Need Help!- Loud noise when laser comes out of datum position

[BuckeyenNJ]

We have been struggling to get our 4 x 8 foot flat bed laser to cut consistently over the entire bed surface. We thought we had it aligned and focused perfectly but when we went to run a test pattern this terrible noise occurred. When this happened before we lost the key in the drive pulley for the X axis (x being the laser head) After the noise and a terrible cut...we rechecked alignment. The 1st and 2nd mirrors are dead center...but the 3rd mirror alignment has shifted.

This is a link to a video of the noise. CNC Laser Head Axis Noise - YouTube

It only occurs when the machine comes out of datum...Also the datum is much "deeper" in the corner then when we move the machine manually. This is a new Chinese laser with LaserCut 5.3 software and the standard Chinese controller.

When we lost the key before the axis overran the limit switch...ruined it and the laser head block was damaged. Both parts were replaced and now we are getting the noise again.

It does not make any sense that this would cause the alignment to get messed up but it must be...any ideas of what is going on? or what we should be checking?

[ho-229]

It would appear your laser carriage is trying to go beyond the programmed soft stops… (Step error?)
It would appear your references may be jacked up… I have the same issue with my Z axis. It does not know a good reference point and smashes into the mechanical limits.
It would seem LaserCut 5.3 has issues when you reboot (unstable)…
](wiki)
Steppers are generally commutated open loop, i.e. the driver has no feedback on where the rotor actually is. Stepper motor systems must thus generally be over engineered, especially if the load inertia is high, or there is widely varying load, so that there is no possibility that the motor will lose steps. This has often caused the system designer to consider the trade-offs between a closely sized but expensive servomechanism system and an oversized but relatively cheap stepper.
A new development in stepper control is to incorporate a rotor position feedback (e.g. a rotary encoder or resolver), so that the commutation can be made optimal for torque generation according to actual rotor position. This turns the stepper motor into a high pole count brushless servo motor, with exceptional low speed torque and position resolution. An advance on this technique is to normally run the motor in open loop mode, and only enter closed loop mode if the rotor position error becomes too large — this will allow the system to avoid hunting or oscillating, a common servo problem.