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Milling 3mm Perspex (Plexiglass, Acrylic) Disc

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  • John Stevenson
    replied
    24 hours to dry 6mm, don't have the equipment to do this or need to do any amounts. Worth knowing though.

    There are quite a few materials that can be engraved but not cut, the hard engraving laminate what we call Abec or Trafolite engraves well but burns when cutting.

    Same with Tufnol or Phelonic, engraves well but burns.

    Good thing is the plastics manufacturers are getting on the band waggon with the increase in low power cheap laser cutters and bringing new materials out all the while.

    Trying a really cheap method this weekend on that Harrison M300 plate I posted about in this thread, method 4 actually.

    http://bbs.homeshopmachinist.net/threads/56306

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  • Evan
    replied
    You can do Lexan John. It needs to be dried first. Here is a very useful document from GE UK.

    http://www.theplasticshop.co.uk/plas...sing_guide.pdf

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  • John Stevenson
    replied
    The laser doesn't like Lexan, makes a horrible black blob so still have to mill this.
    ABS cuts OK but need plenty of ventilation and when you look at the edge in cross section it not square but very slightly dumbell shaped.

    Does toast brilliantly, you can even draw the shape where the eggs and bacon need to go..........................................

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  • macona
    replied
    The single flute cutters are the best for plastic, especially the ones from Micro100. Another option is take a two flute end mill and grind off one flute. This gives you the extra clearance. Mist coolant works great here, the air keeps the chips from packing and the coolant keeps things from melting.

    http://www.micro100.com/inch/sfp.html

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  • Evan
    replied
    I have one spindle that does around 40k. I just bought an electronic tach that goes to 100k so now I can measure them without hauling out the frequency counter and a bunch of wires and a sensor etc. That will be very handy.

    There is a very big difference between any acrylic including Plexy and polycarbonate (Lexan, a brand of PC). The materials may look similar but have very different properties in all areas.

    BTW, Lexan was invented by GE and it was entirely accidental. A chemist mixed some polymer components while studying unrelated matters and not much happened.... Until the next day when the mess had set into and utterly indestructible mass.

    A good substitute for polycarbonate is PET-G, especially in thin sections. It has many of the same properties, is much easier to heat form and is much cheaper. It also doesn't turn white when bent in a brake and it doesn't need to be heat dried before heat forming. No bubbles.
    Last edited by Evan; 11-16-2012, 06:24 PM.

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  • outlawspeeder
    replied
    If it is any help I cut Lexan with a wood router that has a bearing for following a pattern. The key to the cut is clearing the chips! If not they heat up...melt... clump... anf then all bad things happen.

    I do this for motorcycle windshields. to finish the edge I use a file then buff to a nice class look.

    Just a thought

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  • Bob Fisher
    replied
    Why would you not make this on a lathe? You can stack them and make a bunch at one time. For a washer, it would have been my first thought. Bob.

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  • Fasttrack
    replied
    Originally posted by Evan View Post
    Keep the rpm at the very low end like around 5000 rpm. Feed consistent with less than maximum chip load. If it is at all flexible make sure it cannot climb the cutter or it will. Lube with soapy water for cooling. BTW, I am having difficulty imagining "clear black" plastic.
    LOL funny perspective. I'm so used to working with my old manual machines that 5000 sounds like the extreme high end! My fastest machine tops out at 5500 and my lathes top out at 1500 ... I would never think to call 5k the "very low end"

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  • Rich Carlstedt
    replied
    Originally posted by ckelloug View Post
    Rich,

    Plexiglass is just another acrylic. Makrolon (Bayer Materials Science) and Lexan (SABIC, formerly GE) are the two common polycarbonate brands.

    --Cameron
    Thanks, I stand corrected.
    I always use Lexan for exotic parts.

    Rich

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  • Peter S
    replied
    I was just looking at a stack of laser cut acrylic tonight - a beautiful job, long thin strips, dead straight, perfect edges, much better than saw or other machined finish.

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  • dalesvp
    replied
    Be sure to sandwich the acrylic between two stiff/rigid pieces of sacrifice materials such as good solid wood, squeeze TIGHT. Bore through the lot. This method prevents shattering of the fragile material while producing a perfect hole. I have successfully drilled paper, 1/8" acrylic, extremely fragile plastic bottle lids, tin foil and even cellophane food wrap.

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  • browne92
    replied
    Not quite, Rich. Plexiglass is acrylic, or more specifically polymethyl methacrylate. Lexan is polycarbonate. Yes, plexi will shatter before Lexan, but I'm not sure where that fits in here. I've cut a lot of acrylic and never had it shatter. Shattering would be more a worry of the end product, and the good Doctor never said what that was.

    I've been cutting and etching a lot of acrylic lately. I use a (is it 'zero' or 'oh'...looks like a flute to me, but that's what they call it.) flute router bit in my router table to cut it. The cuts come out clean, no chipping, but the finish isn't quite mirror like. Osrund makes the bits. I've tried standard router bits, but they just make a big melted mess.

    I use a 2 flute end mill to etch it, but not without troubles.

    Best of luck.

    Edit: Cameron types faster than I do.
    Last edited by browne92; 11-15-2012, 11:18 PM.

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  • ckelloug
    replied
    Rich,

    Plexiglass is just another acrylic. Makrolon (Bayer Materials Science) and Lexan (SABIC, formerly GE) are the two common polycarbonate brands.

    --Cameron

    Leave a comment:


  • Rich Carlstedt
    replied
    Be careful with Acrylic !
    You want Lexan or Plexiglass, which are Polycarbonates, and will not shatter suddenly, as Acrylic's will.
    The difference is amazing

    Rich

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  • Evan
    replied
    Evan, Ed's not entirely wrong about Perspex being 'clear black' - when you mill it to less than 1 mm thickness and hold it up to the light, it's actually dark green and translucent!
    Yeah, that holds for the dyed acrylic but not the opaque types. Both look the same with any reasonable thickness. I have many sq feet of acrylic and polycarb in a wide variety of colours that I picked up for nearly nothing when a local sign shop went out of business.

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