Sign in to follow this  
Followers 0
Mayur solanki

incremental encoder missing counts

5 posts in this topic

hello everyone,

i am electrical engineer working in steel company. we have bought one new machine which having Siemens s7 300 PLC. there are two encoders in machine. one is used for measuring length of rod whereas other one is used for cutter home position. we got some problem related to encoder. i have checked on HMI screen that during first cut, cutter encoder missed counts. its 2048 ppr incremental encoder. so please can anybody help me to sort it out this problem.

i have changed the encoder but still the problem is same.

regards,

Mayur

Edited by Mayur solanki

Share this post


Link to post
Share on other sites

How did you use the HMI to determine that it missed counts? Watching the HMI (or a laptop) while the axis moves is not a good method due to delays in the screen's update time and communications delays with the software.

Share this post


Link to post
Share on other sites

as Joe stated, can you verify actual length of cut pieces and confirm if there is an error or not?

if there is an error, then troubleshooting is needed (shielding, configuration,..) 

Share this post


Link to post
Share on other sites

Yes, we have checked the length of cut pieces, and we have found the variation in length.  in attached file i have attached encoder details and cutter. the cutter position which is seen in attached file, on this position encoder PPI must be zero. i have set PPI zero on this position of cutter, but after making one cut, while i have checked, i have found that its not zero on this position. that is why we have suspect that there was a problem of missed counts. the encoder which is show in attached file is used only for cutter positioning.

IMG-20171108-WA0013.jpg

IMG-20171108-WA0014.jpg

Share this post


Link to post
Share on other sites

I'm not ruling out an issue with the encoder or controller, but in my experience this sort of thing is most often caused by slip between the encoder and what it's measuring.

We have a bunch of servo stock feeders that feed bimetal strip into forming presses at up to 60 parts/minute. Feed length is around an inch and is constant for each run but adjustable when changing over to another part.  We very frequently get reports saying, "The feed length is varying. There's something wrong with the servo!" At least 99% of the time, the problem is maladjustment of the rollers so that they slip randomly on the strip. And 99% of the remaining 1% is a problem with the previous machine causing increased tension on the strip.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0