Large tooling plate for prepreg

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#1

I have been asked to make some rather large flat panels of prepreg and nomex honeycomb. The panels are 70" long and 35" wide. I typically use polished aluminum plate for this type of work, but the largest plate I have is 36"x30"… Question being, any reccomendations for a large true layup surface for a reasonable cost?

The only thing I am coming up with is holding down a sheet of mylar to flat piece of MDF, and then covering the whole thing with high temp tooling gel, then lay down some glass, honeycomb core, more glass and then maybe some angle aluminum to support? Does anyone have experience with that - I fear the thermal expansion on the aluminum will cause problems, but I have never tried. Any ideas are welcome! Thanks

#2

tempered sheet glass would work great. or you could make a carbon tool off the glass

#3

Thanks -that is a great idea. Its okay to heat cycle it obviously? You think this would have occured to me, seeing as though 4 blocks away is Chicago Tempered Glass Company…ha. Will give them a call, thanks!

#4

yea, it will be fine of course. and its really cheap so if after awhile it breaks due to handling you can replace at very low cost.

#5

I would suggest speaking to a metals supply and price it out. A 4x8 plate is not going to kill you financially. And if you can afford it this go around the next time it’s needed it’s paid or itself. Also depending on grade it might be more financially appealing to you because you may be able to return it or sell it as scrap at the end if the project. Buying a piece of glass is a good option but you can’t build fixtures. Machine or reuse for multiple purposes… As much.

#6

Go with the glass as said before, just make sure it’s 1/4 or 1/2 inch thick so it won’t try to bow under it’s own weight and break while your moving it. Also you can heat cycle it as many times as you like, ive cured parts up to 350+ and probably hundred cycles on each piece of glass. The only downside to the glas is that it scratches easily, and whatever you use for release can make the glass become hazy. It can easly be cleaned with a fine steel wool. I think we were paying $75 for a sheet of glass 28 x 68

#7

Use tempered glass, which is more heat resistant. One thing to be aware of, is that glass, especially tempered glass, is not completely flat. But usually not a problem.

Try and get a piece that was ordered by someone in the wrong dimensions. Most glass companies have stuff like that lying around, which can be bought cheaply.

#8

Check with all metal suppliers in the area. If they don’t have, they might know who has one. It doesn’t seem that large, and I know I’ve worked with one giant sheets of aluminum before (i forget the actual size)
We used a large 1/2" plate for the bottom, and 1/4" for the top. Used rectangle tubing as the mold sides (Sure you can get away with rod bars, or flats, depending on your core thickness.)

#9

Thanks for all of the input guys. I got a quote for aluminum, just shy of the size I need and it was nearly a grand, asked for a glass quote this morning. That said, my oven opens towards the sky, so I am going to have to devise a sort of winch system to lower this is in (just me in the shop) and either glass or aluminum is going to be HEAVY!

#10

That sounds something like what im making up at the moment. Its 6mm safety glass backed with 12mm MDF thats 1200mm x 1600mm. I’ve got a rubber gasket all the way round the edge of the glass. Vac bag sheet is attached to a 9mm MDF frame and breach unit.
I need to find a way to winch it to the roof of the workshop as its not the lightest of molds i have!

#11

Oven opens from the top??? Tip it over man…

#12

I wish it were as easy as that, the dimensions or only able to accomodate this piece in this orientation. I made my oven out of a giant file storage cabinet. 74"x40"x24" … it actually works quite well… I think I am going to cut a door in the end, lay some tracks on the bottom, and that way I can slide it in.