Drive Belt Position Fine-Tune: All Current CMC Models

For Additional Information: See also: Drive Belt Position Alignment

The most common cause for out of square opening is misalignment between the gantry and drive belts.

Remove the gantry covers by unscrewing the screws that hold it in place and set aside.

Slide the gantry just to the right of the vertical clamp until you see the red line on the belt. It should line up with the red mark on the drive cog.

These alignment marks must align on both the top and bottom of the gantry.

If they don’t please see Drive Belt Position Alignment.

Locate the belt anchor adjustment screw, which is the Allen screw that sticks out of the belt anchor, which is located at the left end of each rail; not the round button screw.

The large Allen adjustment screw sticks through the belt anchor and into the drive belt.

Make sure there is about .25” of threads showing to the right of the belt anchor. If, for some reason there are no threads showing, we need to adjust the belt anchor adjustment screw.

Loosen one full turn only the 3/16” Allen belt tensioner screw located on the right bottom side of the lower rail marked with a red dot.

Only loosen it so that there is some movement in the belt tensioner; about one full turn. Belt tensioner springs should be visible.

Turn the belt anchor adjustment screw Counter-Clockwise to move the belt end to the right until about .25” of the threads display.

Tighten the 3/16” Allen belt tensioner screw located on the right bottom side of the lower rail marked with a red dot.

Cut a rectangle that is about 2x24”, NOT cutting the outside, with 2” borders.

Measure the borders to the opening at the bottom of the mat closest to the vertical clamps, then measure the borders to the opening at the top of the mat closest to the vertical clamps.

If the borders are not measuring 2” in both places, continue with “Fine-Tuning Drive belt Adjustment” below.

Loosen one full turn only the 3/16” Allen belt tensioner screw located on the right bottom side of the lower rail marked with a red dot.

Only loosen it so that there is some movement in the belt tensioner; about one full turn.

Belt tensioner springs should be visible.

The belt anchor adjustment screw is the Allen screw that sticks out of the belt anchor, which is located at the left end of each rail; not the round button screw.

The large Allen adjustment screw sticks through the belt anchor and into the drive belt.

Adjusting the Allen adjustment screw moves the belt end of the drive belt to the right or to the left.

Determine if the gantry is leaning to the right or to the left. Note that each drive belt has an adjustment screw.

• Turn the large Allen adjustment screw Clockwise to move the belt end to the left.

• Turn the large Allen adjustment screw Counter-Clockwise to move the belt end to the right.

After making the adjustment, do the test cut again.

Continue with the above process until the test cut cuts 2” on both the top and bottom side of the rectangle.

Go back and snugly tighten the 3/16” Allen belt tensioner screw from the right bottom side of the lower rail and the right bottom side of the upper rail marked with a red dot.

Reinstall the gantry cover(s), replacing the screws you removed earlier.