Misalignment is a common problem encountered by manufacturers of equipment using stepper or servo motors during equipment installation, commissioning, and use. Misalignment may be caused by improper mechanical assembly, mismatch between control system and driver signals, electromagnetic interference within the equipment, mutual interference between equipment in the workshop, or improper grounding during equipment installation.
This article extracts and summarizes the most common causes of misalignment and corresponding countermeasures from numerous application cases. It aims to help equipment manufacturers' commissioning personnel quickly locate problems, take appropriate measures to improve equipment anti-interference capabilities, and ensure proper grounding of equipment to guarantee normal operation.
No.1
Regular deviation
Q : When doing reciprocating movements, the further forward you lean, the more (less) you gain.
Possible cause ① : Incorrect pulse equivalent
Solution: Before shipping, use the machine to draw a square that is as large as possible, then use a ruler to measure the actual size, compare the ratio between the actual size and the size set on the control card, and then add it to the control card calculation. After repeating this process three times, a more accurate value will be obtained.
Possible cause ② : Timing conflict between the trigger edge of the pulse command and the level transition of the direction command.
Solution: The control card ( PLC ) software engineer advances the direction signal. Alternatively, the driver application technician changes the pulse edge counting method.
Q : During operation, the motor vibrates at a fixed point, but it runs normally after passing that point, though it travels a shorter distance.
Possible cause: Mechanical assembly problem
Troubleshooting: 1. Inspect the mechanical structure for the cause of the jamming, such as high frictional resistance or misalignment of the slide rails. 2. Insufficient stepper motor torque. Due to end-customer demands for increased speed or load, the motor, which was originally capable, may lack sufficient torque at high speeds, leading to stalling. Solutions include setting a higher output current for the driver, increasing the supply voltage within the driver's allowable voltage range, or replacing the motor with one that offers higher torque.
Q : The motor's reciprocating motion does not reach the correct position in either direction and the offset is fixed.
Possible cause: Belt clearance
Solutions: If the motion control card has a belt backlash compensation function, it can be used; or the belt can be tightened.
Q : The cutting trajectories do not overlap
Possible cause ① : Excessive inertia
Solution: Increase the Y- axis reduction ratio and use notch filtering to improve the rigidity of the servo drive to solve the problem.
Possible reason ② : The overlap between the blade and the nozzle is not properly adjusted.
Solution: Modify the blade and nozzle position compensation parameters.
Q : Draw a circle into an ellipse
Possible cause: The XY axis platform is not perpendicular.
Solution: Adjusting the perpendicularity of the X- axis and Y- axis of the gantry crane can solve this problem.
No.2
Irregular deviation
Q : During operation, deviations occur intermittently. These deviations are random, and the magnitude of the deviation is uncertain.
Possible cause ① : Interference causing motor misalignment
Solutions: If interference occurs frequently, an oscilloscope can be used to monitor the pulse frequency to determine the timing of the interference and thus identify the source. Removing or moving the pulse signal away from the source can resolve some of the interference. If interference occurs only occasionally, or if the location of the interference source is difficult to determine, or if the electrical cabinet is fixed and cannot be moved, the following measures can be considered to solve the problem:
① The driver is grounded.
② Replace the pulse line with a twisted-pair shielded cable.
③ A 103 ceramic capacitor is connected in parallel to filter the positive and negative terminals of the pulse (pulse frequency less than 54kHz ).
④ Pulse signal with magnetic ring,
⑤ Add filters to the power supply front end of the driver and controller.
Possible cause ② : Narrow pulses appear in the pulse train.
Solution: Investigate the cause of this problem in the controller; is it a pulse interface issue or a software algorithm issue?
Possible cause ③ : Loose mechanical structure
Solutions: For critical components and high-stress structural screws, use spring washers, and apply screw glue to the screws or set screws. Use keyways to connect the motor shaft and coupling whenever possible.
Possible cause 4 : The filter capacitor is too large.
Solution: When adding a filter capacitor, the pulse frequency needs to be calculated, and it is essential to ensure that the maximum passing pulse frequency meets the requirements.
Possible reason 5 : The maximum pulse frequency of the PLC or motion control card is not high enough.
Solution: If the maximum pulse frequency of the host computer is limited, the microstepping of the driver can be appropriately reduced to ensure the motor speed.
