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Jess8bit
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Hi guys, Do you take any particular precaution when you trim your part with your Dremel ? How do you protect the surface from scratches that may occur during the trimming ? I've had this problem : the srface was nice after demolding. After triiming the part, I've jad the bad surprise of observing many scratches and holes in the surface. My assumption is that I made the scratches myself simply by holding the part with my hand (with gloves on) and handling it durng the process (maybe because of carbone dust ?). Hence the question. I'm thinking about covering the surface with a plastic film hold by masking tape all around the part edges. What do you think ? thank you !!
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NikCFC
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Unless dremel hit the surface of the item I don't see any reason how just holding the piece the surface could be damaged. Maybe you washed the item after cutting it and then the defects appeared.
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Jess8bit
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well, no, it was not the Dremel, I did not hit the surface with the tool, but, does the carbon dust squeezed beteween the glove and the part surface could be responsible for such abrasion ? I must precise that there was not any gel coat added to the mold before starting infusion, so the epoxy layer is probably very thin. Could that explain such fragility ? Maybe a picture could help, don't know if you can see very well though 
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fgayford
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It almost looks like the epoxy is not cured to a hard state and the sanding dust is fusing into the soft surface?
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carboncactus
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Jess8bit (05/06/2013)
well, no, it was not the Dremel, I did not hit the surface with the tool, but, does the carbon dust squeezed beteween the glove and the part surface could be responsible for such abrasion ? I must precise that there was not any gel coat added to the mold before starting infusion, so the epoxy layer is probably very thin. Could that explain such fragility ? Maybe a picture could help, don't know if you can see very well though The epoxy layer is going to be very tough. If you didnt hit the surface with the tip, you might have scratched it with the chuck (the piece of the dremmel that spins while it holds the bit), or even the handle, as its vibrating. I have made parts completely useless by not being careful. With air and power tools, mainly spinning ones, you have to be very predictive of how they are going to behave when the abrasive touches the composite in different angles and different parts of the bit/saw. I've had tools catching the part in a nasty way and the tool goes flying either into the air, or worse - the part, or worst - your face/limb. Care is of the upmost with them. If you do end up scuffing the part, worst case you can car body fill it, prime it and paint it. But sometimes you can build up clear coat, sanding between coats.
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carboncactus
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And whats wrong with this forum? it keeps putting comments INSIDE the quote! 
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Jess8bit
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fgayford (05/06/2013)
It almost looks like the epoxy is not cured to a hard state and the sanding dust is fusing into the soft surface?It's a interesting guess Fred. And Yet I left the part cured for 24hrs @20°C before demolding. Maybe I should wait for 36 hrs to be sure and eliminate this hypothesis.
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Jess8bit
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carboncactus (05/06/2013)
The epoxy layer is going to be very tough. If you didnt hit the surface with the tip, you might have scratched it with the chuck (the piece of the dremmel that spins while it holds the bit), or even the handle, as its vibrating. I have made parts completely useless by not being careful. With air and power tools, mainly spinning ones, you have to be very predictive of how they are going to behave when the abrasive touches the composite in different angles and different parts of the bit/saw. I've had tools catching the part in a nasty way and the tool goes flying either into the air, or worse - the part, or worst - your face/limb. Care is of the upmost with them. If you do end up scuffing the part, worst case you can car body fill it, prime it and paint it. But sometimes you can build up clear coat, sanding between coats. I'm very aware of the individual risks. When handling my Dermel, I always wear a mask that cover the whole face, and a pair of kevlar/nitrile gloves (the one I suspect to damage the siurface with carbon dust). I assure you I do not let the tool touching the surface, that can't be the culprit (I feel pretty sure of it). It's something else in the process I'm doing wrong. I plan to make a new part in one or two day, I'll share the results with you. Thank you for your help guys
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Jess8bit
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same problem with quotes by the way 
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carboncactus
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Looking at that last picture....... Take a heat gun to the surface for a couple of minutes. I have taken prepreg parts out of the oven and they looked a bit flakey. Like dry skin, sort of. Applied heat and the epoxy gelled a bit then fully cured, absorbing the dryness.
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