Design for success in micro molding

Design for success in micro…

If you are undertaking a micro injection molding project, there is enormous value in working alongside a specialist sub-contract manufacturer that under one roof has control of all aspects of the product development process from design to high volume manufacturing.

Micro molding projects are by their very nature complicated, and the fact that many require the repeatable attainment of extremely high tolerances demands that there is a collective focus on accuracy when looking at micro tool fabrication, molding, validation, and automation processes. 

However, material selection and design for micro molding are also hugely important, and must be a primary consideration as time, cost, and the frustration of creating a design that needs to be radically altered before it can be manufactured need to be eliminated as much as possible.

It is because of this that it is especially important that manufacturers work with micro molders as close to the beginning of the product development process as possible, as accessing expert micro molding design insight early is the key to cost-effective, timely, and right-first-time manufacturing.

When looking at the design for micro molding rule book, it is worth taking on board a few things that will help you even at the product inception stage, and this article will cover these points. However, the advice again needs to be emphasised, speak to the micro molding expert as soon as you can, as then you will access the precise application-specific advice you will need.

The design conundrum

Many OEMs view the likes of Accumold and other micro molding practitioners as manufacturers. While this is in itself self-evident, we very often view ourselves as consultants. Those micro molding experts that are truly vertically integrated with all stages of the product development process under one roof, as already mentioned, have expertise in design, tooling, molding, validation, and automation. 

What this gives them the ability to do is pool this expertise, and the best time to do this is at the conceptual design stage of any product development program. There is no better time for the tooling manager to put his hand up and advise as to the best design for seamless molding than early in the design stage. Likewise, a judicious word from the assembly manager will potentially save a customer from weeks of delay and spiralling costs if problems are detected early.

As manufacturers begin to conceive a micro molding project, it is important to bear in mind some key issues from the get go. Every project as with so much in life should start with the end in mind. You need to understand the basic design approach, really bottom out what you can and cannot do, as when micro molding, even the smallest design change can be catastrophic and completely derail a project. 

Let’s take a look at what is meant by this. If a manufacturer is considering an application with a 0.005” (0.127 mm) wall thickness, a 5%-dimension change can be the difference between whether a part will fill or not. A material change can also have a profound effect on a part with this level of detail. Any design engineer will be used to considering stack tolerances and stack dimensions, but when parts get smaller and smaller, the amount of change becomes more of a limiting factor.

Design for Manufacture (DfM) is a fundamental consideration when micro molding. In fact there should be a subset of DfM, basically DfMM (design for micro manufacturing), as the rules of the game are so different when designing miniature parts or parts with very precise elements and tight tolerances. 

Design engineers have all the computer power and expertise to create the most astoundingly innovative products on screen, but they can be utterly impossible to make. Sometimes the reason for this is simple to deduce, other times less so. Size is often part of the problem. It is possible to blow up a particular part of a design to fill the screen and nuance aspects of it that are tinkering and adding functionality at the scale of fractions of an inch or a few microns. Theoretically, this can be the difference between perfectly optimised design or a slightly better than average design, but it is impossible to mold. Any design at the micro scale requires careful attention to what might otherwise not be a big deal for larger parts.

Each micro molding project is unique in terms of geometric complexity, shape, and can be made in a wide range of materials, all of which will ultimately affect the ability to manufacture.