The importance of small animal sacrifices.

A project log for DIY Space Grade PCBs

3D print circuits using silver ink and ceramic substrates to make high performance, multilayer, fine line < 3mil, PCBs

chuck-glasserChuck Glasser 07/04/2016 at 02:160 Comments

Today, it was time to bring up the big orange isostatic press. I had previously drained all the mineral hydraulic oil from the air driven hydraulic pump and it was now time to refill it with an organic Soybean oil. For now I'm using ordinary Soybean oil intended for salads and fries. No point in paying extra for the same thing that is certified to be unfit for human consumption but great for your tractor. I've determined that if there is a leak under hydraulic pressure and I get injected by a hydraulic fluid, the outcome of the disaster will be better if it is organic oil rather than a mineral oil. As it turns out, the oil is not under any constant use as in a machine that is running 24/7 so if my salad oil goes rancid I can just turn it to soap. It's a lot cheaper as well. In any case, I finally came to the conclusion that I didn't need to run down to Harbor Freight to buy a transfer pump when a piece of hose and a syphon would work just as well. The oxygen bottle was filled as well as the pump.

In the LTCC process, the various layers of ceramic green tape are compressed with a hydraulic process to force the multiple layers of materials into a uniform and solid body. The best press to use is an isostatic press as it insures that the material will see a steady and uniform compression force in every direction and across the entire surface of the material. The industry standard for the big squeeze is 70 degrees C for 10 minutes. So, I throw the temperature controller switch up, by convention, up is true, and see that the temperature is moving in exactly the wrong direction. Dang, the polarity of the thermocouple is reversed. Got to fix that!

The hydraulic cylinder has two pneumatic pistons attached whose purpose is to move the hydraulic piston up and down to fill the working volume with hydraulic oil and purge air out of the system. The air cylinders operate under the control a pneumatic single pole, double throw air valves energized by a 24 Volt source. Switch up, hydraulic cylinder goes up, switch down ... hydraulic cylinder goes down. The switch is thrown, and ... nada. The cylinder just sits there, not moving. This can't be. There is an equivalent force of several hundred pounds pressing against the hydraulic piston. Yet, it just sits there. Throw the switch and the machine shudders under the forces, but no movement. Ok, perhaps the piston has sealed itself against the piston wall. I'll force it with an irresistible pressure, say 10,000 psi, the rated pressure of the hydraulic pump. Pump on, nada. No movement, whatsoever.

Hydraulics is a lot harder than I gave it credit.

The purpose of a gauge is to report the process parameters. The secondary purpose it to indicate what the hell is going on when nothing works! There needs to be another pressure gauge at the pump, or perhaps just after the check valve, or two... their cheap!

I was successful in making the piston move once after releasing the clamping force of the heater jacket around the pressure cylinder. But it move once, and then no more.

As if Murphy wasn't completely satisfied, the hydraulic seal on the top cylinder cap has been chewed up from poor alignment as the top plat is lowered down to form a seal.

The GFI tripped. OK after a reset.

Time for a small animal sacrifice. I think I'll make a chicken flat bread pizza.