.ini min max issues

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29 Apr 2021 13:31 #207370 by Jeff_in_Wa
With a cnc router with two y motors, and an x gantry...

The Y home switches are at the back of the machine

The X home switch is at the far right of the gantry

In the .ini file, setting up the min / max's for homing...

Is min for each Y axis where the switch is mounted, or at the front of the machine work area?

For the x gantry, is min at the far right where the switch is mounted, or at the far left of the gantry?

My machine work space in mm's is:
X 1117
Y 838

Whatever your answer is, will you please tell me what I should be using for home and home offset in order to move off the switches properly?

Thank you for your help.

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29 Apr 2021 19:37 - 30 Apr 2021 12:53 #207389 by Todd Zuercher
Replied by Todd Zuercher on topic .ini min max issues
There are multiple ways to do this, no one is more right than another. It is up to personal preference. Here are a couple examples. Assuming the Z axis moves left to right on the gantry. If the home switch is on the right extreme of travel and is also the hard limit switch, you could use these ini settings for the X axis if you want the machine coordinates to be all positive use...
HOME = 1115.0
MIN_LIMIT = 0.0
MAX_LIMIT = 1116
HOME_OFFSET = 1117
HOME_SEARCH_VEL = (positive number)
HOME_LATCH_VEL = (positive number usually smaller than HOME_SEARCH_VEL)
HOME_FINAL_VEL = (positive number usually equal to max positioning velocity)
This will give you 1115 of travel within your soft limits plus an extra mm on the end for cushion with the spindle parked at 1115 after homing.

If you wanted the home park position to be called zero and all of the travel in machine coordinates to be negative, then use...
HOME = 0.0
MIN_LIMIT = -1116.0
MAX_LIMIT = 1
HOME_OFFSET = 2.0
HOME_SEARCH_VEL = (positive number)
HOME_LATCH_VEL = (positive number usually smaller than HOME_SEARCH_VEL)
HOME_FINAL_VEL = (positive number usually equal to max positioning velocity)

With both of these set ups the machine will touch the X home then move away two mm and stop and have 1115mm of free travel in the negative direction. The difference is the first option will park at 1115 and have travel to 0, the 2nd will park at 0 and have travel to -1115.

The Y axis would be similar except using different numbers to reflect the shorter travel. (The gantry would have two joints to configure.)
Last edit: 30 Apr 2021 12:53 by Todd Zuercher.

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29 Apr 2021 19:50 #207391 by Todd Zuercher
Replied by Todd Zuercher on topic .ini min max issues
A very good way to understand the relationship between the ini settings HOME = and HOME_OFFSET = are to think of them like this. HOME_OFFSET = is the machine coordinate value given to the point in space where the home switch is latched when homing. HOME = is the position the axis moves to and stops at in machine coordinates at the end of the home sequence. So if the home switch is also the positive limit switch, the HOME= must be less than HOME_OFFSET =. Conversely if the home switch is the negative limit (at the other end of travel) then HOME = must be greater than HOME_OFFSET =.

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30 Apr 2021 00:15 #207422 by Jeff_in_Wa
Replied by Jeff_in_Wa on topic .ini min max issues
I can't even thank you both enough... I have spent hours and hours trying to make this work properly. I plugged the negative values as that is what I wanted and it worked perfectly out of the gate. OMG, so happy!!! Thank you both again.

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