Hello. I have been having some trouble with my CNC leaving small circles behind. It seems to do this every time it has a change in direction. I was wondering if anyone else has seen this problem and if it’s a problem with the bit (60° V bit) or the actual router moving.
I have attached some examples below.
What software are you using for your CAD/CAM work and which type of toolpath are you using for the vbit (ie. vcarve, advanced vcarve ← Carbide Create, or something else)?
I am using Aspire for the designing. Carbide 3d for the toolpaths and they are V-carve no depth limit with a 60° V-bit.
How does that compare to the 3D preview from Aspire?
It looks like something mechanically is shifting — what V endmill are you using? If it has inserts are they well secured and properly installed? Does the V endmill have a flat tip?
The 3D preview looks fine in Aspire, and have never had a problem like this before (I have been using my CNC almost daily since August 2020).
The V-bit comes to a point at the end as well (not flat ended)
Everything seems secure as well. The bit and the collet are quite tight.
Looks like it’s not occurring on every change in direction on the vectors path. Possibly only the areas that have a wider/thicker line allowing the vbit to go deeper into the stock to clear that area and doing that circular motion. Did you notice the movement if it appeared to hesitate/stop in some of those corners possibly doing a quick circular motion before continuing along the vectors path. Maybe the advanced vcarve with a set depth and a smaller tool to clean the bottom (pocket).
I’d also look at the GCode in ncviewer to see if the gcode simulation does this circular motion in those corners to rule out toolpath vs mechanical issue with the machine.
Thanks I will try this.
It might also be interesting to generate the toolpaths using Aspire and the Shapeoko post-processor to see how they compare?
I have had this same issue on some v carving projects. What I think is going on anytime the router momentarily changes direction there is a small pause in forward direction. The spindle on all routers have play and maybe the spindle torque is moving the spindle shaft up/down slightly giving you the “Dimples”. Now this is just a theory because I do not have high speed photography but it is plausible. I have this happen a couple of times on projects that had a lot of direction changes.
can you share the gcode file, I would be interested in taking a closer look at it as well out of curiosity.
We seemed to have solved it. We changed out the collet and everything seems to work better now not perfect but definitely better. It must have been loose even though we tightened it a lot.
Thanks to everyone for your suggestions. I believe it may have been a combination of these issues suggested.
Just as an FYI. I had this issue and all it was is the collet needed cleaned of saw dust debris. Try this if it happens again, you may not need to change the collet at all.
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