CNC Shark Forum

Hello all,
I recently purchased a never before used Shark HD4 and the Vcarve pro software.
I was running a bobcnc E4 with fusion 360.
So, I am producing medallions out of 1/4 inch hard maple at 3.5 and 4.5 inch diameter.
I am using a profile cut with tabs, 1/8 inch upcut endmill, 50 in/min at 20,000 rpm, 3 passes on a Bosch 1618 router.
Here are my issues (and everything is more pronounced on the 3.5 inch medallions)
1) A dwell mark at the lead in and lead out which I am playing with using different entry angle, ramps, and such but still haven’t found the magic combination.
2) And this one is a real mystery. I have two tabs per medallion on opposite sides of the piece. Every time the machine “hops” up, over, and down to create the tab, it cuts into the wall/edge of the medallion. (See pics). It’s as though it is not following the radius of the profile when placing the tab, but rather inserting a square tab on a radius. I started with regular tabs, but moved to 3D tabs to help smooth it out. No dice. I can not find anywhere in the toolpaths to instruct it to stay on the radius path while placing a tab. All I can find is a selection to tell it to avoid corners/curves when placing them.
Any advice would be greatly appreciated. Thank you in advance,
-A

Advice...no, just an observation. Bottom photo magnified looks more like the part shifted. Are the tabs failing before the route is finished? Tried 3 tabs?

While I have had that problem, it wasn't the case here.
However, I have discovered some useful tips. Watching the mechanics of the gantry, I noticed that there are four points where either the x or y stepper motors will pause before beginning to rotate in the opposite direction to continue the radius of the circle profile. Its 3 and 9 o'clock for the x and 6, 12 o'clock for the y. If I position my tabs at these points, the indent marks on the edge of the work all but disappear because the x or y axis is "pausing". Best used with 3D tabs. Again, the larger diameter the circle, the less of a problem it is.
As far as the dwell mark on my lead in, I found a circular lead with a .25 inch radius is best for minimizing that dwell mark.

I had a problem while doing a v-carve where it was making weird deviations around the perimeter. I found a reference somewhere in the forum where someone recommended adding a "G64 P0.01" to the post processor header section for VCarve software. It definitely improved the cut, though is still not perfect and I need to experiment with different arguments (times). I think that the purpose is to make sure that the the previous step is completed before it starts the next one. Worth a try.

Also, if it always around a tab, you might try different tab parameters (width and thickness) or perhaps try some 3D tabs from the clipart library to see if that makes any difference. You could also try making a cut without tabs without but without cutting to full depth. If that works, add another toolpath that starts at that depth that has the tabs and see if you still get the problem. If nothing else you can inspect single pass toolpath to see if you can find something suspicious in the gcode or even import the gcode into a gcode simulator/visualzer like ncviewer.com to see if it has the same deviations.