At work, virtually all my coworker have product development in their “DNA”. We are all creative types, who takes lots of pride in bringing a product from an idea to life. And so consequently, whenever we read about some new widget or tool, we’ve always tried to convince our boss that it would benefit the company tremendously, if only if we have the latest and greatest Super Machine 2000.
Our boss, who’s rarely wrong, always tell us that as design engineers, our time is the most valuable spent designing. “Whenever we need something, and need something quick, we just toss money at someone and have them bang it out and put it in a Fedex overnight box”.
My buddy Dave’s grandparents owns a laser engraver. They own a trophy engraving shop and laundromat down in Renton. It’s really wierd to think of a sweet old lady at the controls of an Epilog 20W CO2 laser system… but she doesreally good work. So the next time you need something engraved, check out the Puhich Dry Cleaners in Renton on 319 Main Ave. South.
I know what a 20W CO2 laser can do; it can do a lot more than mark plastic and burn through anodize layer on aluminum. There was a discussion thread on making lens cap holders, so I drew one up in Soldiworks real quick:
Here’s the test run in paper. So far so good, right?
Unfortunately, the laser engraver is running on Windows 98. It requires a firmware update before it can talk to anything past Win98, and there is always a risk of bricking a machine doing a firmware update. So we are stuck with a computer that works – abet a very slow one, with a parallel port printer connection. (I bet some of the folks I know had never seen one… they went the way of the dodo after USB became popular).
Complicating the problem is that the printer driver runs as a Corel Draw plugin. Corel Draw 8, to be exact. And even the earliest DXF that Solidworks can save the file in, the simple fillets on the drawings don’t quite come through – let alone the more complicated splines and polylines.
The example above worked okay, because the laser cut it out as a *Raster* art, instead of a vector art. But cutting in raster mode drastically drops the laser’s power output. And it’s not like you can run multiple passes over the same piece of PTFE either – the slow heat transfer of doing so just warps the plastic – and the results looked like someone tried cutting the material with a dull butter knife.
Obviously something like this, out of 3mm PMMA, will be a bit out of the question:
So my options are:
1) Try to mitigate the risk of the current laser cutter’s firmware upgrade (maybe see if I can do a hardware replacement of the logic board, upgrade the computer to something snazzy, then retry the Solidworks -> laser cutter workflow.
2) Pay someone like Pololu online to do the laser cutting for me. Essentially, someone else will be eating part of my lunch if these products go on sale. Might be okay if there’s only a few parts, but I’ll have to rethink the design a little bit.
Turns out, RedWolf airsoft out of Hong Kong will happily sell me a 30mm silencer for about $US10.00. Aluminum barrel, both ends with a machined aluminum plug. They even put a 14mm CW thread on one end and 14mm CCW threads on the other, so out of the box, the dang thing will fit on just about every single airsoft gun out there.
In Hong Kong, we have a saying that “the flour costs more than the bread”. The term originated from the housing bubble days where the value of the land gets bid up so quickly that older apartment buildings prices are being outstripped by the land value of neighbouring lots, but it also applies to engineering and business where by some form of competitive advantage (and economies of scale), someone can build a product cheaper than you can even start sourcing raw materials.
Got a cool little bookmark for all my troubles with the laser cutter though…
I’ve really been lagging on my blogging. Here’s a quick update.
I’ve recently found myself working out of the Beaverton office again, so late one night after finishing up I hopped onto the company’s aging, crusty lathe:
These are custom captive screws for the Benro quick-release plates I picked up in Hong Kong. I’m mounting the Benro plates to a piece of 8020 1010 extrusion, and the T-slots are a little bit deeper than an ISO standard camera mount. So, for my application, a custom screw would be needed.
I’m actually pretty happy with how this turned out; the machine is old and the hand-ground parting tool isn’t the best for cutting stainless steel.
To chuck the screw into the chuck without damaging it, I took a page from an old machinist trick of slotting a nut with a hacksaw and clamping it in a 3-Jaw chuck. I started with a 1/4-20 x 0.5″ SAE button head socket cap screw.
(Note: Yes, I am aware that the standard tripod thread is a 1/4-20 British Standard Whitworth – cut with a 55 deg angle instead of a 60 deg angle. I challenge the reader to find one here in a hardware store in the good ol’ USA. A 60 deg SAE thread is “close enough” for this application with some very minor interference)
The resultant screw is a bit too long, so I trimmed it down a little bit with my motor tool.
The tool is a Taiwanese made version of the Foredom – a 600W motor on a flex shaft and a foot pedal for actuation. It takes all the standard Dremel accessories and it’ll slice through stainless pretty easily. I lined the jaws of my Wilton vice with some engineering paper scrap, and used my pano clamp as a clamping base for the tripod plate. Then, using another machinist’s trick, I put a nut on each of the screws to be cut. When removing the nut, the nut acts as a tap and cleans out any debris on the screw threads and restores the proper thread form.
And BTW – at 20,000+ RPM and with 600W of power behind the disc – any slip up is … painful. Warning: somewhat graphic picture ahead:
The wound looks A LOT worse than it actually is. I think the heat from the abrasive blade cauterized the wound – it didn’t bleed much. Digging all the abrasive grit out under running water was a different story – good reminder to be more careful the next time.
And here’s the finished rig! Now, I need to order some 3D glasses…