FACTS Tech Blog

Force induced variations result from

• the way the calender is operated and
• from previous process steps such as feed mill operation
• compound consistency from mixing

In rubber calendering, separating forces generated are quite high; typically 160,000 lbs to 300,000 lbs at each actuator for a 66 inch active roll face producing a 60-inch wide rubber sheet. Those forces literally stretch the calender frame. Variations in these forces will therefore vary the amount of frame stretch and thus vary roll position and calendered gauge. Read more…

Electric screw actuators are the most common type of calender roll end positioning system. The screw and nut operate under very high loads and thus experience significant wear even with proper lubrication.

As the actuators wear, back lash develops. As the back lash increases, the response to small changes or corrections deteriorates. Also with increased backlash the number of corrections required would increase, which in turn causes increased wear.

In addition, most calenders still have fixed speed electric motors with mechanical brakes. The breaks particularly need periodic maintenance. Sticky brakes will adversely affect gauge control results.

Most modern calender rolls are the drilled type. This means that water passages are drilled across the roll face under the surface. This effectively forms a radiator-like heat exchanger around the periphery of the roll.

If these passages become plugged, then non-uniform heat transfer will occur and this results in a thermal ‘out-of-round’ condition for the roll or rolls. This has the same effect as if the rolls were machined ‘out-of-round’.

To avoid this condition only treated water should be used and the rolls should be periodically flushed.

How do you check for plugs? Compare the roll run-out at ambient temperature and at operating temperatures.

Calender roll bearings may have excessive run-out. The result is the same as, and will appear as calender roll surface run-out. Excessive bearing clearance will result in the roll shifting during operation as roll separating forces vary.

These conditions will adversely affect the ability to control the calendered gauge.

When investigating run-out issues, check the calnder roll surface AS WELL AS the bearings!

Calender rolls must be round and free of run-out at ambient temperature. Any run-out of the individual calender rolls will be amplified as the high spots and low spots periodically match up between the roll pairs.

Differences between high and low spots is relatively easy to check with dial indicators.

How to:

• Run the calender without rubber (or your product)
• Make Sure there is a slight gap between the rolls.
• Check the differences between high and low spots with simple dial indicators.

Give us a call - we’re happy to walk you through it and help diagnose your problem. Call FACTS, Inc.- 330.928.2332

Via Touchscreen

(2001FS system)

If the touchscreen is working well enough to navigate through the SubMenu, the calibration can be initiated here. If not, skip down below to see Keyboard instructions.

2. Select Submenu 1
3. Select System Service Menu
4. Enter password if needed.
5. Select Touch Screen Calibration

Read more…

1. Clean all debris from the Roller assembly wheels.
2. Clean all debris from the Gauging roll surface.
3. Put the gauges down on a bare roll.

Read more…

FACTS, Inc. control systems perform best with properly maintained rolls.

Calender rolls must be ground periodically to establish the proper profile.

The profile is selected so that the roll separating forces, which cause the rolls to bow apart in the center, are partially compensated for by grinding the center to a larger diameter. Read more…