Common causes of missed steps

I have been having trouble with my machine missing steps in the Y direction. I am trying to use code from Carbide Create to make a vCarve. It is a complicated piece, but I actually have already made it once. I forgot to flip the image and made one in reverse and other than being backwards, it turned out fine. Now that I am trying the same image flipped, I cannot get it to cut without the machine missing steps in the y direction. It gets roughly 2/3 through and then the machine is off about .125 in. It seems to be consistent, by my best guess it loses tracking at roughly the same time by about the same amount.

I have tried many times now. Some of the things I have tried are slowing the feed rate to 50%, checking the stepper motor set screws, and changing the parameters of the carve (shallower and deeper cuts, as well as changing the stepover). I also thought I might have been hitting a limit, so I changed the work location to be further away from the nearest limit, but that didn’t help either.

I am hoping some folks with some similar issues can help me by providing a list of common reasons why this might occur. Also, could it just be that the file I am trying to do is not playing well with Carbide Create?

The possible causes per the machine operating checklist: Machine Operating Checklist - Carbide 3D , are:

  • Pulley set screws: Checking Pulley Set Screws - Carbide 3D — be sure to check all axes/pulleys including Z (for belt-drive units, also the coupler on HDZ units).
  • Linear motion:
  • Belt tension (see the relevant step in your instruction manual, e.g., Step 5 Belting - Carbide 3D) Note that the X-axis motor is held in place on standoffs and if those bolts are loose this can cause belt tension issues. Also, belt tension for the Y-axis stepper motors needs to be even/equivalent on each side — a significant difference can cause skipping on one side eventually resulting in lost steps on both.

Electronically, check the motor wiring and connectors.

Feeds and speeds could be an issue if too aggressive, but the defaults in Carbide Create are quite conservative.

Post the file and a step-by-step description of how you are securing your stock and setting zero relative to it and managing all tool changes?

Are you using clamps and a dust shoe, and if so is there any chance that you get a collision between the dust shoe and one of the clamps ?
Have you been able to watch the cut, up to that moment 2/3 through when the shift happens ?

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Grey-2.zip (2.0 MB)
Here is my file. I don’t have a bit setter, so I spliced out the V-cutting portion into it’s own file. The V-cutting is what I’ve been having trouble with.

Have a hard stop connected to my waste board on the bottom and left sides of my work piece. The stop is below the surface of the stock. I left a 1/4 inch on all 4 sides of the stock for clamping, and I am using clamps that are ramped/angled out of the work space, so they are out of the way. I am using a dust shoe, but the clamps are loose enough that they would have just pushed out of the way if contact was made in the y direction (this has happened in the past).

I am setting zero to be the bottom left corner of the stock, using the early version of the bit-zero. I set it with a .125 bit, then swap to the V-bit and set the Z-axis.

I haven’t been able to watch the progress, the piece takes over 4 hours, and that is unfortunately time I don’t have to spare.

In the file I did set the speed pretty high I think, but like I said, I reduced it by 50% while cutting with no luck. Maybe it needs to be even slower?

Thanks for the responses!

The c2d file looks clean, and the gcode I re-generated from it does not seem to have anything wrong either

You lost me there: are you talking about clamps used to hold the stock onto the wasteboard, or something else ? “loose” and “clamp” usually don’t go together :slight_smile:

No, the feedrate of 50ipm at 18k RPM is ok. What you could try (but from your original post it seems like you already did?) is using half the depth per pass. 0.1" should work but it may be a tad too aggressive depending on the material. By the way what material are you using? I would maybe try with 0.05" depth per pass (and 30ipm plunge/60ipm feed to compensate for the increased runtime: 217minutes versus the original 212)

Indeed. Maybe you could capture a video of the cut and review it afterwards ?

I forgot to ask: after the cut, if you jog to the zero point, is it 0.125" off ?

One option to rule out the feeds and speeds could be to run an air job, with the stock in the same position as before, but resetting Z0 0.2" above the stock or so, and run it. If after the run the zero has shifted 0.125", you’ll know it has nothing to do with forces on the vbit / feeds and speeds.

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Unfortunately I haven’t had the time to mess with it yet, but I plan to try doing a run with the bit set above the stock, and then see if it is still zero after it runs.

As for the clamps, the way I have my piece held I don’t need to apply much pressure to keep it in place, more like taking the slack out of the interfaces between the waste board, stock, and clamp. Kind of like a firm handshake. If the router or bit contacts the edge of a clamp it just gets pushed out of the way and off the stock. Not ideal, but not the end of the world. I don’t think this would be the issue, as it has lost tracking without doing this.

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