Nuts and Volts - May 2014

by Bryan Bergeron, Editor by Bryan Bergeron, Editor

DE VELOPING

When Additive and Subtractive Technologies Don't Add Up

When I made the move to 3D printing a few years ago, I imagined that by now I would have sold my milling machine, drill press, and other 'subtractive' technologies.

The reality is that 3D printing is simply another tool in my prototyping toolbox. This additive technology isn't really clean or waste free — I’m constantly vacuuming starter strands of PLA and ABS from my shop floor. Plus, the technology isn't completely safe. There's the hot extruder, hot bed, and — as I recently discovered — danger in machining a 3D printout.

I like to prototype in PLA and then use ABS for a final print. Printing with PLA has a number of advantages over printing with ABS: It's relatively odorless; the nozzle temperature is relatively low; there's no need to heat the printing platform (a 10 minute process); and there's no fumbling with the plastic film tape that always traps a few bubbles. I just put down a layer of blue painter's tape on the platform and hit the print button. Within a minute, I'm printing.

I typically take the PLA printout and rework it with a Dremel or other tool to reshape or add mounting holes to the prototype. That is, until now. For some time, I've noticed prickly feelings in my fingertips, akin to what I've experienced after working with fiberglass insulation. I didn't connect the 3D printing with the pain until I switched from natural to black PLA.

Under my workstation microscope, I found dozens of short black PLA shards embedded in my fingertips. After spending an hour with tweezers extracting the splinters, I decided that — as far as PLA is concerned — additive and subtractive technologies don't add up.

I haven't given up on PLA altogether because of the advantages noted above, but when there's a modification called for I do it in software and make a new print. I still rely on my drill press, Dremel, and other subtractive tools to get a prototype into shape, but now only with an ABS plastic printout.

My latest experiment in 3D printing is thermoplastic elastomer (TPE) — basically printable rubber. It's expensive at about double the price of PLA or ABS ($50/500 gm from AdaFruit, not including shipping). However, the ability to print flexible structures is intriguing, and — like ABS — there aren't any fragile shards flying about when I shave an edge or drill a few holes in the printout.

Clearly, 3D printer technology is evolving, and the spools of PLA, ABS, TPE, and other materials will eventually give way to the powders and liquids used in commercial printers.

So, should you wait for those next-generation materials to reach the consumer 3D market? No way. 3D printing is a fantastic prototyping tool that should be part of every electronics experimenter's arsenal. Just take the proper precautions when you work with printouts, such as gloves and eye protection when you're reworking something printed in PLA. NV