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.