3D Printer build

Discussion in 'Workshop Tips and Secrets / Tools' started by FritzW, Dec 18, 2016.

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  1. Jan 7, 2017 #81

    Jay Kempf

    Jay Kempf

    Jay Kempf

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    Cause fabric is too heavy. When you get to carbon fiber you can apply it in the direction of the strength needed or you can just lay fabric on. Bundles are less efficient than tapes one on top of the other in different direction.
     
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  2. Jan 7, 2017 #82

    bmcj

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    I'm sure it's to reduce paid man-hours in a production environment.
     
  3. Jan 7, 2017 #83

    Jay Kempf

    Jay Kempf

    Jay Kempf

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    Actually it is to increase the accuracy of laying the fibers past what a human can do. The two problems with light weight strong composites are actually the number of parallel fibers and metering the adhesive. The machine solves that and has robotic repeatability. So composites to the repeatability of a 6 axis milling machine is the point.
     
  4. Jan 7, 2017 #84

    proppastie

    proppastie

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  5. Jan 7, 2017 #85

    Jay Kempf

    Jay Kempf

    Jay Kempf

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    Not prepreg but individual spread tapes from tow bundles. There is the capability for heat staking but not full cure. There are also machines that can stitch to hold the tapes in place. This stuff is megadollar but simpler could be made. I was involved in installing one in NY in the last year. Pretty significant planning and install. The wider you spread the tows the better the efficiency of the structure. Still gets vacuum bagged and or autoclave cured depending on the part being made.
     
  6. Jan 7, 2017 #86

    proppastie

    proppastie

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    Vacuum infused resin?, Mold did not look right for that unless I am missing something, is the area where spread have bleed cloth and holes below?
     
  7. Jan 7, 2017 #87

    Jay Kempf

    Jay Kempf

    Jay Kempf

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    No it's placing resin as it goes and metering it. You then put it in a vacuum bag and cure it with heat to spread it properly. No infusing involved.
     
  8. Jan 7, 2017 #88

    BobbyZ

    BobbyZ

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    Optimization,you can get all the fibers you need in their exact orientations for the loads with none orientated in a direction thats not needed.
    I used to wonder how boat masts and spars wound a strand at a time could be so strong yet relatively thin and extremely light.Especially when compared to some of the older ones made from the woven tapes.
     
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  9. Jan 7, 2017 #89

    proppastie

    proppastie

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    So if I understand what you just said....that machine wets out the fiber as it lays it down. Do the tow bundles vary in thickness as it is laid down or does it just go back an build up with a set thickness? Does the width vary?
     
  10. Jan 7, 2017 #90

    Jay Kempf

    Jay Kempf

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    Set thickness each tape normally prespread to have xxxxx fibers per tape at xx width. Tape widths can vary but you put a spool of that tape in the machine for each run/part/layup.

    Resin to fiber and resin penetration is the hard thing to control. By wetting each tape exactly to the standards you want you get each fiber even if you have 400 layers exactly right but it is more like plastic coating very viscous and it takes temperature to let it relax under vacuum and/or autoclave to finish the bonding process. Surface tension can be dialed to let the resin travel as you like. In a perfect world you only need a tiny bit of resin where the fibers touch/cross one another.

    This is the obsessive compulsive overly complicated version of laying up composites. :)

    You could also purchase spools of tape and lay them out with a roller layer by layer. But that is a sticky mess to control. But it works. You wouldn't get the even resin fraction but it would work fine. There are also custom fabrics. Textreme is an example of a "standardized" custom non-crimped fabric.

    Sorry we are getting off in the weeds.
     
  11. Jan 8, 2017 #91

    proppastie

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    Still not sure if tapes pre coated or machine coated, precoated is pre-preg to me, but it is 40 yes. Since I worked on the Harrier.
     
  12. Jan 8, 2017 #92

    FritzW

    FritzW

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    My first attempt at printing an "anatomically correct" 1/10 scale VP-1...

    I made the mistake of using a "Brim" which was a huge pain to try to get off the parts (1/10 scale 1/4" ply ribs are only .025" thick!) I'll try it again without it.

    20170107_194847_resized.jpg VP-1 stabilator. Next time, without the brim, the parts should be ready to glue together right out of the printer.
     
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  13. Jan 8, 2017 #93

    proppastie

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    does an added designed support structure help or is it better on a flat piece of glass
     
  14. Jan 8, 2017 #94

    Jay Kempf

    Jay Kempf

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    Prepreg is fabric that is made flat then is cut then applied. Prepreg used to almost always be "crimped" or "woven" fabrics. These are individual fiber bundles in tape form, very close rows of individual parallel fibers. They are being fed directly off of a spool sometimes with a paper backing interleaved sometimes not. Different animal. Not sure if anyone has done a prepreg placement machine but I doubt it. There are a lot of automated pre-preg methods and there are also knitting machines that wet or dry for custom fabrics that have any number of non-crimped layers knitted or tack glued together now. But you have to be Boeing or BMW to afford them normally.
     
  15. Jan 9, 2017 #95

    FritzW

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    Slicer software will automatically add supports or you can add them manually.

    Even if you don't need supports, sometimes you need help keeping the part stuck to the table (rafts or brims).

    A "raft" is a solid(ish) base that your part prints on top of. If everything goes right the raft just peels off.

    With a "brim" your part prints on the glass but has a little, single layer, rim printed around it to help keep the part from peeling off the glass.

    My little parts are just about as thin as the single layer brim so there's not a really good "step" where you can break the brim off. ...but the parts are so thin they probably don't need one anyway.

    It's a learning process, ...and that's 90% of the fun ;)
     
  16. Jan 9, 2017 #96

    Victor Bravo

    Victor Bravo

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    Program the machine to drill all the fastener holes on one pass, then come back and cut the outline of the parts, leaving TWO or even THREE 1/8" wide bridge connections between the gusset and the larger sheet of raw material. The bridge connectors keep the gusset from being moved around during the cutting process, and they keep the gusset from falling out of the sheet. Come back later with a small pair of dikes and clip out the part just before you need it. Ten seconds in front of a small sander and the part is ready for installation.

    Another interesting thing is that you could take the whole sheet after the cutting is done (with the attached gussets) and do an alodine dip process, or anodize, without winding up with a basket of un-identifiable gussets. The diagram printed out from the computer will identify each gusset until the moment you clip it out of the sheet.

    If you ran the sheet through a laser machine before or after the CNC cutting operation, the laser could bar code or numerically mark every gusset.
     
  17. Jan 10, 2017 #97

    FritzW

    FritzW

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    2013-10-01 20.00.58.jpg Yep, that's pretty much the way CNC works :gig:
     
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