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skazm



Joined: 27 Jul 2015
Posts: 4

PostPosted: Mon Jul 27, 2015 2:35 pm    Post subject: vacuum forming Reply with quote

Hey all, I'm a TechShop vacuum-forming newb and I actually got a paid gig (poor bastid) to make some bubble clamshells for an action figure company. Unfortunately we chose .60 pet-g (lousy advice) and well, here's my mold -

https://www.facebook.com/artisanjudaica/photos/a.1434519080175819.1073741827.1425267144434346/1475805849380475/?type=1&theater bla doesn't load in the img

I was told it's gonna be near impossible but I don't care... but what settings (using a Formech 686 Quartz) do y'all recommend for something like this - has anyone ever done something like this? Any advice? You may be tempted but honest help vs. sniggers would be happily appreciated and remembered.
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jegner
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Joined: 30 May 2003
Posts: 2122
Location: Texas, USA

PostPosted: Mon Jul 27, 2015 4:02 pm    Post subject: Reply with quote

From what I see, your depth and hard corners are going to give you issue with that thickness, unless you put that on a pretty tall riser to help thin out the material.
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crashmann
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Joined: 27 Sep 2005
Posts: 496

PostPosted: Mon Jul 27, 2015 6:17 pm    Post subject: Reply with quote

Wow, the vertical sides on your mold are definitely going to give you trouble, especially since the mold is very tall. You're going to get lots of webbing in the vertical corners.



Can you redesign the mold to have tapered sides and rounded corners?

I'm not familiar with the Formech 686, so I don't have any advice for you there. Sorry.

Charlie
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skazm



Joined: 27 Jul 2015
Posts: 4

PostPosted: Tue Jul 28, 2015 7:42 am    Post subject: Reply with quote

yep, on it today! the sides are actually tapered, but it's a bad angle on the shot. thanks!!
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skazm



Joined: 27 Jul 2015
Posts: 4

PostPosted: Tue Jul 28, 2015 7:43 am    Post subject: Reply with quote

tall riser, you mean stick it on a block?
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jegner
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Joined: 30 May 2003
Posts: 2122
Location: Texas, USA

PostPosted: Tue Jul 28, 2015 12:25 pm    Post subject: Reply with quote

Yes, elevating your pattern from the forming platen will help with some of the issues. Those hard corners are going to be an issue.
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skazm



Joined: 27 Jul 2015
Posts: 4

PostPosted: Thu Jul 30, 2015 12:43 pm    Post subject: Reply with quote

Hi, i rounded the corners, did a test run, and thank G-d it was successful, with onlya small webbing issue in one bottom corner, have rounded the mold more since then. I appreciate all the help. Next issue, i was told use mdf and of course the texture of the bubble is grainy. Using sand sealer to try and smooth it but it's not working that well.. What do you guys do to get a super smooth finish on mdf? Thanks again.
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crashmann
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Joined: 27 Sep 2005
Posts: 496

PostPosted: Thu Jul 30, 2015 10:47 pm    Post subject: Reply with quote

You might try some Rustoleum filler primer. It goes on thick, then you sand it smooth. Apply another coat and sand it smooth. Finish up with a couple of coats of heat resistant paint.

Or, make a mold using polyurethane resin from BCC or Alumilite:
http://bccproducts.com/?cat=16

I've had great results from both BC8002 and BC8009

http://www.alumilite.com/store/pg/46-Casting-Resins.aspx

I haven't used Alumilite personally, but it's very similar to the BCC products.

Be sure to purchase a compatible release agent and apply it liberally to one of your vacuum formed pulls. Mix the urethane resin thoroughly, then pour it into the vac formed part.

You'll need to sand it smooth before vac forming over it. You'll be very impressed with the consistent performance from the mold!

Charlie
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spektr
Master


Joined: 07 Jan 2008
Posts: 425

PostPosted: Fri Aug 14, 2015 1:04 pm    Post subject: Reply with quote

Ok, since you went to MDF, you're sort of screwed if you want the part to be clear.
The answer to your problem depends entirely on how many of these you are making.

if more than 50, I'd use your wooden pattern as a mold, pour it in aluminum, polish it all up and call it a day. I have naca duct tools out of aluminum and they are flawless after 4 thousand cycles.....

sometimes it just pays to do it right.

If you are painting the mdf, you will have a hard time with any rattlecan product sticking to the mdf because the stuff melts right in the range where petg lives, I have had luck with high temp header paint BUT the curing of the paint really degrades the MDF.

if you are feeling lucky, and you can get the mdf babys butt smooth, Rattlecan it with a few coats of grey auto body primer and use TIRE WET. TIRE WET from any car store is a silicone-ish spray I use to lube molds. I'd give it a shot. It will not work on grey primer forever, but you might get up to 100 before things turn ugly......

Scott.
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