Chattering problem during cut

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Chattering problem during cut

Postby rayray » Sat Jul 28, 2018 11:27 am

I have an HD-4 with a VFD spindle motor (1.5HP) and I have used it quite a bit with pretty good results. However, I am getting a 'chattering' during cuts sometimes, doesn't always do it. Cutting an elliptical recess in a piece of maple and using an offset conventional cut pattern with a 1/4-in em and a depth of cut of 0.11". Work is 3/4-in thick and the pocket is 0.694-in total depth, set up to make 6-passes, feed is 70-in/min . Most of the pass cut goes pretty well, but in the "NE quadrant" of the cut the bit chatters for about the whole quadrant. The rest of that cut is usually pretty smooth. Does it on every pass and the result is that that part of the recess has a definite roughness to it -- the rest of the pocket is pretty smooth. I have gone through and tightened all the bolts on the gantry and the router carriage, but there still seems to be a bit of 'play' in the carriage. If I grab the dust port vacuum hole , I can move the router bit several thousands just by putting pressure up or down. I don't know if this is where to chattering is coming from or not -- I can't tell where anything in the assembly seems to be moving. I have tried varying the rpm, the feed rate and the depth of cut, doesn't seem to matter -- I still get the chatter on the NE quadrant of the cut. Not just a circular patter either, it will do it on a square cut in the same area. (Referencing the center of the pattern as the datum, the chatter is in the +X and +Y quadrant. During the cut, the bit is moving increasing positive X and negative Y, tracing the upper right part of the ellipse.)

Any ideas????
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Re: Chattering problem during cut

Postby SteveM » Sun Jul 29, 2018 12:31 pm

How old is the bit you are using?
Possibly try a new cutter to see if it does the same thing.
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Re: Chattering problem during cut

Postby bill z » Tue Jul 31, 2018 8:26 pm

Rayray,

Could it be the drive screw being dirty in that quadrant? If it was your bit, it would be chattering more in other areas.

Try cleaning the screw drive and lubricating, then try the cut again just to see.

Let us know.
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Re: Chattering problem during cut

Postby sharkcutup » Wed Aug 01, 2018 7:17 am

I have found this to be a problem too. I have also come to realize after many different projects carved that this is something that is inherited in the way the project board grain structure versus the cutting tool direction are interactive.

There are a few ways to improve but the drawback is they may be time consuming.

1.) Keep things as they are and sand the chatter out.
2.) Change the Feed/Speed to a slower rate on that toolpath.
3.) Adjust cut/carving to leave a little meat on and then add a profile cut in the reverse cutting direction to remove chatter.
4.) Do Separate Last Pass in the reverse direction. This usually helps to eliminate/reduce the amount of tearout on corners/ends.

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