27 Apr The State of MicroManufacturing – 2009

Attending the SME MicroManufacturing Conference last month in Minneapolis, I am optimistic for the growth of the industry. Although there was a lot of participation from academia, the expertise and process capability shown by commercial enterprises is impressive. The technologies will not take long to mature as the members of the relatively young community gain experience and refine these processes.

The conference focused on three aspects of manufacturing – micrometrology, micromachining, and micromolding. Almost every noun is preceded by “micro” in order to differentiate it from the conventional process that spawned it. This is an important distinction because although the processes have high-level similarities, very few of the conventional guidelines scale directly from 100mm to 100um. Generally, the term “micro” is used to categorize processes and components with features ranging from .5um (0.00002”) to 500um (0.0200”), although this is by no means a hard and fast rule even among the conference attendees. The boundaries may be a bit fuzzy because the processes are relatively new and the limits have not been fully defined.

MICROMETROLOGY

Micrometrology involves the technology of measuring parts and features as well as monitoring the processes. In my opinion, it is probably the most mature of the technologies. After all, “if you cannot measure it, you cannot improve it” – Lord Kelvin. Therefore, it’s difficult to know whether micromachined parts, including tools and molds for micromolding, are built to spec without a means to measure them. Manufacturers are creatively utilizing off-the-shelf components such as mirrors, cameras, lasers, and other common, conventional non-contact devices to achieve higher resolution. Additionally, they are creating newly developed technologies, such as interferometers and microvoltage detection, to improve the integration of metrology into the machining and molding processes. For example, one manufacturer presented work that measures the tool-tip location of their µEDM machine based on very small detected voltages so the user can monitor the process and measure the part without having to re-register it to a different machine. This type of innovation is representative of what many of the manufacturers are doing to bring new tools to the industry.

MICROMACHINING

Micromachinists are definitely thinking outside the box when it comes to creating features that are on the order of just a couple of microns. They’ve developed 30um wires for Wire EDM and 5um spade bits to remove material. Additionally, they’re requiring very specific machinery to even use their tools. A 5um bit needs a feed rate around 50mm/sec and a spindle speed over 50,000 rpm. A standard CNC spins closer to 15,000 rpm. Additionally, if the runout for a conventional machine is 1 or 2 um, most conventional machinists would be overjoyed, but that would destroy even a 10um bit on contact. I found that most contract micromachinists were focused on low-volume (1 – 30 parts) with the possibility of higher volumes entertained but not necessarily preferred. Setup time and part inspection can be difficult for such small parts, but I expect there are people interested in the higher-volume runs out there.

MICROMOLDING

Although the processes are far from standardized, the representative micromolders presented an impressive array of precision parts and capabilities. Many of the plastic parts were much smaller than a single plastic pellet, with wall thicknesses and features on the same order as the tolerances of most conventional parts (130um (.005”) to 260um (.010”)) with the limits reaching down into the single-micron range. At this scale, it’s notable that the annual requirement for raw material might only be a handful of pellets! Therefore, the micromolders are limited, with just a few possible exceptions, to stock materials that were originally designed for molding much larger parts on much larger machines. However, micromolding processes require much smaller components, for instance feed-screws are much smaller and internal pressures are much higher as a result of the smaller gates and runners. Therefore, the processes won’t be fully optimized until raw material manufacturers start to find the value in supporting the industry. With some specialized conventional materials costing $3,000 to $20,000 per lb, it may not take long for them to catch on.

With regard to rapid prototyping technologies, I found one vendor that quoted a one to three week turnaround on precision molded parts. I’ve been spoiled by the one to three DAY turnaround on conventionally sized parts, so it wasn’t exactly what I was hoping for. However, it’s much better than ramping up to full production over the course of two months.

Recent work in microfluidics has also required me to look into high-volume molding production capabilities. Of course, the problem with molding very small parts in high quantities is that it is difficult to get multiple cavities to fill evenly, precisely, and reliably with such small tool features. I was pleased to find two vendors with very different yet promising approaches to the problem.

MICROMACHINES

A notable advancement in the micro-scaled industry is the miniaturization of the machines themselves. As parts have grown smaller, manufacturers realized it was wasteful, with respect to floor space, energy, fixturing, and cost, to have conventionally-sized machines performing work on parts that only require 1/10^th of the workspace. This is true almost across the board, as milling, EDM, and molding machines become small enough to fit in your office.

A SUCCESSFUL CONFERENCE

At Key Tech, we’ve been designing micro-scale parts for some time, but finding vendors capable of manufacturing such parts has been difficult. I went to this conference to better understand the state of the entire micromanufacturing industry as well as identify vendors with specialized capabilities. I think the conference was a success on both counts.