Heating blankets to post cure

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Heating blankets to post cure

Author	Message
67redrocket	67redrocket posted 9 Years Ago HOT Topic Details
Group: Forum Members Posts: 49, Visits: 486	I looking for post cure options. I want to make parts as large as a car hood, but I dont want to build a big oven. I have looked at these silicon heat blankets on ebay: http://stores.ebay.com/Flexible-Heaters/Silicone-Heater-Blankets-/_i.html?_fsub=10754115018&_sid=814680028&_trksid=p4634.c0.m322 They are probably way to powerful so I may have to find some one that is not that powerfull per sqare cm. Iam thinking i can put some of these under the mold and wrap the mold with the heating elements with wool blankets. Then meassuring the temperature and control the heating to get the right temperature. Maybe using a PID or a temperature switch. Any thoughts?
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Hanaldo	Hanaldo posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	That's how a lot of pre-preg boat hulls and aeroplane bodies are cured, so they do work. Quite a bit more involved than an oven though I think.
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FLD	FLD posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 468, Visits: 2.7K	I use an electric blanket and a duvet to post cure large parts. Works fairly well.
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67redrocket	67redrocket posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 49, Visits: 486	I will try this, I have ordered a PID controller, solidstate relay, heating pad and a bunch of Type C thermocouples. Thinking about it, I am wondering if I could have the heating molded in the mold. If I could find a suitable and cheap heating cable that has a constant w/m and is cut to fit. Then i could mold this in the middle of the fiberglass layers. any thoughts on this?
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Hanaldo	Hanaldo posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	I wouldn't. You want to keep in mind that PID controllers work by simply switching the heating elements on and off. The heating elements themselves still run at full power for the time they are on and can get very very hot. In an oven, blanket or aluminium mould this is OK, but if you had the heaters moulded into fibreglass then I think you would damage the resin around the elements. I think for things like this, the KISS rule is always a good idea... Edited 9 Years Ago by Hanaldo
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ajb100	ajb100 posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 346, Visits: 4.4K	Another vote for bed hot blanket and an aloof double duvet
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67redrocket	67redrocket posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 49, Visits: 486	Thank youfor the advice. I am familiar with PID controllers, I work with automation andprocess control daily. The trick to get this to work well Is probably to use aheating cable with moderate power and tune the regulator to have slow ramping against set point with no overshoot. The measured can be placed in the mold or in the vacuum stack. Each mold would require tuning and different PI parameters to be optimal. Far away from KISS but still a interesting thought. Hanaldo (20/04/2016) I wouldn't. You want to keep in mind that PID controllers work by simply switching the heating elements on and off. The heating elements themselves still run at full power for the time they are on and can get very very hot. In an oven, blanket or aluminium mould this is OK, but if you had the heaters moulded into fibreglass then I think you would damage the resin around the elements. I think for things like this, the KISS rule is always a good idea... Edited 9 Years Ago by 67redrocket
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Warren (Staff)	Warren (Staff) posted 9 Years Ago HOT Post Details
Group: Administrators Posts: 2.5K, Visits: 8.5K	Postcuring to reasonable temperatures can be done with a simple electric blanket and duvet for insulation. Modern blankets have a temperature safety cut out so should not get too hot. However, fire safety is a priority and we recommend not to leave it unsupervised just incase something were to go wrong or the blanket heating combined with exotherming of the resin is enough to set it alight. In home experimentation, in a 20C room I have seen 60C on the mould surface of a medium sized mould wrapped in a double heated blanket and double duvet, so useful temperatures can be achieved. Even in the garage where the temperature was hovering at 10-15C I would easily get it to 40C and above so for the cost can be a worth while "DIY" method of postcuring without an oven. Warren Penalver Easy Composites / Carbon Mods - Technical Support Assistant
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Dravis	Dravis posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 592, Visits: 1.9K	If you can make do with 99 deg. C.. why not mould in silicone hose .. then run hot water through the mould .. No fire-danger -- the temperature can be quite precisely controlled (Large tank of water, high capacity water pump, PID controlled heating of the water) On alu-moulds, use heated oil .. I just use polythene bags of hot water and old fleece blankets for insulation -- Not to post cure but to speed up the primary cure .. Could be used for post-cure as well -- "Sapere Aude"... Dare to KNOW! The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind... 103% of all people do not understand statistics... Do not adjust our mind, theres a fault in reality :-)
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