Composite Vacuum Table

General Composites Discussions Composites Talk
#1

Hi there

Has anyone out there had any success in building a composite vac table? I have been involved in the construction of several, and all have had their problems. Of course, there are many considerations. And different construction methods may suit depending on what is being made on the table. The kind of table we need is 3m x 1.5m. And able to cook up to 20mm QI C Plate at a minimum of 85degrees, so would need a resin system with a tg of ~120deg. Flatness +_ 1mm max.
After trying a couple of different things and not meeting the standard required, we looked to a supplier who makes heated moulds, and asked them to make a heated table. Their first attempt failed. The second was very good but developed problems after the first couple of plates were made.
So I am looking for the ideal layup spec, suggestions around monolithic or cored, embedded element heated or oven cured, resin system tg…
Also any suggestions regarding Aluminium vac table tops if anyone has any experience here? I am starting to think maybe the life cycle of an Ali top may be better, all things considered.
Thanks
Matt

#2

I have made my heated table from tempered Glass and a heating paint on the back side. Works perfect, gives a perfect surface and can go ul to 200C.

#3

Hi, Thanks for the response!
I am not sure what you mean by a heating paint? What laminate thickness are you laying up on the table?

#4

I have tried a tempered glass table and Laid up a carbon QI plate of 10mm, 1270 x 2400. It shattered into a thousand pieces when the plate was being DE moulded!!!

#5

I have made layups up to 35mm on the table. Important is that you use a good release agent and never bring forces to the edges of a tempered glass.
So if your part is always 100mm smaller than the table it should be no problem.
The heating paint was especially made for us, it is a carbon fibre nano tube paint that becomes warm if electricity will flow through it.

#6

Thanks for your help

I assume that you would be limited for size if you chose tempered glass as an option. What if I wanted a 6 meter x 1.5meter table?

#7

Ask your glass dealer😉

#8

I’m not sure what exactly you mean…

but for my home setup I use a tempered piece of glass for my table. I have a vacuum pump and I layup parts directly on the glass and then bag to the glass. I release the glass with wax and use epoxy resin.

At work we have aluminum tooling tables that are 1.5" thick or so. They’re machined for a tolerenced surface. These are on metal frames with casters and go into the oven. Parts are bagged directly to the tables. We release them with freekote.

I’m also working toward building a flat plate that is heated so I can make flat panels using vacuum and bolts to clamp the top to the bottom.

#9

Just opening up a discussion on vacuum tables, and hoping for some input from anyone who has made their own composite vac table tops.
In response to the last comment, is the aluminium table that you use milled from a cast or rolled plate?

#10

The only way toughend glass shatters is if it’s been impacted on the edges. I have a 6mm thick glass at 1.4x1.6m I learned the hard way with glass you can drop all sorts on it and really give it some well but edges get a tap and pop full lot goes

#11

It can also shatter if thick laminates cure. If you use the wrong resin you van get exothermic hot spots and they can cause the big plop. But if that happens you sonor so have a problem because parts of the laminate will be burned.

#12

Thanks

We laid up the 10mm QI C plate probably within 50mm (?) of the edges. Shattered during de moulding, so it makes sense now!

#13

Exotherm on the 10mm plate never went over 110 degrees. Not a problem for the tempered glass I wouldn’t think?

#14

No, everything below 250 Celsius should not be a problem. You should buy a glass with heat test.
If it shattered during demoulding you hit an edge or your release agend failed

#15

IF the glass shattered then it would have been toughened. Toughened glass is know for spontaneous breakage so an additional process of heat soaking is used. If the glass brakes in the head soaking its no good (obviously) the glass you had may have had some impurities in it that caused the glass to shatter when heated up.

toughened glass is also weak at the edges as it can not be toughened all the way the edge so they either need protection or keep away from them. From memory heat strengthened glass is heated to a higher temp than heat soaking so might be an option to get either

Laminate heat strengthen or toughened heat soaked. Heat soaking the glass is heated to around 280-300 deg so if your not exceeding that it will be fine.

#16

DDcompound, can you tell me more about the nanotube laced resin/paint that you used that allowed you to conduct current across your part and get heat out of it? Thanks!

#17

It is a paint from futur carbon.
www.future-carbon.de the page is in english

#18

Thanks a lot DD!

#19

Im sure this has been done within a resin has it to remove external heat sources?