Alternatives to Polyester for Molds

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#1

Hi guys

I need to build a 10m2 mold. If I build this mold with Optimold II I get according to the user manual a weight of 18 kg per square meter after laminating 7 layers of 450g/m mats. That makes for a total of 180 kg for a single polyester mold. I am worried about the handling of such mold. It will require 4 people when ever i need to manipulate the mold. I am even worried if it will break at the middle if lifted from the ends.
Are there any alternatives to poliester? Can anybody recommend a cheap epoxy system suitable for molds (no shrinkage…)? How many layers would I need to laminate if I use epoxy instead and how much weight could I save?

#2

Polyester is most definitely the least expensive option, but a mold of that size will be heavy. Epoxy and mat will be nearly the same weight, but will be stronger and will have less shrinkage. Using epoxy, you will be able to get away using fewer layers of mat lamination, which will reduce weight. Another option is to laminate fewer layers, and back the mold with some heavier pour foam, 8lb or more. This will greatly increase the strength of the mold and reduce flex, and will most likely yield a lighter weight mold that can be manageable.

Foam has a tenancy to shrink as well, so you want to complete the entire laminating process followed by the foam backing before you de-mold the plug, very important.

#3

You can skip 1 or 2 layers of 450g/m. I make my mold with 1 layer 450 with a vinylester and then 4 or 5 layers optimold or a similair resin system. Epoxy isn’t going to give you big amounts of extra stiffness. A mold off this size is going to be heavy. For strenght you can add some metal or aluminium profiles at the back, but this is not the best solution when you’re going to cure them in a oven. You can also add a sandwich or a honeycomb to make if stiffer and stronger.

#4

Thanks for the replies.
The user manual states that you need 1,75kg of optimold resin for every square meter of 450 g/m2 mat. That sounds too much to me. How much resin do you consum per m2 in your molds?

#5

Nope, 1.75kg sounds spot on. Tooling resins like optimould need to be layed up at a resin:fibre ratio of 4:1.

I’m not sure, but I believe this will be because of the expanding additive in the resin. It makes the resin heavier, so you’ve got less resin per kg. The fibreglass still needs the same amount of resin, so you need to use more to wet out the fabric.

#6

I build my big toolings with Lantor Coremat XM 10mm, resin uptake is 6.5 Kgr./m2

#7

Do you combine the Lantor Coremat with poliester resin or epoxy?

#8

I utilize polyester resin, not Optimold but something similar, Nord Composites tooling resin that I combine with CSM 450 gr/m2 and Lantor Coremat XM 10mm to build my big toolings. Resin uptake is 1.1 Kgr. of resin for square meter of CSM 450gr/m2.

#9

Very interesting. Nord Composites was my other alternative. Would you be so kind to describe how many layers of 450 mat you wet out below and above the coremat?
Do you laminate in one shot or like in Optimold where you laminate 4 layers and afterwards 3 additional layers?

#10

I laminate in two shots. First was three layers of CSM 300gr/m2 with vinylester resin also Nord Composites. Second shot with three layers of CSM 450gr/m2 - Lantor Coremat XM 10mm - two layers of CSM 450 gr/m2, all this with polyester resin.

#11

If you don´t want to utilize two different resins, first shot with polyester tooling resin is also ok, but build it in two shots is important to achieve better quality tooling

#12

The layup you propose would save 1 kg per m2, if I count 1,1kg of resin per layer of 450g/m2 mat. With such a thick layup schedule, dont you get elevated exothermal reactions?
Using Coremat looks to me in this context as an intelligent solution. Like it.
Do you have any preference between nord rm2500, rm2550 or rm3000?

#13

I think you are thinking wrong here, a good mold is heavy (in this case). Maybe you can save 10 or 20 kilo on your mold but does that make a difference ? It will be a heavy mold and it will be difficult to handle or it is 150 kilo or 200 kilo. On a 10 m mold I whould think about making it stronger and not lighter.

I prefer optimold over rm 2000 and rm 3000 because price, smell, heat and the wetout of the glas.

#14

No problem with exotherm, I prefer RM 1000/50 it´s slow cure time.

#15

Thanks for your help. Will ask the distributor for information on RM 1000/50. Didnt knew that product.
Just wonder if laying on one side three layers and on the other side of the coremat 2 layers could produce distortions due to the asymetry.

I prefer optimold over rm 2000 and rm 3000 because price, smell, heat and the wetout of the glas.
I believe Nord resins are cheaper than OPtimold. A sandwich structure should be stronger I believe.

#16

180 kg for a 10 sq m mould is not heavy. Mount it on wheels and put plenty of lifting points on it. There is a reason why shops with large moulds have plenty of chain blocks.