CNC leaves mark on the initial move

[maguru]

Hi all.
I built a CNC router but there's one issue I can't get rid of no matter what: when starting the program, and the router moves from the Zero to the Start plunge point, it leaves a deep groove, around 1.5mm.
I have improved the structure many times, bought better materials, levelled the wasteboard with a facing bit. But I can't get rid of that issue.

Is there any setting I should be paying attention to? Any workaround to avoid this?

I use Fusion 360 for design and CAM. And UGS (Universal Gcode Sender) for running the arduino based CNC.

Thank you

[ihavenofish]

I don't quite understand what you mean. can you post a pic?

if you are talking about the cutter leaving a mark on the side of the work when you contour, this is caused by flex, mostly in the tool itself. the tool gets pulled into the work when you plunge, stop, or retract. This will happen on all machines. The way you get around this is by making and arced path into the cut, or starting and ending away from the contour. Fusion should have some settings for this.

Otherwise, I'm not sure what you're asking.

[Jim Dawson]

If I understand you correctly, it sounds like the clearance or retract height in not set correctly in Fusion when you are doing the CAM work. The Top Height should be the top of the work, the retract height and clearance height should be above (+Z) that.

[machinedude]

one other thing is when you are contouring you can extend your tool path past the end point too this will help with gouging also and blend things better. i would work on using lead in and lead outs as well like someone else suggested. you never want you tool path retracting from the finishing location. if you are getting 1.5 mm that is a very substantial amount and have some other things going on. that much gouging sounds like a rigidity issue more than any thing. if this is the case entry and exit tool paths will be something you are going to have to put some extra thought into.

[machinedude]

one other thing to try is rather than plunging into the part use a ramping tool path. you have a lot more control over the load on the tool with this kind of tool path.