How To Build With Delrin and a Laser Cutter 28
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.
My sharks don't use plywood anyway (Score:1)
>> laser-cutting steadfasts of plywood and acrylic
Don't worry - my sharks don't use plywood anyway.
Re: (Score:2)
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.
Re: (Score:2)
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.
And your favorite, hobby laser cutter is... (Score:4, Insightful)
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?
Re: (Score:2)
Yeah I wish he went more into details on this.. he mentions a 60w laser at one point. Watts, wavelength, thickness, inches per second would have been nice.
Re:And your favorite, hobby laser cutter is... (Score:5, Informative)
Yeah I wish he went more into details on this.. he mentions a 60w laser at one point. Watts, wavelength, thickness, inches per second would have been nice.
All commercial CO2 lasers for cutting use are the same wavelength, 10,600nm. Conveniently, that wavelength is completely blocked by almost everything except air - including glass, plastics, and water. This makes it comparatively safe to work with, as high power invisible lasers go. Standard shop safety goggles provide complete eye protection, and a direct beam to the eye is necessary to cause injury since the light cannot penetrate the cornea to focus on the retina like most laser beams. But I digress... The power needed to cut a material depends on the thickness, edge quality required, and speed required. Like welding, there are no clear rules, only general guidelines based on experience. 60W is not much power for laser cutting, and would be unlikely to make a clean edge on 1/4" plastic at any reasonable speed, or to give an acceptable cut on 3/8" material at all unless assisted by a compressed gas jet, which cheap and low-powered laser cutters do not use.
Re: (Score:2)
I have a £550 Ebay 50W laser which can cut 6mm acrylic well (though with bevelled edges currently - I'm hoping to be able to do something about this though with some better set up). I've done 6mm ply but it all came out rather burnt. Again, I'm hoping to do better once I find the ideal settings. Overall I've been impressed with what it can do for the price.
Re: (Score:3)
I have a £550 Ebay 50W laser which can cut 6mm acrylic well (though with bevelled edges currently - I'm hoping to be able to do something about this though with some better set up). I've done 6mm ply but it all came out rather burnt. Again, I'm hoping to do better once I find the ideal settings. Overall I've been impressed with what it can do for the price.
A compressed air jet can greatly improve performance on thick material. If your edge quality issues are a result of melting in the heat-affected zone, that would be a major improvement. If it's a beam diameter problem, then a longer focal length lens will help. It's also good to make sure your focal point is inside the workpiece, not on the surface, if you are seeing a wider kerf on the bottom than the top.
Re: (Score:2)
I have air assist cutting which is why it can get through 6mm acrylic though I don't think it is very well designed. The kerf is wider at the top than the bottom and is noticeable on 3mm which implies the set up is poor. I suspect a poor beam shape but haven't confirmed it. Any suggestions on what to check are very welcome.
Re: (Score:3)
check your Focal length and focus height. If you have a very short focal length the the beam is very fat a few mm or less from sharp focus. Try to get sharp focus at the center line of your material and see how that cuts. Worse case is you will need to compensate for the depth of the bevel in your cad program and then sand it down. If you can, go for a longer focal length lens. Another idea is to check the air assist pressure, might be too low. At work we typically run 5.5 - 7 bar (~80-100 psi). Big cutting
Re: (Score:2)
Ha, ha. I think you missed the bit where I said I paid £550 for the system (new).
The focal length is approx 60mm. I see the advantage in increasing this but due to the bed depth, my options are limited. Something to look at anyway.
My air pressure is 0.02MP (3 psi) and does a good job of keeping smoke away from the lens but probably not a lot else. Increasing the airflow is an option but I think the air exit nozzle needs improving as well.
Re: (Score:2)
Up your cutting pressure and what that does. A cheap air compressor can be had from one of those Chinese junk importers (In the states we have a chain called Harbor Freight).
Normally, the cutting assist jet is a nozzle that encloses the lens or isolated form the lens via a sacrificial cover glass. The gas jet is in parallel with the beam and the lens is kept free of contamination due to the cavity in the nozzle being at a high positive pressure. Sounds like you assist jet is external and designed to be alig
Re: (Score:3)
Do a websearch on laser cutter engraver.
There are dozens for under $6K USD, and still a good handful down at $3K.
The proviso being that many of the inexpensive ones arrive in what is claimed to be ready to run but they're actually more like kits because of the poor quality of assembly: parts rattling around loose in the case (in one friend's experience) and various bits of hardware missing.
I have two friends who have purchased them and ripped out the control electronics, and replaced them with 3d printer br
Re: (Score:2)
Or a makerspace/hackerspace, where a laser cutter is pretty much standard equipment.
Scoff at the maker movement all you want, but the creation of dedicated spaces with a wide variety of tools (from 3D printers and laser cutters and CNC machines to basic hand tools, sew
Re: (Score:2)
Re: (Score:2)
It's half way between. They cost a few thousand dollars (maybe 6 or 7) for a decent one, and often require external ventilation (the more expensive trotech ones don't), and the cheaper ones require a cooling system. Unless you're cutting a lot you don't want one at home, but they are sufficiently affordable that many makerspaces/hackspaces have one.
Depending on where you live it's usually around $8-$40 dollars a month to join and there's usually a modest hourly maintenance fee on top since parts the laser c
Re: (Score:1)
Re: (Score:2)
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.
Re: (Score:2)
can you remake in another plastic? Reltek adhesiv (Score:2)
Do you need Delrin, or can you remake the parts from a different material? This company makes adhesives for Delrin:
http://reltekllc.com/adhesives... [reltekllc.com]
Re:Whoah, Delrin? (Score:4, Informative)
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).
Re:Whoah, Delrin? (Score:4, Interesting)
(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.