Roll Size Optimisation: Background Info

In this section you find more in-depth information on some central aspects of Roll Size Optimisation. Should you have questions that aren't answered here please contact us.

Data Required by Roll Size Optimisation

If you want us to perform a Roll Size Optimisation for you we need your order data from several months of the past containing the following information.

Order Data Order Number Customer Name (not mandatory, but nice to have) Due date Board grade Flute type Quantity to produce (finished goods) Number out in conversion Corrugator sheet width Corrugator sheet length No Trim Required (flag indicating orders that can be run on the corrugator without side trim)

Corrugator Data Machine width Minimum roll size which can / should be used Minimum trim Minimum run length Overrun tolerance Cost per production hour Machine speed per flute

How Roll Size Optimisation Selects Orders to Schedule

When trying to schedule the orders of several months in retrospect, it is unknown which orders were available for scheduling when the planner planned them, and which paper sizes were available. Therefore, Roll Size Optimisation (RSO) can only try to simulate realistic conditions, and does this the following way:

First RSO assumes that the date given in the order is the date the order should run on the corrugator. Then, RSO creates a schedule for each date for which there are orders, by scheduling each grade of that date.

For a given grade, RSO first attempts to schedule exactly the orders of that day. If it can successfully plan them all, it continues with the next grade. If not, RSO will try again including of the next day; if it finds a complete result, that result is used; if not, RSO adds another day (up to 5 work days may be added).

If no complete solution can be found, then RSO will leave the problem orders (completely or partially) behind.

Simplifications of the Roll Size Optimisation

Roll Size Optimisation must function in reasonable time, with data limited to what can reasonably be provided. This means that certain restrictions are disregarded:

• Orders are selected for optimisation schematically, but the actual orders available for planning at any given time are not known (see the section How Roll Size Optimisation Selects Orders to Schedule).
• All roll sizes are supposed to be available; in reality there might sometimes be no stock for some grades and sizes.
• Orders are scheduled without observing limits for the number of scores or tear tapes, or scorer distance problems.
• Cut-Off and Take-Off length limitations are ignored.

Only very few runs will actually violate limitations, the bulk of the orders are not affected. Thus, the grand picture doesn't change much.

Treatment of Problematic Orders

During the first optimisation run, orders may be left out for various reasons (full machine size etc.) for which actual planning obviously had solutions. We eliminate those �idiot� orders and repeat the first analysis without them to avoid having optimisation make efforts to find solutions where a known solution obviously exists.

During subsequent runs, again orders may be left out or be partially scheduled, in particular when small roll sizes are eliminated. Typically only a very small percentage of orders is concerned, and it can be safely assumed that a solution would be found for them in real life planning.