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quadrant protrusion in Y axis, but only in high feedrates, while backlash already set!

Created by: justbabak at: 12/10/2010 11:50 AM (15 Replies)

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12/10/2010 11:50 AM	Rate (0)
justbabak Posts: 11 Rating: (0)	Hello everybody, I have a strange problem in making circles with my milling machine with 802d sl controller. the problem islike quadrant protrusion in Y axis,but only in high feedrates and the point is I have set backlash parameter in controller carefully. I have already set backlash of Y axis; there is no reversal motion error while checking by dial gage, andit can make perfect rectangles. also, It can make perfect circles but just only when the feedrate is below 800 mm/min. when I go to higher feedrates, the error goes high as well, for instance, by F=2000 I get 0.07mm error in Y axis quadrant point, and by F=3500 the error goes up to 0.25mm! i guess the problem is because of big backlash of Y axis regarding other axes backlashes(I found BL= 0.33mm for Y axis, hence it is about 0.04 for X & Z axes) and maybe relatively low acceleration of Y axis motor. I think it is possible to compensate this error in NC parameters, maybe by #32200,but I am not sure how, so I think it is better to ask a professionalfor this, thats why I am writing here!! your advices are greatly appreciated, Babak P.S.: some more data: the motion transmission is Ball screw, there is no scale for the axes, only motor encoders
justbabak Posts: 11 Rating: (0)	Last edited by: justbabak at: 12/10/2010 12:25 PM
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12/11/2010 8:10 AM	Rate (0)
Ekalavya Posts: 2964 Rating: (484)	Hello.... Could you check a Circularity Test for all the axis may be there is error... This test can be done through HMI Strartup.... Check it out and revert back.... Regards, Ekalavya
Ekalavya Posts: 2964 Rating: (484)
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12/11/2010 8:52 AM	Rate (0)
OvidiuNastac Silver Member Joined: 1/29/2008 Last visit: 7/26/2022 Posts: 419 Rating: (19)	Ekalavya Hello.... Could you check a Circularity Test for all the axis may be there is error... This test can be done through HMI Strartup.... Check it out and revert back.... Regards, Ekalavya Hi As I know, the 802DSl doesn't have a Circularity Test option. Much more, because it doesn't have linear scales on the axis, the test would be unconclusive. If you have a big backlash you can use MD36500 to divide the backlash in several IPO steps and thus you'll have a smooth movement at the reversal points. Good luck Nit

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12/11/2010 8:58 AM	Rate (0)
justbabak Posts: 11 Rating: (0)	thanks Ekalavya , ok, I can try although I have not done this before! but, how the measurements are done, as there is no linear encoder (scale) on my machine installed, so how the circularity test is done?
justbabak Posts: 11 Rating: (0)
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12/11/2010 9:06 AM	Rate (0)
justbabak Posts: 11 Rating: (0)	Hi Nit, how many steps are optimum? do you have any idea for dividing amount of 0.33? on the other hand, It seems to me that the problem is that in Y axis quadrant point,the Y axis can not travel fast enough the big distance of 0.33mm against X axis that will travel a small amount of distance (say about 0.1mm)to be there on time! so they dont meet eachother at the point and the circle gets faulty in this point. what is your idea? this idea comes up from the fact that the deviation occurs only in high feedrates.
justbabak Posts: 11 Rating: (0)	Last edited by: justbabak at: 12/11/2010 9:09 AM
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12/11/2010 9:44 AM	Rate (1)
OvidiuNastac Silver Member Joined: 1/29/2008 Last visit: 7/26/2022 Posts: 419 Rating: (19)	Hi Usually a step of 0,05 mm or around it will be not observed on the surface of the piece. You must try and see. It would be better if you can perform a test with a Ballbar instrument (similar with the Circularity test from the HMI but as a stand alone system) which can show you the results at different speeds. As about the incapacity of the Y axis to travel fast enough, I'm not agree with you since the X axis is moving at the maximum speed at the Y quadrant transition and the Y axis must stop at that point (for a split second). The real issue is that the Y axis motor jumps suddenly at that point in such a way that it must compensate the entire amount of the backlash (in a single IPO cycle) even if it must move only some microns. Good luck Nit

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This contribution was helpful to 1 thankful Users justbabak

12/11/2010 10:00 AM	Rate (0)
Pee El Sea Gold Member Joined: 1/19/2008 Last visit: 10/2/2024 Posts: 992 Rating: (64)	hi, As Nit says the ballbar would be a useful tool to you for this problem. I would probably start looking at the axis gains both the speed loop to get a crisper response from the motor and position loop to get better control at higher speeds. Pee

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12/11/2010 12:27 PM	Rate (0)
justbabak Posts: 11 Rating: (0)	thanks for the advices, so I will check backlash dividing and comeback , though I dont have a ballbar in my workshop or my friends.
justbabak Posts: 11 Rating: (0)
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12/11/2010 3:17 PM	Rate (0)
Ekalavya Posts: 2964 Rating: (484)	Hi Nit.... HMI advance PC/PG version 7.2 above series can be used for Circularity in 802DSL. I have check it is working.... Also on 802DSL tool box CD there is a Startup tool if you install this also you can have HMI screen installed but before installing it read the information in siemense.rtf This is just a information i would like to want to share.... Your right we can have ballbar test check for such type problems.... Regards, Ekalavya
Ekalavya Posts: 2964 Rating: (484)
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12/11/2010 3:42 PM	Rate (0)
Ekalavya Posts: 2964 Rating: (484)	justbabak thanks Ekalavya , ok, I can try although I have not done this before! but, how the measurements are done, as there is no linear encoder (scale) on my machine installed, so how the circularity test is done? Hi.... Attach Document is PDF file check out the procedure how the Circularity test is done.... Check it out.... Regards, Ekalavya Attachment Circularity_Teast_8X0D.pdf (456 Downloads)
Ekalavya Posts: 2964 Rating: (484)
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This contribution was helpful to 1 thankful Users justbabak

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