Troubleshooting Guide for Installers, Users, and In-House Personnel
Applicable to ASI's MS-2000 and MS-4000 Stage and Z-Drive Systems
(Some tests and repairs are only appropriate for ASI service personnel.)
General Info: If you are experiencing difficulties of any sort, dump the error log. This is the first place to begin troubleshooting. Do this using the command “DU Y” from HyperTerminal. Check the dumped log for Fatal Errors against the current error list. Please note that for several of the two and three digit error codes, the last digit is an axis identifier. Usually on XY(Z) systems the X-axis is 0, Y-axis is 1, (and Z-axis is 2). On Z-drive systems, the Z-axis is 0. Use this convention to identify which axis is suffering the error. Do not be concerned about a multitude of non-fatal errors. Errors 10,11 are common, indicating some overshoot on the move. Some of the move error term errors (90, 100, 110, 120, 130) are also common, especially when moving close to the maximum speed of the stage.
PROBLEM: Error codes 20, 21, or 22; 50,51, or 52. The move is incomplete on commanded moves. Stage doesn’t get to target.
Check the error log for the error codes above. Error 50’s indicate that the accumulated errors during the commanded move became too large to be able to discern the move intent so the move was halted. Error 20’s indicate that no motion of the axis was detected for several move cycles – the axis is assumed dead, the motion is halted.
Causes: Trying to move faster than the stage is capable will cause #50 errors. Unplugged stage cables will cause #50 and #20 errors. Attempting to move very slowly with sticky mechanisms can cause #20 errors.
PROBLEM: Error codes 60, 61, or 62. Constant re-engaging of the motors to finish the move - characterized by "M" appearing on the LCD display line.
This problem occurs when the controller cannot get the stage to stay put on the final target location. On all stages first check the following:
- Be sure the stage bearings are clean and the stage plate moves freely. Disconnect the stage plate and run it back and forth by hand to see if the operation is smooth. If not – clean the rails and re-assemble.
- Be sure the drive card is aligned. Zero the drive card. Try slightly increasing or decreasing the feedback.
Rotary Encoded Stage: This is caused by stored energy in the antibacklash gears of the motor causing the encoder to run backward after a move.
Solution: Loosen the bearing nut on the leadscrew cartridge. Re-tighten to 40-in.-lb. more or less. If still a problem, be sure stage is moving freely.
Linear Encoded Stage: Caused by instability in the finish move. Solution not entirely clear. Stored energy in motor anti-backlash gears could contribute to this problem.
Solution: Try loosening bearing nut as for rotary stage. Try reducing the Drive card feedback alignment value. Try re-zeroing the drive card. (AZ command). Try changing the KD parameter. Usually set to -1.
Final Solutions: Increase the "e" drift error number to a larger value. This will always get rid of the ‘M’s but at the expense of accuracy. Get latest firmware, which aborts attempts to re-correct position after several failed attempts.
PROBLEM: Joystick operation in slow speed mode is erratic, often stopping. Joystick is to slow or too fast.
Solution: Check adjustment of drive card. Increase feed back value using AA command. Use the “JS” command to set the desired speed ranges. If the motion stops in the slow range, either increase the JS Y=slow speed setting, or/and adjust the feedback on the drive card slightly higher to get over “rough spots” on the stage using AA command.
PROBLEM: In Linear Encoder Mode both axes are uncontrolled, chatter and run.
The XY stage cables and XY linear encoder cables being on opposite axes cause this problem. Check X and Y stage cables, X and Y Linear encoder heads, and the X and Y connections on the cable between the controller and the linear encoder electronics module.
Solution: Plug the cables into the correct connectors.
PROBLEM: In Linear Encoder Mode Z-drive runs away.
Wiring of linear encoder Ch A, Ch B is opposite that of the rotary encoder.
Solution: Swap Orange and White wires on J3 inside controller.
PROBLEM: In Rotary Encoder Mode Z-drive runs away.
This usually only happens if the user gets a controller for drive configured for the wrong side of the microscope.
Solution: Jumpers on J5 need to be rotated 90 degrees.
PROBLEM: Not passing repeatability requirement.
- Be sure the stage plates are running freely and all of the screws are tight.
- Check straightness of the non-adjusted ALM rails with a straight edge. There should be no observable deviation from perfectly straight. Re-adjust as required.
- Look for cases where Y-motion leads to X errors and vise versa, or where there is a high correlation between X and Y errors and the same move. This suggests warped rails.
- Check to see if the stage is not coming back far enough, or going too far. Not far enough usually means the stage need a little tightening. Overshoot can mean something is not moving freely – too tight.
- Be sure adjustment rail is not at end of its travel range and binding on screws rather than tightening the rails. If this is the case, make adjustments to the fixed rail.
Linear Encoded Stage: Several factors can contribute to repeatability problems. The problems are most pronounced on the Y-axis of Inverted stages.
Check encoder miscounts using scope and circle. Stage should return to same point on circle after repeated moves and move backs. If controller says zero but spot on circle is changing – then you are seeing miscounts. Full circle is 4 microns.
Rotary Encoded Stage: The stage should be adjusted looser than for LE stage, but not so loose that there is any play.
PROBLEM: Stage is drifting after several moves.
This is usually a problem only with linear encoded stages. Check that the analog circle at the linear encoder test port is centered and large enough using an oscilloscope. Be sure that the circle is OK across the entire scale. Dirt on the scale can cause the circle to deviate enough to lose counts. The circle should be >0.7V Peak (1.4V PP). Counting errors can occur if the circle gets less than 0.4V from center.
If there is no circle, check laser. Be sure it is bright and with speckle. Replace encoder if damaged.
Re-align the encoder head to make the circle large enough.
PROBLEM: Motion seems uncontrolled.
Make sure encoder counts are being registered. Flip DIP switch 1 to show both target and encoder positions. Move stage with joystick and be sure encoder counts are being registered on the left set of numbers on the LCD display.
If no encoder counts: Be sure all cables are securely plugged in to their correct locations. If a linear encoded stage, put in rotary mode and check again to see if the linear encoder is malfunctioning. Be sure jumpers at J6 and J7 are installed correctly on the main board, or that there is the appropriate linear encoder switch installed at J6 and J7.
PROBLEM: Stage doesn’t move or seems to be binding.
Be sure that the Joystick is not is slow mode and that you just don’t see the motion.
Check for mechanical interference.
- On upright stages, be sure that the stage mounting bolts are not extending so far as to be interfering with the middle plate of the stage.
- Be sure limit switch magnets are not binding against the leadscrew cartridge.
- Be sure condenser is not interfering with stage movement.
PROBLEM: Controller is not communicating with computer.
RS-232: Be sure that you are on the correct port and that the software is talking to that port.
Using a program such as Windows HyperTerminal to verify that the controller and computer are capable of communication:
- Launch HyperTerminal and set to the appropriate COM port. The settings should be 9600 baud, 8 data bits, no parity, 1 stop bit, no flow control. In ASCII Setup select “Echo typed characters locally” and “Append linefeeds to incoming line ends”
- Connect a null modem cable to the serial port on the computer.
- Short pins 2&3 of the free end of the serial cable with, e.g., a paperclip, and type some characters on the keyboard. You should see double characters returned on the screen. When you remove the short, only single typed charaters should be displayed. This shows that the serial port is working.
- Connect the serial cable to the controller. Verify that when typing the “Enter” key the controller responds with “N-1”.
