Editor's Note: The four figures that accompany this story are contained in a 4-page PDF document that may be accessed by clicking the "Download Now" button at the end of the article.Maintaining packaging efficiency is essential to meeting the cost and productivity challenges inherent in todays pharmaceutical manufacturing. Packaging lines must run at optimum levels and experience as little downtime, planned or otherwise, as possible. Accumulating buffer systems offer manufacturers one clear solution to address these issues.Accumulating buffer systems are temporary storage spaces that allow product flow to continue whenever backups or downtime occur. With any such system, if the disruption on the line is cleared within a short time frame (typically within a few minutes), product is automatically metered back into the production flow.The systems can be installed in various locations along the line, depending on which process steps tend to experience the most stoppages. A common location is before the labeler, which historically experiences more downtime than other line equipment. Most packaging lines installed in pharmaceutical plants today feature at least one buffer.The cost of installing and implementing a buffer system is not minor, but the return on investment in most cases is quickly realized. Since buffer systems isolate individual consecutive processes, they enhance the ability of each machine to achieve maximum performance and facilitate continuous production flow. While they usually do not contribute to the packaging process like filling or capping machines, buffer systems add value to the line by helping to balance production and increase throughput. A common misconception is that buffer systems hide inefficiencies in the line, whereas in reality they enhance efficiencies.This article discusses the myriad choices available in buffer systems and provides suggestions for firms to conduct their own buffer studies to see if such systems are practical or beneficial. In addition, we provide a case study of a successful buffer analysis at one pharmaceutical plant.An assortment to choose fromThere are several types of accumulating buffer systems available, each with different geometries, requirements, capabilities, advantages and disadvantages. They are dependent upon product size, shape and orientation on the line, line speed, and accumulation requirements. Major accumulation categories include:
Figure 1 illustrates one of the simpler accumulation simulation charts prepared, for the case packer. The case packer had only one unscheduled stoppage (product jamming at the loading system), lasting for three minutes, and a mean time between failure of 150 minutes (2.5 hours). The horizontal axis shows the total shift period (from beginning to end) in minutes, the vertical axis the number of accumulated products at the case packer infeed.Up to the first stoppage (the first peak), the flow was steady, so no accumulation was experienced at the case packer infeed. The dramatic upward slope indicates product being accumulated at the infeed, which illustrates the equipments first downtime (three minutes). The downward slope after the peak suggests that the stoppage had been resolved and the machine had started production again.The peak also indicates that the maximum number of products accumulated at this stoppage was 700 bottles. For this particular case packer, speeds range from 200 BPM (operating speed) to 240 BPM (maximum speed). Given this difference of 40 bottles per minute, 17.5 minutes are required to deplete the accumulated product at the case packer infeed and return to steady state. The case packer accumulation simulation chart indicates that the maximum buffer capacity required was 700 products for the case packer at an operating speed of 200 BPM.Figure 2 shows a labeler accumulation simulation chart and depicts the three different stoppages: the scheduled labeler roll change (black line ), an unscheduled outsert feeder magazine jam (magenta line ) and the scheduled outsert backside tape roll change (cyan line). It also illustrates the sum of all accumulated product at the infeed of the labeler due to these stoppages (brown line).Figure 3 shows the buffer accumulation simulation prior to the labeler. It includes information for the equipment in the secondary linethe labeler, case packer and palletizer. It is common to combine equipment in one chart, which allows an analyst to simulate the accumulation required prior to one point.The chart shows that the maximum buffer capacity required was 1000 products or approximately 160 feet. At the operating speed of 200 BPM, the buffer had the capacity to absorb all the accumulation produced by the stoppages.Figure 4 shows how the buffer accumulation behaved at non-optimal speeds. At 235 BPM, there was a dynamic speed range of 235 to 240 BPM. This difference of just 5 BPM meant the buffer was not capable of depleting accumulated product during the mean time between failures, resulting in downtime whenever there was accumulation of more than 1000 products. After the accumulation of 1,000 products, we see that the accumulation level never goes back to zero, but keeps growing with time.To evaluate whether results were correct, the analyst calculated the theoretical throughput of the line running at 235 BPM. Figure 4 indicates an approximate line downtime of 127 minutes. The lines total production was determined by multiplying 235 BPM by 293 total running minutes (420 minutes on a shift 127 downtime minutes), or 68,855 products. Dividing production output (68,855) by total minutes (430) equaled a throughput of 160 BPM, which was very close to the actual throughput of 168 BPM.Based on the results of this buffer study, the analyst made several recommendations to the manufacturer:
- in-line continuous accumulators (serpentines, alpines and extending belt systems)
- batch indexing accumulators (vertical and horizontal)
- random continuous accumulators (bi-directional, counterflow and turntables).
- First-In First-Out (FIFO) systems ensure that the first product entering the queue is the first product to leave. Often in alpine form, FIFO systems have a small footprint and utilize a small amount of floor space when compared to other buffer configurations. Ideal for pharmaceutical manufacturers, FIFO buffer systems allow for product accountability (i.e. lot number, production time) for tracking at a later date.
- In First-In Last-Out (FILO) systems, products leave their queue in the reverse order from that in which they arrived. FILO buffer systems are available in horizontal or vertical formats.
- The most common systems operate on a First-In Random-Out (FIRO) basis. Often in turntable format, FIRO buffers are either bi-directional, or counter-flow operations. Of course, FIRO systems offer no product accountability or sequencing.
- running speed of 240 bottles per minute (BPM)
- 72,250 products made during a 420-minute shift
- unknown downtime.
- The priority of the line was to maximize filling machine operation;
- The only machine on the line with scheduled stoppages was the labeler;
- Unscheduled stoppages prior to the labeler were minimal;
- The labeler had three different stoppages: the labeler roll change (scheduled), an outsert feeder magazine jam (unscheduled) and the outsert backside tape roll change (scheduled);
- The case packer had one unscheduled stoppage: product jamming at the loading system;
- The palletizer had one unscheduled stoppage: the robotic arm failing to pick up product.
Editor's Note: The four figures that accompany this story are contained in a 4-page PDF document that may be accessed by clicking the "Download Now" button at the end of the article.
- Locate the buffer before the labeler;
- Install a buffer with a capacity for 1000 bottles (approximately 160 linear feet);
- Decrease the line operational speed to 210 BPM.
- An increase in throughput of 20%, from 168 to 200 BPM (conservatively)
- With this increase of 32 BPM, an additional 13,760 products (32 x 430 minutes) could be output per shift.