Calibration of a technological process monitoring parameter of a two-roll mill

Abstract

The paper discusses the calibration of a monitoring system for a rubber and plastic laboratory mill and associated problems. In a somewhat broader sense the need to calibrate appears to be common to a large number of processing machines of which the parameters have not been quantified and for which there is no provision for machine performance or acceptance tests.

The isolation of a technical processing control parameter is important but the ability to monitor this parameter reliably and with sufficient accuracy is more important still. The presence of an adjustment on a machine other than that which is necessitated by wear may indicate the possibility of influencing one or more of the technological parameters. But the validity of a presumed parameter cannot even be established let alone controlled unless a parameter control setting and the technological effect which it has is monitored. The parameters readily available which were measured in this case were nip, nip force and the mass of material which enters the nip of a mill roll. The only variable monitored continuously was nip force. The other two remained constant and predetermined for each set of experiments as indicated in detail elsewhere by Brichta and Welding¹ and Brichta³.

Boundary monitoring factors relevant to the milling of rubber are considered and their technological importance are proposed.

It is suggested that monitoring cannot be satisfactorily done without calibration of each individual instrument separately and the whole monitoring system jointly to verify the overall effect. Since calibration involving electronic equipment may require frequent check of range and zero drift, a secondary load standard was used for this purpose because a constant half full scale deflection input was not available. The calibration method used is presented in detail in the paper together with some of the results.