Strange effect while moving head

Device is build - during z-axis calibration I´ll have a strange effect. While moving the head to auto home the head moves to the right - back position. Short before reaching the end switches I have a very noisy sound from both (x and y axis) motors.

If I try now to move the head in 10 mm steps to the left it doesn´t step 10 mm it´s only round about 5 mm so after having 20 steps the head is moved only until the middle of the print area. Same is with y axis but here is the sound very very noisy.

Next I try is disabling motors and move the head manually round about 2 cm from back home position to the front and the same to the left. If I try now to move the heads in 10 mm steps everything works fine.

So the noisy sound and the not correct stepping width is only in the back and right home position and round about 2 cm around. For me it looks like a mechanically blocking but can´t see any. If I disable the motors I can move the head easilly to each position.

What could happen???

You’re experiencing a bad axis alignment. Check in the [color=#408040]Wiki [/color]how to adjust the axis.

I experienced a similar effect for the homing of the print head.

The printhead was blocked by the pulleys before it could reach the end point position. By shifting the pulleys a few mm towards the printer sidewalls, this effect was removed.