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How To Build With Delrin and a Laser Cutter

Posted by Soulskill on from the now-you're-thinking-with-lasers dept.

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.

7 of 28 comments (clear)

  1. And your favorite, hobby laser cutter is... by Overzeetop · · Score: 3, 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?

    --
    Is it just my observation, or are there way too many stupid people in the world?
    1. Re:And your favorite, hobby laser cutter is... by mpoulton · · Score: 4, 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.

      --
      I am a geek attorney, but not your geek attorney unless you've already retained me. This is not legal advice.
    2. Re:And your favorite, hobby laser cutter is... by mpoulton · · 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.

      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.

      --
      I am a geek attorney, but not your geek attorney unless you've already retained me. This is not legal advice.
    3. Re:And your favorite, hobby laser cutter is... by smellsofbikes · · Score: 2

      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 brains, as those are better-understood than the custom hardware that's windows-only, proprietary-software-only shipped with the cheaper machines. That frees people up to use arbitrary modeling, cam, and post-processing programs.
      Epilog lasers are very high quality (and their price reflects it, but it's way less than $100K, more like $10K.) They're made in the USA and are a mainstay of makerspaces because of their reliability and durability. I know a couple of people who work at Epilog and think highly of their work.

      --
      Nostalgia's not what it used to be.
    4. Re:And your favorite, hobby laser cutter is... by LoRdTAW · · Score: 2

      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 shops run really high pressure, upwards of 34 bar or more. BTW, focal length is from the center line of the lens so measure from there. Our lenses range from 100mm to 300mm depending on what we need the beam to do.

      Reference: I work in an electron beam and laser welding/cutting shop.

  2. Re:Whoah, Delrin? by Anonymous Coward · · 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).

  3. Re:Whoah, Delrin? by Slugster · · Score: 3, Interesting

    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.