Zero (a hobbyist's problem)

[luhukay]

Hello together!

This is my first topic I hope you can help me.
At home I got a nearly converted CNC mill and it is ready to move for its first time. So last friday I went to a workmate and asked him if he could help me out with a quite simple program for the first try. He works with mastercam (don´t know what version. Might have to ask him) and after he left I was left alone with it Quite impressive program! So after a while (hours) I ended up with a NC program. I set up clearance whatsoever and saved it. Back at home I imported the g code and there was a problem:
When locating the zero I used a 6mm endmill, got close to the edge and set zero. Did this for x and y. Then lifted the tool moved over 3mm and set zero again. With Z I moved the endmill down till I saw light scratches on the surface. So then I had my zero set right on the corner just where it was set in the CAD program as well.

This is what the first few lines look like:
N102 G0 G17 G40 G49 G80 G90
N104 T1 M6
N106 G0 G90 G54 X-62.845 Y14.146 A0. S0 M5
N108 G43 H1 Z24.8
N110 Z4.8
N112 G1 Z-.2 F100.
N114 X-62.79 Y14.1 F75.

The problem is that from the zero position it only moves x and y. Z scratches over the top of my workpiece
In the right position (108) it then raises the tool and brings it down slowly.

Does anyone know how to make mastercam inserting a line telling Z to move up before moving x an y? Or in other words: telling it to go to clearance before moving the other axis? I think he set me up a blank machine that I´m not changing any values that might be important to him.
I´m a hobbyist and I don´t want to bother my workmate, hold him up or make him staying longer. So hope it is quite easy to solve. It would take me probably weeks to work it out with so many buttons in front of me!

[txcncman]

See attachment:

[luhukay]

From what I can remember I did set these values

[Superman]

What is needed is a couple of lines inserted at N103, before the toolchange line
N103 G91 G28 Z0. M9
N103 G90

What this does is make the spndle head retract to it's machine origin at the top of it's travel, before going to do any other operation ie toolchange, or any X/Y move across/through your part.
This would mean that your post needs modifying to have it inserted at the correct place each time
Some machine builders have this retract incorporated into their M6 macro.

Note----you still have not set all the tool parameters ie RPM ( S0 ) or coolant ( M8/M9 )
most machines need to have the spindle rotating before it will allow movement on a G1 command

[Joe S.]

most machines need to have the spindle rotating before it will allow movement on a G1 command

The HAAS we have in the shop seems to require it but the Fadal is happy to move with spindle off.

[luhukay]

Hi Superman,

I didn´t set up all those things like RPM's etc. My program at home doesn´t mind it and for the start I wanted to put in a piece of wire instead of an expensive tool for the case that I hit something.
Today I gave it another go. Did the same thing with positioning like yesterday but then moved the spindle up a fraction with the jog. It then started and didn´t move Z till it got to the point were it was to move it anyway. Well this is cheating. So I hoped the problem was more like I didn´t tick a box I should have or so
I´ll try to get another file set up next week if I find the time to do so and then try to remember what I filled in.
So thx for your help so far!

[txcncman]

When you are working on your new file, get version information, machine definition, and post processor used and make screen shots of what you are doing. Also give a copy of your part print and someone can try to walk you through it step by step.

[MMTZ]

I think you need to re-read Superman's post and manually add to the program the lines he recommended and given a pretty good explanation; you are missing them on your program and that's why this last time you didn't have an issue since you were already above the part on Z.

If that works, then you need a really simple post modification so the lines will come out from Mastercam every time you make a new program.

Then again, give SPM advice a try and let us know how it works.

HTH

[luhukay]

I havn´t had time to get back to the problem.
@MMTZ
How do I change the program making it inserting the Z movement right at the start of the program?
Do you know where I could find a tutorial?

[MMTZ]

Hi there, well first of all, Did you try superman's suggestions? Did they work? If you did let us know and we'll point you on the right direction.

[luhukay]

I´ve always added them by hand. All I need is the G90 Z100 to be the first step before the machine does anything else.
Hope you can help me with this single line.

[MMTZ]

Did you ever try this?

N103 G91 G28 Z0. M9
N103 G90

That's the safer way on my opinion as your G90 Z100 is moving the spindle up 100 MM but not to "Z" home position.

Anyways, it should be a pretty easy fix to do either one, upload a copy of your post when you get a chance.