Weiss VM25 Z axis power feed.

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Dec 27, 2020
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Arizona, USA
I finally got tired of cranking the the Z axis up and down. So I decided to have a go at adding a power feed.

There are plenty of good ideas out there for me to copy and I decided to use a wiper motor to power the axis via a timing belt.

I purchased a wiper motor from Amazon, $33.49 free shipping.....

The Black ("motor negative") is internally grounded to the motor housing.

I completely disassembled the wiper motor and discovered that the circuit board allows for either floating or grounded motor "negative".

The "negative" brush holder is connected to ground via a HCET HC-02 motor overload protector.

The modification is fairly easy. Just unsolder the HCET HC-02 from the circuit board and move it to the board location designated for the "floating negative" configuration.

I have the unit reassembled and tested. Appears to work fine. The suppressor capacitors are still connected to the motor housing, so they should still function as designed.

Yellow is High speed and green is LOW speed. The white and red wires are for the "Park Switch".

I'm sure there are wiper motors out there that have a floating negative, but I decided to wing it. I got lucky on this one.

Hopefully someone may find this useful. Taking apart the wiper motor was fairly easy. No rivets. Just some metric screws and one pesky circlip (you have to remove this clip to get the armature assembly out of the housing).

Just don't break the brushes or loose the tiny springs that extend them.

You can "park" the brushes in the fully retracted position by looping the braid over the end of the brush holder.


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I ran a quick test to measure the output RPM of the wiper motor gearbox at low and high speed from 6VDC to 13VDC.

No Load slow speed (green wire) = 39 RPM @ 12VDC, 1.86A. Speed is approx. 3.25 RPM/V

No Load high speed (yellow wire) = 51 RPM @ 12VDC, 2.75A. Speed is approx. 4.2 RPM/V.

I'm using 2ea 3D printed 3mm, 48T 15mm Wide HDT timing pulleys with a 447-3M-15 Timing Belt from:

D&D PowerDrive 447-3M-15 Timing Belt - Off Road Belts LLC

The Z axis moves at 0.113"/s (down) and 0.113"/s (up) in slow mode.

The Z axis moves at 0.161"/s (down) and 0.135"/s (up) in fast mode.

No, issues so far. I just need to add a Fast/Slow maintained toggle switch and a momentary Up/Down switch.

I will also add some limits switches to prevent running into a hard stop at either end of the travel. Top one will be fixed and the bottom one height adjustable.

I do have some Aluminum HDT timing pulleys on order, but I may not need to use them. PLA printed parts seem to be robust enough when printed at 50% infill.


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