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Thread: Problem Engraving and Cutting Clear Acrylic Sheet

  1. #1

    Problem Engraving and Cutting Clear Acrylic Sheet

    I'm having trouble engraving and cutting clear acrylic sheet. I'm getting some blow-off residue on the surface that looks a lot like smoke residue after engraving wood, except it is a frosted clear color. This is on 1/8 sheet acrylic, and it remains next to both engraved and cut lines.

    After experimenting to find the right settings, this is what I am using: engraving 100/40 and cutting 15/85/5000. This is with the exhaust fans running and with air assist running. I got similar results after trying again with the air assist off.

    I haven't had this issue before with acrylic. Does anyone have any ideas or suggestions?

    Thanks,

    Ric

    Epilog 60 watt Helix



  2. #2
    If you haven't had this issue before, then maybe the acrylic is extruded. Extruded engraves more clear than cast and stinks a bit.
    I design, engineer and program all sorts of things.

    Oh, and I use Adobe Illustrator with an Epilog Mini.

  3. #3
    Join Date
    Oct 2005
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    Moreton, Wirral, UK
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    3,287
    Ric, I agree with Doug, it doesn't sound like you have cast acrylic there. Cast acrylic smells sweet, when bent it will snap easily. Extruded stinks, when bent it will flex. There is a noticeable differences.
    Epilog 45w Helix X3/X5 Corel Microflame Generator (flame polisher) Heat Bender


  4. #4
    I agree that you probably are using extruded acrylic. The smoke cannot be removed unless you spend enough time on it to buy new material.

    So far all the cast I've bought has paper protective covering while extruded has plastic.
    Mike Null

    St. Louis Laser, Inc.

    Trotec Speedy 300, 80 watt
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    Woodworking shop CLTT and Laser Sublimation
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  5. #5
    Join Date
    Dec 2009
    Location
    Vermont
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    1,484
    I'm no expert, but from your description it sounds more like
    what happens when I accidentally pick up polycarbonate instead
    of acrylic.

  6. #6
    If it yellow ish marks, I agree with Chuck. You may want to check to make sure that your Air Assist is
    working and pointing in the right direction. I have had the tube get bumped and knocked of "course"
    Martin Boekers

    1 - Epilog Radius 25watt laser 1998
    1 - Epilog Legend EXT36 75watt laser 2005
    1 - Epilog Legend EXT36 75watt laser 2007
    1 - Epilog Fusion M2 32 120watt laser with camera 2015
    2 - Geo Knight K20S 16x20 Heat Press
    Geo Knight K Mug Press,
    Ricoh GX-7000 Dye Sub Printer
    Zerox Phaser 6360 Laser Printer
    numerous other tools and implements
    of distruction/distraction!

  7. #7
    I appreciate all of the comments so far, and my responses are a mixed bag. The plastic was given to me by a friend, so I wasn't able to look for specifics while purchasing. The brand is Plaskolite.

    It is paper-covered, which would indicate cast. The engraving is nicely frosted, which would indicate cast. However, I pulled the paper out of the trash and printed on it I did find a small arrow with "extrusion direction". I guess that would indicate extruded.

    With the paper covering, I just assumed it was cast without reading the small print.

    Ric

    Epilog 60 watt Helix



  8. #8
    When we get plastic sheet extruded for us, we can specify which protective covering is applied. I wouldn't trust the paper=cast / plastic=extruded method.
    I design, engineer and program all sorts of things.

    Oh, and I use Adobe Illustrator with an Epilog Mini.

  9. #9
    I have had this before with the extruded acrylic. My experience was that small items could be wiped clean if done immediately, but the "fog" seems to set up or harden fairly quickly and doesn't wipe completely off after a very short time. You can use a paper or tape mask if the engraving design is amenable. I've had good success using Novus #2 polish to clean it up but, again, easier to do ASAP after engraving.

    -Glen

  10. #10
    Well, I took the suggestions to heart and made the presumption that the acrylic was extruded. I went to a plastics dealer and bought some more 1/8 acrylic and was assured that it was cast. After discussion with the owner, I'm convinced he knew what he was talking about, and I showed him a sample of my problem. I brought the new acrylic home and did more testing, with the same results. The "fogging" appears around the cut lines, while the engraved lines seem to be ok.

    I've attached a pic. It's hard to photograph, but you can see the fogging around the cut areas. The cut edges are all pretty nicely polished (the photo is a close-up which shows more detail than when viewed naturally, the edges really do look good when viewed naturally) except on the left edge there are 4 tics, I don't know what caused those tics.

    I tried different settings, 15/85/1000 and 15/100/1000 with identical results.

    Does anyone have any more suggestions? I really don't want to get bogged down hand polishing each piece, especially if I receive a large order from a customer.

    Many thanks,

    Ric
    Attached Images Attached Images

    Epilog 60 watt Helix



  11. #11
    Glen,

    Many thanks for the input. With the test pieces I did wash them and wipe them clean immediately after the laser stopped, and now I'm sure I'm working with cast acrylic.

    I'll try again with a tape mask. I think the fog is on both the top and the bottom (mostly on the top), so I guess I'll have to try masking both sides.

    Thanks,

    Ric
    Last edited by Ric Taylor; 04-04-2012 at 8:09 PM. Reason: spelling

    Epilog 60 watt Helix



  12. #12
    I think what you are getting is just the PMMA (acrylic) vapor condensing on the surface of the plastic. Acrylic turns directly to a gas when lasered; if the air assist and exhaust system does not take it away and it condenses on the part, it will cause it to frost. When I cut acrylic I always mask both sides; then if marking is needed I remove the paper from that side alone. I prefer to keep the paper/mask on as long as possible.

    It just takes one spot of acrylic vapor to spoil a part. Although it may be possible to polish it out, I find that trying to save parts usually costs too much in labor.

  13. #13
    Engraving front to back might be worth a try to help minimize the haze.
    I design, engineer and program all sorts of things.

    Oh, and I use Adobe Illustrator with an Epilog Mini.

  14. #14
    I just did a bunch of cast acrylic ornaments today and as soon as they came off the laser bed I threw them in the sink and covered them with water. This was to loosen the paper backing on the complex snowflake shaped pieces (I leave it on the back only) ... which normally are hard to peel clean. Two things happened: the paper backing came off VERY easily and there was NO fog left on the pieces from cutting. I normally have to clean them with DNA. I can't believe I never did this before, since I've made many hundreds of these... I only tried it because I had a kid helping me and wanted to make her peeling job easier... it always works for me when I'm working on plastic mah jong tiles so I figured why not clear cast?

    cheers, dee
    Epilog Mini 18/25w & 35w, Mac and Vaio, Corel x3, typical art toys, airbrush... I'm a Laserhead, my husband is a Neanderthal - go figure

    Red Coin Mah Jong

  15. #15
    You can also try to mask it with a wetted A4 paper - soak a sheet of A4 paper in water and then place it onto the acrylic. The wetted paper should help to absorb the residue

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