Hi.

I'm doing a simple 2d contour.
My machine homes automatically. And my workspace is in positive X Y and negative Z.
I just moved the spindle to approximately x10 y500 and auto zeroed Z on top of the stock.
I ran the program (cutting out simple one letter) and it finished.
And just as it finished the refs went crazy: suddenly I'm at X-94  Y-742 Z116 which is also machine cords X+32 Y208 Z0.
Afterwards machine goes towards zero points but passes them and is hard stopped by home switches.
The end of the program (done in Fusion 360) looks as in the attached image.

Can you help me explain this behaviour, please?
PS. Similar thing happened when I put hold on feed (yellow button). That is when I broke a bit after resuming because it didn't retrace and just cut into stock plunged more than suggested for such a small bit (2mm).

Hi,
your machine is missing/gaining steps badly.

In the first instance double and then triple check the stepper to ballscrew connections.
If they are OK run the same program but above the material, ie not cutting, with the spindle off. Does it still lose/gain
steps?
If its OK with the spindle off there are two possibilities:
1) Electrical noise from the spindle is interfering with your stepper signals (step/dir)
2) The cutting forces are exceeding the torque capability of your steppers.

Craig

Hi. This is impossible.
This machine has has 6Nm motors with 10/10/5mm pitch X/Y/Z and was running a 3mm flat end mill on max 4mm layers of depth at around 2000mm/min.

Today I did 266 holes hexagonal in my wasteboard 16mm x 7mm deep and a hole fi8 22mm in depth inside. All has been perfectly alligned.
There must by something in these instructions plus my setup. Any clue where to start diagnosing if we assume it is about the settings rather than mechanical issues?

The G28 lines send the machine to the home position.

You could replace then with :-

G53 Z0
G53 X0 Y0
M30