SOLUTION
After observation and technical analysis, Shriram came to a conclusion that the problem was due to noise, which was generated by the VFD. They used different techniques to eliminate the noise but the problem persisted.
Finally, they came up with a solution to replace the existing HMI and PLC with the Horner EXLW controller, model 5. The feature of the frequency filtering utility for HSC inputs on the EXLW proved it as a better choice. This feature could be used to control the unwanted noise.
Keeping the same VFD they programmed the EXLW and completed some wiring changes. They also configured the analog output of the EXLW for varying the frequency of the VFD.
They started testing their logic and observed that the same problem was occurring, in that there continued to be a length variation in the profiles. They adjusted the filtering of the HSC inputs which produced a significant change in the result. Yes it’s true, they were able to eliminate the noise completely! After the elimination of the noise there was a consistency in the length of the profile.
The client was finally satisfied and appreciated the decision of changing the PLC. They immediately ordered two more EXLW controllers to replace them in the other two machines.
