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quadrature lines will become active again. Confirm that the "encoder error" shown by the controller
clears and that any additional diagnostic information on the display is correctly updated.
Overspeed test
This line is set low when an overspeed condition is detected by the laser head. An overspeed
condition occurs if the quadrature processing circuitry detects that an invalid quadrature transition has
occurred between two consecutive clock cycles.
The overspeed condition is a difficult one to simulate, because it is not usually possible to cause real
axis movement at 2 m/s or above. This error will however been seen about 50% of the time whenever
a beam block is caused. This is because the loss of the beam can cause an invalid transition in the
laser detection circuitry. Therefore the overspeed condition can usually be tested by causing a beam
block.
Quadrature check (direction and resolution)
The objective of this test is to confirm that the encoder sign convention and resolution settings in the
controller and HS20 are set correctly The machine axis should be moved by a small, known amount
under manual control ( i.e. without closing the loop using HS20 - perhaps by using motor encoder
feedback), whilst the axis position is monitored. The distance actually moved should be recorded
perhaps using motor encoder readings or using a digital vernier calliper. This distance should be
compared with the displayed readout. If the sign correction is incorrect, then change the appropriate
setting in the controller, or on the controller axis card, or swap AQUAD /AQUAD wires from HS20. If
the distance moved does not match, adjust the HS20 resolution using the dip switches or adjust the
controller settings. Repeat the test until the direction sense and distance moved and the axis readout
agree.
WARNING: It is important to set the system direction sense correctly. If it is set incorrectly,
the machine will move in the opposite direction to that expected, and may accelerate until it
!
reaches the axis limits. In the case of parallel twin rail drives, it is important that the
direction sense of the slave axis is set to match the master axis. Failure to do this will cause
opposite ends of the cross-member to move in opposite directions, possibly causing
damage to the machine.
Successfully completing these tests provides confidence to move onto the next stage where machine
movements are made using HS20 for closed loop control.
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