Another plasma component...

Andy

Thank you for the reply. I have also considered a simple dash pot, probing is done a low speeds so there shouldn't be too much effect when probing. The other thing I have considered is using counterbalance springs and then using a solenoid or RC servo to drive the floating head against the stops while cutting.

I have actually considered using a pneumatic cylinder in the past for probing. It seems to me that once I go to the trouble of mounting a cylinder and the associated plumbing that one might as well go for gold standard probing. Placing a LVDT or precision snap switch on the cylinder which is extended while probing and retracted out of the way when cutting. The extended probe is a fixed offset from the cutter so the probe location can be adjusted in Gcode.

John

Well, my idea doesn't need any plumbing, other than a Tee of the cutting air supply to the cylinder.

Andy

Thank you for the reply. I think the idea will require a fair bit of plumbing. The air supply to the plasma cutter is away from the machine and would need to be plumbed through the all the drag chains to the floating head. The air connection from the plasma power supply to the torch head is in a composite cable and is not access-able. I will have to consider whether using this air supply will be a problem. The blow back torch uses the air pressure to move parts to strike the arc and then the cutting air pressure at the torch is controlled by the power supply box for the correct cut. I actually can do this as my torch is actually a ?Franken Torch" made from parts of two manufactures, most people will be loath to start altering their expensive and carefully calibrated torch assembly.

John

On further thought this will not work. The post cut airflow is usually still happening when you want to be probing for the next cut. So yes it will work for single cuts but not for the much more common many serial cuts. I could hack the plasma power supply air solenoid circuit but the results of interrupting post cut cooling flow aren't known to me.

John

OK, so a separate valve would still be needed. The idea might still work, but not as easily as I thought.

But those guided cylinders really do look like a floating mount waiting to happen

Well, there is another reason to plumb air up to the Z axis and that is to operate a pneumatic engraver. Normally, this requires 2 feeds, one to operate the air ram and the other passing through an oiler to operate the engraver. The separate feed to operate the air ram is required to control the down pressure applied when engraving. I did buy an engraver for this purpose and kinda a have it back on the agenda as I have to replace the drag chain with a larger one and add Ohmic sensing now I have a larger plasma cutter that supports Ohmic sensing. I must get some 6mm air line and plumb it in while I am at it!