This is a simple little prototype tester used to discover the properties of textured pickup rolls that are used on coating equipment.  By using this tester I was able to prove that texturing pick up rolls did not significantly improve the rolls ability to pick up coating and would cause coating to foam earlier at lower RPM's.

Below is the experiment report that I wrote and presented to the engineering department.

Introduction:

The objective of this experiment was to determine what are the significant differences, if any, between smooth and textured pick up rolls. Michelman has traditionally used only 100 rms textured pickup rolls on their rod coaters; However, some customers such Westvaco of Newark, Delaware have replaced textured rolls with smooth pick up rolls. Such incidences have helped inspired some discussion about the properties of smooth and textured rolls.

Theoretical Background:

The theory behind a textured pick up roll is that the texturing adds "hills and valleys" to the roll surface increasing total surface area. This increased surface area may improve roll performance, for picking up coating, as it exits a bath of coating. These valleys may also increase the tendency for air to be trapped on the roll surface as it enters the coating bath. Air trapped on a roll surface would reduce roll performance and increase the possibility of foaming.

Experimental Apparatus:

	Custom test fixture approximately 16" wide and 10" tall.
	Plastic pan
	Four 3" diameter pickup rolls including smooth, 50 rms, 100 rms and 150 rms matte finish.
	Variable speed mixer motor with built in tachometer.
	Stopwatch
	1000ml graduated beaker
	water
	Coating ME39235 of 22 centipoise (thin)
	Coating EE44337 of 440 centipoise (thick)

Experimental Procedure:

Place pick up roll and pan into test fixture, connect motor and fill pan with coating or water. Set speed of motor to 60 rpm, engage pick up blade, start timer and place beaker under outlet of pick up blade. After 60 seconds or as beaker approaches full, disengage the pick up blade and stop tester. Record elapsed time, actual rpm and volume of liquid collected, repeat test two more times and take an average for all three tests. Repeat for 120 rpm and 240 rpm for each of the four rolls. Start the tester and gradually increase the rpm of the tester and record rpm when foaming occurs and when liquid begins to sling from the rolls.

 

Results:

Water:

Volume Collected: All four rolls picked up water equally at all speeds within 8% of each other.

Foaming: When approaching higher speeds the textured rolls would produce bubbles in the water and on the roll sooner that did the smooth roll.

Slinging: The rolls would not sling water below 500 rpm.

 

 

 

 

 

 

 

 

 

 

 

Thin Coating:

Volume Collected: All four rolls picked up coating equally as well within 7% of each other.

Foaming:

When approaching higher speeds the textured rolls would produce foam in the coating sooner that did the smooth roll but not by a significant amount.

Slinging: All four rolls slung coating at approximately the same speed.

 

 

 

 

 

 

 

 

 

 

 

Thick Coating:

Volume Collected: The higher textured rolls picked up more coating than did smoother rolls. The textured rolls collected, on average, collected 16% more coating at 47fpm and 11% more coating at 94fpm than did the smooth roll. Data was not collected for the 188fpm range because of excessive coating volume.

Foaming: This coating seemed to be more sensitive to foaming. When approaching higher speeds the textured rolls would produce foam in the coating sooner that did the smooth roll.

Slinging: . When approaching higher speeds the textured rolls would sling coating sooner that did the smooth roll.

 

 

 

 

 

 

 

 

 

 

 

Discussion:

The accuracy of the data collected is difficult to quantify, however I believe it does provide valuable data that can be used to help understand the differences between smooth and textured rolls.

Conclusions and Recommendations:

Textured rolls seem to have little influence when picking up lower viscosity coatings and water. Textured rolls do seem to improve the performance in thicker coatings, however this improved performance may be irrelevant because thicker coatings are much more efficient to pick up and the roll must slow down to compensate. Textured rolls also create foam sooner that do smooth rolls in foam sensitive coating.

Pick up roll speed has traditionally been linked to a percentage of line speed. After evaluating the data from this experiment I learned that doubling roll speed doesn’t double the coating picked up. Doubling the pick up roll speed only improves performance by seventy percent. We may have to develop a new formula for controlling pick up roll speed as our equipment operates at higher line speeds in the future.

I do not recommend that we make any change to existing equipment based on this experiment alone, more data needs to be collected. We need to develop a formula to calculate sling and foaming based on roll texture and diameter. We should pursue more testing because corrugators and offline systems will continue to increase speeds and our customers will demand faster coaters.