Monday, January 27, 2020

DIY CNC 3018 Adding Limit Switches

I am in the process of adding some limit switches to a CNC3018.  It can be done without any adapters.  For the Y axis I used some 3/4 inch 4-40 screws.  The screw head goes through a washer that is cut flat on one side, so it can fit in the T slot groove.  Then a large bolt goes into the slot of the platform.  Something square would make the switch levers hit more evenly.  I might make something out of aluminum for that purpose.
This is the completed, front Y axis switch with a aluminum square block on the bolt.
CNC 3018 Pro Y Limit Switch

Here are pictures of the first X limit switches.  These were later changed to smaller switches like the ones used on the Z axis.

This is the Z axis limit switch.  It is required as the Z axis is tested first.

This is how a major website shows to wire the CNC 3018 PRO.  This is TOTALLY wrong!  The platform will crash when it tries to go back because the wires and wire ties are in the way..
Here is how I wired my CNC 3018.  I used some black electrical tape to cover the wires from the Y axis stepper motor.  The wires to the X axis stepper are folded in thirds within the wire wrap.

 This is how I wired the Z axis.  This works quite well and allows the cable to move freely.
CNC 3018 Pro Z axis Wiring

I improved the wiring harness and the X axis limit switches.  The wiring harness now looks like, and could be, one continuous piece.
CNC 3018 Pro Wiring

The new X axis limit switches are micro switches like the one I used for the Z axis.  The biggest problem with these switches is that a 4-40 screw is too big.  You need a 2-56 screw.  I found some screws that came with servos for use with the servo horns.
CNC 3018 Pro X and Z limit switches

It is finally working!

The problem was calibrating the driver voltage/current.  With a voltmeter on ground and on the center of the trimmer adjust for .7 to .8 volts.  That results in 1.4 to 1.6 amps to the coils and much cooler drivers.  If you do not have a voltmeter and are using 8825 drivers set the trimmers to match this picture or to about 25 degrees to the right of straight up.

This is a picture zoomed in on the trimmers.

Here is the code to work with the limit switches and to make "home" the 0,0 position.


After going to "home" set the Z axis down to the surface and then set the X, Y and Z to "0".

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