3d Finish Pass Redo

[Jstumbo1974]

Hello there,
I am working on a 3d waving flag and I am needing to redo the finishing pass after a few changes, corrections, and the addition of epoxy to the stars (Will rethink the process for the next wavy flag project).

There is no longer the initial Z point due to the roughing/finish toolpath completion.

I am looking for a suggestion on how to accomplish a Finish Toolpath redo.
1) Should I "Z" off the highest wave point?
2) Should I use extra material that is the same height as the original material?

[Adrian]

I would zero off a piece of material the same thickness as the original.

I always zero off the table surface on my projects (I have an adjustable touch off point) to avoid issues like that.

[Jstumbo1974]

Probing for Starting Material thickness worked! Once I had the starting Z, I adjusted accordingly.

Thanks!

[Jstumbo1974]

Thank you for the suggestions, I went with a piece of material the same thickness and was able to make it work.

Thanks again!
Jason

[adze_cnc]

Since then, I have rang into another issue with a new Finish Pass. This time (on a new piece), a portion of the wavy flag missed a portion of the upper wave in one of the areas.

Rough pass went fine, but the FInish pass miss a section. Not sure why. I did push the bit a little faster in the feed rate, but the bit did not slip. I tried to lower the Z height for an additional FInish Pass, and no luck.

The 3d preview looks good, toolpaths look good, I am lost at the moment.

As with most cuts if the preview looks good and the result doesn’t it’s generally something that “we” are doing or not doing.

Can you post a detail photo of the bad result and a screenshot of the preview? The screenshot can be made with the Windows Snipping tool or you can save a previe image from the preview tab (after zooming in to the right spot).

My initial thoughts when hearing about increased speed and curves being miscut is that some controllers use “constant velocity” to ensure that the machine doesn’t stutter and get jerky. The drawback is that some angled shapes get cut blobby. An extreme would be hexagon that gets converted to almost a circle.

[Jstumbo1974]

What I think happened, sort of along the lines as Adze_cnc was saying, the controller had a "not happy" moment with the higher speed, the controller went lower in "Z" hieight and caused a more drastic rough cut in one particular section of the higher waves.

For the Finish pass, I slowed the Feed rate down a little and I lowered the starting "Z" Height to clean up the finish pass.
In the end, another learning lesson.

Thank you for your help!
Jason