heater control for curing oven

I'm into recumbents and am exploring building a mold for a prepreg
carbon setup. This looks like an active site for composites.

Can anyone recommend a heater control to adjust the heating/cooling
ramp rate (5 degrees a minute, etc)? I'm obviously trying to keep
costs down so something surplus or homemade would be best.

Also, if I do a pressure bladder inside a female mold how do I apply
the vacuum between the composite and the inner mold line (so that the
bladder inflates)? Or should I just only apply pressure to the bladder
and not try to pull a vacuum on the mold?

Thanks airplane guys.

Joe

Check both the Grainger and McMaster Carr listings. They both have
fairly reasonably priced ($90- $400) temperature controlers that can be
programed with ramp rates and hold times. Add in a solid state relay
and a thermocouple (another $40) and you can build a nice curing oven.
They are simple to set up and use. Eurotherm is one brand name that I
remember from my lab days........ http://www.eurotherm.com/
===============
Leon McAtee
Building bents for kids and experimenting with my first bent trike

Make your oven out of urethane foam insulation. Line it with aluminum
foil. Install 100 watt lightbulbs as needed to get the desired heatup
rate. I used 8 or 10. Put aluminum foil reflectors over the bulbs to
keep them from shining directly on the part and creating hot spots.
This is the oven I used to bond some honeycomb repairs to a Gulfstream
G-II flap, a 250° cure process. Of course, I used a hot bonder to
control and monitor it, but a simple thermostat would work just as well.

The biggest factor in your heatup rate will be the mass of your mold.
Less massive will make life easier. You'll need to have thermocouples
right on the part you're curing.

Don't use vacuum with a bladder. Apply pressure. About 2 atmospheres.
Make sure you consolidate your layup by applying pressure at
elevated temperature for a few hours before the cure cycle.

I have two Vision R-40's.

wrote:
I'm into recumbents and am exploring building a mold for a prepreg
carbon setup. This looks like an active site for composites.

Can anyone recommend a heater control to adjust the heating/cooling
ramp rate (5 degrees a minute, etc)? I'm obviously trying to keep
costs down so something surplus or homemade would be best.

Also, if I do a pressure bladder inside a female mold how do I apply
the vacuum between the composite and the inner mold line (so that the
bladder inflates)? Or should I just only apply pressure to the bladder
and not try to pull a vacuum on the mold?

Thanks airplane guys.

Joe



--
J Kimmel

www.metalinnovations.com

"Cuius testiculos habes, habeas cardia et cerebellum." - When you have
their full attention in your grip, their hearts and minds will follow.

In article .com,
wrote:

I'm into recumbents and am exploring building a mold for a prepreg
carbon setup. This looks like an active site for composites.

Can anyone recommend a heater control to adjust the heating/cooling
ramp rate (5 degrees a minute, etc)? I'm obviously trying to keep
costs down so something surplus or homemade would be best.

Also, if I do a pressure bladder inside a female mold how do I apply
the vacuum between the composite and the inner mold line (so that the
bladder inflates)? Or should I just only apply pressure to the bladder
and not try to pull a vacuum on the mold?

Thanks airplane guys.

Joe

I don't know anything about composites, but I do know something about
temperature control. If that's critical to the process, I sure wouldn't
use anything like an oven thermostat. The hysteresis in those is way too
wide open.

For close control, you need a good PID controller hooked to an accurate
thermocouple or RTD probe. And, you need to "tune" it to your particular
usage. That involves setting the proportional, integral, and derivative
(PID) values in light of your requirements. Those would be different if
you were trying to heat a swimming pool with a hair dryer than they
would if you wanted to roast marshmallows on the sun.

Many PID controllers are "auto tuning" which means they can self-select
PID values, but they need time to "learn" your process. Until they have
time to do so, expect wide temperature fluctuations and significant
overshoot of your target temp. (And don't expect to auto tune an empty
oven and then use those values for one with parts in it.)

Omega, by the way, is a graphic arts company. They put out slick full
color glossy catalogs, but they don't manufacture temperature controls.
Peel the label off an Omega controller and you'll find the real
manufacturer, Love Controls or one of a handful of others. I don't mind
buying from distributors, but it irks me some to see distributors posing
as manufacturers.

By the way, I love the idea of carbon fiber bike frames. I think there
would be a great market for an electric recumbent that was set up for
practical short commuter use. Good luck.

Good info, thanks.

This post brings up a couple of questions...

1. Do I need breather with a bladder (to allow the air to be forced
out)?
2. Is there any concern with vapors building up in the oven and
causing a fire?
3. Perhaps it would be a good idea to put 2 bars in the bladder and
then put the whole thing in a vacuum bag so that the mold only sees
approximately 1 bar? This would keep the fumes out of the oven too.
4. Can thermocouples be joined together to "average" without using
software?
5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe

wrote:
Good info, thanks.


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe

Try e-bay item 7546821715. I have one which I have used a couple of
times and am satisfied with.

Dan, U.S. Air Force, retired

"Dan, U.S. Air Force, retired" wrote in message news:1KiYe.29212$dm.24132@lakeread03...
wrote:
Good info, thanks.


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe

Try e-bay item 7546821715. I have one which I have used a couple of times and am satisfied with.

Dan, U.S. Air Force, retired

47 bucks delivered with the thermocouple! Does it do PID? Heck of a deal it looks like...

..Blueskies. wrote:
"Dan, U.S. Air Force, retired" wrote in message news:1KiYe.29212$dm.24132@lakeread03...

wrote:

Good info, thanks.


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe


Try e-bay item 7546821715. I have one which I have used a couple of times and am satisfied with.

Dan, U.S. Air Force, retired


47 bucks delivered with the thermocouple! Does it do PID? Heck of a deal it looks like...


I'd be able to answer if I knew what PID is.

Dan, U.S. Air Force, retired

Dan,

Does this unit allow you to set the ramp both going up and coming down?
Does it work with a solid state relay? How easy are the directions to
follow (assuming I can't read Chinese!)?

PID is described in the message below.

Joe

In article .com,
wrote:


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?



Joe

A stand alone, full PID with ramp and soak? Several hundred dollars, I'm
afraid. Keep an eye out on ebay, but the one Dan referenced isn't such a
beast.

Again, I have absolutely no idea what your requirements are as far as
accuracy and precision. If you can clarify those, you might find that
you need less sophistication. Also, as someone else mentioned, you might
find PC based software to do the work of a temperature controller. I
don't know what's out there in that regard.