What is meaning of doing calibration of a industrail robot?

Hi,guys,
Some times I heard that if some parts of a industrial robot changed, it need to do some calibrating? And what's the meaning? Why and how to do it?
Thanks.
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face=Arial size=2>...</FONT></DIV> <DIV><FONT face=Arial size=2>&gt; Hi,guys,<BR>&gt; <BR>&gt; Some times I heard that if some parts of a industrial robot changed,<BR>&gt; it need to do some calibrating?<BR>&gt; And what's the meaning? Why and how to do it?<BR>&gt; <BR>&gt; Thanks.<BR>&gt;</FONT></DIV> <DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV> <DIV><FONT face=Arial size=2>The control program has a model that it thinks the robot conforms to.&nbsp; If you change a part, that might change the model.&nbsp; E.g., if you put in a new joint, the resolvers for that joint may have a different reading for the zero-angle position, so you must update your model.&nbsp; Some calibration also takes out measurement errors in the model, by putting the robot in a known position, and massaging the model until it agrees.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV> <DIV><FONT face=Arial size=2>Mike Ross</FONT></DIV> <DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV></BODY></HTML>
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face=Arial size=2>...</FONT></DIV> <DIV><FONT face=Arial size=2>&gt; Hi,guys,<BR>&gt; <BR>&gt; Some times I heard that if some parts of a industrial robot changed,<BR>&gt; it need to do some calibrating?<BR>&gt; And what's the meaning? Why and how to do it?<BR>&gt; <BR>&gt; Thanks.<BR>&gt;</FONT></DIV> <DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV> <DIV><FONT face=Arial size=2>The control program has a model that it thinks the robot conforms to.&nbsp; If you change a part, that might change the model.&nbsp; E.g., if you put in a new joint, the resolvers for that joint may have a different reading for the zero-angle position, so you must update your model.&nbsp; Some calibration also takes out measurement errors in the model, by putting the robot in a known position, and massaging the model until it agrees.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV> <DIV><FONT face=Arial size=2>Mike Ross</FONT></DIV> <DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV> <DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV> <DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV> <DIV><FONT face=Arial size=2>No two parts are created equal. Whenever you change a part, crash the machine, or sometimes time alone, will cause the machine to lose it's bearings. Then you recalibrate to maintain exact repeatability. We have&nbsp; 8 axis CNC's that require recalibration on almost a daily basis due to the inherent vibrations that are caused by their normal operation. In a nutshell your just pointing out home to the computer.</FONT></DIV></BLOCKQUOTE></BODY></HTML>
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None sense , thats make work , and
uncompetitive , no one would buy such
a "costly" ROBOT !
ROBOTs have many levels of precision ,
the fine level is so clever and adaptive , it
corrects for tool wear as CNC do ..
Trade Unionists !
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Then explain why the government sets industry standards for calibrations if machines can be so perfect? (Why pay for yearly / bi-yearly certifications?) And then why do the machine manufacturers include calibration tools with the equipment when they sell them to you? Do you trust the scale you purchase your meat from? I have ISEA robots that are self homing and self recalibrating, but they still require a confirmation setup from time to time, as well as a certification from a licensed technician on a timely basis, and the technician uses special calibration tools to know how much deviation must be adjusted in the operating parameter to maintain repeatability.
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Thank you. Mike.
"By putting the robot in a known postion"?? does it mean that before changing the part of the robot ,you must record the reference point and save it as a point file,then move the robot to the point after finishing changed. Then check the error and calibrate it. Right??
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Thank you. Mike.
"By putting the robot in a known postion"?? does it mean that before changing the part of the robot ,you must record the reference point and save it as a point file,then move the robot to the point after finishing changed. Then check the error and calibrate it. Right??
I guess that is one way. Usually you're interested in the tool position being right, so you use some pre-made and pre-measured jig to grab with the robot's end-effector, thus placing it in a known (i.e. repeatable) position.
Mike Ross
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It's very nice of you.Mike.

calibrating industrial robot, don't it ?
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I have worked on industrial robots for quite some time. The calibration, in general, means fixing the robots coordinate systems to known setup. In case of cartesian robot arms, for example, you have limit sensors at each end of the travel lenght of each axis. Three axes are supposedly mechanically perpendicular to eachother.
Well, the problem is, they never are. So if you want a half-millimeter- precision positioning, you have to fix the coordinate system transforms so that the mechaniocal irregularities ( a small angle between the axes ) are taken into the account. Thats part of calibration. You also want to make sure that +- directions of each axis is correct, and the "zero point" of coordinates is reached properly, this usually involves adjusting the limit sensors ( moving them a little this or that way )
Once calibrated, the robot will know its position after each powerup and homing procedure with a very high precision. An uncalibrated robot might move irregularly, i.e. you give it a command to move +10 mm in X direction, but it moves 9.5 in X and 0.2 in Y or somesuch.
hope that explains it.
-kert

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Thank you very much for your detailed explaination about calibration. kert.
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