Calibration issue or something else? (Page 1 of 2)

You will want to follow the instructions laid out in this video to resolve this issue:

It seems the printer is sort of touchy about this.  I was confused why I was having issues then I noticed that the set screw in the right collar (me facing the front of the printer assembly) is stripped out and has been since the beginning.  I can't tighten and I can't loosen it at all with the 1.5mm hex key.  I get just enough traction in the head to feel like it is screwing and unscrewing but clearly it is not.  Lucky me getting that off is going to be a chore.

Here is a link that Ian posted the other day for the pulleys, you can find them elsewhere also. Do you have the means to fix the collar or drill and tap a new locking hole in it or maybe put an extra locking collar next to it and then couple both together.

https://sdp-si.com/eStore/PartDetail.as … roupID=347

I could but to me it seems more effort than taking the unit all the way apart.
Possibly grinding flats in that shaft as well while I am at it.
Then reassembling.

I doubt that temporary thread locker led to this screw being over tightened like this.
I bet when I get that shaft out they'll be evidence of slipping so someone monkeyed down on it.

If I find that I'll post a picture.

But the thing about the flats or keys I am not sure if you can do that and prevent binding. Because the carriage and rods might not be true they need a little slop or it will bind. and right now when you loosen the pullies you allow the left and right one to slip separately so the right number of teeth line up, fine the center, then you lock it down.

I bet that each pulley is not in same position or index to each other. Now in machine build you would do this but then your pushing the alignment and index out to the belt. So would have to ensure you have the right length and teeth from each pulley to the belt or at least you would have to adjust the alignment by moving the belt by the #teeth on the pully.

At that point I'll get my shrink tubing out and my hot air tools.  Shrink a new collar to the old one.
I ordered those pulleys.

Ronsii,

You have any other part# or web links for the SD?
Like the bushings in the Y carriage, stepper motor and boards, cpu and board

Correct on the 6 and 5 mm sizes I don not have part numbers with me right now but it really isn't that hard to figure most of them out... nothing is 'special' just about everything is 'off the shelf'

Generally the solution to the axis twist on gantry machines is to increase the contact surface to the rails such that the twist is minimized and then reduce the loading on the movement by driving both sides.

The issue is that generally the larger the distance between the load bearing guides on the rails the further from the edges of the machine your working area gets.  So your work surface gets smaller.

In CNC machines that are plasma / router this means that a 48" x 48" gantry will have a smaller working area than the outer dimensions of the machine.  The more widely spaced the linear bearing blocks are the smaller the working area because it is supporting the other axis.

I'm not sure if you approach this as such you won't end up reducing the work area of the machine.

I do have some Thompson linear bearings that I could try to figure out how to put in there later.  Course those linear bearings and rails cost nearly $100 each at the time.

What they did here is invert a rack and pinion drive you might find on a CNC plasma / router system.
Course the risk they created is that obviously a fixed rack made of bronze does not have nearly as many issues as a cogged belt.

My other printers I actually made use linear positioning systems with AC servos on multiple start screws.
Each axis easily exceeds the cost of one SD2.  On the plus side once those systems are homed they are highly repeatable over repeated movements.  Clearly the more times these axis transverse the machine they start to move ever so slightly making it hard to go and come back to exactly the same spot every time.

For such a small workspace I don't see why they did not pull and push the X carriage on the support rods from directly over the top in the middle.  If you think about it if you were directly over the center of the X carriage there would be no twist at all and the machines are not open at the top in the enclosure anyway.

It would not have been all that hard to fabricate a bridge that is high enough over the X carriage with the extruder and filament feed so that it could traverse under it and still attach to the axis above.  You could easily make it with polycarbonate or even laminated birch plywood.  Just print corner blocks.

Plus this way you replace the round rods on the sides with square stock.  Use real ball bearings to run up and down them.
The result of driving it this way is like pushing a little car from the top center.  So you put the little car on tires and those tires are the bearings.

I could see making a modification for this.  However it would make the machine taller and given how the frame is integral to the system I'm pretty sure some cutting would be required.  Though maybe there's a way to do it.  Will have to look at the system more closely.  I'm pretty sure the cover would need to have the top opened up to make room for this even if the frame could be worked around.  Unless some Z axis working range was sacrificed (what fun is that?)

They are idlers so it shouldnt matter anyway