Changeover time in sewing line is the time taken from producing the last good quality piece of the completing style to the time taken in producing the first good quality piece for the new style.
The above definition will give the changeover of the entire sewing line. This is because the completing style will transition smoothly in the line while for the new style in every operation we need to set the machine and other things. Therefore with every passing operation the time gap between both the pieces will start increasing and the changeover time will keep adding.
So if the difference at the end of the line is calculated the output will be sum of changeover time of every operation.
But to control the changeover time we should be able to measure the changeover time of every operation. This data will specifically pin point in which operation the changeover time is the maximum and changeover time reduction tools like SMED can be applied.
To measure the changeover time of every operation RFID, barcode or manual data record can be used.
Calculating Changeover time in a digital factory
Factories don’t measure their changeover on daily basis. The project is done once in a while and then the outcomes becomes the constant measure. But with every passing style we need to know what is the changeover only then we will be able to accurately achieve the target set on the day of changeover.
Therefore having an automated system for calculating Changeover in a digital factory becomes an important factor in operations management.
The foundation for getting changeover time in a digital factory is getting to know when quality is passing a piece out of a sewing line, so the first step is:
- Having quality recording system where every passed piece is entered. I am specifically saying quality and not sewing data because though the first piece of the upcoming style may be stitched after one minute we cannot be certain if it is of the right quality. Therefore we must take only quality data for changeover calculation
- When we will have quality pass data we can calculate the changeover by using the formula
Time of first good quality piece for the new style – Time of last good quality piece of the completing style