DfMM — it’s no small matter!

Aaron Johnson, vice president of marketing and customer strategy, Accumold, explains why successful medical micromoulding depends on collaboration and design for micromoulding. 

Although many medical device OEMs are well versed in the use of micromoulding in their product development cycles, there are a larger number who recognise the business need to produce increasingly smaller, and often more complex and innovative, products and components, but cannot see an obvious route to attain these goals. 

There is a general understanding throughout industry that micromoulding is not just “macromoulding but smaller”. There are a certain set of rules and understandings of the moulding process at the macro level that simply don’t work at the micro level. The flow of molten plastic, its cooling, warpage, necessary venting and gating and so on are all different when moulding at the microscale, and to a greater or lesser extent the process needs to be relearned.

Most, if not all, medical device OEMs undertaking micromoulding at scale outsource their production, so the ‘way’ that micromoulding works, while relevant, should not be seen as a barrier to engagement. Your chosen micromoulding expert will remove the need for you to understand the vagaries of the characteristics of thermoplastics when moulding small. There are, however, other areas that any OEM must focus on beyond the micromoulding process itself.

The product development process

Micromoulding is only one part of the overall product development process, and it is important for medical OEMs to appreciate that various departments involved in a micromanufacturing project must be engaged from product design inception.

Reassessing the relationship between OEM and moulder in a micromoulding scenario is critical for success. Micromoulders should not be seen as a job shop, but rather a full and collaborative product development partner. The reasons for this are numerous, but begin with the understanding that just as micromoulding and the macromoulding are different processes, so too are the design for manufacture (DfM) rules.

Design for Micromoulding (DfMM) is essential, and the expert in the room to offer advice and counselling is the micromoulder. Frequently, the less complete an idea is when the micromolder is engaged the better, as the earlier that the design of a microproduct can be influenced and adjusted to optimise manufacturing outcomes, the better the cost and production timeliness.

Essentially, DfMM ensures the end product will be fit-for-purpose and optimised for the production processes that will be used which, in this case, is micromoulding and automated assembly. The micromoulding team that medical device customers work with must be able to advise on such issues as material choice, draft angles and undercuts, part lines, ejector pin locations, gate locations, the likely flow of material in the mould, and wall thicknesses.

Microtooling and assembly

Perhaps the key enabling technology when micromoulding is microtooling. Tooling in any manufacturing scenario is always the most expensive and time-consuming part of the product development process, but when looking at micromoulding, the tolerances and complexity that are often required in micromoulds make it critical, and often very expensive. 

For medical device OEMs it is vital to work with micromoulders that can design, build, and maintain moulds in house, and have the expertise and experience to optimise tool fabrication. One size does not fit all when looking at microtooling, and it is important that OEMs engage with micromoulders that can work alongside them to drill down into the specifics of a particular application, understand the effects of a certain material, cycle time expectations, part criteria, and expected volumes before beginning to cut steel.

In-house tool fabrication — in fact vertical integration in general, ensuring that design, moulding, metrology and validation, and automated micro-assembly are all undertaken in the same facility with departments working collaboratively — is vital in micromanufacturing, where tolerances are so tight. The probability of successful outcomes increases exponentially when the responsibility for project and production, timeline, and execution are controlled within a single entity.

Unsurprisingly, a micromoulder should be expert in micromoulding. Engaging with a company that has the right technology and forming a collaborative relationship that allows total transparency at this stage of the product development process is essential for success. 

Every stage of the product development process in micromanufacturing is driven by a total focus on micron and sub-micron tolerances. It is key that OEMs engage and work alongside a micromoulder that has the necessary business acumen and experience, an expert team of engineers, an understanding of the correct manufacturing methodologies, and the tooling and processing expertise to ensure optimised outcomes.

Finally, when dealing with miniaturised plastic parts and components, the assembly part of the product development process must be discussed and considered early in the design cycle. When dealing with micro-scale parts and components, the cost of manual assembly is prohibitive, and often requires levels of precision when dealing with sub-micron tolerances that are impossible to achieve. Automated assembly is therefore a must in most micromoulding scenarios, requiring that medical device OEMs select a micromoulding partner that is able to understand the methodology of micro assembly, and achieve the extreme positional accuracy required.

Partnership and collaboration

Collaboration and transparency are not just required between the micromoulder and the medical OEM customer, but also between the teams within the micromoulding facility, which is why working with a vertically integrated company is essential. Although project success depends to a great extent on the expertise of the micromolder, customers still own the projects, and it is they who should remain central to all conversations and reviews that occur during product development. There is little value in producing a microproduct or component that is fit-for-purpose, easy and inexpensive to mould and assemble, yet bears no resemblance to the OEM customer’s vision. Transparency, therefore, is vital in ensuring the OEM customer understands the decision-making process and works with the micromoulder to problem solve and optimise outcomes, while maintaining control.

Internally, all teams involved in the product development process must also work with clarity and transparency and collaboratively. Producing a plastic product with micron or submicron features, repeatably, economically, and on time means abandoning the ‘over the wall’ approach. A true inter-disciplinary approach will result in an optimized product made to specification repeatably.

Product development teams working collaboratively from project inception allow for a singular focus on quality assurance, which begins with design for manufacturability reviews to ensure the project starts on the right foot, and extends through to the development of control plans to assess critical part features, failure mode and effects analysis (FMEA) results, high-resolution in-line vision systems, and high magnification microscopic measurements to verify tool and finished part dimensions.