Bambu Lab Printer X-Y Squareness Check Adaptors to be used with Kent set squares. 

I will Add more detail when I have time.

After any adjustments always run a full calibration.

The following is to be preformed after following the Bambu Lab belt tension procedure. Pay particular attention to whether the adjuster blocks move freely.
 

Printed parts:

X1-C Stand off for Kent Set Square: Print 4 off

Adjuster A: 1 off

Adjuster B: 1 off

Belt Adjuster P1P_X1-C_V2 A: 1 off

Belt Adjuster P1P_X1-C_V2 B: 1 off

Skew Adjuster A: 1 off

Skew Adjuster B: 1 off

Skew Adjuster B2: 1 off

Added Adjuster Parts A-B to aid in Applying preload in a controlled and repeatable way. The adjustment bolt on the spreader needs to face away from the centre of the machine.    

 2 x  M3 x 16 bolts are needed for the hinge and 1 x M3 x 10mm bolt for adjustment.

Added V2 Preload clamp for P1P and X1-C 
1 x M3 x 20 bolt.

Using a M3 tap will make installing the bolt a lot easier.

Added pulley Skew Adjuster.                            2 x M3 x 10 Bolts.

For reducing surface artefacts by mechanical adjustments there are a combination of factors that need to be considered, X-Y squareness, equal belt tension and belt rub on the idlers flanges. All these need to be addressed and will interact with each other during the adjustment process. It’s a subtle adjustment and very easy to go the other side of the bell curve giving the impression that the adjustment has had no impact. After careful and methodical adjustment to my machine the return to previous print quality after the negative step change post preforming the Bambu Lab belt tension process proved that the issue was the squareness of the X-Y motion system and possibly belt tracking causing belt rub on the pulley flange.

I think just holding the X gantry square to Y doesn’t give the required result. That is why I have a datum point (set square) that I adjust the X gantry to. This way you are able to see the effects of adding or removing preloaded from the adjusters.

I think the initial tension from the spring is a good starting point, it is important to make sure the adjuster moves with the bolts loose and it is not catching on anything.

add more preload to the adjuster that has the spring with the least amount of compression (Longer spring) to square up X to Y. After tightening the adjuster bolts check the belts are not walking up and down the idler excessively or slammed against the flange by moving the print head around.

Start with the print head centred and  towards the front of the machine. Place the two set squares opposite each other using the printed adaptors clipped onto the Y rods with the long edges aligned. Make sure the short edges are are pushed fully into the adaptors. Use 2 bulldog clips to keep the set squares in place. 
Pull the print head towards the rear of the machine until the ends of the X gantry touch the squares. 
If one side touches and the other side still has a gap then this indicates the X gantry is not square to the Y rods and one belt requires slightly more tension. 
 
I think the initial tension from the spring is a good starting point, then added more preload to the adjuster that has the spring with the least amount of compression (Longer spring) to square up X to Y. Also making sure the belts are not walking up and down the idler excessively or slammed against the flange.

If the belts are moving up and down or riding a flange chose the skew adaptor to suit the tensioner being worked on. Notches go towards the bottom of the machine.

Place the printed adjuster in position. and snug up both bolts, install the zip tie to hold the moving end in position.

Loosen the top bolt on the printed adjustment clamp 1/4 of a turn.

Loosen the top belt tensioner bolt.  Move the print head around and the belt should drop to the bottom of the pulley.

While moving the print head back and forwards along the carbon rods slowly start turning the top bolt on the printed clamp.

You should see the belt start to move up the pulley, when you see it move stop tightening the top bolt and continue to move the print head around to see where the belt is sitting.

I found having the belt near the top flange but not touching to be the best position for my machine.

Once you are happy with the position of the belt tighten the top belt tensioner bolt and remove the printed adjuster.

Repeat on the other belt tensioner if needed.