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How To Build With Delrin and a Laser Cutter
szczys writes: Laser cutters are awesome, but you have to bring your mechanical engineering A-game if you want to build resilient stuff using laser-cut parts. Joshua Vasquez has been building up his bag of tricks using Delrin and a laser cutter to build with techniques like press-fitting, threading, snap-fits, etc. that aren't possible or are non-ideal with the laser-cutting steadfasts of plywood and acrylic. Delrin (PDF) won't shatter like acrylic, and it has more give to it, so even the less precise entry-level lasers can cut joints that will have a snug fit.
Don't worry - my sharks don't use plywood anyway.
I have found laser sharks very useful for cutting into the bottoms of fiberglass hulls.
The only thing necessary for evil to triumph is for it to be pitted against a slightly greater evil
It is how I steal the loot from drug running semi-subs. My dolphins are trained to locate, the sharks with lasers cut open the hull, and then the dolphins snatch and grab.
I pay the sharks with the crew ( which also cleans up witnesses), I pay dolphins in puffer fish, (they can't get enough of that stuff)
I make out like a bandit.
i thought once I was found, but it was only a dream.
Is this a topic for those with access to the university's shop with the $100,000 laser all the students get to use for free, or is there an actual CO2 laser that can cut 1/4 or 3/8" delrin and plywood that's affordable for occasional home use?
Is it just my observation, or are there way too many stupid people in the world?
I happen to need some weird Delrin parts for a 1960s oscilloscope. My parts have cracks and Delrin is almost impossible to glue unless the surface is chemically prepared.
I wonder if Joshua can tell us if there's a way to prepare the surface correctly at home? And what specific adhesive works?
Nothing sticks WELL to Delrin/acetal. Epoxies can be used to bond it, but it's not recommended at all if any other means of connection is feasible. Its non-reactive and low-friction properties are directly related to its very low surface energy, which makes bonding work poorly. Acrylic is much better if you need to glue, since superglue (cyanoacrylate) bonds extremely well and matches its mechanical properties fairly well. Polycarbonate is also good.
I am a geek attorney, but not your geek attorney unless you've already retained me. This is not legal advice.
Do you need Delrin, or can you remake the parts from a different material? This company makes adhesives for Delrin:
http://reltekllc.com/adhesives...
Use Loctite 770 to prep the surface, then use regular super glue (cyanoacrylate). They also sell it at hardware stores as "glue for hard to bond plastics" as a 2 part system (the 770 and superglue). I've found the bond to be very strong this way (getting up to the point where Delrin will fail before the bond).
Delrin is a thermoplastic; my first thought would not be to glue it with some other substance.
(assuming you are in the USA, which you may not be)
Harbor Freight makes a plastic welder for $65. There's better name-brand ones around for $300-$700.
Two other possibilities for cheaply welding plastic: cheap soldering irons (~15W - 30W heat, $20) and mini heat guns ($10 - $30).
If it is not a cosmetic issue, I have also seen thermoplastic parts repaired the following way... You get a small piece of aluminum screen, place it over the break and rub it in with a hot soldering iron.
Try double sided tape, I've managed to stick pieces of Teflon together with some of those for test setups. But for acetal sheets if you really *must* glue first use 250 - 300 grit abrasive cloth and then an epoxy based glue.