mold help

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#1

Hi this is my first post here and I would like some technical advice regarding a mold I own.

The picture attached shows a seat mold however the picture doesn’t show properly what the issue I “will” have if I make a part in it.

If you could imagine sitting in the seat mold on the side parts that your backside would sit/touch this area has a negative draft. If you could imagine having a large backside if you got past the uprights of the seat there is a larger cavity deep in the seat!!

So if anything is layed up in this mold it will more than probably won’t be able to pop out.

So the only way I can see being able to use this mold is to cut the mold in half from the bottom of the picture to the top(black line). Remake a flange on the back of the mold and same for the opposite half.

This is the only thought I have had and can’t come up with another less invasive approach. I do however know I will loose the width of the cut if I go down this road. I believe this will probably leave me a part line(prefer not to have one).

Im willing to make support brackets and aligning points before I cut the mold in half so I can keep it in perfect alignment to minimise the creation of a part line.

Can anyone shed any light on what I can do to turn it into a 2 part mold or how they would approach this? P.S I didn’t make this mold.

#2

tuff saying but you may be suprised, looks like the seat maybe be able to get pulled forward out of the mold. whoever made the mold got the plug out. Try making a thin part first to see how well it pulls out. no reason to cut up a mold unless your sure.

#3

The plug came out, so the parts should to. View it at different angles and you should find the way to pop out the parts.

#4

Yea, since the plug came out your item will also, just make sure you put few gooooood release coats of wax or pva, especially for the lower corners. Also the way I see the mold I can assume that the item made will be able to flex a bit so it will help you with the release.

#5

Thanks for the input. I do not if they got the plug out without destroying it. This i cannot be sure of. I want to lay this up with pregreg and make a one stop part ready for service. i do not have the ability to “try” if this will pop out. I haven’t included in the post but when i got the mold it had a layed up fiberglass uni with 2-3 layers skin in it from what i can see. It was wedged into the mold and i tried to remove it. It was a little difficult but it did come out without breaking. However 3 layers of cloth without reinforcement is a fair bit different to something that has a solid core and a few layers of carbon facing it.

Does anyone here ever seen a seat mold like this? are they one piece or 2 section mold.

The issue i have is i do not know if the part will have enough give to get it out or if the part is layed up heavy it will have little flex to pull it out.

Maybe do 2 skin layers and vacuum a core down and then pull it out and then finish it off outside the mold with additional layers?

#6

I suggest to make in the middle of the mold some very-very small holes (maybe 2, one in the middle and one in the upper side). When you make the part you can close them with just a tape. When the part is qure then take the air gun and put it in one of the holes that you create in the past. This will make strong pressure to the part for take it off. Usually i do the same for my parts.

Notice: The air compressor must be strong.:smiley:

#7

i made a mold out of a fiberglass sparco seat. after studying the original seat i saw that there are no parting lines that would suggest the use of a two piece mold, so i did a one piece. the original came out fine, though it was tough, but after i will have conditioned the mold, the parts should release easily. if your mold really has negative drafts, then all you can do is cut it i guess…

#8

Since it has several 90 bends and large flat sides, if the sides were not braced well, it is very likely that the sides caved in (warped) somewhat and what used to be a 1-2 degree positive draft on the sides is now a 1-2 degree negative draft, so even if the plug pulled out originally, the mould would snap into a new shape at the very moment the plug is removed and get worse as time goes on. This problem is especially true with polyester moulds with a high resin to glass ratio, not so much with epoxy moulds. If you can’t get the part out, I’ll be happy to help you with the technique of splitting it and still having keys, flanges and a tight seam, it is a little work though.

#9

Don’t glass the edges as that seat mold was meant to only have straight up edges. No flange as that is there to strengthen the mold only.

The laid up part will shrink some so that also will help to remove the part too…

#10

Actually, on my Sparco race seats they do have that U shape around the perimeter. It stiffens the seat quite a bit, and the fabric covering has a stretch cord that wraps around that.

#11

OK, makes sense to me but my oval track race seats are all just the flat edge…but then they are Alum.!