MakerGear Forum

Hello All,

I'm new to the forum and to 3d printing. I bought a M2 kit a while ago and assembled it in quick order, but due to renovations it has never printed any models. It is an older model, with the two PSU units (19V), the V2 hot end, etc. The build went very smoothly and there were no issues, but I did notice the print bed seemed a little stiff in the z-axis travel. I could crank up the bed with the lead screw knob easily enough and when it was raised to the highest point and released, it would lower itself slowly to about mid-height above the controller and stop. OK, I guess, I thought to myself since the z-axis was already pre-assembled when I received the kit; maybe that's the way it is supposed to be. I continued on and finished the wiring.

I went to the you-tube video on how to level the bed and I saw how easily the bed was raised - by one finger! And when it was released, it lowered itself rapidly and smoothly almost right to the bottom. Something was amiss, as they say, with my build/kit. My lead screw does not spin that freely. Undaunted, I continued, hooking up Simplify 3D and connecting to the printer - no issues. I was able to move the bed in x, in y, in both directions - no issues. I tried lowering the bed in z and from the top most position it was fine, but at around the mid-point it slowed right down and sounded like it was really working the stepper motor. Not risking raising the bed from that position, I raised it close to the upper third of the range, and tried raising it from there - no go. I stopped immediately; I was not going to burn out the stepper motor in trying.

In trying to determine where it may be binding, I loosened the stepper motor, and it helped, but very minimally. I progressively loosed the guide rods, then the bottom mounts, than the upper mounts, testing how easily it spun each time, but there was not a lot of improvement. I stopped short of taking out the lead screw entirely to see if it is bent, or possibly a sticky ball screw (it's not a ball screw mechanism, but I'm sure everyone knows what part I'm talking about). I presume the lead screw is a press fit onto the stepper motor, but I could be wrong.

As mentioned, when the bed currently 'falls' by itself, it is slow, but it relatively smooth until it hits the mid-height range. If the lead screw was bent I suspect there would have been an area of maximum resistance and then it would ease off as it passed the area of the greatest period in the oscillation. In loosening all the mounts and guides, I was thinking there might be enough play between the components to compensate for a lead screw not being totally parallel to the guide rods. This didn't seem to be the case either.

I'm looking for direction in determining the next steps in finding out where the binding is. I could tear everything apart, but maybe I do not need to and there are several tests I could conduct before I go that route.

Looking forward to hearing back from the group, upgrading to new PSUs, new hot ends, and of course, getting model to print.

Regards,
Pierre

Here's an update...

I took apart the z-axis assembly and the problem seems to be with the stepper motor. The rails were fine - the bed moved up and down freely with no binding.

There was quite a bit of resistance when turning the the leadscrew and holding onto the stepper motor. I took off the endcap and put everything back together and everything was much smoother; it was moving almost as easily as the setup that is shown in the bed leveling video.

So before putting it back together, I hooked up the cabling and tried the control panel in Simply3D to see if the z-axis moved any better without a load. It was not much better - it sounded like it was spinning but the leadscrew would not move very much - it seemed that it was slipping. I tried playing with the z-axis speed in Simply3D and I got the best result at around 1200, but I'm still not sure it will be able to raise the bed. I don't want to put it all back together and it still not work.

One thing I noticed is that the stepper motor and leadscrew spin freely when it is not connected, but as soon as I connect it to the wiring harness, it does not spin as freely (I do not disconnect the motor when it is powered up as per the instruction manual -the power lead are physically disconnected from the board).

So, the questions:
1) Should I get a new stepper motor?
2) Is it normal that when the stepper motor is connected that there should be more resistance, even when there is no power?
3) Should I upgrade to the 24V single power source, from the dual power supplies I originally received with the kit

Thanks,
Pierre

Pierre

I'm having the same problem right now
how did you fix yours ?

thank you in advanced

jose

The stepper motor is acting as a generator when you turn it by hand. When connected to the wiring there is a electronic circuit that absorbs part of that energy. Yes you can burn out the electronics if you insist on doing this a lot or very rapidity. I think there is even a caution in the Owners Manual about turning the steppers by hand.
Spinning and not turning the shaft, check for a loose set screw in the coupling.

Also, your z-axis screw may just need some fresh lithium grease to get the "freefall" effect. Every so often my bed will fall slowly or stop mid fall. I apply a small smear of grease on the screw every 4-6 weeks as needed and it will easily drop.

Your steppers should turn easily when you move them slowly, but quick movements will generate power and resistance, so be careful.

sorry for the delay on my answer
and thank you so much for the information
trying to get the white lithium grease ..but in colombia only found the one in spray
would the spray works ?

thank you again

I would not spray it directly onto the machine. Spray it heavily onto a cloth or napkin, then use the cloth to wipe a thin layer onto the screw. It does not take much. Then run the Z-axis up and down a couple of times under power.

You may have to try a couple of applications or apply it a bit more often since the spray is thinner than the regular grease.

thank you again

will try and let you know