Messages

11

General Mach Discussion / Re: Homing position is not absolute

« on: May 01, 2011, 09:05:31 PM »

HelloGerry!

Thanks for the makro. Thats what I like much more :-)
Burkhard

12

General Mach Discussion / Re: Homing position is not absolute

« on: May 01, 2011, 09:04:03 PM »

Hello TP, hello Ray!

Set the acceleration of your machine to , let us say, 10. Then do the homing. You will see what i described. That axis run into the switch, slow down to stop. Go back increasing speed til switch release, slow down to stop, and then resetting the coordinates. The machine is not moving again and the machine coordinate is set to zero (if you don't set an offset). And that position do depend on speed! Do the homing with different speed, look at your stepper position (a marker or screw) it will be different while the machinecoordinates in all cases is shown with zero.
If you were right, and as we see, the machine is not moving again towards the switch, the machine will not show the position zero, but the distance needed to come to stop  .
I understand that the switch need time to flip, no matter how fast the knob is hit. But why travel the long way with low speed when that is only needed for the way back to release the switch? Is it not stupid to let a fast machine move slow across the whole table while only a few step are needed on that speed?

Burkhard

13

General Mach Discussion / Re: Homing position is not absolute

« on: May 01, 2011, 02:11:50 PM »

Lower your homing speed in Config >Homing/Limits. It sounds like you're homing at 100% speed. Try 10%, or less.

Hi Gerry!

Thanks for your advice. My machine is not very fast and 10% is really slow, especially when there is a long way to travel. And, it will only lower the effect, not eliminate it. I'm using light barriers for homing and I would like it exact as it can be. If i later change the homing speed the homing position will move, I don't like that. May be I can use a macro. Fist homing run with 100% to come close to the switch and a second one, step by step.
With the light barriers the signal needs max 2 steps to flip and I don't want to give this away.

Burkhard

14

General Mach Discussion / Homing position is not absolute

« on: May 01, 2011, 12:48:25 PM »

Hello everyone!

I'm not happy with the homing function in Mach3.
When starting the homing, the machine runs into the switch. It then slow down and stops. The number of steps needed to stop depends on the speed in the moment the switch is closing and the acceleration. The machine is then trying to get to full speed in the opposit direction til the the switch is released. In the moment the switch is released it will be on the same speed like the moment the switch was closed because the distance and acceleration are the same. Now the machine slow down again and stops. And after that the position is set (to zero). This position is the number of steps away from the switch-release-point of needed to come to full stop.
If the the machine is verry close to the switch before homing, may be 4 steps, it will not reach max speed, so not the max breake distance is nedded. 4 steps vor speedup means 4 steps needed to break. In this case the new zeroposition will be ca. 4 steps away from the switch-release-point.

The homingposition depends on the position from where the homing ist started. And if you change the motortuning the position will move as well.

I would like the machine running into the switch. Break and stop while counting the steps needed. As I know a switch (mechanical or optical) can't be released by now. Then travel back these number of steps. Now go on step by steb til the switch is released so the machine can stop with only one step after releasing the switch. This position will never change.
What do you think?
Burkhard (Germany)
(sorry for my bad english)