[kxkid]

Hello all. I am new to the board and new to CNC Plasma. I have a custom table with a hypertherm powermax 1000 and using mach3 to run it. My question is how to set zero for the torch height. The guy that I bought it from says to move z down to where it touches and then move it up just high enough to where a business card moves freely. I am trying to find a faster way to zero z. Thanks for the help.

[flyinwilly]

It depends on how your machine is built.

Do you have a floating head on the Z axis ? Does it have a Z axis home switch ? If you do, then one way is to add the following command to your G code.

Put "G28.1 Z0.00" in the G code before the pierce height is set. This will move the z axis toward zero until the home switch is tripped. At that point the torch should be on the material and the z axis will be set to zero. All you have to do is then adjust the pierce height to account for the slop in the switch.


If you are using Sheetcam, you'll have to modify the post processor file to insert the command into the G code. It goes into the "on Pen Down" function before the command to set the pierce height.

Willy

[kxkid]

I am lost on what you said. There is a ref home button that brings x y and z to a home.

[LeeWay]

Can you snap a few pictures of the Z axis?
A z axis with a floating head and switch finds it's own zero each time prior to a pierce.

It goes down until the switch is hit and then comes back up to a specific point that is previously been measured. Then goes from there.

[kxkid]

Its is just like the torch mate setup

[LeeWay]

Not familiar with Torch mate. Sorry.

[kxkid]

Here is a pic of my z setup

[LeeWay]

So no floating head.
You move the Z down until it touches the plate and that is zero.
Works fine if you always have a perfectly level and flat material.
In reality, that is pretty rare.

With no torch height control or floating head design, that is about the best you can do.
You could still put a floating head on it though without a THC and it would function better.
Several ways to do it fairly inexpensively. You already have wiring to a switch there. It could be used for a floating head.

[kxkid]

I have a proma THC and it seems like its not working. They guy I bought it from said zero should be about 1/16 off the metal but I can't find anything on the net for zero or pierce height.

[C.Michael]

- - - Updated - - -

Attachment 195614

In your picture, what are these 2 wires,circled with the red oval doing?? Home switch??

[kxkid]

Limit switch/home switch

[LeeWay]

Here is a short video showing how my floating head works.

My Video - YouTube

Zero is the surface of the material you are cutting.
Pierce height and cut height come up from there.
Different machines, consumables and materials may require different pierce and cut heights.
As an illustration, my Hypertherm PM45 needs a .1" pierce height and a .02" cut height for most of the materials I cut. This is sheet stainless, steel and aluminum less than .125" thick.

To get an accurate zero for each pierce, you should not rely on THC alone. Your consumable life will suffer if you do. My THC doesn't even take over until well into the cut after the pierce. It takes over and follows a preset voltage that I set on the screen for the particular type material being cut. This helps eliminate any error due to material not being perfectly flat, because the voltage is sensing the plate and maintaining the height by regulating that voltage.

[kxkid]

I know how a floating head works. I am trying to figure out how to get zero with my head. Also refer to my other thread on the problem I am having

[LeeWay]

You move the Z down and touch the tip of the torch to the plate and hit the Zero button on the Z axis on screen. That is zero. At least in that spot on the plate. I use a page from a phone book. When that stops moving, that is close enough for me.
Zero will probably be different around the plate if not initially, then if thin sheet, after cutting if any warping occurs.

[kxkid]

You move the Z down and touch the tip of the torch to the plate and hit the Zero button on the Z axis on screen. That is zero. At least in that spot on the plate. I use a page from a phone book. When that stops moving, that is close enough for me.
Zero will probably be different around the plate if not initially, then if thin sheet, after cutting if any warping occurs.

OK and that is when I have problems on the next cuts where it is touching the sheet and goes up to where it thinks it should be but is not high enough. And this is on a fresh piece of 3/16 steel that is dang near flat. My table is also dang near level

[LeeWay]

Mine is .05" variance across the 4' by 4' area. That is very good for a plasma surface I think. But even with that, a cut height of .02" could be trying to cut at .07" or on the plate itself. Neither of which will work well. That is why I use the floating head. No matter what the actual surface height is, it goes down and when the switch is triggered, comes back up a given amount. This amount is called the switch offset and is input into Sheetcam. In the Post Processor and as a variable setting that goes into operations on it's own line. My setting is like .5475". That is the amount it comes back up once the switch on the floating head is triggered. That equals the zero or the surface of the sheet. Sheetcam then raises it an additional .1" to the pierce height. Pierces, then reduces itself to the cut height and starts cutting a bit, then the THC takes over from there through the end of that cut.

The very next pierce or cut, it goes through all that again.