PROdry Technology Inc.

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Creping Blade Process

The creping process is arguably the most important process step in tissue production. The relationship between the web’s adhesion and cohesion and the mechanical forces of the crepe doctor is one of many variables that effect the crepe process, blade life, operating efficiency and product quality. Blade changes, Yankee cylinder grinds and web breaks at the crepe blade are the major causes of downtime for many tissue machines. Our focus at PROdry is to provide the customer with the desired product quality and improve paper machine efficiency through:

Doctor blade alignment and set-up
Doctor wear analysis
Doctor vibration analysis
Strain-gage analysis of doctor load profiles
Load uniformity

Strain-gage analysis of blade loading can be useful in several ways. Shown at right is a strain-gaged blade mounted in a towel machine for testing. The blade (outlined in yellow) has been instrumented with multiple strain gages which yield the load distribution across the dryer. These blades are precision-constructed by PROdry technicians for specific machine applications using the same blade stock used by the mill. Gages are concentrated near the edges of the dryer to give better definition in the region of the compound crown, but a full profile is obtained.

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The graph at the left shows two load profiles (in terms of PLI) obtained from a machine before and after changing the doctor back. Note the ragged profile from the original doctor back (in red) compared to the profile from the new back (blue). In each case, edge relief accounts for the drop in load near the back edge; more relief is needed near the front.

Data obtained from strain-gaged blades can also be used to determine very accurate load vs. air pressure curves for setting loading parameters. Since the measured parameter is the actual strain on the blade, effects of linkage maladjustment or "sticktion" are eliminated. PROdry's strain-gage load display is monitored real-time, providing instant feedback and easy observation and rapid correction of problems such as cylinder travel limitations.