to deliver components on time 90 percent of the time is because of the robust process we have developed. It is quite a statement to say that 50 percent of your tooling projects are either (a) initially failed by others (and MTD is successful) or (b) not a single molder/mold maker in the industry has quoted it. With this in mind, we are able to fall back on experiences, reach into our toolbox, and come up with a solution. The process at MTD has been refined over several years, and every person involved in the process has accountability and understands MTD’s guiding star of “Be the First, Be the Best.” The culture, work ethic, craftsmanship, and passion at MTD is a wondrous sight and is felt by every person who tours our facility.

D2P: MTD was a Supplier Innovation Award Finalist at MD&M East in New York last year. Why was MTD chosen as a finalist for this award? What were some of the difficulties of the project that MTD was able to overcome?

Lindsay Mann: MTD Micro Molding was chosen as a finalist for this award for molding multiple micro components together at once. This technology, launched in late 2014, can improve medical device companies' drug-delivery cannulas.

Traditional manufacturing methods for the development of cannulas have used the heat-forming process of converting fluoropolymer extrusions to cannulas. Next-generation products could follow the new advances that MTD is enabling by instead using polypropylene for cannula products. In terms of technical execution, it is difficult to make a long, thin, straight part such as a cannula. The challenge lies in the fact that for a 0.005-in. wall thickness to flow long-distance, a tiny, delicate core pin must be centered precisely in the cavity.

With long length of thin flow, it is impossible to fill an annular ring if material flow becomes uneven. When flow becomes unbalanced, a hydraulic effect is created on one side and pushes the core pin, which produces an ultra-thin wall on the opposite side. This, in turn, causes fill problems and distortion. Precise control over the position of the core is critical, which is why highly capable tooling and molding machines are required to successfully mold a thin-walled cannula for drug delivery. This control makes molding walls as thin as 0.03mm possible at MTD.

—Edited by Design-2-Part Magazine

This technical information has been contributed by
MTD Micro Molding

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