Building a post cure oven, what shape is best

General Composites Discussions Composites Talk
#1

So I’m planning a post cure oven. Intended to be big enough for motorcycle pieces. I will be doing infusions and ooa prepregs.

My question is will the orientation of the mold (vertical or horizontal) have an impact on the final part while the resin is thinned at temperature? Will I possibly get pooling of resin if I stand a flat mold on end instead of laying it flat?

This would alter the shape of the oven if it does. I wanted a 3’x3’x5’ oven standing like a refrigerator for floor space minimization.

Thanks for the input.

#2

It shouldn’t matter. the resin is under vacuum, then the pressure will be equal and you shouldn’t really notice any difference. Ultimately building the oven that best suits your space is best. I would say that having a fan and keeping molds in the air flow would be the most important issue for an even temp through out the oven.

#3

That is not completely true, even under vacuum you can get resin pooling. The best way is horizontal position, also that works the easiest. You can also make a tall oven and make some different levels in it.

#4

You can get some pooling of resin. So if it’s critical then don’t do it. But I’ve cured plenty of parts standing vertically or on an angle rather than horizontally and don’t usually have any issues. It tends to be more of a problem if you make the part a bit too resin rich, so you’ve got less pressure on the bag and more resin to pool. If you get your ratios right then it doesn’t usually effect things much.

Depends a bit on the mould and part too of course.

#5

Also a horizontal oven will have less of a temperature difference top to bottom, though probably not a huge issue on parts of the size being discussed here

#6

Thanks guys, I guess I will plan the upright oven, parts may need to go in at 45 angle… not the worst thing.

#7

How could I design the plumbing hoses for vacuum through the wall of the oven? What type of fittings should I use and hoses?

Until now with my room temp infusions I was using PVC hoses without problems in collapse etc but with the higher heat (up to 120C) I’m betting the hose would get too soft and collapse cutting off vacuum…

#8

Typically you would have a steel tube go through the wall, then a manifold on the inside with quick disconnects to connect multiple vacuum hoses

#9

Any pics of what that might look like? I cant picture it…

#10

Not the best pics, but should give you a better idea

#11

What would be suitable tubing to use inside an oven? I’ve used PVC at room temp without problems, but it would either melt or become too soft and collapse at elevated oven temps.

#12

typically steel is used, but really depends on your curing temps. Check the rating on PVC tub and compare to your curing temp. IMO I would just make a steel manifold system as its not expensive.

#13

now I’m just trying to brainstorm on how I can affix it to the inner/outer walls of the oven and pass thru the insulation. I don’t have any welding capabilities…

If anyone has suggestions they are more than welcome.

I will document the build.

#14

You dont need to weld it. Just drill a hole and push the tube through. Its not an autoclave, so there no big deal doing it this way. I have seen many professional ovens this way.

#15

I’ll try and search for a threaded nipple of sorts…

#16

yea, you can definitely piece together a bunch of off the shelf threaded tubes and other fittings to make a nice manifold. check mcmaster-carr

#17

would teflon tape be sufficient for sealing or somethings else?

#18

thread tape? Its good. Once you set up your vacuum system just do a leak check on it. Best to use an absolute pressure gauge to check this.

#19

A1 manifolds us a great source for reasonably priced manifolds for vacuum and air line systems

#20

thanks I’ll have a look.