Limit and Home Switches

A decent 3-axis CNC machine needs 6 limit switches. This prevents damage and/or injury if the machine should try to run over its limits. In addition, it and should have 3 home switches. Usually, each of the home switches is combined with one of the limit switches. Here's what the manufacturer recommends:

Instead of mechanical switches, we could also use inductive proximity switches (which is recommended for more precise homing position)

Best result so far:


Configuration:

limit switch connected as normally open (NO)


             

 

homing works: click on home axis and the element will move to the left until it hits the switch, then it stops and goes to the home position. After the axis has been homed, the stepper will not go below the home position and beyond what is is allowed by axis parameters.

Combine Minimum limit and Home Problem

When the LinuxCNC software is started, the axes can be moved with the keyboard. If the axes have not been homed, it is possible to go beyond the switch with the keyboard jogging commands and the machine can be damaged.

So far, I have not been able to use the same switch as a home and a limit switch.

11-6-2015:

try

http://www.mycncuk.com/threads/3276-EMC2-home-limit-switches-only-acting-as-limit

I found this in the LunuxCNC "Getting started Manual"

• Home Switch Location - The location at which the home switch trips or releases reletive to the machine origin. This item
and the two below only appear when Home Switches were chosen in the Parallel Port Pinout. If you combine home and limit
switches the home switch location can not be the same as the home position or you will get a joint limit error.




Things tried:

test: set pin 11 to minimum limit + home X and not invert

result: as soon as we power on, we get the joint 0 on limit switch error.

test:  set pin 11 to minimum limit + home X and invert

result: click on home, x-axis moves in the wrong direction (to the right)

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test: wire home x and emergency stop together
 set pin 11 to minimum limit + home X and invert

result: click on home, x-axis moves in the wrong direction (to the right)

test: wire home x and emergency stop together
 set pin 11 to minimum limit + home X and not invert



result: as soon as we power on, we get the joint 0 on limit switch error.

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test: wire home x and emergency stop together
 set pin 11 home X and not invert

result: homing is not completed because when switch is activated, emergency stop is active and power is turned off

test: wire home x and emergency stop together
 set pin 11 home X and invert

result: emergency stop is always activated, cannot unclick







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