Fonterra Canpac 24 Hour Cyphers
Fonterra sites label production outputs with a cypher code, representing the date of manufacture. Normally production runs are part of a continuous process which last the best part of a day, so the cypher shows the day when the production began, even if it continues past midnight.
However, operations at Canpac are different to most Fonterra sites. Filling of bins, cans, and sachets is more of a batch process, with production runs varying from a couple of hours to more than a week. Generally the cypher code is replaced with a 'unit' code (an incrementing number), which reflects both the day of filling, and changes in input ingredients (i.e. powder of a different cypher).
Traditionally the 'day of filling' corresponded to calendar day, which meant that a short job which ran over midnight would produce product with two different 'unit' codes, even if the input ingredients did not change. Sampling and documentation requirements associated with this wasted a great deal of time, to the point where it was more efficient not to do anything for a couple of hours rather than starting one of these jobs.
In 2008 Tait Controls were asked to modify the control systems, so that 'day of filling' represented 24 hour periods from the use of the first powder for a job. This relatively small change meant that the 'unit' code more closely resembled the cypher code allocated at other sites, and resulted in large savings and much improved effiency for small jobs.
The PLC changes required for these savings were not extensive, but were more technically challenging than normal. Canpac did not want 24 hour periods to vary, even if there were problems or changes in the PLC code, so Tait Controls chose to work with the internal PLC clock rather than discrete timers. This involved division of 64 bit numbers, using 32 bit functions, but meant that accurate times could be maintained even if the PLC was stopped or a new program downloaded (provided that record of job start times was maintained).
TCS (NZ) Ltd manufactured and supplied large 24 character Ethernet message displays for each production line. These were used to display a 24 hour count down for each running job, so that operators all knew when 24 hour periods were coming to an end. Other information was also displayed – job numbers, coding requirements, and status information when jobs were not running – all of which contributed to further improvements in effiency.