Hello

I want to try to mill something for the first time, and have a little problem with Z axis. 

My Z axis is homing in the positive direction, from -60mm(limit) to 0(home/limit).
If I want to miil something, I want the Z axis to move down to my table in the negativ direction, but the G code Z has a positiv value. When I start the program the first thing that happen is, the Z axis hits the home/limit switch.  Anybody know how to change the Z direction without messing the rest of the Z setup, like homing diretion ect.

Thanks
Adam

If you touch the tool on the bed of the machine and press the zero Z Mach will datum up on that face. all your z moves are then up from the machine bed.

Graham.

Hi, Adam

If your Z axis shows Pos values going "up" to home, That is correct.

Your G-code Z values need to be Z-## in your Posted G-code.

If your using LazyCam, Layers Tab at Bottom Set cut depth to a negative value " -##", and click on "Set Layer" and or "Set All Layers".

Then Jog Z down to the top of your Part's top Surface and Zero Z Axis.

After you get your G-code stratined out, Your machine will show neg. cut's.

Hi, Gram

Haven't used your method, Can see that it will work Fine, Just it's Bottom's Up,  Instead of Top's Down.

Hope this Helps, Chip

Thanks Chip, I will try that.  I wrote an "E" letter with LazyCam and want try to mill it.

What if I get a large 3D job with many Z movement - do I have to correct all the positiv values to negativ manualy?

Graham - do you mean I have to zero the Z Offset Coordination when the tool is touching my table?   Because I can`t zero the Machine Coords down there. Only the home switches can do that.

I`m confused her. What is the order?

1. I home all the axis
2. I put a piece of material I want to mill somewhere in the middle of my table
3. I move all the axis until all of them (my tool) touches my material ( Offset Coords)
4. Zero all axis(Offset coords)
5. Regenerate toolpath
6. do I have to Home ?    
Graham - when to zero the Z, touching the bed of my machine?

... and I can`t wait to push the Start button.

That what I call Offset Coords - is this what you call DRO?  Is it when there is no red ring around the Machine Coords button?

Adam

What Graham is meaning is you home as normal, this sets the Machine Coordinates. You can then jog to any place you want and set a work offset zero by pressing the Zero axis button at the side of that axis DRO. When you do this the DRO will read Zero but if you press the Machine Coords button you will see that Mach has remembered the true position.
 So by Grahams method you are setting your table (or lowest part of material) to zero as an offset and as your code is all positive it will work fine. Its normal to have your code as zero for top surface of material and all cutting in the negative but some people like it the other way.
Hood

Thanks Hood

The positiv Z value is only 0.1 unit, but i don´t have that thin material to mill in. If I use a piece of blue foam which is 1cm high, how do I move the tool to the top of it, if Z moves only 0.1 from the buttom?

Adam

Go to the top of your material and type 0.1 into the Z DRO and then press enter. Really though its best to get your code sorted for normal operation. If your CAM programme is outputting all positive values it should be possible to alter the post processor or a setting somewhere to make it say zero is the top.
Hood

This is not easy. Much harder to understand than my foam cutter I`ve build for 6 years ago.

When I move my tool until it touches my material and zero the axis and regenerate toolpath, is that the position when I start the milling or do I have to home first?

Adam

If you are still working Z plus.

Move to top of job

In Z axis DRO type 0.1 and press ENTER

Move away from job a safe amount ( 1" or 25mm)

if you are working Z minus.

Move to top of job.

Press Z axis zero button next to DRO.

Move away a safe distance

------------------------------------------

Run program with care.  Turn on single block and slow rapids down to a crawl.

Graham.

This is not easy. Much harder to understand than my foam cutter I`ve build for 6 years ago.

When I move my tool until it touches my material and zero the axis and regenerate toolpath, is that the position when I start the milling or do I have to home first?

Adam

You need to home when everytime you start  Mach but thats all unless you crash and loose steps, then you need to home again.
Hood