I've got myself a vacuum press setup that is rated at 28inHg (~.95 bar) and the next thing I want to do is purchase a heating blanket.
Will a vacuum press setup create sufficient pressure to properly press a set of skis. I know 13-14psi over a large area adds up to a decent force, but how would this compare to a firehose press with 45-60psi of air in it?
Now that I've got the vacuum press setup I'm faced with a major problem: how am I going to run the leads from the thermocouple from inside the bag to outside the bag? As far as I can tell, Michaels does not offer a blanket with a single setpoint. Perhaps I'll have to contact them about that.
Judging from this picture:
The entry point of the power cable and thermocouple lead produces a bump on the heating blanket. Will this telegraph through to my skis, or should I order a longer length so that this section is beyond the workpiece. Or would an aluminim sheet like the Leangs used be advisable.
My heat blanket has lots of wires running through it. The first time I used it I got lots of ripples in the topsheet of my skis. However, these ripples don't seem to really affect the ski function, and I have skiied 10 days on that first heated pair (the better rockets). Lately though, I have been putting a sheet of thin plastic between the heat blanket and ski, and it seems to help a lot. There are still ripples, but they are really small. Next I am going to try some aluminum sheet, and i think that should solve the problem.
I would bet that with your heat blanket, if you used an aluminum or steel sheet, you wouldn't have any problems with it.
The bumps are only on one side. We have a couple layers of 1/8" hardboard over the ribs of our mold. I made a cutout in one layer to accommadate the bumps and then laid a sheet of aluminum over the blanket. The bumps face down in the cutout. Here is a pic: Not the best picture, but I think you get the idea.
You can get vacuum tape and bag material and rather than putting your whole mold in a bag, you would tape down tha bagging material to the top of your mold.
You can buy single setpoint controllers from www.omega.com
Michaels does offer a termostatically controlled blanket that functions at a single temperature. I'm sure it will produce more error than a PID setup would, though I'm confident that as long as it is within 10deg of the setpoint I should be fine.
I'll check out the vacuum bag/tape idea. Setting up the PID controller along with the SSR is about the only way I'll managed to get school credit for this project.
I vac bag my mold inside a 36" wide nylon tube-bag. With this setup I have run plenty of wires out of the bag (for thermocouples on the mold) by squeezing the wire between two strips of mastic tape on a sealed end. mastic has plenty of give and can easily seal around wires...i regularly get 28 and 29" vacuums with plenty of wires! I would be interested to hear if setting the blanket on top of the bag works though, since i am planning to try this. my blanket arrives soon and i dont want it to deform inside the bag (i need to heat from above, not below...hard to explain why)...so i dont think i can have it under pressure. if you try having the blanket outside the bag, please let me know how it works!!!
