SD3 Noob: Random Y Shifting

everyone says tighten the pulleys and I am about to throw this POS out. there are NO SET SCREWS ON THE PULLEYS they are not keyed or set or anything they float on a chewed up rod. They only are held in place by collars that have set screws that for the most part if they do slip will do little to let pulleys shift left to right.

The real key is the belt tension since the betl tension has to be tight enough to prevent slip, not to tight to bind two axis, and you have to balance the front and back of the belt.

needless to say my SD2 is printing total crap repeatable now after ripping it apart at least 4 times, lube, steeper voltage checks. tensions checks. I am dialing it in now trial and error but I can not get a 5+ layer circle of any size to print without at least 5-10mm skip per layer.

i removed teh zwobble and recall everything again it helped but even a solid square print now is good to about a 1" tall and the whole print shifts 2-3mm forward (or bacK) and continues printing.  adjusting front belts (left right) or back does produce any repeatable results by trial and error

yes all 3 collars have set screws but the black pulleys do not and they are not keyed

really? I can spin the collars without the pulleys and seperate them

That may be the cause of your problems. They are supposed to be fixed together, the whole idea is so you can tighten the setscrew on a shaft and the belt will not lose position relative to the shaft. Since these collars are aluminum and the pulleys are composite they are pressed together and usually glued with some sort of loctite.

Actually you can't switch them.  The back pulleys have a 6mm bore and the idler pulleys are all 5mm.  If you can turn the collars independent of the pulleys, then they are broken.  I would be surprised if they were all broken like that, but it only takes one.  Solidoodle needs to send you new ones, make sure they understand it is the back 6mm pulleys.  Send at least 2-3 copies of the same email, because they apparently gmail loses them all the time.

If you want to get the pulleys on your own, these will work - https://sdp-si.com/eStore/PartDetail.as … roupID=347

They are MXL pitch timing pulleys with 18 teeth, 6mm bore, 2 flanges and hub. about $5 each.

I've had trouble with burrs on the rod caused by set screws.  There was one pulley that wouldn't slide on the rod unless I used a screwdriver and a hammer to give it a tap.  Once it slid over a little it would spin, and once it rotated a little it could slide back over that spot on the rod without catching on the burr.

Before you pack it all away, can I just suggest one little test.

The best way I have found to check for slack/backlash/loose screws/play in the X axis is to simply grab the collar on the stepper motor and turn the motor by hand (make sure the motors are off, even so it is quite stiff). You only need the tiniest of movement on the motor end and then look at the pulleys or carriage. You should see the instant you start to move the motor that the farthest point turns, for the X axis I just use the front pulleys as reference as they are easiest to see.
Just rock the motor back and forth and it should be pretty obvious if you have a problem.
I have been able to reduce errors in a number of places by doing this as you can clearly see where the problem is.

Clearly this won't highlight if the is a sticking point on a shaft but it you at least make sure you test the motor over one turn and that everything moves as it should you can be sure the printer is trying its best to move where it is being told.
I guess if you wanted to manually check for sticking points you could undo the setscrew on the motor, the carriage should move freely (I've never had to do this yet) and you would then be able to feel for any tight points as you spin the pulley on the motor shaft. You would be able to feel a pinch point much easier by hand rather than using gauges or measurements.

It might be the motor.  You can check that it is getting the right voltage - http://www.solidoodle.com/how-to-2/troubleshooting/ (the section about the stepper chips).