3 sides cut great, one choppy x2

[billsnogo]

I have an X2 mini-mill converted to cnc using a cncfusion kit. I have not used it in a while, and decided to spend a little time on it, and while cutting a 1.75 cube, I noticed all wall finishes are great, except when going Y+, that side is kind of choppy. I am guessing it is either the gibbs, or the lovejoy coupling? My X has one of the zero backlash couplings, but the Y still has the lovejoy coupling. My question is why is it only going one direction?

PS,
I tried different feeds/speeds, DOC, ect and same thing happens.

thanks for anyone responding who may have had the same problem and found the cause allowing me to spend less time troubleshooting, and more time cutting.

Merry Christmas

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[kawazuki]

I would guess that if your code was configured to cut the cube all clockwise or all anticlockwise there will be two sides cut normally and two cut climb. If there is sufficient backlash in the Y axis then the cutter will pull or push the piece and so induce a degree of 'chatter'........well that's my theory!

[Fastest1]

Do you use backlash comp? Have you varied the direction of cut with the same results?

[billsnogo]

I am using backlash comp, but just have put the steppers back on after wiring new cables due to corrosion issues, so I probably should test backlash again.

I have only climb cut, but going clockwise on the outside of the cube, and CCW on the inside of the cube (hollowing it out) and it shows on both when going Y+

thanks so far

[pippin88]

I would guess that if your code was configured to cut the cube all clockwise or all anticlockwise there will be two sides cut normally and two cut climb.

Umm what? That makes no sense.

[kawazuki]

Umm what? That makes no sense.

Made sense to me when I was typing it ! I guess what I should have said was 'each side in same direction'?

[gtrdude]

I seem to have a similar problem when cutting circles (conventional milling) on my X2. I get chatter occurring at 45 degrees and 225 degrees though. Buggered if I know why. Not sure why motion in any particular direction would cause vibration and not in the other????

[MCRIPPPer]

wondering if spindle bearings could affect this, or something else in the head. if you think about it, if you got a belt drive it will pull the top of the spindle toward the motor if there is any slop in the bearing. going one way the end mill will simply pull it harder that way, but going the other way it might overcome the belt tension force and pull in any slop that might exist with the ball bearings.

[gtrdude]

Interesting theory. However I would have thought that the tension on the bearings would easily be greater than the tension on the belt?? Not really sure how to test this other than loosening the belt to it just about slips...

[MCRIPPPer]

since the mini mill comes stock with regular old ball bearings i think there should not be preload on it, and ballbearings have a slight amount of play. with tapered rollers there should be no slop at all.

[gtrdude]

I don't think the X2 would come with radial bearings (if that's what you mean by regular). They should be angular contact, deep groove or tapered bearings. All of those need to be run with pre-load.

[MCRIPPPer]

my mini lathe came with regular deep groove. not angular contact. upgraded to tapered rollers.


have not taken the mill head apart yet but im guessing there the same cheap china deep groove ball bearings.

[gtrdude]

Did you notice any improvement in cutting? What about noise, did that increase/decrease?

[MCRIPPPer]

cuts much better. it is much harder to turn the spindle though, but i also run oil seals on it to keep crap out of the bearings. noise is very low. only sound comes from belts and motor. i do notice on my mill (still has stock ballbearings) i can hear the balls rattling around at high speeds.