Odd stepping problem

Hi, I thought I would check to see if anyone has had this problem already before tearing down my machine to find a solution.

The machine is producing a stepped, layered progression on inclines on the contouring (finishing pass), that started recently.
Has anyone had this problem? Any suggestions on the source?
See images

Foreground carve is ok, background carve displays the problem
closeup of problem

I am using Kiri:Moto to produce the toolpaths, and running them through UGS platform.

Thanks in advance for your suggestions.

@Markus - Doesn’t look too bad. Need a little more information as to what bits you are using and bit parameters. Stepover, etc. It appears to me stepover may be to high. Are you using a tapered bit?

Adjust whether the spindle is vertical, or the specific parameter value of the spindle

Thanks to you both so much for your responses! :grinning:

Heyward, Yes I have intensified the stepover down to .05 from .08 on this carve, using a 1/8 ball mill from Sienci. 1st time using it (in metric). Wasnt sure about stepover values for it, so I kept experimenting. Since I havent disassembled my XZ gantry for maintenace in a while, I wondered if it might be askew slightly or in need of additional cleaning & lubrication.

Rosexing, I have wondered about that as well… Im not sure how to best confirm perfect vertical alignment with my existing resources however. “The specific parameter value of the spindle” Im not sure what you mean

I will be taking apart the XZ gantry for a thorough clean & lube this weekend, likely replacing the v-wheels with ones that are exactly the same size(I noticed during the initial build that they can vary slightly in size)

I look forward to any ideas you may have, thanks!

@Markus I tend to think that @Heyward43 is on the right track, but I’m confused by the pics.You say that the foreground carve is ok but the background carves are not. Your first pic seem to be a roughing pass, then the second is a finishing pass. The third seems to a be a zoom of the first. Is the correct?

With a 1/8" bit using a 5% stepover, I would doubt that this is a tramming issue. Do you have this issue with other files?

1 Like

Gwiki- The top image depicts both the successful carve (finishing stepover at .08, lower part of image) and the problem carve (finishing stepover of .05 upper part of image), 2nd image is closeup of same problem carve.

I had done another carve done that gave me trouble so I chose to redo the good carve seen above a 2nd time with a .05 stepover.

You think that the .05 stepover could cause this problem? That would be a relief!

I disassembled my XZ gantry, cleaned and lubricated it, checked vwheels & found no issues that might seem to be causing a problem. My experience and limited tools are making tramming troubleshooting difficult.

Thanks for your input! Perhaps now I will test another carve finishing with the 1/8 ballnose at .08 or .09 stepover…

@Markus I may not have explained myself well. I don’t believe that the 5% step over could cause this problem. In fact, lowering the step over from 8% to 5% would help, if anything. I’ve never gone lower than 8% and use 10% for many of my carves, depending on the bit.

My point about the 5% was only to say that using that bit and a 5% step over, I doubted that your problem is owing to tramming, as @Rosexing suggested. I could well be wrong, but when you figure that a 5% step over with that bit means that you are only moving 6 thousandths of an inch at each pass, I doubt that tramming plays much of a role in the issue.

I’m with @Heyward43 in saying that your second image looks pretty good considering that it is carved in what looks like pine or fir, both very soft woods, prone to tear out. You should not expect to be able to carve in soft woods without doing some touch up sanding.

Thanks for the advice! I have experienced other similar stepping issues in soft wood before, but only recently again when starting to use a ballnose… I will keep looking for what Iam doing wrong.

Looks like it was as you said - soft wood.

@Markus Glad to hear it, Markus. Have fun. Be sure to post your projects in “Show Off”.

As the original issue has been addressed, I’m closing this topic. If anyone else has a similar concern, feel free to start a new topic, which will ensure that it is addressed promptly.