rollie

Having problems with the Y Axis and calibrating it. I have used the calibration tool and the two sides are within a mm of being parallel. When I move the extender it pushes fine, until I tighten down the pulley's. After I tighten down the pulley's it becomes more difficult to push the extruder that direction. The other direction pushes very easily. I 've had some issues with belts slipping and tightening is making the motors work really hard. Any help would be great. Thanks.