[nelZ]

I will have to put prox. sensors on a 2 axis system for cutting some parts. I do need .001" precision and steppers aren't closed loop.

I'm new to LinuxCNC and have noticed the greatly different G-code from what I'm used to in CNC.

If I want to do a homing procedure after each cut can I do that in the G code or is it somewhere else.

If you want to share an example THANKS in advance.

Nelson

[109jb]

Homing is normally done once at machine startup and is for setting machine zero. If your steppers aren't losing steps then re-homing after each cut won't really gain you anything. If they are losing steps then you need to fix it. Fixing it could be problems with the machine, adjustments to the machine, stepper setup in linuxcnc, etc. Bottom line is that if you find it necessary to re-home for each cut then there is something wrong that needs to be fixed.

[nelZ]

Thanks!

Then there is a homing routine in LinuxCNC. Seems that in manufacturing one tries to work the machine as fast as possible. Not being closed loop, a stepper in LinuxCNC could possibly lose a step or two when taking the heaviest cut possible.

Perhaps it would be like a "passive closed loop" double check to fix the tiny errors instead of waiting for them to accumulate enough to see in the all too infrequent measurement of the parts one is producing.

I do see what you're saying. Given a homing procedure in the morning, how is it done? In the G-code?

Thanks!

[109jb]

Homing is part of the control software. To automatically home the machine you must have homing switches installed on the axes. When you power up the machine, you just press the Home button and the machine goes through the homing routine that has been stored during machine setup. See attached picture.



As for lost steps. Again, if you are losing steps then something is wrong. In a properly designed and set up machine you will not lose steps.

There are closed loop stepper systems, but they cost as much or more than closed loop servos of comparable size/capability. The closed loop steppers use special stepper drivers to accomplish this. You can't just add an encoder and achieve closed loop with steppers. What you can do though is add an encoder that will stop the machine if the following error gets too large. All this type of setup would do is stop the machine though. It would not automatically correct for the error.