Problem- Is my encoder malfunctioning ?

[Ashish B]

Hello All,

As you can see in the attached figure, I have clamped a part on my machine. I find the centre of part (slot) by holding a test indicator in collet. The problem to me is that there is a variation in the slot centre calculation. I find the slot centre manually and i can see a variation of 0.09 mm in the centre.
I am really not able to foresight the root cause...Everything is ok...The part is firmly clamped, the test indicator, collet and tool holder are in working condition.

Can't get out of this problem.
Need help.

Is this something related to encoder ? Is my encoder malfunctioning ? How should i revalidate the doubt that the problem is with my encoder ?

Thanks
Ashish

[neilw20]

Nothing attached. No picture or figure. More information please.

[Al_The_Man]

Turn the test slot 90° and see if there is also an error in the perpendicular axis, if none, it could be a backlash error?
If the same result, it could be error in calibration of the measuring probe?
Basically a process of elimination.
Al.

[Ashish B]

Sorry for incomplete posting....Figure attached now.



Thanks
Ashish

[Al_The_Man]

Did you rotate and test it on the Y??
Al.

[Ashish B]

Hello Sir,

Actually i am not getting your opinion clearly. What should i turn ?
Should i clamp the part in Y axis and find the slot centre in Y axis.

I had the same doubt of backlash a week ago. I clamped a plunger dial and then probed it against a part for no. of times. The Dial readings and the m/c readings used to match perfectly.
Also one more trick to remove backlash, is SINGLE POSITIONING SYSTEM. If i have to go at X400.0, then I continously crank the handwheel to go to that position. I neither retract back in Y as well as Z directions.

Thanks

[Ashish B]

Also, I experienced 1 more unusal error. It goes as follows -

I started my m/c, i homed it and i moved it to a X position (X200.0) & Y position (Y-345.0). Then i switched off machine and again turned on the m/c. After starting the machine, i did not move the machine.

I see the positions as X199.985 AND Y-345.012.

Its really a strange error? I cant believe it. The m/c should show correct position.


Need help.

[Al_The_Man]

Originally Posted by Ashish B Should i clamp the part in Y axis and find the slot centre in Y axis. Thanks

Yes.

Originally Posted by Ashish B I started my m/c, i homed it and i moved it to a X position (X200.0) & Y position (Y-345.0). Then i switched off machine and again turned on the m/c. After starting the machine, i did not move the machine. I see the positions as X199.985 AND Y-345.012. Its really a strange error? I cant believe it. The m/c should show correct position. Need help.

There is nothing strange there, I assume you still had the controller under power or else the display would normally show 0,0.
If it was just the drives that were powered off, then the natural mechanical relaxation that occurs when the motors are no longer driven is normal, however, the controller normally knows this as the encoders are constantly read.
What type of controller do you have?
Al.

[Ashish B]

Yes, definately I will clamp the part in Y axis and let you know asap.


I dont know the controller name, but the machine is PINNACLE 1100S. And yes, i cross the strange error on my 5 turning centres. They too show such behaviour.

Thanks, for replying.
Ashish

[Ashish B]

Hi,

I clamped the part in Y axis and i did not found any error...The slot centre is calculated within 0.010 mm...I have done it for 20 times and still though the centre is been calculated within 0.010 mm...


Then what may be the cause of error in previous position ? Is my X axis faulty ?

Thanks
Ashish

[Al_The_Man]

As the probe seems calibrated and working OK, It would appear the problem may be in X axis error, you need to perform a backlash check.
Al.

[Ashish B]

How a backlash check is performed ?