There are a certain set of rules and understandings of the molding process at the macro level that simply don’t work at the micro level. The flow of molten plastic, it’s cooling, warpage, necessary venting and gating … are all different when molding at the micro scale, and to a greater or lesser extent the process needs to be relearned.
Roger Hargens CEO/President, Accumold
Companies may recognize the business need to produce smaller and smaller and often more complex and innovative products and components, but cannot see an obvious route to attain these goals.
In general, companies understand that micro molding is not just “macro molding but smaller.” There comes a point, though, when making things smaller that the process to achieve this needs to change, and here the analogy of folding paper is often used. When you fold paper in half, you have a piece of paper half the size of the original. Fold it again, it is a quarter the size. However, when you get to the 7th fold, it is impossible to achieve, so to reduce the surface area the process (folding) has to change.
Many designers undertaking micro molding at scale outsource their production, so the “way” that micro molding works, while relevant, should not be seen as a barrier. Choosing the micro molding expert takes away the need to understand the vagaries of the characteristics of thermoplastics when molding small. However, there are a number of other areas that any designer must focus on beyond the micro molding process.
The product development process
Micro molding is only one part of the overall product development process, and it is important for designers to appreciate that various “departments” involved in a micro-manufacturing project should be engaged at product design inception.
Critical to success is reassessing the nature of the relationship between customer and molder in a micro-molding scenario. When dealing with contract manufacturers on the macro level, the relationship can quite acceptably be that of a job shop. The design is presented, the quote is secured, and the parts are delivered. Job done.
This cannot and will not work when undertaking a micro molding project, which necessitates that the OEM and the chosen micro molding company enter a fully collaborative partnership relationship.
The reasons for this are many, but begin with the fact that just as micro molding and macro molding are completely different processes, the design for manufacture (DfM) rules are also entirely different.
DfM for micro molding is important, and the expert in the room to offer advice and counseling is the expert micro molder, your product development partner. Often, the less baked an idea is when the micro molder is engaged the better, as the earlier that the design of a micro product can be influenced and adjusted to optimize manufacturing outcomes, the better in terms of cost and timeliness of production.
Essentially, DfM ensures that not only will the end product be fit-for-purpose but that it is also optimized for the production processes that will be used to manufacture it, in this case, micro molding and automated assembly. The micro-molding team that you work with should 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 mold, wall thicknesses, and so on.
Perhaps the key enabling technology when it comes to micro molding is micro tooling. Tooling in any manufacturing scenario is always the most costly and time-consuming part of the product development process, but when looking at micro molding, the tolerances and complexity often required in micro molds make it especially critical.
Micro tooling is an art in itself, thus, designers should work with micro molders that can design, build, and maintain molds in house, and also have the expertise and experience to optimize tool fabrication.
One size does not fit all when looking at micro tooling. Micro molders can 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, molding, metrology and validation, and automated micro assembly are all undertaken in the same facility with departments working collaboratively — is important in a micro-manufacturing scenario where tolerances are tight. The probability for successful outcomes increases exponentially when the responsibility for project and production, timeline, and execution are controlled within a single entity.
The differences between macro molding and micro molding are stark when it comes to the molding process. Every stage of the product development process in a micro-manufacturing scenario is motivated to attain micron and sub-micron tolerances.
Finally, when dealing with miniaturized 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 preciseness for sub-micron tolerances that are impossible to achieve. Automated assembly is, therefore, a must in most micro-molding scenarios.
Collaboration and transparency are not just required between the micro molder and the customer, but also between the different teams within the micro-molding facility.
To a greater or lesser extent, designers rely on the micro molder to guide them in appropriate design choices. Transparency is absolutely important, ensuring that the customer is on the same page, understands the decision-making process, and works with the micro molder to problem solve and optimize outcomes while always ultimately being in control.
Producing a plastic product with micron or sub-micron features, repeatably, economically, and on time means that the “over the wall” approach has to be abandoned. Success in micro molding requires an inter-disciplinary approach, as it is only in this way that the ultimate goal — an optimized product made to specification repeatably — can be guaranteed.
Success in micro molding is predicated on the forging of a truly collaborative and transparent relationship between micro molder and client. Decisions made at the early design stage will have effects when it comes to micro tool fabrication, micro molding, and micro assembly. Because of this — and the need to have an unswerving focus on the achievement of extremely tight tolerances and to validate design intent — all departments involved in the product development process must work together from the inception of a product design to ensure successful outcomes.