Hi, I am having problems vacuum pressing copoly polypropylene.
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For some odd reason, it is not resulting in a smooth press, the always seems to be a lumpy ridge in the arch of the orthotic and the colour isn't as shiny, it just a poor press and I can't seem to understand why.
I am using the following,
Vacuum press from algeos with a compressor,
membrane is 2mm thick of the vacuum press
The plastic is heated using the correct heating temp.
Where am I going wrong? I don't want to waste anymore plastic (I am a student)!
Regards,
Arthur
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are you using something to allow the air to escape? - stocking over the cast
is the membrane not pulling hard enough? - add an EVA sheet under the plaster cast
are you getting a complete vacuum? check -
Make sure plastic not too hot, cast too damp. Add thin layer of neoprene between cast and poly when vacuuming. Dont worry about it not being shiny you need key it for top cover anyway.
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Raise cast with EVA block 10-12 mm.
EDIT: Sorry Mike, didn't read you had already suggested thatLast edited: Jun 30, 2011 -
I have tried with and wothout a stocking net.
Yes the membrane is pulling enough.
Yes it is a complete vacuum, what I mean by that is there is no part of the membrane being open. -
I'm loosing the shine on the extrinsic side of the shell.
I have also sprayed silicone to the membrane, no luck.
I used a thin layer of poron 1.6mm between the cast and poly. Again bamboozled why this is happening! -
This is googly, and I cannot solve the problem!!! -
get the infra-red oven checked out
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Or you could try a different material. I've found Mandrillian (high molecular weight poly) to be both easier to work with and more durable. -
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Mandrillian does sound like a supervillian. "mandrillian's lair" has a nice ring to it. I think more orthotic materials should have cooler names. -
Isn't Bobba Fett supposed to be wearing Mandrillian battle armour in the Star Wars film? Just checked geeks-ville and its Mandalorian armour- close, i think they've missed an opportunity there. -
Not shiny on the B side? Not sure that's going to make any difference to the function of the device, but hey-ho. The shiniest devices I ever saw were made by the late, great Paul Rasmussen of Precision Intricast. If memory serves, he once told me he used a stone tumbler to finish the devices. Which ever way he did it they had a beautiful finish. Kevin will be able to confirm the method (unless is a trade secret).
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One day Simon, you and I will sit down to a game of star wars trivial pursuits. In this one area, and one area alone, I'm pretty sure I can take you.
Starflex sounds a bit like a B movie baddie... -
I'm assuming 40 years after the battle of Yavin, he's well into his 70's... Lets apply some logic: In episode 2 he's what 12ish years of age? In episode 3, when Luke is born this is several years later than episode 2, jeez gestation takes 9 months. In episode 6, Luke must be in his late 20's early 30's, Leia is looking fine and in her prime, so Bobba is pushing his early 40's here minimum. 40 years on he's badass and in his late seventies early 80's? Yeah, I'm ****ting myself, rather he probably is, complete with colostomy bag, hearing aid, glasses, zimmer frame, dementia and reflexes of a house brick. Viz. I'm going to fart on him and he'll fall over in that armour. Or did I miss the bit when he stopped ageing?
You know Robert, you can be too geeky. The sad thing is I'm off to age Carrie Fisher (Still a pin-up in THAT bikini) and Mark Hamill when Return of the Jedi was made, take their mean age and work all of this out. -
Check the heating time. When you put the plastic in the oven, it's room temp. Depending on how how the oven is, It will take variable amounts of time to reach the perfect temp to press it. There is a too hot and a too cold. It might be that you are heating it too long and when it cools it shrinks at different rates causing the lumpiness.
Eric -
My wife opened my sealed collectors edition star wars and lord of the rings monopolies. Can you adam and eve that? The worst thing is that she opened them for the kids to play with and they subsequently trashed them. Nice
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So, here we go, probably the most important question ever posed on the Arena....
Pick your favourite Star Wars episode...
Me? I'm old school, I swing between all three of them. At the moment I'm an Empire man.. I know it'a an in-betweener (great series BTW), but it's cool (hence all the snow and ice at the start)
If anyone can be arsed then put it up as a poll. You're wrong anyway, 'cause at the moment it's "Empire". We'll do the Alien films another day... -
Oh and I'm with you. Empire. Although comparing the original 3 to the prequels doesn't really work so I'd also register a strong affection for ROTS. But it has no millennium falcon and no Han solo so it can't compare. -
Your problem is most likely related to uneven heating of the plastic as stated above.
1. If possible try a convection oven.
2. If you have to continue with the present oven, put a rectangular flat stoneware plate in the bottom and sides if possible to even out the heat. Like bricks in a big pizza oven.
3. Preheat the oven to the desired temp.
4. Cut your plastic closer to the eventual size you will trim.
5. Bring the plastic out as soon as you think the heel will shape without a wrinkle.
6. Only use enough vacuum pressure to shape the plastic. Then shut the pump off as long as it will hold the vacuum. If not, open the valve enough to let air escape and reduce pressure. -
I used to use a cheap toaster oven and managed to get it to work by shielding the orthotic plate from the heating element and sitting it on a ceramic tile so that it had some heat from the bottom.
You could also simply flip the orthotic plate over half way through for more even heating.
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