SMALL BATCHES | PROCESSING
Making a success of small batches
As production batches get smaller the need to get compounding lines turned around and back into stable production grows. Peter Mapleston learns more
If you want to be a successful small batch com- pounder, you need to get up to optimal production quickly, stay there without wavering, come down quickly, take as little time as possible moving to the next job, and then do it all over again with a different compound. The idea is simple enough — the difficulties often appear in the execution. “Small batch compounding requires flexibility,
fast response, short lead times and — obviously — shorter production times than conventional compounding. Getting up to regime faster and keeping the steady state provides a competitive advantage, especially when you are formulating thousands of recipes per year,” says Luis Roca, Leader of Compounding at Spanish research organisation Aimplas. “Besides looking closely at changeovers, companies should analyse the time it takes to arrive at the steady state for collecting the com- pound, what are the main causes of any drifts away from that steady state during compounding, and to find the origin of both issues. Over time, they could represent an important amount of lost time and money,” he adds. Roca identifies a number of key factors to
consider, starting with having a reliable and robust process, where all the equipment and ancillaries are working accurately (feeding, pelletising, vacuum venting and the like), with the right configuration for each type of filler or compound. He says he has
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seen cases where configurations remain the same even when the polymer or a filler generates problems when feeding and pelletising, possibly leading to blocked vents and production halts. When it comes to process control, different aspects need to be considered. “The first is the state of the sensors on the extruder. When melt temperature or pressure sensors are not working properly, problems like die build-up can arise if temperature profiles that are too high are set up, or vacuum is not working in the right way,” Roca says. Another issue to pay attention to is the possible
lack of response procedure when response variables — such as melt temperature, pressure or torque — change. “Understanding what range of deviations on
torque, SMI, Tm and Pm are acceptable and its evolution in time is mandatory to keep quality standards. Besides alarms, it is highly advisable to establish a range of acceptance in the extruder response variables, which all the technicians should know in order to detect compounding problems and to minimise rejects,” Roca says. “A standardised procedure that correlate the possible deviations of response variables with the possible problem and its sources will minimise the time of reaction and also the consequences of the problems. Troubleshooting and how to react against unexpected events should be part of the quality system of any compounding company,” he adds.
� April 2022 | COMPOUNDING WORLD 53
Main image: Efficient small batch com- pounding requires a good under- standing of process set-up and control
IMAGE: SHUTTERSTOCK
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