Method of operating an off-line finishing device for fiber webs, in particular an off-line slitter-winder for winding fiber webs

Patent metadata

Field	Value
Publication number	US-11142422-B2
Application number	US-201916662756-A
Country	US
Kind code	B2
Filing date	Oct 24, 2019
Priority date	Oct 24, 2018
Publication date	Oct 12, 2021
Grant date	Oct 12, 2021

Abstract

A method of operating an off-line finishing device for fiber webs, in particular an off-line slitter-winder for winding fiber webs, wherein in operating the off-line device the running speed is automatically optimized to minimize cost of web breaks. The method considers the costs associated with a web break during unwinding in addition to the cost benefit of maximizing web unwind speed so as to maximize machine utilization. The method determines an optimal web break stopping time in a web break situation and how often a web break is predicted. Automatic optimization incorporates limitations including the maximum rotation speed of the parent roll, the maximum speed of the fiber web being unwound, the maximum positive torque which can be applied to the parent roll to accelerate the parent roll to a rotation rate which produces a desired web speed, and maximum braking torque.

First claim

I claim:

1. A method of operating an off-line slitter winder finishing device for fiber webs, having an unwinder and a parent roll mounted thereto, the parent roll having a fiber web with a fiber web length, the unwinder having a maximum web speed, and at least one torque drive motor for controlling an unwind velocity of the parent roll, and at least one torque brake, wherein said at least one torque brake comprises at least one of said torque drive motor and a mechanical brake, the at least one torque brake having a selected braking torque, the method comprising the steps of:
using a model of the off-line slitter winder finishing device for fiber webs to pre-calculate a limit of a web break stopping time required by the selected braking torque in relation to the parent roll inertia and web unwind speed and how much setting a maximum web break stopping time decreases capacity of the finishing device for fiber webs by decreasing average web unwind speed;
collecting continuously data relating to frequency of occurrence of web breaks per parent roll to determine probability of occurrence of a web break;
calculating expected value of capacity loss based on the determined probability of occurrence of a web break and the web break stopping time; and
while the web unwind speed is lower than maximum running speed, adjusting the maximum web break stopping time and thus the web unwind speed such that the expected value of capacity loss is minimized, wherein the expected value of capacity loss is continuously adjusted as the probability of occurrence of a web break is updated.

2. A method of operating an off-line finishing device for fiber webs, the device having an unwinder and a parent roll mounted thereto, the unwinder having a torque drive and a torque break, the method comprising:
selecting a maximum web speed for unwinding the fiber web;
determining a web break frequency based on a history for a selected number of parent rolls which have been unwound most recently, by dividing the number of web breaks by the number of the selected number of parent rolls which have been unwound;
defining a web break cost as a function of parent roll rotation speed;
defining a cost of incremental increased time to unwind the parent roll caused by reducing web speed below the maximum web speed; and
adjusting parent roll rotation speed so as to minimizing a total cost due to web breaks and cost of increased time to unwind the parent roll due to unwinding at less than the selected maximum web speed.

3. The method of claim 2 wherein the web break cost is a function of one half of the parent roll rotation speed at break, times the selected time to stop rotation of the parent roll plus a fixed cost corresponding to a web break at zero web speed.

4. The method of claim 3 wherein the cost of incremental increased time to unwind the parent roll is a function of an allocation of total cost of operating the off-line finishing device for fiber webs on a time basis.

5. The method of claim 3 wherein the time to stop rotation of the parent roll is determined based on a self-learning algorithm using multiple data instances selected from at least one of: an occurrence of web breaks, total time to unwind the parent rolls in the off-line finishing device for fiber webs, cost of web breaks, total cost of processing the parent rolls in the off-line finishing device, and time to stop of the parent roll following a web break.

Assignees

• Valmet Technologies Oy

Inventors

• Paanasalo Jari

Classifications

• B65H2511/14

  Diameter, e.g. of roll or package · CPC title

• B65H2601/525

  Cost of application or use, e.g. energy, consumable · CPC title

• B65H2557/24

  Calculating methods; Mathematic models · CPC title

• B65H18/08

  Web-winding mechanisms · CPC title

• B65H2301/4148

  slitting · CPC title