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nreindel
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+xCould just be your aluminium mould is sucking up much of the heat so assuming you are just measuring the air temp and timing from this your part is under cooked as it takes 45min to heat a mould like that. I usually put my oven controller thermocouple in the air and just set my cure time to be 1 hour more than the cure time stated. You can't overcook it but you can under cook it. How did you come up with 45 min. extra cure time for OP's mold size? Is there a good rule of thumb to calculate cook time to add by mold mass/volume?
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f1rob
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Just get a remote thermocouple or you pid one and tape it to the bag of your laminate at it's thickest point.
You won't be too far off the temp of your laminate.
If your final cure temp is 1hr at temp at the very least allow 1.5 hrs,preferably 2hr extra as an allowance for an Ali tool
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Jeff Clemmons
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+xI'd also recommend buying a remote thermocouple unit. You can buy these fairly cheaply on places like Ebay If you get one that has two probe wires, long enough to extend outside of your oven, you can gum tape the ends onto selected places on the part in the mould and monitor actual temperatures there rather than reply upon the fixed thermocouple on your oven set-up These will, hopefully, provide you with much better assurance of the temperature your mould is running at My idea exactly Mark, I already have a remote thermocouple unit. I have drilled holes about 3/4 the way through the mould from the bottom and plan to manually read the temperatures of the mould itself at various points in the mould during a dry run through a cycle. I put 9 holes in it, some close to the cavity, some near the edges of the mold. Once I know how long it take to get the entire mould to the soak temp, I should be able to merely add that amount of time to the suggested soak time and everything work. I plan on running this test this weekend. Thanks for your suggestions!
JC
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Jeff Clemmons
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So what I have done is drilled holes up through the bottom of the mould which are 1 1/2" deep in 2" mould. My plan is to run the mould empty through a cycle and testing various places in the mould as it heats. Once I see that the entire mould is up to temp, I will add that amount of time to the "soak" time. That way my air inside the mould isn't ramping to quick and I will know everything is leveled of at the correct soak temp. I plan on running this test this weekend. Thank for the comments guys!
JC
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Fasta
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+xPlacing thermocouples in direct contact with an aluminium mould can also cause trouble though, as the PID thinks the oven isn't heating up and so it tries to crank the heat as fast is it can. This heats the air up to extreme temperatures, so you can lose control of your ramp rates and your soak temp. This is the exact reason I read from the air with a heavy metal mould. I also cook multiple parts/moulds of different sizes in the each cooking session. When oven goes crazy trying to heat a metal mould at 2 deg per min the heat from the elements just run flat out can fry the other parts a bit with near burnt bags from the radiant heat. Just adding an extra hour to the cure time means that all the parts get enough and work out. In the end all that matters is that a part gets it correct cure temp for at least the minimum time.
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Hanaldo
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Placing thermocouples in direct contact with an aluminium mould can also cause trouble though, as the PID thinks the oven isn't heating up and so it tries to crank the heat as fast is it can. This heats the air up to extreme temperatures, so you can lose control of your ramp rates and your soak temp.
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MarkMK
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I'd also recommend buying a remote thermocouple unit. You can buy these fairly cheaply on places like Ebay
If you get one that has two probe wires, long enough to extend outside of your oven, you can gum tape the ends onto selected places on the part in the mould and monitor actual temperatures there rather than reply upon the fixed thermocouple on your oven set-up
These will, hopefully, provide you with much better assurance of the temperature your mould is running at
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Warren (Staff)
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Yes you can't really cure for too long. You can "overcook" it in the sense that you use too high a temperature for the resin system or you ramp up too quickly for the resin to flow properly.
Leave it in the oven to naturally cool before demoulding. it is possible that with a large mass billet tool at high temperature and a cool air the other side of the carbon, it sets up some slight cooling warping causing pre-release and potentially some surface dulling or print issues. Although it would be hard to be sure if this is significant without testing it.
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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Jeff Clemmons
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Thanks Warren,
I'll get those things done. Do you agree with the statement " You can't overcook it but you can under cook it." ? Also, when it says at the end of the cycle to let everything air cool, would you suggest leaving the oven over the mold and waiting till its all cool, or raising the oven off so it can cool quicker. I raised it off as soon as the high temp cycle was done, and I'm thinking that may have been the wrong thing to do.
JC
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Warren (Staff)
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Air circulation probably won't help. You might want to add some insulation to help improve efficiency. Also a rubber seal around the base to help reduce the escape of hot air. Knowing the temperature at the mould face would be ideal as you can then taylor the cure cycle to take into account how the mould heats up.
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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