[Summary]Using the friction compensational function can be eliminated the hump due to the over-limit of the arc machining, so that improving the machining accuracy of the machine tool.
The friction is mainly used on the driving equipment and guiding of the machine tool. The desired torque when the feed axis is started that is much more than the normal operation one, due to the effect of the friction; and then the feed axis will be generated the bigger following error when starting. When the two axes are performed the interpolation motion at the same time, if one axis of the motion direction is changed and when the velocity is passed to the 0, the interpolation axis will be stopped a moment to generate a contour error because the alternation of the state of the frication; and this phenomenon is especially obvious when the workpiece of the arc contour is processed; a axis has been reached to the top speed instead of another one is 0 where the arc changes its quadrant; a hump wave or dent will be then generated. The GR driver is installed a frication compensation function in order to improve the contour error of over-quadrant of an arc. The frication compensation can be obviously improved the contour error of over-quadrant due to the effect of the frication.
GR drive offers two kinds of compensation modes of frication based upon the reason of the over-quadrant bump:
(1)Low velocity compensation function (Enabled for position and velocity methods).
PA42--- Character speed of compensation function at its low velocity (It is default as 50 and does not need to adjust).
Pa43--- Low speed compensation coefficient
(2)Interval acceleration compensation (Position method enabled).
PA135--- Interval acceleration compensation gain
PA136--- Interval acceleration compensation time
One customer processes the aluminum cover ornaments for one Perfume Company from overseas, the product has an obvious arc over-quadrant bump that does not reach to the acceptance standard of the overseas company, and the customer requires that the over-quadrant bump mark should be eliminated.
The customer’s machine tool is Baoji TK36S horizontal hard rail machine, which configures with the common-use GSK 980TDI system and GR2050 drive.
The friction of the horizontal hard rail machine is bigger; it should be adjusted by the friction compensation function based upon the customer’s requirements; and use the low speed compensation function in prior when adjusting.
During the adjustment:
We can view that there are four bump pointed angles on the over-quadrant of the round based upon the above-mentioned figure; the reverse jumping is 0.0047mm, the integrated roundness is 0.0057mm; and that is the quadrant error caused by the friction of the machine tool’s mop.
(2)Using the low speed compensation functionAdjust to PA43=500, and perform the roundness analysis again.
Continuously enlarge the PA43=1000 test that you will found that the improvement of the pointed angle of the over-quadrant does not more error of the PA43=500; so the parameter value of the PA43 is changed back to 500 and then use the reverse acceleration compensation function.
(3)Reverse acceleration compensationThe over-quadrant error is obviously reduced after the low speed compensation function is used, and firstly the reverse acceleration compensation gain will set a smaller numerical value.
Adjust PA135=20 PA136=100, and then continuously collect data to perform the roundness analysis.
The customer is performed the processing again after adjusting, the bump wave of over-quadrant on the surface of the sample is eliminated and the product reaches to the acceptance standard of the overseas company.
It can be greatly improved the bump wave of arc over-quadrant caused by mechanical friction after using the low speed compensation function and reverse acceleration compensation function; and it’s up to you to select the low speed compensation function or the reverse acceleration compensation function based upon the requirements.