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Micro moulding: How to secure reliable volume manufacturing

Micro moulding typically requires the achievement of truly exacting and sometimes almost impossibly tight tolerances

There are many stages in the product development process for micro parts and components, but ultimately OEMs require parts to be produced at volume and repeatably. Trey Barwick looks at what influences the ability of micro moulders to mass manufacture successfully

Let’s start with a fact. Not all micro moulders are the same. Indeed, not all companies that promote themselves as micro moulders are in fact micro moulders. 

You see, when it comes to size, there is a scale, and this scale can be described in different ways to promote competencies. Some suppliers describe themselves as precision moulders, others proport to achieve nebulous levels of accuracy (nebulous because accuracy and indeed claims of precision without some degree of qualification are effectively meaningless).

Precision for company ‘A’ maybe be anything but precision for company ‘B’, so the phrase has a degree of opacity that is unhelpful. Precision moulding services therefore cover a huge spectrum of part sizes and feature sizes on parts. When looking at the larger part size and lower tolerance side of the market, vertical integration and the ways that customers and supplier ‘partner’ and interact is less critical to success. If parts are produced close to specification, are delivered close enough to time, and on cost, job done. Scrutiny on who in the supply chain is producing what and when is less relevant than is the case when moving into the area of micro moulding.

Micro moulding typically requires the achievement of truly exacting and sometimes almost impossibly tight tolerances, and in many instances the demand is for tiny parts sometimes the size of a grain of salt, or slightly larger parts with sub-micron feature sizes. When micron tolerances matter, suddenly the customer and micro moulding provider must enter into a different and closer partnership in product development, and it becomes hugely important that the micro moulder owns, manages, develops, and innovates in every aspect of the supply chain.

True micro moulders can achieve micron tolerances on parts that are typically less than a gram in weight and can be as light as less than 0.001 grams. For manufacturers unused to such levels of accuracy, and more attuned to the injection moulding process on a macro scale, the thought of mass manufacturing parts with such dimensions and tolerances may seem all but impossible, but micro moulders do this daily, and often require zero failure rates for parts and components used in safety critical applications.

Attention to detail and attention to process is everything, as not only do micro moulders need to make tiny parts with tiny features repeatably and attaining micron tolerances, but they need to do this in a cost-effective and timely fashion. So saying, what needs to be avoided at all costs is having to go back to the drawing board with designs, having to review and change manufacturing processes, and having to recut already extremely expensive and time-consuming to make micro tools. 

The headline over every activity is ‘get it right the first time’.

Vertical integration enhances the quality, compliance, and conformance to design intent. Micro moulders need to understand the CTQs (Critical to Quality characteristics) to manufacture parts successfully, and these characteristics are important to the functionality of the product in terms of the end-user experience and embrace moulding, assembly, and packaging.

Good lean principles can be used to exemplify this importance. Value-stream thinking — from concept to order fulfilment — drives customer value. Vertical integration supports a shorter value stream reducing silos and sub-optimised processes.  

Basically, the longer the value stream, the more disconnected the value stream, and the more variables can be introduced causing customer issues.

Key issues for volume manufacturers

As a micro moulder, Accumold is uniquely positioned due to the physical size of its premises to gear up to long-term volume manufacture for its customers. It also boasts 6 class 8 clean rooms (29,000 square feet in total), and 3 class 7 cleanrooms (10,000 square feet in total). 

However, there needs to be a continuous focus on improvement, and here the company’s highly skilled tenured workforce comes into its own. Variability is the enemy of high-volume manufacturing, and so the focus needs to be maintained on implementing process controls that drive repeatability all the way from cutting micro tool steel to measurement and validation methods.

In essence, customers want the highest quality products at the lowest possible cost. Product quality requirements are driven by Voice of the Customer (VOC), which enables good micro moulders to identify critical product characteristics which need to be verified during production. 

Cost is more than just the price charged to mould a part. It also includes the time it takes to get a product to market, whether defects make it to market, and also the levels of consistency of supply. So micro moulders should strive to supply the highest quality products, through validated processes, with short timelines to market.  

Realistically, this can only really be accomplished through vertically integrated processes and utilising process validation.

So saying, when short-listing potential micro moulding suppliers, from a production perspective there are some key questions that need to be asked to ensure that the micro moulder is equipped to achieve often exacting objectives. First, do you design, build, and maintain your moulds? Second, what measurement capabilities do you have on site? Third, what are your methods of validation (DOE, IQ, OQ and PQ)? Finally, what resins do you have experience with in production?

The successful manufacture or micro moulded products is almost entirely down to the VOC. But it is important to realise that the end user isn’t only the customer, there are customers throughout the entire value stream.  

The shorter and more centrally located the value stream the quicker concerns can be raised and resolved.  


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, demanding a collaborative and pragmatic relationship between OEM and micro moulder. When dealing with micro scale parts and components, the cost of manual assembly is prohibitive and often requires levels of preciseness when dealing with sub-micron tolerances that are impossible to achieve. 

Automated assembly is therefore a must in most micro moulding scenarios, requiring that OEMs select a micro moulding partner that is able to understand the methodology of micro assembly and achieve the extreme positional accuracy required.

The demand is for a laser-like focus on design for micro manufacturing (DfMM), which crucially influences the success of every part of the overall product development process, including assembly. The importance of considering assembly at the design stage of a micro moulding product development process is huge, and is an important factor for any project. Micro moulding just adds more variables that need to be controlled than a standard sized product for which there are many different manufacturing solution partners in the marketplace.  

Micro moulded parts can be difficult to feed, inspect, and manipulate without causing damage.  

Capturing a micro moulded part as it come out of the mould is often very difficult, as is orienting a micro part after moulding. Capturing a part at mould ejection and immediately assembling is often the only route to efficient assembly with low waste. 

Such considerations should all be bottomed-out at the design stage to keep costs under control so a customer can maintain margins and provide a product to the market-place at an acceptable price.


Before embarking on a micro moulding project, customers should focus on the mould design, mould build, and quality measuring capabilities of the vendor they are engaging to mould their parts.  

If moulders lack the ability to design, build, and measure high quality moulds to extremely tight tolerances they will struggle to produce consistently high-quality parts to tight tolerances.  

Producing products to specifications that only allow microns of variations to a specification is much more challenging than producing a product with significantly larger variation allowances.  A poorly designed and built tool can eat up your entire variation before you even mould a part, essentially killing the project.

Trey Barwick is the VP of Production at Accumold.

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