In some cases, a linear bearing may shift during transit. The bearing can rotate inside the gantry block or move slightly from side to side. When this happens, the bearing may contact the dust cover, or the bearing stickout may become uneven.
Incorrect bearing position can cause:
- Homing failures
- Motor errors
- Rough or restricted movement
- Contact between the bearing and dust cover
- Damage to graphics on cover
- Rubbing of black plastic of the ball screw cover.
You will need a 2.5mm hex key for the grub screws.
Before You Begin
Power off and unplug the machine before making any adjustments.
The gantry block contains separate upper and lower linear bearings. The yellow line in the photos shows where the upper and lower sections of the housing divide.
- Red arrows: Grub screws securing the upper bearing
- Blue arrows: Grub screws securing the lower bearing
Each bearing is held by six grub screws: three on the front and three on the back.
Bearing Contacting the Dust Cover
If the C shaped bearing is contacting the dust cover, it can affect homing, rail movement or sticker damage.
If the upper linear bearing has rotated and is contacting the dust cover:
- Loosen all six grub screws securing the upper bearing—three on the front and three on the back.
- Rotate the bearing until there is a visible gap between the bearing and the dust cover. (red arrows indicate rotating, you may need to rotate front to back or back to front to create the gap from the bearing cover to the ball screw cover).
- Confirm that the bearing is no longer rubbing against the dust cover. (Yellow arrow points to point of contact we’re ensuring that has a gap).
- Check the bearing position and stickout before retightening the screws.
X-Axis Bearing Adjustment — 60 mm Tubes
The bearings on the 60 mm X-axis tubes will normally extend slightly past the sides of the gantry block.
Check that:
- The stickout is equal on the left and right sides.
- The upper bearing stickout matches the lower bearing stickout.
- The bearing is not contacting the dust cover.
- The gantry block moves smoothly across the rail.
Loosen all six grub screws for the bearing being adjusted. Reposition or rotate the bearing as needed, then tighten the screws evenly.
Y-Axis Bearing Adjustment — 50 mm Tubes
The bearings on the 50 mm Y-axis tubes should sit approximately flush with the sides of the gantry block.
Check that:
- The bearing is flush on both the left and right sides.
- The upper and lower bearing positions match.
- The bearing is not contacting the dust cover.
- The gantry moves smoothly along the rail.
Loosen all six grub screws for the bearing being adjusted. Reposition or rotate the bearing as needed, then tighten the screws evenly.
Grub Screw Torque
Tighten each grub screw to:
4.3 inch-pounds
Do not overtighten these screws. The linear bearings are C-shaped, and excessive screw pressure can clamp the bearing too tightly around the rail. This may restrict movement and cause homing or motor errors.
After tightening, move the axis through its full travel by hand and confirm that it moves smoothly without binding, rubbing, or tight spots.
(example digital torque wrench: Amazon.com)