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Thomb
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Group: Forum Members
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Hi all, Im still having some problems with the xpreg in gelcoat moulds. When i use aluminium moulds all is good. When i use the high temp gelcoat moulds i always get a dry finish on the mould side. I tried some longer times and diffrent temperatures but i keep getting these results. I only use breather underneath the mould but that always worked for me and only the bag where it it packed in to press on the carbon. Does anyone have a clue what could be it or what i can try? 
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Lester Populaire
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Group: Forum Members
Posts: 311,
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+xHi all, Im still having some problems with the xpreg in gelcoat moulds. When i use aluminium moulds all is good. When i use the high temp gelcoat moulds i always get a dry finish on the mould side. I tried some longer times and diffrent temperatures but i keep getting these results. I only use breather underneath the mould but that always worked for me and only the bag where it it packed in to press on the carbon. Does anyone have a clue what could be it or what i can try? Sounds like a temperature ramp problem to me. The aluminium moulds probably have a way higher mass and heat slower than a composite mould. Would probably be worth to stick a temperature probe in there and monitor that!
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Shaneer22
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Group: Forum Members
Posts: 156,
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+x+xHi all, Im still having some problems with the xpreg in gelcoat moulds. When i use aluminium moulds all is good. When i use the high temp gelcoat moulds i always get a dry finish on the mould side. I tried some longer times and diffrent temperatures but i keep getting these results. I only use breather underneath the mould but that always worked for me and only the bag where it it packed in to press on the carbon. Does anyone have a clue what could be it or what i can try? Sounds like a temperature ramp problem to me. The aluminium moulds probably have a way higher mass and heat slower than a composite mould. Would probably be worth to stick a temperature probe in there and monitor that! Having similar problems myself.i wonder if it's the way the molds heat up due thickness and expansion.
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Hanaldo
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How did you post cure the mould before putting it into service? And has the mould lost its surface finish at all, or only the components you make from it?
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Shaneer22
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Group: Forum Members
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+xHow did you post cure the mould before putting it into service? And has the mould lost its surface finish at all, or only the components you make from it? Would the surface finish affect resin flow.if the surface is Matt finish or satin how would that affect resin flow.
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Thomb
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Group: Forum Members
Posts: 23,
Visits: 656
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+xHow did you post cure the mould before putting it into service? And has the mould lost its surface finish at all, or only the components you make from it? post cure done just like datasheet, mould is still the same after each release, its just the carbon that is dry and full of pinholes. and always with the 160 high temp epoxy moulding stuff.
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Thomb
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Group: Forum Members
Posts: 23,
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So a little update, I tried various temps and soaks but the end result is the same, always these dry finishes. I tired a little 5x5cm piece same 2 layers in the same mould and this comes out perfectly. What i am doing wrong? already tried with perforated release film and peelply on the back but same results. Result with small carbon layup in same mould with same times: 
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Chris Rogers
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Group: Forum Members
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What are you using for a bag stack - peel ply, perf film, breather - on top of the laminate? You mentioned using breather under the mold - not sure what you mean... you need a way for the air to escape so a breather ply over the peel ply and perforated release film is necessary. Totally agree on the heat ramp idea - resin viscosity vs cure onset temperature could be a problem. The slower the ramp rate the lower the resin viscosity gets before gel starts. Seems you tried that. Mold surface finish can effect surface tension and the ease with which air escapes the mold surface... metal molds always seem to leave nicer finishes... or at least fewer pinholes. The small sample suggest an air-entrapment or moisture issue. Is the part only one layer? Did you debulk the first ply into the mold before laying up more? What is the release coating?
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Hanaldo
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Group: Forum Members
Posts: 2.5K,
Visits: 28K
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+xWhat are you using for a bag stack - peel ply, perf film, breather - on top of the laminate? You mentioned using breather under the mold - not sure what you mean... you need a way for the air to escape so a breather ply over the peel ply and perforated release film is necessary. Totally agree on the heat ramp idea - resin viscosity vs cure onset temperature could be a problem. The slower the ramp rate the lower the resin viscosity gets before gel starts. Seems you tried that. Mold surface finish can effect surface tension and the ease with which air escapes the mold surface... metal molds always seem to leave nicer finishes... or at least fewer pinholes. The small sample suggest an air-entrapment or moisture issue. Is the part only one layer? Did you debulk the first ply into the mold before laying up more? What is the release coating? XC110 requires an unperforated release film with the breather only on the back of the mould. But unusual, but can confirm it works perfectly like this. Thomb, your test result is very interesting. Was this sample made with the exact same batch of pre-preg that you have been using to make the parts with?
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Thomb
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Group: Forum Members
Posts: 23,
Visits: 656
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+x+xWhat are you using for a bag stack - peel ply, perf film, breather - on top of the laminate? You mentioned using breather under the mold - not sure what you mean... you need a way for the air to escape so a breather ply over the peel ply and perforated release film is necessary. Totally agree on the heat ramp idea - resin viscosity vs cure onset temperature could be a problem. The slower the ramp rate the lower the resin viscosity gets before gel starts. Seems you tried that. Mold surface finish can effect surface tension and the ease with which air escapes the mold surface... metal molds always seem to leave nicer finishes... or at least fewer pinholes. The small sample suggest an air-entrapment or moisture issue. Is the part only one layer? Did you debulk the first ply into the mold before laying up more? What is the release coating? XC110 requires an unperforated release film with the breather only on the back of the mould. But unusual, but can confirm it works perfectly like this. Thomb, your test result is very interesting. Was this sample made with the exact same batch of pre-preg that you have been using to make the parts with? Yes same prepreg same mould same times.
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