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Thread: cnc carving foam

  1. #1
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    cnc carving foam

    I wanted to post this new thread to stop the hyjack I helped with on Robert "Aconcepts" Elana thread.

    If anyone has questions or suggestions let's do it here.

    Mike

  2. #2
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    Re: cnc carving foam

    so, once i have the entire car shaped from foam...whats the next step to making it a real kit-car?

    Spraying the hardening agent?

  3. #3
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    Re: cnc carving foam

    Well that might be hard for me to comment on since I only carve the foam. I have researched enought to have a fairly good grasp of how to do it, but having never done it I hesitate to give advice. I know the foam I use can and is attacked by heavy solvent content so what ever you use to coat it with needs to be compatible with the foam you use for your buck. If I ever do get to do one of my own I will use epoxy resin as my hardening surface. Epoxy does not hurt this pink foam.

    After getting a hard surface on the foam the next step is body work just like you would do on a car body. This form you are building needs to be as good as a show car finish. The better the finish, the better the molds. Once you have the body done it needs to be prepped for the molding process and that is an area I have never ventured into. I know it requires several coats of a special wax and some even go a step further to use a spray barrier that will give even more protection.

    This link http://www.hotrodder.com/32Blowpar/page10.html
    is the best I have seen on the web for a step by step process of making a mold. He molded from a real car body, but the process is the same whether using a body or a buck like you are talking about making.

    Mike

  4. #4
    Bobi1
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    Re: cnc carving foam

    Mike is right - using of epoxy resin will protect the foam from damage. The other advantage is that you can make the surface of your plug very hard even if you use only 1mm thin layer of epoxy resin.

    Bobi

  5. #5
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    Re: cnc carving foam

    ok so now after you have your plug, you layer the paint on the resin and layer the fiberglass to make a MOLD of your car-part.

    So once you have the mold....what do you pour into the mold to make the actual part?

    more resin and fiberglass?

    Has anyone looked into making parts from Polyurea??
    It's the same stuff they use in truck-bed liners and more recently the stuff they use for blast protection in Iraq, since its insanely shock resistant.

    So once you have the mold you spray in a thin-layer of polyurea, let it dry, and then pull it out and there you have a part. If you made the layer thin, you could keep the weight low but still have enough stength for day-day applications, im assuming no one is taking their kitcar to a war-torn locale.

    am i way off on the process, help please.

  6. #6
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    Re: cnc carving foam

    I have experimented. I do a lot of testing. Most Polyurea change physical properties with temperature especially stiffness. Now a thicker part is stiffer but often too thick for our applications where we are looking for a skin. I have experimented with a composite that I am not quite ready to discuss that uses a polyurea as part of the laminte.

    If you keep the layer thin, you will find on hot summer days you can ball in up in a ball. Polyurea once cured has similar properties of Kevlar in that it has extreme strength in tensile but very, very low strength in compression. That is why both make such good bullet proofing material.

  7. #7
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    Re: cnc carving foam

    This has to be the most bizzare and ridiculous topic I have ever read in my life. If you really think you can apply epoxy or any other suitable resin known to man on to a foam mould and expect to achieve a finished article or even an article you can eventually obtain after hundreds of hours hand finishing of every curve and line on something as big as a car as an every day average person with no previous experience and just some misguided research then this is something I can't wait to see.
    Why don't you do yourself a big favour and apply this magical theory on to a 2" cube of foam and see how long it takes you to produce a mouldable finish on that.
    Or better still try it on a 2" dia ball of foam and see how you get on with that. Then divide the total surface area of a car of your choice, by your tiny sample and then come to the conclusion, oh how come the real manufacturers are now on to their 3rd or 4th car and I haven't even pulled a mould yet????
    I'm not saying it can't be done, but on this forum I don't think this should even make off topic.This belongs to the real car makers in this world who can utilise this technology. Not kit car people.
    Technical and hands on engineer

  8. #8
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    Re: cnc carving foam

    By the way, MANY inventions were discovered by so called "misguided research". So i personally see a lot of value in tinkering. Who knows.

    Well, you are wrong. Yes this shouldnt be here, but there is no reason why this shouldnt be in off-topic. If you were the moderator you could axe the topic, but since you aren't, why don't you email the moderator and formally complain that you don't think this topic should exist and see where that takes you.

    Also, polyurea CAN and IS used on EPS....

    http://www.polyurea.com/spps/ahpg.cfm?spgid=18

    In conclusion, why can't kitcar builders do research? Is it somehow hurting you that other people want to research? No, right, ok then, so you sit tight and wait for your car manufacturers to act and let others do their own thing. Is that ok?


  9. #9
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    Re: cnc carving foam

    The answer is dependent on where you start!. have you got a fully detailed surface model ??, - not one of those freebies or an import from a racing car game- then materials and machine time will run you about 10,000, plug prep and molds about the same .If you need to "scale up" from say 1:12th then add about another 10,000 to go to 1:4 scale and "fix" all those out of scale features, so if you were going to do a top notch job, and allow for those " its just not quite right" surface tweeks then have 50,000 in the budget and you will be in a position to start producing high quality bodies in about 12 weeks

  10. #10
    Bobi1
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    Re: cnc carving foam

    Quote Originally Posted by detroitbrit
    The answer is dependent on where you start!. have you got a fully detailed surface model ??, - not one of those freebies or an import from a racing car game- then materials and machine time will run you about 10,000, plug prep and molds about the same .If you need to "scale up" from say 1:12th then add about another 10,000 to go to 1:4 scale and "fix" all those out of scale features, so if you were going to do a top notch job, and allow for those " its just not quite right" surface tweeks then have 50,000 in the budget and you will be in a position to start producing high quality bodies in about 12 weeks

    I'm totally shocked 50,000 what? US Dollars? ??? Just for the plug and the molds? Believe me you can do them for less sum.

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