I’ve tried many times. It works with reversing z, problem is that it only plot travels and not any shapes… 
The gcode for lifting Z that is generated using grbl post processor is not accepted with fluidnc…
Trying out chatGPT:
User
Hello there
ChatGPT
Hello! How may I assist you today?
User
I’m struggling with making the z move in the right direction on my home made pen plotter using fluidnc and a RC servo for the pen lifting. Do you have any ideas to help me in the right direction?
ChatGPT
Sure, I’d be happy to help!
To make the z move in the right direction on your pen plotter, there are a few things you could try:
Check your firmware settings: Make sure that the direction of the Z-axis is correctly configured in your firmware settings. You may need to invert the direction of the Z-axis movement in your firmware settings to get it to move in the correct direction.
Check your wiring: Double-check the wiring of the stepper motor that controls the Z-axis. Make sure that the wires are properly connected to the stepper driver and that the stepper driver is connected to the correct pin on the controller board.
Check your G-code: Make sure that the G-code you’re using to control the Z-axis is correct. For example, if you’re trying to move the Z-axis up, you should use a positive value for the Z-axis movement in your G-code.
Check your servo: If you’re using an RC servo for the pen lifting mechanism, make sure that the servo is properly connected and that the servo arm is positioned correctly. You may need to adjust the position of the servo arm to ensure that the pen lifts and lowers in the correct direction.
I hope these tips help! Let me know if you have any other questions.
User
The z axis moves correctly when inverting the gcode, in opposite direction. But when using the regular direction the z only moves down and stays there.
ChatGPT
If the Z-axis only moves down and stays there when using the regular direction in your G-code, there are a few things you could try:
Check your endstops: Make sure that the Z-axis endstop is not triggered or stuck in the “down” position. If the endstop is triggered, the controller will think that the Z-axis is already at its lowest point and won’t allow it to move any further in that direction.
Check your limit switch connections: Ensure that the limit switches are correctly wired to the controller board and are working properly. If a limit switch is not functioning correctly, it could prevent the Z-axis from moving in one direction.
Check your G-code: Check your G-code to make sure that there are no commands that are preventing the Z-axis from moving in the desired direction. For example, if there is a “G28 Z0” command in your G-code, this will move the Z-axis to the home position (which is usually the lowest point) and set it to zero, which could prevent the Z-axis from moving down any further.
Check your firmware: Make sure that the firmware settings are configured correctly for the Z-axis. You may need to adjust the maximum and minimum travel limits for the Z-axis to ensure that it can move in both directions.
I hope these tips help you get your Z-axis moving in the correct direction. Let me know if you have any other questions or if there’s anything else I can help you with!
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It missed, make sure you do not HAVE to home Z first…so close.
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It’s still neat to use the list as a reminder of what to rule out!
That is mind blowingly amazing. I mean, it could do another scrape about that info and catch my post and next time the question is asked it will be that much better. Think about all the recent articles with people making fun of the things it got wrong. That is just like learning at school, except it doesn’t forget. So each correction or article very well could train it to do it correctly the next time around.
Insane, scary, awesome. All at the same time.
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The plotter is finally alive! It’s been quite a ride, with many bumps in the road. Now remains encasing the card, fixing up the wires and tuning the speeds. Thanks a lot for a nice machine, @SupraGuy !
How do I embed a video directly? I’ve seen others do it.
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I think I have only seen videos loaded to YT or google photos and people post the link. The link gets embedded.
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And now with a z stepper instead!
Found a pancake stepper from a salvaged printer. Perfect size, but it gets quite hot! If I turn down the voltage, the torque slips. How hot is too hot?
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The rule of thumb for PLA is about 50C. Above that, the PLA creeps faster and you deformation of the mount.
That tiny stepper probably can’t handle much current.
The mounts for the stepper is plywood, so it could handle plenty more than 50C. But alas, today it just stopped working while stress testing! Not sure if it stopped because a wire shorting or from heat and stress. The torque needed to lift the pen must be neglible, but still. I guess I’ll try a bigger one:
Wow, somehow I missed this entire topic, this is an awesome one!!!
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Man when you have your machine in a HOT (and i really mean hot) environment. Your steppers and pla pieces works against you -and running AC all day long isnt cost effective. 
SHOOOT. I was trying to remove the metal spur gear from the stepper - and I RUINED it. It was quite fitting for this application. Now I only have bigger (uncommon) printer stepper motors, that are even bigger and only runs on 24V.
Edit: I guess I can try my luck with the 28BYJ-48, 5V, again. I didn’t figure out how to run it on the MKS DLC32, with TMC2209 drivers and fluidNC. Well well - the rabbit hole goes on and on!
Edit 2: I did try to convert to unipolar 28BYJ-48 to bipolar, to use it directly with the control board. But now it only hums when running it, with no movement.
Edit 3: OOOH - this one is nice!! https://www.aliexpress.com/item/1005005101736266.html I wonder if it has enough torque. But I sort of defeats the whole idea of building the plotter as a re-purposing of old parts.
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I saw someone used a Cheap peltier to push their electronics. May work here.
These little 28BYJ-48 steppers are geared way down and you need drive them with a lot of steps to move any distance at all. Put in a pretty large steps/mm number (1000?) and try moving a convenient distance (10mm)… hopefully it perceptibly moves. If it does, measure the actual vs commanded movement and compute the scale factor (commanded/actual) to multiply the current steps/mm by…
They actually can be driven with our little stepstick drivers. You just need to set in a very small Vref that keeps the current low enough to keep the generated heat manageable… they’re drawing current even when holding position. Unfortunately I don’t remember the numbers I used way back when…
Eventually the Z-axis morphed to this…
and then ultimately became beltless in favor of a printed leadscrew.
Here’s the portion of my long thread where I played with this little motor. IIRC I think I ditched these belt-driven Z-axis designs because because I kept losing my focus distance every time I powered down and the motor ran hotter than a firecracker… 
– David
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I often refer to my journey into the reprap world as tumbling down a deep rabbit hole, leading into caves of both knowledge and confusion.
And here you are David, along with all the other friendly souls - showing up in your tunnel boring machines! I’m so thankful for all your knowledge and patience you share! At times I feel like a frantic rabbit, while you guys have dwarven fortresses full of treasures.
Well. I did try increasing steps/mm a lot and tweaking vref. But the only movement I got was random jumps. Nothing predictable to work from. I feel like moving the whole plotter down to the basement, to tidy up the mess in the living room. I’m tempted to order the nema 14 mentioned earlier. Do you think it’ll be up to the task?
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More like a cluttered mess that continually frustrates the heck out of me when I can’t find stuff… possibly a “dwarven fortress full of treasures” only because I keep ordering stuff I already have just because I can’t find anything.
I’m sure a Nema14 would be the better choice. I never could really get Vref dialed down enough to keep the 28byj-48 motor from running hot, while just holding the laser in focus position. Plus I don’t think it was really all that accurate at positioning anything… probably due to the gearing.
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For completeness sake, I happened to run across this video… if you’re still interested in playing with the 28BYJ-48 steppers. He’s modified them for bipolar operation, of course, and determined the coil pairs… orange/pink and yellow/blue. He also had to rearrange the wires to directly plug into the shield.
It also appears he sets up the A4988 drivers with no jumpers so he’s using single-stepping IIRC. Later, and after he demonstrates movement, he shows that he’s using 250 steps/mm… which he later changes to 500 steps/mm for some reason. He never mentions his Vref settings that I could see… but it will be quite low, maybe 0.1V?
Could be fun if you like to tinker… and I did play with them enough to convince myself that they do work and, in some use cases, could be useful.
– David
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Thanks for new insights from your dwarven fortress! I did try the bipolar mod, but to no avail. Still only shaking and jittering. The plotter has been exiled to the basement, and I’ll bring it back up when the Nema 14 has arrived and I’m ready to start my new career as a plotting artist.
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David, i want to come over and learn!!! Wish u were in michigan!!!