Industrial Engineering

A Case Study of Packaging Line Process Improvement

 

https://www.iise.org/iemagazine/2019-06/html/case-study/case-study.html

ISE Magazine June 2019 Volume: 51 Number: 6

By Raj Sanne

 

In every manufacturing organization, packaging plays a very important role in shipping products to customers. The main functions of packaging are to prevent damage during handling, shipment and delivery to the customer. In terms of cost, packaging does not add value but is an essential part of the process. Packaging design depends on many factors such as size, weight, how delicate is the product, product features, shelf life, temperature and the mode of shipment.

This is a case study of packaging materials used for protecting products from damage during shipment to end customers and distribution centers. There are several different shapes of parts molded on special type of molding machines using two chemicals and film roll. The machines, chemicals and film are all proprietary materials supplied by one company. The molding machines were purchased some time back and consumable items are bought as required from the vendor.

The packing materials made by these machines were placed inside corrugated boxes and sealed at the end of the packing line. The boxes were placed on a wooden pallet and moved to shipping by a forklift. Twelve different parts were molded on these machines, which operated 9.5 hours per shift for two shifts, five days a week. The average cycle time for making a part is about 1.28 minutes. The average efficiency assumed was 90%. The parts were stored in seven kanban carts designed to hold specific quantities based on average daily usage by three assembly lines with integrated pack stations and included safety stock for at least one shift.

Twenty-four rolls of film were consumed in a week making these parts. These lines assembled six different high-dollar volume products that constituted 70% of sales made in the plant. Maintenance was responsible for start-up and any major issues that affected the operation of these machines.

There was a small packing line where miscellaneous products were being packed in boxes. The quantities were not significant, and the line operated in first and second shifts. This line was close to molding machines. One person was assigned to this line for packing products, ensuring continuous availability of packing materials used by the three packing lines making high value products, checking all carts at the beginning of the shift to see how many had parts, and speaking to assembly line setup workers to monitor what was planned to be made on the shift. This person was trained to change molds, load film rolls, do minor trouble-shooting of machines and ensure all carts and lines were stocked with parts required in the shift for packing and meeting of production goals.

Issues affecting function of the cell

No study had been done to determine actual capacity of these machines. There were no good metrics to monitor the installed capacity or use of equipment. Because of variations in product variety and quantity on a daily basis, it had a ripple effect on molded parts required for packing.

Some types were found to be inadequate and during other times were far in excess of actual requirements. This also had impact on storage because carts were not available. Some carts had parts that were not required during the shift, resulting in kanban cart shortages. There was no system of communication for the packers to know what was planned to be assembled in the shift or the quantity of parts on hand other than a visual check and discussions with assembly line setup workers. This made it difficult for any meaningful planning for the machines to run in a shift. This was compounded by the responsibility of a packer having to pack miscellaneous products and complete shift work.

In the first shift, two technicians from maintenance helped the packer start machines, which took about 30 minutes, as well as plan and make parts for the lines. This was considered to be nonvalue-added work as the technicians were also responsible for maintenance of machines in case of major problems, along with attending to problems on the assembly lines. They were doing part of the work that was supposed to be done by the person assigned to pack products. This also had a ripple effect on other maintenance issues that occurred in the shift on other assembly lines in the division.

In the second shift, only one per-son (the packer) was managing both the small packing line and five mold-ing machines. Maintenance was called in whenever there were issues with the molding machines. There was no help from maintenance in the second shift for the packer.

Project objective. Determining one person was not able to do all the assigned work covering packing and managing the production of parts on these molding machines created conflict between production and maintenance over smooth functioning and meeting daily productivity goals. An impartial review of the situation was undertaken to develop solutions that once implemented would improve the functioning of the whole cell.

Study methodology. The independent review project was assigned to a group of industrial engineers. They had discussions with supervisors, packers and managers to understand cur-rent processes and factors affecting the smooth functioning of the cell. The focus of the study was on the use of molding machines considered important in making parts for the assembly lines. It was decided to observe the operation of these machines and identify any causes for stoppage covering both shifts. Studies over an extended period were done to gather representative andreliable data for determining the reasons and understand the issues affecting these machines.

Capacity utilization. Snapshot of studies for two weeks to cover both shifts were done to identify downtime that had an impact on the capacity and workload of the packer assigned to man-age these machines. The average scrap rate was 5%. As no study had been done to determine the theoretical capacity, it was decided to focus on estimating use of existing machines.

From the table, assuming the events are mutually exclusive, it is clear the cumulative probability of uptime for up to five machines is 62.5% in a shift. From this, we can infer that in a shift of only about five hours, four to five machines were working. This equates to 37.5% of lost installed capacity. It is clear there is scope for improving capacity to meet any additional demand before increasing operating shifts and adding more machines in the cell. These calculations

excluded factors like an ideal run rate and the scrap generated because of various reasons. If these are factored into calculations, the actual uptime will be less than 62.5%. Some major reasons contributing to downtime identified during the study are discussed in the following sections

  • Mold. Because of the process, the film sometimes was getting clogged inside the mold, resulting in bad parts and stoppage of the machine. Stop-ping the machine and cleaning inside the mold occurred about 22% of the time in a shift.
  • Film. During the process of making parts, the film sometimes would jam between rollers, leading to stoppage, which required opening the rollers to clear the jam and resume operation. This happened about 11% of the time in a shift.
  • Pile up near machine. There was no good system for collecting parts coming out of the mold. They were thrown out from the mold and fell on the floor near the machine. As the pile built up near the machine, it sometimes obstructed the closing of the mold door, leading to stoppage. Parts lying on the floor were picked and later arranged in carts about 22% of the time in a shift.
  • Machine problems. Sometimes the machines had problems, leading to stoppages that required review by the maintenance team about 11% of the time in a shift.

By addressing the above major list of action items, it is possible to improve the available capacity from 60% to about 77.6% without incurring any additional cost.

Floor space: In the area where the machines were located, space was limited and it was difficult to bring in carts to park in the area. A rack was in the middle in front of machines, hindering free movement and storage of carts. Also, space was required for two carts on which molds were kept at point-of-use (POU) close to machines. Rolls with 24 to a pallet were not close to POU. On average, each machine required one roll per day. Assuming 80% of available free space, the estimated number of empty carts for molded parts that could be parked in front of ma-chines was 30

Suggested improvements

Film. It was decided to add storage space to the existing mold storage carts for keeping three rolls of film on each cart at POU. That would ensure all materials required for molding parts are at POU near machines.

Floor space. In the existing arrangement, there was a rack on which packing materials were kept that was acting as a monument in the middle of the cell. The sketch of the proposed lay-out is shown in Figure 5. It was decided to free up space in front of the machines by removing the rack in the center. This added 15% more free space for keeping the carts and arranging parts near the machines. It would enable five more empty carts to be parked in the area.

Labor. Based on discussions, it was decided to first implement the suggested changes before determining a need for a dedicated resource. Based on the outcome of improvements after about a month, it was decided to review and make a decision on having a dedicated resource only for doing all tasks covering inventory management, loading molds and making parts and minor troubleshooting to ensure that parts required for both shifts are available as required. This person was expected to be given additional work of packing products and concentrate only on making pack materials.

Standard work and training. It was decided to standardize and document the entire process to ensure the consistency of work in the cell. It was also decided to invite the equipment supplier to train maintenance and operational technicians on the machines.

Implementation plan

A meeting was held with the manager and supervisors to discuss the recommendations and develop an implementation schedule. It was agreed to first implement the layout change as part of the improvement process. Based on discussions, a matrix of action items, start and end dates and responsibility was developed for implementing the layout change.

It was decided to monitor improvements and make necessary changes as required for a period of one month. Based on the workload, the need for a dedicated resource would be deter-mined at a later date.

The study illustrates how simple approaches to problem-solving using appropriate tools can lead to substantial improvements at low cost and have a big impact on productivity. It is clear that before any investment decisions to augment capacity are made, it is necessary to determine the current use of existing equipment. By addressing the causes and reducing downtime to improve utilization, it is possible to add capacity without adding to costs and meet the actual requirements of assembly lines.

This is an example of the Toyota Production System on the need for continuous focus and problem-solving to maintain stable production. It is wise to address “low-hanging fruit” issues first and resolve them before addressing bigger issues. By not addressing such issues, any major improvements made are suboptimal and will not yield full benefits.