[Problem Solved] Chattering on plywood

I cut a simple piece the other day out of 18mm plywood. Size came out OK, (a little bigger in the Y direction - which I can fix as I’m still doing some tuning.) The finish not as good as I’d expect (it’s fine for the application). It looks like chattering - what’s the most likely cause? As far as I can tell, belts, pulleys and wheels are all tight
It’s a makita router, feed rate 2000mm/m, doc 1mm. The surface shown is an outside surface from a profile cut (using CamBam for toolpaths). Bit is 6.35mm two flute spiral downcut.

Is the circle from CamBam, or imported from another program into there? I’ve noticed that the circles and arcs I import from Sketchup all are series of line segments instead of smooth curves.

It may also be that you need to bump the pots up (or down), slow down your feed rate, or double-check that the belts and V-wheels aren’t too tight. They take a bit of time to figure out, so don’t discount them yet.

The circles were generated in Cambam. I hadn’t considered that it might be a problem with small arcs or line segments. The pattern seems very regular all the way around the outside of the item and the lines extend the full depth of the cut. It would have been 18 or 19 passes.

No pots to adjust as I’m using a Gecko G540 and Linuxcnc to drive the X-Carve.

This could be due to your feedrate speed. I find that at faster speeds i start getting a finish like yours.

I have been having chatter issues with my X axis using a 1/4" bit.
When I climb mill I get chatter in x axis moves even at 25% my normal feed rate. (At the slower feed speed it isn’t bad but it is there.)
Switching to conventional milling eliminated the chatter.
There has been a few other threads about it. It is weird that it is just the X axis that is affected. There is a theory that it may be a symptom of a damaged V wheel? (over tightening? or wear?)
Mine seem ok but I plan to get some replacements, just in case, when I make my next order form invenables.

This is an interesting point. I just created a circle profile in V-Carve and looked at the code. The code does NOT use circular g-code. It is using segments! Weird. I wonder if it differs by post-processor. (5x5x.25" stock, .125" End mill, 0,0 at center of circle)

Code attached.Cirlcle1.tap (6.2 KB)

WOAH. Check this out - changed the post processor to G-Code Arcs. Look at the difference - it actually uses arcs instead of segments. Must research this some more.

Profile GCodeArcs.tap (271 Bytes)

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What did you change/add to enable Arcs?

this looks typical to climb vs conventional milling.

The post processor in Vectric. It turns out, I wasn’t even using the appropriate Mach3 post processor. I will experiment with this more in the coming weeks.

Checked the CamBam settings and conventional milling is used. Post processor is Linuxcnc.
gcode is using arcs (g3).
I’ll try re-cutting with a slower feed rate and DOC - the one I cut was the wrong size anyway :frowning:

big_pipe_flange.nc (21.5 KB)

Problem solved! Reduced the feed down to 1500mm/minute and here is the result
Thanks for the helpful responses.

Finished job


Looks great!