I’m wondering if anyone uses coremat to build thickness and rigidity into their molds?
I’m looking at using the 2mm stuff and hoping to use it instead of layers and layers of time consuming glass. Is it suitable for wet lay open molding?
Also any concerns with dimensional stability if used in an oven for postcuring in mold?
I use it on my big moulds like bonnets etc. Seems to work just fine, I haven’t noticed any defects because of it.
I don’t post-cure in an oven though, don’t have one big enough for these size parts. In summer I put them in the sun and they reach 90-100 degrees with no stability issues, so I imagine they would be fine in an oven too.
Any insight into which thickness should be used?
What is your lay up schedule?
I think it depends on the size of the job. For anything small, like less than 0.5sqm, I just make it monolithic fibreglass, no core. Cores aren’t cheap, fibreglass is, so it only makes sense when I’m laying up big things and it saves me 2 hours of lay up time.
For bigger moulds, say 1sqm, I’ll use 3mm coremat. My normal layup schedule is 225 csm for the skin coat. Then once that’s cured I follow it up with 2 layers 450 csm, then the core, then another 2 layers 450. I don’t place the core over the entire part unless it’s completely flat, I cut sections to size to fit any large flat areas that will be prone to flex. For moulds that need to be especially solid, I’ll follow up the skin coat with 2 layers 450 csm > core > 1 layers 850g woven rovings > 2 layers 450.
And for any moulds that are very large, say >2m in any direction, I do the same layup schedule as above including the woven rovings. Then once it’s cured, I’ll cut lengths of 16mm thick MDF, and bond them on vertically with epoxy adhesive. That makes for a super stiff mould, and using quality low shrink vinyl esters and tooling resins I’ve never had any issues with print through or distortion.
A word of caution when using Coremat - use plenty of resin. It is prone to shear if it is not thoroughly wet out. This is not as big a deal with a mold as it would be with a part that sees some dynamic loading, but if you can avoid a possible problem, why not?