shringage after vaccum

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shringage after vaccum

shringage after vaccum

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KOSTAS	KOSTAS posted 7 Years Ago HOT Topic Details
Group: Forum Members Posts: 30, Visits: 244	On my first try to produce a composite part a came across this unexpected issue .I 3d printed a fork core for a bike frame i wrapped the core to CF and then vacuum bag it.But when i measured the dried part the fork legs were closer(25mm-1') they previously were !!! here my photos why this happened ?How can i over come it ?Should i alter my design in order to compensate for the shrinkage ?Should i build a support to hold the fork legs in the vacuum bag ?Thanks in advance!
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shringage after vaccum

KostasBiz - 7 Years Ago

The actual process of pulling the air out of the vacuum bag contracts the bag and can tend to pull flexible parts out of shape. I have solved this by adding support struts on the outside of the bag.....

Steve Broad - 7 Years Ago

thank you steve for your idea , i will try to build something like a support structure . is this phenomenon encountered in other cases ? for example in a closed triangular shape , can vacuum send my....

KostasBiz - 7 Years Ago

Difficult to predict, but as you are exerting over 14lbs of pressure over every square inch of your mould with a wrinkled vacuum bag there is bound to be some pulling and pushing going on. Any...

Steve Broad - 7 Years Ago

This issue really bothers me a lot , cause i could not predict it and i could not explain it .After some study i have a theory , i cant say its the cause but might be an explanation. I printed a U...

KostasBiz - 7 Years Ago

If you close the print, the're is no force in the core itself when you pull vacuum. The pressure outside the bag is 1 atmosphere, as is the pressure in the core. The pressure between core and bag is....

oekmont - 7 Years Ago

That's a better way of explaining it than mine :-) However, I would still would place a bar of some sort between the ends of the fork as you evacuate.

Steve Broad - 7 Years Ago

Absolutely. The bar will keep the ends at the right distance. Than you only have to worry about bending the two arms. But this should be less of a problem.

oekmont - 7 Years Ago

Dosent matter how big you make your bag or how careful you vac down it will never pull down symmetrically, there will always be resistance from one point or another If your bagging somthing that can....

f1rob - 7 Years Ago

I would be really interested to see any kind of picture if avialiable to have a better understanding , thanks

KostasBiz - 7 Years Ago

Will be in big trouble if I photograph these !!!!For exampleFrom the centre of 1 fork end to the other is say 150mmWhen you print your fork at the ends in the exact centre of each you print your 6mm....

f1rob - 7 Years Ago

Thank all of you so much for your fast and though insight , this is such a good place to be and learn, i spend quite a time here reading :) As you may see from my picture i have bought and use a...

KostasBiz - 7 Years Ago

Unless I'm looking at your pic really funny you have your job across the bag ???Just run your job along the bag an cut your bag a lot longer

f1rob - 7 Years Ago

Yes you are right , i was a lot stingy with my consumables ... and i learned that in order to save small you spend big . That was exactly what i had in mind , i just finished redesigning my forks...

KostasBiz - 7 Years Ago

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