X-axis shift on CNC Piranha

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Tom Riley
Posts: 19
Joined: Sat Jan 31, 2015 7:34 am

X-axis shift on CNC Piranha

Post by Tom Riley »

I am using a CNC Piranha and 3DCut software.

I am having a persistent problem with shifting of the Home location in the x-axis shifting during milling. The shift can occur during Rough or Finish milling and is typically 1.5 inches in the –x direction.

I ran a test with one of the sample files, a baseball plaque 2-A.stl, which shows the problem clearly (Images available). The mill slipped 1.5” in the –x direction between the two 45 degree finish passes. When the milling was finished the mill carriage finished in a shifted location which showed in the monitor as the new Home.

Does anyone else have this problem?

Does anyone know how to address it?

Does anyone know exactly how the Home feature was intended to be used?

Thanks,
Tom Riley

4DThinker
Posts: 951
Joined: Wed Jun 27, 2012 9:00 am

Re: X-axis shift on CNC Piranha

Post by 4DThinker »

A shift can be caused by bumping into one of the hard limits, a coupler on the X shaft slipping, other blockage that keeps the axis from travelling all the way to its limits.

You won't be able to cut all the way out to the extents of the t-track bed. I recommend you jog your router out to where it can't go any farther in X and Y directions, then mark the bed somehow. You want to keep all cuts with this limit box. The machine has no way to know if it hits an edge, and the coordinates will keep advancing despite the bit not moving in that direction. The amount it wanted to go past a limit will be the amount all cuts are shifted past that point.

4D

Mimbler
Posts: 76
Joined: Sat Nov 29, 2014 5:37 pm

Re: X-axis shift on CNC Piranha

Post by Mimbler »

Tom, I know you already know about the hard limits from your previous posts, so I'm trying to think of something a little less common. Contamination issues can cause lost steps or cables snagging, etc. However, are you saying it is always exactly 1.5 which would imply software or control issues or "about" 1.5 ?
Mike
Tom Riley wrote:I am using a CNC Piranha and 3DCut software.

I am having a persistent problem with shifting of the Home location in the x-axis shifting during milling. The shift can occur during Rough or Finish milling and is typically 1.5 inches in the –x direction.

I ran a test with one of the sample files, a baseball plaque 2-A.stl, which shows the problem clearly (Images available). The mill slipped 1.5” in the –x direction between the two 45 degree finish passes. When the milling was finished the mill carriage finished in a shifted location which showed in the monitor as the new Home.

Does anyone else have this problem?

Does anyone know how to address it?

Does anyone know exactly how the Home feature was intended to be used?

Thanks,
Tom Riley

Tom Riley
Posts: 19
Joined: Sat Jan 31, 2015 7:34 am

Re: X-axis shift on CNC Piranha

Post by Tom Riley »

Joy tonight.

I added a 24 inch tie-wrap to the cable to the z-motor so that it would form a nice even loop that cannot get caught in the carriage when the x is fully to the left. This worked well.

To check it out I ran the carriage over the complete work area in both x and y. I found definite areas where material had built up on the x-ball screw that made it complain and probably loose steps.

I carefully cleaned the entire x-screw and reran the baseball plaque test. It ran perfectly.

Clearly I need to add a process for cleaning the ball screws to my larger process. Simple vacuuming them is clearly not enough. The screws need to rotate in the cleaning process and a brush applied.

I assume that you should not use a grease or oil in this very dusty environment. They recommend a dry lubricant like graphite or Molly?

Thanks,

Tom Riley

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