General Discussion

Topic: DIY Curing Oven help 

1.  DIY Curing Oven help

This message was posted by a user wishing to remain anonymous
Posted 28 days ago
This message was posted by a user wishing to remain anonymous

Hey everyone, Our college student club participates in the SAMPE Beam competition every year. We've been using donated (and usually expired) CF/GF prepreg to make 24" long I beams for the competition. This year however we don't have access to an industrial oven/autoclave, and we are (desperately) thinking of making our own. We have a fairly decent budget (not enough to buy an industrial oven ourselves tho). However we don't have a lot of hands on experience in oven making. Are there any good resources/DIY guides on that? Any help will be greatly appreciated. For reference the material we have has a cure temp of 250-300F. Since we'd cure our beams with tooling material (usually aluminum bars), we'd probably need inner dimensions to be 14" x 26" x 10". Power bills are not an issue since we use university resources anyway. An idea that was floated around was to simply modify and extend a regular kitchen oven and add heat guns for even heat distribution. Thoughts? Ideas? Thank you!


2.  RE: DIY Curing Oven help

Posted 27 days ago
​I have taken a simple kitchen oven and wired it to the lower heating element a proportional controller of my design. It runs off 220 VAC and is stable at any set point between 50-200 degree centigrade. In my application I needed to measure air speed at elevated temperatures. Hence, I drilled a hole in the side of the oven and through a shaft controlled  the air speed inside the oven. I calibrate my air flow sensors by doing this. If you go to wind-probe,com you can learn about our product. Good luck.

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Harvey Harrison
President of Wind Probe LLC
Andover MA
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3.  RE: DIY Curing Oven help

Posted 27 days ago
Fairly simple solution as folks do this often when they have large structures but small ovens. It is not unusual to "build your own "oven" surrounding the part you need to cure. Typically one builds a framework of fairly open cell metal cage material (say Lowe's hardware store 2-inch cell size, heavy gage metal (not plastic). Find some insulation material that will not burn to cover the exterior set up heat lamps (typically infrared) on metal frame stands inside the larger overn "shell" you made. Employ fans toward the end of your new "oven" to move and circulate air. Have safe distances away from anything flammable. Sometimes even a small frame close to part (say 2-3 inches away from surface) on rigid wire gage screen, overwrapped with heating tape -- easily gets up to 250-300+ heat range -- made those for creep sample testing in the 1970s.) Be innovative. 
 
Just don't use your mother's, wife's or girlfriend's oven at their home or apartment.
Epoxy stinks and they will not forgive you !!!


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Scott Beckwith
[JobTitle]
BTG Composites Inc.
Taylorsville UT
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4.  RE: DIY Curing Oven help

This message was posted by a user wishing to remain anonymous
Posted 27 days ago
This message was posted by a user wishing to remain anonymous

What is your notion of "fairly decent budget"? These working dimensions are tiny, almost the size of a household oven as you pointed out. If you have any budget I would buy a real composite oven and avoid potential safety issues with trying to make one. If not, build a metal pizza box, insulate it, add a small heater (5kw?) and a fan for circulation with a minor return duct, an inlet and vent that you can safely modulate with potential hot exhaust, add a tc to a coupon or your beam, and add a simplified control system to loop back onto that TC. Or you can buy something around 10k and avoid the headache and time.


5.  RE: DIY Curing Oven help

Posted 27 days ago
Where are you located?  We have a small autoclave that can handle the size and temperature but would need more details.


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Thomas Rose
President
Thomas Rose
Norman OK
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6.  RE: DIY Curing Oven help

Posted 25 days ago
Dear Anonymous,
An autoclave is a pressure vessel, so it could be dangerous to jerry-rig one on your own.  You would be better off contacting someone like Thomas Rose for a real one.

A much simpler alternative is to consider the use of vacuum bag curing.  Consolidation pressure will be 14.7 psi, which is OK for most applications.  Then you will only need a simple temperature-controlled oven with feedthroughs for vacuum and temperature.  Don't forget the vacuum pump.  You would have needed one anyway if you were going to do autoclave cure.

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John Kesapradist
(prior) Composites Engineer
Space Systems/Loral
Palo Alto CA
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7.  RE: DIY Curing Oven help

Posted 23 days ago
  |   view attached
Jerry rigging an autoclave is not only dangerous but may be illegal as well. I know that in Utah the fine years ago for having an unregistered autoclave was $7,000 - per day going back to the first usage! Be very aware of the safety and regulatory environment before taking such steps.


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8.  RE: DIY Curing Oven help

Posted 23 days ago
Very good point, Steve. Reminder to all members to keep state safety regulations in mind.

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CJ James,
SAMPE
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9.  RE: DIY Curing Oven help

Posted 22 days ago
Interesting discussion which, however, seemed to deviate to autoclave "safety" although not one of the responses suggested actually trying to build their own autoclave system (pressure) to accomplish what the original person was asking for for. The original  request, from someone lacking an autoclave, asked if an oven (no pressure) might be available or how to improvise. If not an autoclave, composite manufacturers with large structures who needed an oven to cure parts (again, no autoclave an no pressure) often found innovative, safe, and economical ways to cure structures. Even my initial response never suggested trying to build a make-shift autoclave. Not sure how someone even suggested any of the responses went in that direction. Heat blankets, heat lamps, infrared lamps, ducting, insulated structural walls, fans, hot air, etc. -- all are options to developing safe, economical ovens that have been used by many reputable manufacturers to solve "large structure, no oven, no autoclave" curing.

Scott Beckwith
BTG Composites, Inc.





10.  RE: DIY Curing Oven help

Posted 22 days ago

Here is a simple and affordable curing platen that I use for I Beam Construction  Out Of Autoclave

The inside blocks are aluminum as well to translate heat to center beam. Just vacuum bag the sides and drape the unit in a heavy 1597 woven glass cloth.

Using autoclave material usually gives you surface porosity but minimal as the ramp rate, due to the mass, is slow.

 

 

Thanks in Advance

 

"Plan your work and work your plan"

 

Chuck Aitken

Composite Tech Spec II

Gulfstream Structural Test

Charles.aitken@Gulfstream.com

912-965-7517 Office

720-252-7261 Cell

912-395-0197 RDC Lab

 






11.  RE: DIY Curing Oven help

Posted 21 days ago

Being that you are only curing a part 24" long one can make a chicken wire "BOX" inside and out and use 2" thick industrial stone wool for insulation Use heat guns for your heat source but make sure you vent out for circulation and deflect the direct heat of the part because if you don't than you will get hot spots

It gets hot so not put it on a table top use it only on a cement floor!!!!!!

 

 

"Plan your work and work your plan"

 

Chuck Aitken

Composite Tech Spec II

Gulfstream Structural Test

 






12.  RE: DIY Curing Oven help

Posted 16 days ago
Great suggestion from Charles Aiken -- exactly the type of innovation approach that many folks use to overcome cure approaches for fairly simple problems with safety also in mind. No autoclave necessary as previously noted. Thanks, Charles.

Scott Beckwith
BTG Composites, Inc.





13.  RE: DIY Curing Oven help

Posted 20 days ago
You never did answer regarding your location.  We provide control systems for autoclaves and as such have access to a number of autoclaves throughout the county we I'm sure a college project would be welcomed with little or no charge if the part is bagged and ready to cure.  I haven't seen a reply to any of the people who responded to your request.  Just a word from an old guy in the industry....When a request is posted, even a note that says.."never mind....Problem solved" makes it more likely you will get help in the future if you really do need it.  Good luck on the project!

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Thomas Rose
[JobTitle]
Thomas Rose
Norman OK
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14.  RE: DIY Curing Oven help

Posted 11 days ago
Hi Thomas,
Apologies for the late response! As I said in my followup response to the main post, somehow my post got buried in the Mega forums (I had posted this question ~3 months ago)  and only recently resurfaced- I didn't get any notifications! The only reason I checked was because the question and wording looked familiar.
We are an undergraduate student team from the University of California, Los Angeles. We did end up using a makeshift oven, but since we are using donated prepreg material that is meant for autoclave curing, I do believe an autoclave would be a better option. U
nfortunately we did have some scheduling issues with a previous benefactor for borrowing autoclave time - we barely made it to the competition held last year at the SAMPE conference in Seattle! That's why we thought of making our own oven, to make our teams self-reliant for future years too.
However, with the limited resources of a student club, we are always looking for better options to improve on our designs and manufacturing process. We are still facing some issues with the makeshift oven- we would be very grateful for any advice. Thanks for responding to my original post, and I do apologize again for the late response.


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Nachiket
UCLA Student Team lead
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15.  RE: DIY Curing Oven help

Posted 11 days ago
Edited by Nachiket Shah 11 days ago
Hello everyone, thank you all for the thoughtful responses. I had posted this quite a while ago but somehow it resurfaced on the forum. I never got any updates or notifications!

We did end up using a modified lab oven that one of our faculty advisors helped us build. Unfortunately by extending the oven we do get uneven heating due to the length of the beams based off competition rules (approx 26") and the heating element being in the back of the oven. We tested one of our beams based off its curing specs but 1/4th of the beam (part furthest away from the heating element) did not fully cure.

We were thinking of using something like a high-temp fan for better heat flow. Another question was whether "over-curing" is detrimental for the mechanical properties of the part (i.e can we just hold it at the curing temperature for a longer time, instead of the fan idea). Thoughts?

PS:I am a team lead from the UCLA student team that has participated in the competition for the past 2 years now. We started off with wet-layups but switched to prepreg material the next year. Having faced several scheduling issues with companies offering us autoclave time, we had set out to try making our own oven with vacuum bag curing. Apologies for the poor wording, making an autoclave is impractical (and I agree - not a safe DIY project to work on!)
To clarify: We did end up using a "no autoclave" option, and are working on a makeshift oven - still ironing out a a few kinks like uneven heating.

Our resources are fairly limited and we have a ~$1000 team budget; the composite prepreg we use is usually donated so that defines the curing cycles/temps.

Once again, thank you for all the responses!

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Nachiket Shah
UCLA student team lead
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