Close

Never tell your wife you took a shower in hydraulic oil!

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 07/08/2016 at 01:550 Comments

Twice.

If you look at the big orange machine and study it a bit you will see that the top hydraulic cylinder applies the clamping force at one point. The image of course being that the force holding the top seal in place is along the centerline of the hydraulic cylinder.

After taking several showers in hydraulic fluid as the seal gives way I can guarantee that the clamping force is nowhere near the centerline of the cylinder. In fact the present clamping mechanism is a disaster that can NEVER work reliably and SAFELY. So it will have to be rebuilt. Not necessarily much bigger, but certainly a lot smarter.

I'm thinking a set of 4 linear slides at each corner of the top plate that constrain the movement of the top cylinder cap for movement in ONLY the Z axis.

There are other issues. When the top cap is lowered into place to form a seal it is under no load. Then, as the pressure is raised, the load that was in place to hold the top and bottom in place is reduced.

To be truthful, it's a bit scary! Two hydraulic pumps going chuga, chuga, big "I beams" bending. You know, just your ordinary day at the mill.

So, once the top cap goes on, it needs to be preloaded such that it never moves.

On the ceramic green tape processing here is what I've found.

Green tape, the ceramic tape before it is fired comes from the supplier on a mylar carrier film. The tape itself may be supplied in various thickness fro 1 to 10 mils. In my case the tape is 5 mils thick. It has the mechanical properties and tear resistance of wet tissue paper. When the CO2 laser hits the material it chars and fuses to the carrier that may have also burned away, or not. The material itself is far cleaner when a shield gas such as Argon is used.

If I had my own formulation of binders I would use acrylics as they are know to sublime without residue, but I don't and so I'll have to adapt to the needs of the materials I have.

After laser cutting the tape is stuck to the carrier film. If the carrier is removed and the tape cut directly on the backing plate, today I used a ceramic kiln support plate 7" on a side square, the tape will be stuck to the support.

It's looking very muck like a cutting plotter and a via punch should be two of the stations on the large bed CNC machine!!!

It is essential that the blanking and punching operations not produce a situation that will later induce an operation that will change the dimensional properties of the tape. This is not presently the case. So, while slipping a sharp edge spatula between the tape and carrier may seem like progress, it really isn't.

Registration of the multiple layers of tape requires a fixture. Experiments suggest that staking the various layers onto a platen press with registration pins may be a good solution as alignment and pre pressing in a platen press may keep the layers together sufficiently for later pressing in the isostatic press.

Discussions