Problems with 2nd pass clean up

[droutt]

I am having problems with a 2nd pass clean up. After the first run, I have been doing a 2nd run of the file for clean up purposes. My 2nd if off by approx. 1/32 of an inch in the direction of the Y+ axis. I have checked to make sure the piece is securely clamped and have even marked the piece on the table to make sure it hasn't moved, which it hasn't. All indicators on the control software show the return back to 0,0,0 after the first run and as best I can tell the bit has properly retuned to the original starting position. Can anyone tell me what is causing this issue? I don't know if this is a software or hardware problem.

[drueth]

Droutt

With out a lot more information like has this happened before. Are you sure the bit did return to the zero point. are you sure you did not hit something like a hard stop or something laying beside the shark ( not that I ever did that, NOT) How aggressive is the cut, You may be going to fast and trying to cut to deep. It could also be the set screw that is used to attach the drive screw to the steper motor. If the second cut is only cutting about 0.02 material I would have to guess the Shark has lost it place on the first cut. So check that the bit is really at the zero pint.

[tonydude]

Check the coupling, make sure they are tight.

Tony

[droutt]

Thanks for the 2 answers. I will check the set screws for sure. The cuts aren't deep. I am using a 60 degree triple wing Rockler bit at the recommended feed rate at 16,500 rpm. As best I can tell the bit is returning to the starting point. I have it set up for a center work piece start and lowered the bit to make sure it was at the cross hairs penciled on the piece. The only things that comes to mind is the feed rate on the software. I slowed it to 85% and the project file has a number of small "swishes" in it. That's how I saw it was off, the swishes weren't dead on for the clean up.

[Eagle55]

I can't pretend to know what might be going on in your situation. For me the repeatability has been real good like if I have to stop mid-run or something and retrace a carve to finish. One thing I would like to add in is that in the interest of not needing a second pass I would recommend that you maybe experiment with feeds, speeds and rpm so that you get a good clean cut the first time, thereby eliminating the need for a second pass. You should be getting clean cuts even in something as soft as pine. What are you doing?? is it engraving letters or clip art or a 3d carve? I have don't roughing passes with a finish pass on 3d carves but never a second finish pass and always have relatively smooth finished results with minimal sanding. Just some input to consider.

Roger

[milo30]

A second pass is common for some to run. Normally hit it with some shellac first to raise the grain and clean it up. I hate running mine a second time but sometimes it needs it and it is faster than me sanding the problem areas.

[Consultingwoodworker]

Why not just program in the second pass so it is part of the original program? If you STILL have the issue, then you know the problem is mechanical not software. Plus it is just easier.

You can either copy the original toolpath and repeat it, or you can adjust the cut depths to add a final pass at 0.01" or something. You can do this when filling in the toolpath data. Look for the number of passes button.

Ralph