Heat controller program

[falls]

Well taking the next step, couldn't stand the feeling of actually having money accumulating, so implementing heating for the press.
I have a blanket and controller built and have deciphered the algorithms for programming the controller too.
My plan is to ramp the temp from room temp to 70C over half an hour, then soak for 60 minutes then cool in a linear fashion back to room temp.

2 questions:

1. Is it best to use the controller to reduce the temperature at the end and if so how long would people say it takes for their press to cool from 70C (158F) to 25C (77F), or should I just cut the heat totally after the soak and let it cool by itself?

2. How quickly does the press heat up? Is 25C to 70C in 30 minutes achievable, or too slow?

The materials will be in a cassette of aluminium 1mm thick top piece. The blanket will be on top of this then a sheet of insulating board. Aluminium cat track above this. Blanket is 2400W, so 2W per square inch.

Thanks.

[Alex13]

1. You should retain heat for quite some time in your press. I switch mine straight off from 85C, takes an hour or more to drop to 50C or so when I can remove it. I don't think it's necessary for a "ramp down" program.

25C to 70C in 30mins sounds about right. I think I heat mine 25 - 85C in that time. They heat up extremely fast if you need, you could hit 25-90C in less than 5min with my setup (2x 2000W blankets).

Your program sounds basically the same as mine, only I cure at a slightly higher temp.

[falls]

Thanks alex.
I re-read the epoxy info and I need 1hr at 80 degrees. So the 30 minute ramp sounds like the way to go.
I have the auber ramp soak PID.

[Brazen]

I have .125 wall steel cat track in my press and they retain a lot of heat, so I've been just turning off the PID's and letting it cool on it's own. So far, so good.

[Alex13]

If you need some help setting the program up let me know. It can be finnicky and annoying. I have the same controller.

[falls]

Thanks alex. I think I have it working ok. I ran the program and it heated from 20C to 70C in 30 minutes. I then ran the autotune and it seemed to go well then stay at 70. Then stopped the program and it cooled down relatively quickly.
Glad all my wiring etc seems to be correct and that the heat blanket works.

[Richuk]

strangesnowboarding appear to have a press offering a soak function. They posted recently in the apres section, perhaps they will share?

80C will give you a certain Tg value, if you have a lot of carbon Sicomin recommend an extra 20 mins (but that was an 'off the cuff remark' they made).

There are a few notes in my journal about ramp time and how voids are formed, but I suspect you have researched this already

Hope it heat goes well for you!

[ggardner90]

This may be a dumb question but where do you put the heat blanket in the press. above or below the cattracks and do you but aluminum sheets on both sides of it or just one?

if it does go above the cattrack how do you regulate temperature with all the airflow in the cattrack?

if it goes under it what do you do with the thermocouple?

or is it best to put it under the ski? again do you surround both sides or just one side with aluminum sheets

[vinman]

There is nothing in that question that can't be answered with the search function and some reading....

ideally you have 2 blankets, top and bottom protected by aluminum on both sides.

layers bottom to top would be

bottom mold
alu skin
blanket
alu skin or cassette
lamiate
alu skin
blanket
alu skin
cat track
bladder
top mold

[Brazen]

^ what he said.