Case Study: BPX films
Bryce is the dominant converter of light-weight film for snack packaging and related uses. Efforts are focused to serve three specific markets in the United States:
- Snack Food Packaging
- Candy and High Performance Packaging
- Document Protection
bpx films, a wholly owned subsidiary of Bryce, is located in Houston, Texas.
The primary business objectives of this project revolved around improving the yield of the plastic film master rolls produced at the plant by obtaining trim patterns will less "edge waste". This was to be obtained with minimal impact on slitter efficiency and in bottleneck situations, "tilt the balance the other way" by emphasizing slitter efficiency first.
Some of the production needs to go to a secondary machine (e.g. a metallizer) for additional processing of the film. The "parent rolls" sent to the secondary machines should utilize the most of the width of those machines for best equipment efficiency and come in as few different widths as possible to optimize roll handling.
These results had to be obtained while keeping quantities produced within the customers' tolerances, as quality of service remains the key element of the business. It was decided that a key enabler in achieving these objectives would be a software package that would be highly configurable, deliver consistently better results, and be user-friendly. BPX selected Greycon's X-Trim product based on Greycon's ability to meet numerous BPX requirements best illustrated by describing the business processes.
X-Trim is also used to cut small orders from available stock rolls. Here, X-Trim's ability to trim from many different parent roll sizes makes the scheduler's work extremely efficient.
X-Trim is configured to run on users' individual workstations, running on Windows 2000, and accessing data centrally located on a file server.
The import of data is currently done using the "copy and paste" feature of X-Trim with a small program that writes the orders in an Excel Spreadsheet. A more usual "direct" interface is expected to be put in place when the current system is upgraded.
The export of the selected solution back to BPX's production tracking system is done through an export file, which is read by an ad hoc program that then integrates the new slitter patterns in the plant's database, where they become accessible by the operators.
The user at the film production plant activates periodically a program to extract all current orders of a given product into an Excel spreadsheet. Using the "copy and paste" feature of X-Trim, these orders are then brought into X-Trim's main program.
The user then starts the optimizer to get a set of patterns that will produce the orders with minimal trim waste. The user will also often run the alternative optimizer to obtain different solutions that will sometimes be better suited to the situation.
The user examines a number of parameters -- edge trim waste, number of sets in the solution, number of different "physical" patterns, number of slitter changes -- and chooses which solution is best suited to the run's needs. In some cases, he or she can modify some parameters for example, adding one or two out-of-cycle orders, to improve the results and obtain a new solution.
Once the user is satisfied with a solution, the user validates ("releases") it, and the solution's patterns are automatically sent to the plant's production tracking system, where they become visible by the slitter operators.
Below is a typical X-Trim solution without secondary processing:
Note the very low waste percentage (0.789%) and the alignment of rolls to give a small number of slitter changes.
In cases where secondary processing (like metallizing) is required, the solution may look like the following:
Note that there are only two different sizes of parent rolls (28.25 and 41.5) even though the dotted lines clearly show that different sizes will be cut from them.
Factors: Optimizing Waste
Since many of the sizes trimmed correspond to repeat business, there is room for overrun tolerance on most orders. This allows X-Trim to obtain extremely efficient solutions with small amounts of trim waste.
When a secondary process is required for some of the orders, then X-Trim also has the possibility of "juggling" between possible parent roll sizes to get optimal use of the maximum width of the primary extruder while utilizing the secondary machine in an efficient manner.
Side rolls: in some cases, where the mix of sizes does not produce an excellent good solution, the user has the ability to throw in a few "side roll" sizes, which will typically turn potential trim waste into sellable rolls. This is done in just a few clicks of the mouse, and the side rolls are automatically integrated into the plant's production tracking system.
Factors: Optimizing Inventory Use
Small, urgent orders are typically cut from available stock rolls. The "stock roll" option of X-Trim allows the user to specify how many stock rolls are available for a given grade and in up to eight different widths. Orders are then imported in the same manner as the standard process, and X-Trim calculates the most efficient use of the stock rolls to produce the orders.
As an added bonus, the user is allowed to specify a minimum usage of some (or all) of the widths. This allows the user, for example, to quickly get rid of some stock rolls whose sizes are not standard.
Factors: Optimizing Production Time
To reduce the amount of non-productive time spent positioning slitters, it is essential that X-Trim minimize knife movements by reducing to a minimum the number of patterns to produce and by sequencing the production to minimize changes.
In some cases, where the primary slitter has become a bottleneck, an alternative trim calculation algorithm is available to the user, who may choose to have some trade-off between trim waste and the number of patterns and knife changes.
Process improvement summary
The values of the improvements described in this summary overlap and cannot be separated without proper adjustments.
- Reduced product waste. It is estimated that waste was reduced an average of 1.0%. The eliminated waste was instead sold as product. With an average value of $1,500 per ton and an average yearly production of 16,000 tons, this would correspond to a yearly savings of $240,000.
- Reduced non-strategic overrun. By keeping trim solutions within quantity tolerances, a reduction of non-strategic overrun from 8% to 4% was expected. This non-strategic overrun causes costs in various types: cost of carrying stock, cost of reworking overrun in order to sell it (20% of overrun must be reworked to be sold); and cost of overrun that ends up never being sold (1% of the overrun). These add up to a figure more than $600,000 yearly.
- Improved customer order fill rate (no under-run).
- Increased inventory turns.
- Reduction in parent roll sizes. For orders where a secondary process is required (e.g. metallizing), X Trim produces solutions with a small number of different parent roll sizes. This simplifies roll handling, reduces lengthwise waste, and optimizes the secondary process, which has fewer width changes.
- Reduction in user trimming time. An enthusiastic scheduler told us that the timesavings obtained through the use of X-Trim are almost better than the trim waste savings. He may now spend more time working to improve customer service.
- X-Trim user satisfaction. It is fun to use X-Trim. Planners want to do their jobs well. X-Trim offers them a tool that gives them great visibility of the organizational impact of the solutions they create. The tool is intuitive and quick; it allows the planner to make a significant, positive contribution to the organization. - X-Trim's ease of use facilitates the spread of knowledge: Alternate users have been able to step into the job more easily and with more consistent solutions thereby easing reliance on key personnel.
X-Trim has given us a 1% waste reduction on our Bryce orders, which account for 70% of our volume. This is exactly in line with our expectations, so X Trim hasn't let us down. David Long, Scheduler, bpx films (Houston).
The timesavings are tremendous, almost better than the waste savings! I can now concentrate on improving customer service. David Long, Scheduler, bpx films (Houston).
When our slitter becomes a bottleneck, I switch to the alternate algorithm, and get a solution with fewer patterns. We end up doing this for about 10% of our runs. When the bottleneck is resolved, I switch back to the regular algorithm, which gives me the best waste reduction. David Long, Scheduler, bpx films (Houston).
X-Trim allows me to utilize our stock rolls and overrun rolls with minimal waste and in a very time-efficient manner. Sylvia Wilson, Scheduler, bpx films (Houston).