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  1. SIKAXIS's Avatar
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    Nov 6, 2014, 1:27 PM - Vacuum forming troubles #1

    I have finished my Halo Reach EVA helmet and now I have cut out the visor already so I decided to head on to vacuum forming. because my oven was so small I had to cut the sheets down to about 15 x 20" . The sheets I use to vacuum form are 1/16" Petg sheets. I have been cooking the sheets for maybe 15 mins at about 225 Degrees Farenheight and when it starts to sag about 3-4 Inches I would pull it and put it on my vacuum form rig. It just doesn't cover the whole buck or wrap around the edges like I imagined it would. I am just using a regular old shop vac and I really couldn't tell y'all the details on that but I just want to know what I am doing wrong. It almost seems like the plastic isn't melted enough to be able to wrap around it and I was thinking maybe I need to let it sag more or cook it at a higher temperature for a shorter time. I am unsure and I only have one sheet left and would like any advice I could get from people who have experience with this sort of thing. I will post pics later when I get home of some failed attempts.
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  3. 405th Midwest Regiment Member rickrtickr's Avatar
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    Nov 6, 2014, 2:44 PM - Re: Vacuum forming troubles #2

    Can you show us some pictures?

    That might be helpful.
  4. 405th Midwest Regiment Member Virti's Avatar
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    Nov 6, 2014, 4:03 PM - Re: Vacuum forming troubles #3

    On YouTube Cosplay4usall and Xrobots have some good videos on vacuforming, and if its a suction problem try using duct tape on the board on the edges or areas where you dont need suction
  5. 405th Pacific Regiment Member Katsu's Avatar
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    Nov 11, 2014, 1:22 AM - Re: Vacuum forming troubles #4

    If you are just getting steep rounding or loss of definition at the bottom, you need to stand the part away from the vacuum surface more.
    If it's just in indented or pocket areas you need to add holes in the plug to suck into those pockets.
    If it's everywhere it is probably a pressure problem as mentioned above.
  6. SIKAXIS's Avatar
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    Nov 11, 2014, 2:25 PM - Re: Vacuum forming troubles #5

    Originally Posted by Katsu View Post
    If you are just getting steep rounding or loss of definition at the bottom, you need to stand the part away from the vacuum surface more.
    .
    It's kind of like that, the plastic won't pull over all of the buck it just covers maybe 3/4 of it. I kind of destroyed my best pulls trying to fix them and I guess my Dad threw away the reject bucks so I don't have any more pics showing what I did but here's a rough sketch of what's happening.



    Basically the plastic doesn't even touch the vacuum forming table like how I've seen in most vacuum forming TUTs. (By the way the blocks on each side represent the frame which the plastic is screwed to. )
  7. 405th Colonial Regiment Member
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    Nov 11, 2014, 6:24 PM - Re: Vacuum forming troubles #6

    It sounds like you have an issue of not enough suction, and you need to get your buck up a little further from the surface. You could place a small stand under your buck to lift it half an inch higher. For more suction I would not use a shop vac. I would use your vacuum cleaner. It will tend to have a little more suction power then a shop vac has.
  8. 405th Mountain Regiment Member Gilmortar's Avatar
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    Gilmortar's Xbox Gamertag gilmortar
    Nov 14, 2014, 3:55 PM - Re: Vacuum forming troubles #7

    Here are a few things you can do.

    Raise your buck up... I'm guessing your table has ONE central vaccumm hole in it connected to your vacuum hose right? By setting the buck directly over it, you are losing all the suction. I use Popsicle sticks. Stack up 2 or 3 in multiple places under the buck but DO NOT cover the suction hole with it.
    I modded one of our Vac Tables to that has peg board that pulls suction over the entire bed of the table.

    I can probably help if you take even some camera photos, if you don't know how to post them on here, PM me and you can Email them to me. I have been thermoforming since 2002 with major full scale production companies...so I have a little experience.
  9. SIKAXIS's Avatar
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    Nov 15, 2014, 2:52 PM - Re: Vacuum forming troubles #8

    Originally Posted by Gilmortar View Post
    Here are a few things you can do.

    Raise your buck up... I'm guessing your table has ONE central vaccumm hole in it connected to your vacuum hose right? By setting the buck directly over it, you are losing all the suction. I use Popsicle sticks. Stack up 2 or 3 in multiple places under the buck but DO NOT cover the suction hole with it.
    I modded one of our Vac Tables to that has peg board that pulls suction over the entire bed of the table.
    Okay So here are some pics of my vacuum form box and frame. Its pretty simple (maybe too simple). As you can see It is a bunch of holes in the top (not just one.) I plugged up the ones I wouldn't need after I had to resize the frame so it would fit in my oven. The buck is just reiforced with cardboard and Its rasied with cardboard as well, but as you can see from the pics it doesn't plug up any holes. Maybe I need a different vacuum table so that it is just one hole. I am sure it takes a lot of the suction away because it's so big. The frame is just a few 2x4s that I screw the plastic sheets on. When The plastic starts to droop I pull it out and flip it over on to my buck (with the vacuum turned on). And because it might be mentioned later, yes, the seams of the vacuum box are sealed with silicon. Hopefully this is enough to figure out what's going wrong.



  10. 405th Mountain Regiment Member Gilmortar's Avatar
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    Gilmortar's Xbox Gamertag gilmortar
    Nov 15, 2014, 7:29 PM - Re: Vacuum forming troubles #9

    Ok, I think I'm seeing your issue. You plastic doesn't have any grip on your push frame... And so it causes it to not have a seal. When the plastic gets hot and soft, it will stretch, so when you push it over the mold it just stretches on one side and there goes your vacuum deal. So here is what one of our vac tables looks like:



    So I use weatherstripping foam on the entire perimeter, making sure each strip pushes against each other to create the tightest air seal I can get.

    Now this is what our gate looks like:



    We just used some cheap window screen frames. On our other table I used some 1" poplar boards cut to size and hinged that close with a screw through it and the plastic. So the point of this gate is it pinches all edges of the plastic so it won't pull out and this keeps suction on the plastic. You put the plastic in as follows:





    We just use large folder paper clips to secure it. But then we have a heater element built in to that table, so we heat it up right there and can flop it on there instantly. So if you are using your oven, keep close eye and then make the switch from oven to the table VERY FAST. So what we do is turn on the vacuum, have it going when you pull the hot plastic from the heating element/stove and then you press the frame on the foam with a bit of pressure to ensure a good vac seal:



    I guarantee if you change it up like that you will instantly get the best results. I really think it's all due to not having the plastic secure in the gate and loosing all suction.
  11. SIKAXIS's Avatar
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    Nov 16, 2014, 1:40 AM - Re: Vacuum forming troubles #10

    Originally Posted by Gilmortar View Post
    Ok, I think I'm seeing your issue. You plastic doesn't have any grip on your push frame... And so it causes it to not have a seal. When the plastic gets hot and soft, it will stretch, so when you push it over the mold it just stretches on one side and there goes your vacuum deal..
    Okay, so I understand that I need to create a tighter seal for vacuum form and I really like what you did with the two window frames.
    First I'd like to say thank you for all your advice and Second I was wondering about the heating element you used. I kind of don't like having to use my oven.
    Also A couple things weren't 100% clear to me.
    Originally Posted by Gilmortar View Post
    On our other table I used some 1" poplar boards cut to size and hinged that close with a screw through it and the plastic.
    pretty much this entire sentence was hard to follow

    Originally Posted by Gilmortar View Post
    We just use large folder paper clips to secure it
    You mean to keep both frames and the plastic sheet held together during the process right? (like how its shown in the second picture. )

    Sorry for all the questions. I really want to do this right so I'm not wasting any more plastic and you do seem to know quite a bit.
  12. 405th Mountain Regiment Member Gilmortar's Avatar
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    Gilmortar's Xbox Gamertag gilmortar
    Nov 16, 2014, 3:17 AM - Re: Vacuum forming troubles #11

    As for the 2nd question about the paper clips, YES, you are 100% correct. As for making the gates, the first question you referred to about not understanding, this is what I used:



    1" x 2" poplar boards. I cut them and attach them with L brackets and hinges (and because it's too cold to go in the shop and take a picture):



    step one, cut poplar to proper size step two, add l brackets to connect all the pieces using the L brackets
    step 3, screw in the hinges to make the two frames open like a laptop
    step 4 put in the plastic
    step 5, close the gates and screw a wood screw so it doesn't move anywhere else.
  13. 405th Midwest Regiment Member Virti's Avatar
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    Nov 17, 2014, 4:56 PM - Re: Vacuum forming troubles #12

    A problem that i could see is the large cavity under the helmet, try sealing that up with some more cardboard so you can get a better vacuum
  14. 405th Mountain Regiment Member Gilmortar's Avatar
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    Gilmortar's Xbox Gamertag gilmortar
    Nov 17, 2014, 6:45 PM - Re: Vacuum forming troubles #13

    More so, with that mold you are going to experience some HORRENDOUS under cuts... I would so much suggest getting some air clay, and building up that undercut a bit more flush that way it will pop out of the plastic a bit easier.

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