Do Your Homework to Solve Telescoping Roll Problems

I've been busy, even though some of you may have seen me live a couple months ago at CPP EXPO, but that kicked off a seven week tour. I feel like a rock star. Not the arena-filling kind; it's more like the oldie band playing at the local casino.

So while on my far and wide travels, someone asked about roll telescoping, and I thought my blog followers might find my response useful. To better understand their product and process, I proposed the following questions that you can also ask yourselves.

Here is some critical information you must gather to address telescoping rolls:

1. When does telescoping occur? A) during winding B) in roll handling C) during unwinding?
2. What shape is telescoping? (Pictures can greatly help answer this question.) Where are the shifted layers radially (near core, X distance from core, outer layers)? What do the shifted layers look like (step change, tapered change, curvy shifting, shootout of a few layers)?
3. Are there any trends of telescoping? (What machine, spindle, product, season does telescoping most likely occur?)
4. What product variations have more telescoping, including web thickness, width, roughness, coefficient of friction (side A to side B)?
5. What winding conditions or roll geometry have more telescoping? Core material, core inner and outer diameter, core support method (chucks or through shaft), winding speed, roll start accuracy (misalignment?, wrinkles?), final roll diameter, roll transfer method (at speed or zero-speed at full-machine or accumulator-based stop).
6. Other important winder information: Winder supplier, winder elevation diagram, winding tension control plan, winding process nip roller design (mechanism for loading, winding nip roller design: diameter, wall thickness, material, width, rubber covering thickness, rubber hardness).
7. What are the winding process settings: Starting tension, taper tension (and what equation is used for tapering, versus diameter, versus speed), winding nip roller control (starting nip load, tapering versus diameter or speed).
8. What is the stack modulus? One of the biggest factors in winding is the mechanical compress properties of your product in stack form. You likely don't have this information, but it is required to truly model your product/process roll pressures and torque capacity.

To resolve a telescoping problem, first we need to understand the mechanism of telescoping. Most telescoping falls into one of four categories: 1) cinching-induced, 2) roll handling damage, 3) air lubrication, 4) creep (usually adhesive).

Answering these questions will provide insight into the telescoping cause and suggest remedies appropriate to that cause.

Tim Walker