I keep losing steps on the X and y.

I keep losing steps on the X and y. The previous Frankenbot was using larger stepper motors ok the X and y so the issue might be with the motors, but I don’t hear it skipping. Belts and pulleys are tight and I have messed with the current from 30-65%. I have also been messing with my slicer but could the issue be my jerk and acceleration settings in the firmware being too high?

Any advice would help. Need to get the other kids’ printers working soon!

I think I would look at the acceleration and jerk as you suggested - the smaller motors may have the power to move the axis but may not have enough to change direction as fast as you are asking them to do. The reason I say this is that your machine has a lot of beefy components (higher mass) - much more so than the typical printer.

@Alan_Thomason thanks!! I figured that was the issue as I know those motors are being hit with the most force (or torque I guess) when changing directions. I’ll try to mess with the values. I know I changed them up on the other one but I guess the little guys can’t take it.

Definitely try low jerk and accel (like 5 and 500, respectively) to see if that fixes the problem.

What motors are you using, and what current? If you’re not trying to protect plastic mounting brackets, try raising the drive current closer to the rated current. (They should be hot.)

@Ryan_Carlyle thanks I’ll try those values and post an update! I’ve messed with around I believe an amp or more through them. They are definitely getting warm which I don’t like. It leads me to believe it’s the jerk again as they seem fine aside from they lose steps when switching the velocity quickly.

They are small nema 17. I could give you a measurement in the morning if you are curious.

Steppers can be so hot that you can only hold your finger to them for a few seconds. One of my steppers has been in use for over a year and it is very hot to the touch.

Right, steppers are supposed to run hot, if they’re not even warm then you’re severely under-driving them. Using the RATED current will normally make them too hot to comfortably touch. I can see not wanting to do that since these are for kids, but “pretty warm” should be your minimum current setting.

I read somewhere that it could be a defective driver chip,

Stepper motors skipping steps is a very complicated issue.

A stepper motor has no inherent feedback on any movements made by the shaft in response to the coil current. Current is pushed into the coils to step the shaft, and the assumption is simply that the shaft then takes a step in response to the new coil current.

There are several reasons why a stepper motor shaft may not turn in response to coil current, or may turn despite being held by coil current.

One possible reason is that the shaft is connected to something too heavy for the coil torque - the load on the shaft has too much inertia.

Also, when then the shaft must come to a complete stop, the motor is still energised with holding currents in the coils, which is supposed to prevent the shaft from moving. But sometimes the load on the shaft is so heavy and fast that its momentum can overwhelm the coil’s holding current, and so the shaft can move past the expected stop position anyway.

Another complication is that stepper motors contain permanent magnets, which can be destroyed by very high coil currents, so the solution to these problems with the inertia and momentum of the shaft’s load is not to simply keep on increasing the coil current.

The complex electronics that drive the coil currents in a stepper motor do allow for the currents to be increased - to a point, but there is obviously a limit to the effectiveness of extra current - which is the point when the coil current is so strong that it demagnetises the permanent magnets.

Lastly, the stepper driver uses power transistors to deliver coil current, and these transistors can be destroyed by too much heat. The stepper driver electronics can be designed to protect the power transistors, by backing-off the coil current when required. Therefore it is also possible for the motor to skip steps after the driver board has been operating for too long in a hot environment.

It is best to keep the power transistors cool with heatsinks or cooling fans, if stepper driver electronics must operate continuously for long periods of time in a hot environment.

Where is the GitHub for the frankenbot

Just bump your current higher until it stops skipping. 80% is the most I’ve run steppers. That should fix it. You could also turn travel speed down… 80? 60? Also, you could enable acceleration. The Big-E relies on acceleration b/c of the huge mass.

@Glenn_West search G-Rap and it should come up.

Like I said I have higher jerk and accel than normal so I will mess with those values and the current. It seems to be skipping on hard direction changes which leads me to believe it is those issues. I’ll report back.

Just changed the XY jerk down to 10 from 25 in the eeprom. I can’t try it now but will when I get home. Fingers crossed!!!

Messed with all the values. Accel down to 500 and jerk to 5. Current from 30-70 and still no difference. Here is an update with the video for a better view for you guys. Any advice is greatly appreciated as always.


you need to tighten the bolts on the neck

All bolts are super tight.

Just wanted to give everyone a heads up. The issue is resolved. It turned out to be a faulty printrboard as I switched the one from the good orange and black not to this one and it printed flawlessly. Just put another new on I had lying around in it and it has gone hours without an issue. Glad the motors aren’t the problem.