The friction force mainly acts on the transmission device and guide rail of the machine tool. Because of the influence of friction, the torque required when the feed axis is started is much larger than the torque required during normal operation, and the feed axis will have a larger following error when it starts. When two feed axes are interpolating at the same time, if the direction of movement of one axis changes, when the speed passes 0, the interpolating axis will have a short-term stagnation due to the change of the frictional force state. Contour error. This phenomenon is particularly prominent when machining circular arc contour workpieces. At the arc transition quadrant, one axis has reached the maximum speed while the other axis's speed is 0, there will be a convex Grain or dent. In order to improve the contour error of the arc crossing the quadrant, the GR drive adds a friction compensation function. Friction compensation can significantly improve the over-quadrant contour error caused by the influence of friction.

 

solution

 

According to the cause of the over-quadrant bump, the GR drive provides two friction compensation modes:

Low speed compensation function (valid in position and speed mode);

PA42---Characteristic speed of low speed compensation function (default 50, generally no need to adjust);

Pa43---low speed compensation coefficient.

Reverse acceleration compensation (valid in position mode);

PA135---Reverse acceleration compensation gain;

PA136---Reverse acceleration compensation time.

 

 

Applications

 

 

      A customer processed the exterior of aluminum alloy bottle caps for a foreign XX perfume company. The processed product had an obvious arc over-quadrant protrusion, which failed to meet the acceptance standard of the foreign company. The customer requested that the over-quadrant protrusion marks must be eliminated.

      The customer's machine tool is Baoji TK36S flat bed hard rail lathe, and the system configuration is the commonly used 980TDI system supporting GR2050 driver.

      Flat bed hard rail lathes have relatively large friction. According to customer requirements, use the friction compensation function to make corresponding adjustments. The low speed compensation function is given priority when adjusting.

Adjustment process:

Use acquisition software for roundness analysis

 

 

Through the above figure, we can see that there are four raised sharp corners where the circle crosses the quadrant, the reverse jump is 0.0047mm, and the overall roundness is 0.0057mm. This is the quadrant error caused by the friction of the machine tool mop.

Use low speed compensation function;

Adjust PA43=500. Perform roundness analysis again.

 

 

 

 

  After using the low-speed compensation function, it can be seen that the four convex corners of the rounded quadrant are obviously reduced, the reverse jump is 0.00134mm, and the comprehensive roundness is 0.0019mm; the arc's over-quadrant error has been significantly improved.

     Continue to increase the PA43=1000 test and find that the improvement of the raised sharp corners over the quadrant is not much different from that of PA43=500. Change the PA43 parameter value back to 500 and use the reverse acceleration compensation function.

Reverse acceleration compensation:

After using the low-speed compensation function, the over-quadrant error has been significantly reduced, and the reverse acceleration compensation gain should be set to a relatively small value;

Adjust PA135=20 PA136=100 to continue collecting data for roundness analysis.

   As you can see in the figure above, after using low speed compensation and reverse acceleration compensation, you can see that the four convex corners that have circled across the quadrant have become extremely slight; the reverse jump is 0.00087mm, and the overall roundness is 0.0017mm.

     After the above adjustment, the customer processed it again, and the raised lines on the surface of the sample that crossed the quadrant were eliminated, and the product reached the acceptance standard of the foreign company.

 

 

summary

 

      The use of low speed compensation and reverse acceleration compensation can improve the arc over quadrant convex lines caused by mechanical friction. You can use the low speed compensation and reverse acceleration compensation functions as needed.