Contour corners are rough but straight passes are fine, do I tune motion or toolpath first?

[JudeRanster]

Has anyone chased the problem where the straight sections are fine, but the corners look rough or slightly blown out? I feel like I’m missing a basic concept and I don’t want to keep randomly changing numbers.

A specific moment was last week when I ran the same contour twice and the bad finish showed up in the same corners, so it feels repeatable. Do you usually start by tweaking toolpath smoothing and corner settings, then look at acceleration and jerk, then adjust feeds for cornering and radial engagement so the tool is not suddenly loaded up at the corner?

 

[Alan]

If it’s repeatable in the same corners, I’d start in CAM first. Check corner behavior like “stay down” vs lift, smoothing tolerance, and whether it’s outputting a million tiny segments. Then check if you’re asking for a sharp inside corner with a tool that can’t physically do it without rubbing. After that, look at the machine side like backlash or servo following error.

 

[SeventhAnguis]

If straight passes look good and the same corners repeat bad, I start in CAM before I touch accel and jerk. Check if the toolpath is doing a slow down and a sharp direction change with a little dwell, or if it is leaving a tiny cusp because of tolerance settings. I usually tighten tolerance a bit, add a small corner radius or smoothing, and make sure the cornering feed behavior is sane. If the finish still blows out after that, then I look at acceleration and lookahead.

 

[Tom S_]

@JudeRanster try to check if your CAM has a Feed Optimization or Corner Feedrate setting. You can tell the software to automatically drop the feed rate by 30–50% when it detects a tight turn.

This reduces the cutting pressure exactly where the tool gets loaded up. It’s a lot faster than manually messing with your machine’s acceleration or jerk settings, which affects the whole program