[greygabe]

So I'm in the middle of a fairly important project and need help ASAP!

My Syil SX3 has started showing weird issues. The x axis just sounds bad whenever moving (like grinding - I oiled it but it didn't help). Also, it's very hard to move manually by spinning the motor by hand when the mill is off and sort of springs back a few steps when let go. I've ignored the issue for a couple days, but I just found out it doesn't seem to be cutting right.

Here's an example of a circle it tried to cut using G-code that I know has worked before:
http://img64.imageshack.us/img64/4686/img8096i.jpg

It came out like something between an oval and a rectangle with rounded edges...

Any ideas/tips?
It's been oiled and cleaned and I glanced at the wires to look for anything obvious falling out, but didn't really take stuff apart to look for issues yet...

Thanks in advance

[mikemill]

Yes I have had same problem its down to the dreded crimps and contacts
Take of back cover and go over all conections to the motor drivers ( with power off) with screwdriver tighten all contact screws, should solve problem!!

Mike

[greygabe]

I looked around and didn't see anything loose. I also jiggled some wires while running the axis to see if anything changed the noise. And I swapped the axis motor drivers to see if they were bad and the x axis still made the noise.

Would loose connections make it very hard to move manually when off by spinning the motor by hand and sort of springs back a few steps when let go?
Sounds mechanical...

Is there any chance the stepper motor is dead? Would these be the right symptoms?

[greygabe]

OK - I know more now
I just decoupled the stepper motor from the lead screw and spun both by hand
The motor turned smoothly
The lead screw was nearly impossible to turn

Thoughts?

[mikemill]

Its a rare event for a ball screw to sieze up, as there is normaly plenty of grease in the ball cage???

[metalworkz]

Hello,
It sounds like there is a drag on the X axis. Check the gib screws to see if they are adjusted correctly and not too tight? Lube the X axis on front and back and make sure there are no obstructions that would cause a drag on it. For the oblong circles I would suggest you check the set screws on the axis motor connections for the X and Y axis.
My SX3 was cutting circles with partial flats or egg shaped results and the set screw had come lose just enough to allow backlash at 90º intervals when the direction changed. I also had to tighten the Z axis connector to eliminate some irregular depth cutting and that fixed it for me. It really sounds like there is some drag on the X from your description so you might want to make sure there are no chips or other foreign materials causing the drag.

[greygabe]

Checked everything from your all suggestions.

I think I know the problem now. It seems like the bearing on the left side of the x axis is dead. I'll work to replace it and try to remember to post the results.

Please let me know if any of you think of something else.

Thanks for the suggestions

[greygabe]

Just did a test with no load (which should demonstrate if the bearing or other drag is really the issue). Basically, I put a pen in the collet and drew with the mill at about 2 ipm and still ended up with a bad circle.

Thoughts?

[The Engine Guy]

Just did a test with no load (which should demonstrate if the bearing or other drag is really the issue). Basically, I put a pen in the collet and drew with the mill at about 2 ipm and still ended up with a bad circle.

Thoughts?

The most common causes I have seen on full size machines of the problems you have are:

1) The X and Y axis motors are not synchronised correctly (Servos) or in the case of Steppers one axis is losing steps due to excessive load, damaged motor and/or damaged drive.

2) It is very likely the ball screw is not straight, by that I mean that the end bearings and the ball nut are not in line.

I had this once with a Hurco machine I bought, it was very tight towards one end of the X axis travel, so I disconnected X axis motor from the ball screw and turned the ball screw by hand, at the same time I slowly loosened the bolts holding the bearing housing at the end nearest to the motor, all was the same.
I then did the same at the end furthest from the motor and "voila" as I loosened them it got easier to turn.

Remedy, I took the bearing housing off, put new bearings in it and then aligned the ballscrew with a DIY measuring Laser, I found that the housing had been wrongly pinned to the table and I had to drill 2 new holes for the locating pegs, after that I could easily spin the ball screw and send the table from Zero to it`s full 787mm travel with just finger and thumb.

Basically, if a bearing is even a small amount offline the constant back and forth movement will soon "kill" a bearing due to the high side load that it isn`t supposed to have ! !

Worth checking anyway, just another suggestion for you to try #

Regards
:rainfro::rainfro::rainfro:

[Leous]

Hi, I also have an SX3 that just recently converted to CNC and am seeing the same issues with circles (arcs), I don;t know if it is a mechanical issue or a Mach3 issue. The tolerances between the straight contours in some of the pockets are good +/- 0.02mm but when it comes to doing circles, arcs, ellipses or anything round there is something really wrong. The error seems to be symmetric or when there is a change in direction but in different quadrants (1-3 or 2-4), I replaced the stepper couplings to helical zero-backlash with no luck, still see the same issue.

Please any recommendations??? I have attached photos.

Attachment 214986
Attachment 214988
Attachment 214990
Attachment 214992
Attachment 214992

[metalworkz]

Hello.
Not knowing the axis direction of your cuts does not help to deduce which axis is the suspect but it looks like there is backlash in direction changes, and in my case the couplers had either worked lose of were never correctly tightened on all 3 axis. I see you mentioned changing to helical couplers but are the screws tightened onto a flat of the driven shaft?? I filed some flats on my shafts when I worked with this problem so as to make a more definite spot on the shaft to lock the screws onto. As far as the helical couplers go I have not had very good luck with my use of them for the Z on my 48" x 48" CNC router build and I just recently made a solid aluminum coupler to replace the helical coupler and it has improved my Z axis. If the ballscrew and motor are in line then you might try a more solid coupler, but I can not say for certain that this is your problem. Have you done motor tuning and tested the axis for accuracy with mach to ensure correct steps are being used? You can probably do some tests to check if you have backlash and what it amounts to that might help narrow down the problem axis(s).