Possibly a strange question: I am building a second Mostly Printed, but then for use as a plotter / drawing machine. Based on some MPCNC customized parts, but with the same electronics. I do not need the heavy middle section with the Z-axis. The portal is given an H-shape (seen from above).
Instead of the Z motor I would like to use a servo or a small and light stepper motor to lift the pen a little bit.
Since I do not know anything about electronics, I would like to ask someone who can tell me if this is possible. And if so, can I still use gcode files?
I use an Arduino Mega with Ramps, such as the package from the MPCNC in early 2017.
Jack, I’ve written a “Pull Request” on Marlin to emulate steppers with a servo, but even if it works well, it’s not really easy to use.
It wasn’t updated to take into account recent updates, so would need some software work to be ported to a recent codebase, but would cover your requirement:
I have now connected a Nema 8 stepper motor 1.8 step, 3.9V, 0.6A to the Ramps (Z). I have lowered the stepper driver current to 0.4 and removed the MS3 jumper under the driver for the 1.8 step. Wirecolors connected to: blue>2B – red>2A – black>1A – green>1B.
Sometimes the motor runs well, but after a while trembling fast from left to right and v.v. The motor becomes very hot.
What and where should I change something in the firmware?
Hmmmm its seems as if your trying to go 2 directions at one time. My thoughts are since you have gotten the servo to work could you import the dxf lines into excel and use the find and replace function. Then export back to dxf?
So flow would be
Dxf notepad file > excel > excel find,replace > dxf notepad file??
Bare in mind i haven’t worked with any files but i know you can copy the code lines… only stands to reason if you can copy you can paste…
That is a good thought. But I’ve already tried it. In Wordpad you can immediately search and replace in the stl file. But it’s an extra job and mistakes are quickly made. In addition, I want precise control over the Z-movement of the pen. It is not intended that the pen bounces on the paper.
I also think that the Nema 8 is not powerful enough for a pen-lift system. The carrying capacity is only 180 grams and that is too little.
I am now working on a unipolar cheap $ 2 stepper motor that I have made bipolar with help of a YouTube instruction. That little motor is much more powerful. I do not know yet if it needs firmware adjustment.
Thank you for your response. If anyone has any advice… please.
Just for ensure that your nema8 hasn’t an internal defect. Ok, so time by time it stuck even without workload. Hmm. Just check maybe a one wire sometime loses contact. I haven’t another idea at the moment
You said two jumpers, why not all three, and what drivers are you using? Are you positive you got the step rate correct in the firmware? Max speed and accel?
This is the problem. You have a homemade gear on there, one mm should be a tiny fraction of one turn. The step rate you highlighted can be confusing, put all three jumpers on and calculate your correct steps at 32nd stepping. Do a test, tell it to move 10mm and see how far it actually moves.
Steppers do not have any guess and check or calibration needed they are precise, you should have an exact number to use.
Thanks for your offer. But besides the lack of power I think that the printed gears are not the most ideal solution too.
So I decided to take another turn. I am going to use a short piece of leadscrew and a smaller Nema17 (1,33 kg/cm) and put it above the middle of the lift. The middle part will have approx. 0,25 kg more weight, but we’ll see what happens.
