X and Y Axis stucked

Hello everybody,

I am brand new in this forum so I will explain a little bit about my machine and my problem(s)…
On December I finally found a place where I can build my first MPCNC and I decided to use the V1 system.

I built a quite large machine (1,2 sqm) with an Arduino One control board and connected with Estlcam.
I made some test cuts and the machine is responding well with a nice precision but sometimes the motors (X or Y axis without distinction) fail and get stuck in the same position while the CAM project goes on.
This is translated in an error on the cut.

What could be my error (I am trying to figure it out)? Stepper motor not strong enough (55 Ncm)? Belt too loose or too tight? Something I can not figure?

I have a video I made to record the problem, if should be useful I could attach it.

Thank you

Welcome to the forums! :slight_smile:

Videos can’t be uploaded here, you need to use Youtube and give us the link.

From what you are saying it is not clear what happens, so a video might help. :slight_smile:

Hello @Tokoloshe Philipp, thanks for your answer,

here the link to the first video where you can see the motors blocked during their movement, I send a link also where you can see the error in the cutting during a test.

The second video looks normal, but I can’t say what the issue might be. Is the brrrr Sound from the steppers?

The second video is made to record the error on the movement (the second pass of the router should be exactly in the same position of the first but as you can see is the machine is cutting in a different position).

I made another video where you can see that the router is not moving although a movement is recorded from the software.

Sometimes when I cut or engrave the machine does not proceed in her path while the software goes on with the project… this situation results in a wrong position of the router.

Hope to be more clear

Thank you

Did you check your cables? This could well be a connection that is loose. If Estlcam runs out of memory it stops the program, so that isn’t it.

That’s called “missed steps”.

The software has no way of knowing the router didn’t actually move, it just feeds instructions. Once you start missing steps the project is toast.

Your seriously went over the size of a simple machine. It’s letting the steppers get out of square in relation to each other, which then makes everything bind up. That loud noise is your steppers trying, and failing, to turn. I would be surprised if it wasn’t having issues.

Your basically asking an 70s Honda civic to perform in F1.

@Tokoloshe I checked the cables, everything is working, seems to be more like @Nathan_Doty says.
@Nathan_Doty Do you thing the only solution is to reduce the size of the machine or could I solve with more powerful stepper motors? If I have to resize my working area, 1 sqm could be enough?

Thank you both

You can salvage all the expensive parts and build a lowrider. The structure for the primo style is very lacking for that size of a machine.

This does not make sense at all. Yes, the machine is too big, but that’s not a reason as to why the steppers would go out of square. It also moves when not square, I know because I had that for the first few cuts when building it first.

The steppers are binding, yes, but that’s definitely not the reason.

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When you’re dealing with small distances, small errors don’t matter. The longer the distance the greater the effect.

Both axis on the primo are basically just sitting on very loose pivot points. It’s really not hard to get them out of alignment and cause binding. And the longer the axis, the easier it is, the longer the lever that has to be overcome to get moving again. The steppers may compensate after a second, but actually look at how many instructions have been passed in the gcode in that time frame.

Once you start missing steps the project is likely dead.

Out of square for cutting vs out of alignment enough to physically stop moving.

2 different things.

It didn’t skip steps before. The length of the rails is irrelevant, it’s not going to bind like that if out of alignment.

Francesco, I have had a similar problem with one of my steppers. I am not sure how it happened but I had a stepper that was getting stuck randomly and it turned out to be very small metal pieces being caught between the rotor and stator inside the stepper. The metal chips are very small but would randomly cause the stepper to stop. I am not sure if this was caused from operation on the MPCNC or if it was present when they were manufactured. It was an easy fix to take apart and clean the rotor. I have also had similar behavior from a bad wire connection.

I think I had this same issue… one of mine bound up and I replaced it. You could feel the bind spot by moving the axis by hand. Every rotation of the motor it would catch making the movement easy-hard-easy-hard until it would skip and then be off. I tried loosening bearings, and eventually replaced the motor. In the process, I found that both trucks had cracked and the core was cracked as well.

  • It cannot be overstated to ensure the system is square and the trucks are running square to the frame. This is critical.
  • Once that is certain, then make sure the pipes and bearings are clean and the system can be moved by hand with some resistance, but not pulsing regions of hard and easy movement.
  • Then verify the wiring isn’t binding or catching on something while moving that would cause a missing a step because of a solid core break or a bad pin (had both of those happen as well) or simply holding the thing so it can’t move.
  • And then as always, check the grub screws and make sure they are tight and secure.

With the larger mpcnc, it is possible the centers of the tubes will sag. you can print mid-supports for them or you can make it smaller. I started with a 30" x 40" cut size and chopped it down to 20x30 and it is easier to manage. I made a jig for placing the feet to make sure it was square to begin with and then made certain my end stops for squaring were dead on. It made a huge difference.

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The stepper noise sounds like one coil is open I would be looking very closely at the wiring Checking all solder joints, splices, connectors. Your wire needs to be stranded wire. Double check any splices . As others have said,mack sure you’re wires aren’t catching on something.
Nice looking build.

A long axis could make one of the motor skip steps as the force would be higher on one of them if its cutting close the edge.

The sound in the first video sounds like the motor is skipping steps. And what you see in the second video is the result of skipping a few steps. It’s possible that since your axis are quite long, when you cut something in the edges one of the motors can’t keep up with the stronger force, compared to the opposite motor on the same axis. And in turn causing it to lock up.

I would say its a combined problem of small motors and to long axis.

Assuming that your frame is completely square I’d say to try again but maybe cut slower, as a stepper have more power at low RPM and there will maybe be able to hold its position. Maybe even cut more shallow.

But in long term, if you want such a size you’ll want to upgrade to either a lowrider or something else. MPCNC is great but limited in size due to deflection of pipes from the weight of the router and the cutting forces.

Edit. You can also easily check if the problem is that its out of square by measuring the distance from the ceased axis to the corners on both ends.

That would mean the LowRider wasn’t possible. The steppers really don’t care about that…
It takes more than that for them to skip steps.

Missing steps generally isn’t in the motor. Its the gantry sitting still while the gears skip over the belt. So nothing moves, but the software/controller doesn’t know that. The motor can turn all day long, but if the gantry doesn’t move you’re missing steps. The longer the point between A and B the easier it is for those 2 points to get out of alignment enough to make it miss steps.

In reference to the above, if the router is stuck on the far left just long enough for 1 tooth to skip, the other side is now 1 tooth ahead. The next time it sticks in the same place, it’s now 2 ahead. It’s cumulative damage (to the work). It progress until they’re far enough out of alignment to physically bind.

It’s a limitation of the design. It can be infinitely long, and as long as no stepper ever skips a tooth, no issues. But it becomes infinitely more likely that it will skip a tooth the longer the axis becomes.