Help me get started on a complex mold

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#1

Hey guys,
I have been working with fiberglass and CF for a number of years now… But never anything overly complex, just your standard overlays, single piece molds and general fabrication.
I have come across an opportunity to make a couple reproductions of some pretty complex pieces. I have attached some pictures of the piece I am looking to reproduce and would like to get a few ideas from some of you seasoned mold builders out there.

What would be the best plan of attack for these? Alignment of the tabs on the back will be critical. Also, what material would be best for the tabs on the back once the mold is in service?

I can clearly tell that this original piece is glued together, there is a front skin and the rear bracing. I will be unable to separate these pieces, so I am in need of another plan of attack.



Thanks much!!

#2

You will not be able to mould off the back side of that part, it is too complex. A better idea for those parts would be to get several of the origional plastic parts and overlay them.

#3

The OEM piece is $600… so unfortunately that is not cost effective. And this piece is actually cast aluminum.

I was thinking that I will need to mold the tabs separately from the rest of the piece and attach them post cure. Thoughts?

#4

I think you can do a simple one piece mold to build the overall(face) piece and then do a separate simple “L” angle mold to layup some bracket stock. Just make the L angle stock and cut all of your brackets from it. Cut/trim out your individual pieces, drill your holes and glue the pieces into place like the original tabs and standoffs.

#5

I’m with Finite here…make the facing one piece, and the tabs as angle pieces bonded on. I would try to make a fixture for the tabs, so they always remain in the correct position during bonding.
However, not sure what you can do about the “thing” in the opening. Hard to see in the pics provided…those might be able to be molded with the face sheet.

#6

What are they for and how many are you planning to make? I may have a solution for you.

#7

Thanks for all the reponses guys, this forum is proving itself quickly! :smiley:

This piece is an interior trim piece from a BMW. The cutout is for the radio and will be easily molded as part of the front piece. I am mainly worried about the tabs and getting the proper alignment and depth setup on the reproduction.

I will be reproducing a minimum of 10 pieces and will have no maximum production. Please inform me on this potential solution :slight_smile:

#8

[FONT=Tahoma]Those tabs are going to be interesting. Molding with silicone then epoxy casting the panel might do it, then you would need a mold to bond the finish carbon to the cast panel perfectly. Basically two molds - one silicone, and one hard epoxy.

Why not just do a thin clip on carbon piece? Is the interface to adjacent panels an issue?

Is the silver piece crimped to the die cast part? Hard to tell from those pictures.[/FONT]

#9

It looks to actually be bonded with some type of adhesive… If you look right on the edges you can see a 1/32" of adhesive between the sandwiched pieces.

Are you suggesting that I actually mold the back piece and pour cast it with epoxy?

#10

Yes, why not. You can even load an empty caulk cartridge with epoxy and a mixture of (carbon) fibres, then inject the mould.

Making the silicone mould can be a challenge, for the holes in the lips, but that can be solved. (2 piece mould, actually a 3 piece mould, for the face plate). Some bracing or a support mould can be neccsary to keep things in shape.

Then make the face plate, and glue or putty it on.

Or if possible, make a clip-on face plate. Much simpler. 1980’s wooden dashboards were made that way every time. We just glued them in place with CA glue.

#11

Yep, the holes that are in the tabs should be filled with clay or some thing before making the mold. These can be drilled into the epoxy castings after. Really a pain though…

Why not do a swap out program where you remove the silver piece then install a new carbon one in the same fashion the manufacturer has? That way you can avoid the hassle replicating the die cast part.

#12

I am unable to do the swap out program as some of the units will be shipped out of state. I am liking the ideas flowing so far!!

I think I’ll need to make some sort of Jig to make sure I get the rear tab alignment and depth perfect every time. The front portion can be done with a single piece mold.

#13

Don’t fill the holes with clay, that will cost you too much time for redrilling. Just make sure there is a separation line halfway the hole in your silicone mould. That way you just need to true up the holes a bit after demoulding. Time is your enemy here, definately with 10+ castings.

#14

Regarding the backside…one option would be to make a Platinum silicone mold (backed up with a rigid fiberglass glove)2 parts in the end.

You would then cast the interior of the silicone flexible mold with a spec shore hardness resin. (similar to what plastic dashes consist of).

Then once de-molded from the silicone,it could be secondarily bonded to the previously molded front CF side and re-use the factory spring-clips that held it tight.

In effect…you’ll end up with similar results to how the whole cast base plate bonded to outer alloy skin shown in your images.

#15

Appreicate the ideas guys! I will definately post pics as I move into this process over the weekend.

I am however, interested to hear what TET has to say as well!

#16

make a bucket mold out of silicone… then mix up resin and light weight filler ( the stuff you fill surfboard core repairs with, basically fiberglass dust) mix hot. pour into the silicone mould and have a tounge depressor stuck into the mix. like a popsicle. then when it kicks just pull the tabs out…

tip #1

fill the holes with clay and get them nice and smooth. then take a thumb tack and poke a very small center mark so you can drill later accurately.

tip 2:
a separate mould should be made for all tabs. mix enough resin for the main panel infusion plus all the tabs. when youve got your part completely wet out. mix the light wieght filler in the left over resin from the resivour and begin pouring into the silicone tab moulds.

tip 3.
make a dependable tool that locates all tabs with the main panel fixed. this fixture should allow you to bolt the tabs to the fixture and then clamp the main panel to the tabs for bonding.

tip 4.
Mix black coloring into the tab resin mixture so that you cannot tell it is a pour…

there are alot of materials you can use as your filler… balsa sawdust (safe and cheap), phenalic dust (health hazard), micro ballons (health hazard), fiber glass dust (irritant and hazard). ect… be creative and test out a sample pour on a piece of glass or a bondo board to get in idea of how strong the tabs will be when finished. balsa dust is suprisingly strong and with a wet mixture pours extremely well.

#17

Awesome ideas!! I am going to start playing around tomorrow morning, I’ll get some pics of my progress up soon. I am almost considering even making a sand mold and casting my own aluminum tabs…

#18

lol that would be awesome… but might as well do it with resin. you could do it with plaster but silicone would make a dependable multi use system. good luck

#19

This complex part need silicone / rubber. You have to make border to all the part and then (First you must mixed the silicone with harderner) fill all the part with silicone / rubber. After 24 hours your mold is ready and you can take it out very easy. Then you can fill your mould with polyester or epoxy or enything else.