Pneumatic Snowboard Press
I've completed the a pneumatic snowboard press to replace my vacuum bagging system. The combination of my current CNC machine and the press support boards up to 210cm in length. The press cavity is 92" long x 16" wide x 12" high. It is built with W12x40 I-beams. The long beams are 9' long and weigh 360lbs each. Total press weight is right around 1,700lbs so far. There are two 5" fire hoses which operate between 60-80psi depending on board surface area. There are two heat blankets, one on top and one on bottom, for a total of 3.5W/in^2. The blankets are 14"x85", 240V for a total draw of 17.35A. It takes less than 5 min to heat a board from 70F to 170F.
I'll add a complete parts list later. Those of you who are building your own press may find the info about the bladder construction below helpful.
The heater control has one PID controller with ramp/soak for controlling the heat of both blankets. Temperature is measured below the center of the board. It also has a second temperature sensor to monitor the heat transfer in other locations. It's helpful to see the lag between the heat on the bottom and on the top of the board during pressing.
The un-pressurized press.
Mmmm... warm...
1/2" Grade 8 steel bolts, zinc & yellow plated for extra bling!
The first board from the new press.
Close-up of the tail showing the nose/tail spacer fit. The spacers and sidewalls are white PTEX.
Close-up of the logo, showing the glass and wood under the top sheet. This top sheet is not actually 100% clear... it has a "blue sheen" over it that gives it a somewhat iridescent look in person.
Bladder Construction
People usually have a lot of trouble constructing leak free bladders. They usually seem to end up with a lot of "goop" involved in an effort to stop leaks at the ends and at the through couplings. These bladders are essentially leak free to 90psi with only Teflon tape.
The ends are held together with standard 1" angle iron from Home Depot using seven 3/8" Grade 8 bolts: two on the outside ends, one in between the hoses, and two through each hose. They're torqued down pretty snug, but we didn't kill ourselves tightening them. I'll figure out what the torque was and add that info later. No silicon sealant, plumber's goop, etc., and no leaks.
The through couplings were more of a challenge. We went through a few tests before settling on what you see below. Click on the image for a full size view. If you look closely at the full sized image you'll see a little soapy water around most of it. This picture was taken with the bladders at 90psi. Again, no goop. The secret here is the combination of the three kinds of washers, and the simple fact that the nut for the panel mount coupling is on the outside of the bladder. The washer configuration is repeated on the inside. The 1/8" thick rubber washers are against the bladder, then the steel, then the Aramid/Buna-N between the steel and the brass nuts. The result is a great seal with the bladder, and a great seal to the nuts. This is not super-tight... just snug, with a little deformation in the rubber washer visible during assembly.
The steel washers are the standard 3/4" washers from Home Depot. Here are the other parts and the McMaster-Carr part numbers:
| Med-Pressure Extruded Brass Thrd Pipe Fitting 1/4" Pipe Size, Panel Mount Coupling | 50785K273 |
| 3/4" Screw Size, 2" Od, 1/8" Thick Large-Od Extra-Thick Reinforced Rubber Washer (10) | 90131A106 |
| Aramid/Buna-N Washer 3/4" Id, 1-1/2" Od, .0625" Thick (5) | 93303A317 |
These parts aren't super-cheap, but they're completely worth it.
