eliminating the future state map are the
eliminating the problem of poor worker utilization. The future state map suggests that scheduling should be controlled at the bottleneck, in this case, the rubber presses. This simplifies scheduling and the potential for communication errors.
In a cellular environment, quality checks do not need to occur by every process. This is because the product is moved quickly from one process to the next in one piece or small batches; parts can be checked after several operations and corrected without the risk of large losses. The most obvious changes to the manufacture of rubber modular screen panels’ in the future state map are the utilization of manufacturing cells. The cells are groups of processes that are manned by a single person or a team. The idea of the cell is to promote one piece from one process to the next without stopping. Machines are placed in such a way that facilitates easy movement of the product from one process to the next. Taking a look at the finishing cell, one can see that three processes, trimming, clinkering, and sawing are manned by one person.
As product arrives from the rubber press, the operator of the cell removes parts from the first-in-first-out lane. This means the first part to arrive in the queue is the first part to be processed in the cell. The operator first trims the part, then clickers the part then saws it before placing it back on a pallet. This is repeated until all the parts in the job are completed (Gündüz, 47)Moreover, effective cross-training is required since operators will need to operate all the machines in a cell. A benefit to cross training is it will eliminate the WIP that is created when the product must wait for an operator. A balanced production line can be created as worker move to the process that needs an operator.
The most profound benefit of a cell can be seen in the time that the part is waiting in process. In the current state map, a screen panel would have had to wait in queue 1 day for trimming, % a day for clinkering, and 54 a day for sawing for a total of 2 days in queue. In the future state map utilizing the finishing cell, the part would have only been in a queue for only 3 hours and processing completed only 22 minutes later.
This is accomplished without having any new, faster machines or the operator working any harder. Lead-times in the future state have been cut from 2 days to 3 hours; that is an 86% time reduction based on 21-hour workday. In the future state map, a controlled bottleneck has been created at the rubber press. The rubber press has longer cycle times than the other operations and is an expensive piece of equipment for which to buy extra capacity; therefore, the rubber press is a good choice to make the controlled bottleneck. Scheduling is focused on the rubber press; the maximum amount of throughput that can be produced in a given period of time will be controlled by the amount of product that can be processed through the rubber press.
To maximize throughput, it is important that the rubber press is never waiting on upstream operations to feed it. Therefore, an inventory system has been placed in front of the press. In this case, first-in-first-out and supermarket inventory systems are used. These systems assure that there is always a product to be processed at the rubber presses without letting inventory numbers get out of control. A first-in-first-out inventory system is also placed after the pressing operation. This system is used because a continuous flow out of the press would be impractical.
Downstream operations are not close to the press requiring parts to be transported to the finishing cell. It would not be cost-effective to move the press and there is limited space around the press to move downstream operations closer. Therefore, jobs are moved in practical batches to a queue in front of the finishing cell. Here parts are processed in the order they are received.
Production control schedules only the rubber presses. The metal fab department receives instruction from the rubber press leads on frames that will be needed. Frames are built only by request and in order of the scheduled press date. The frames enter a first-in-first-out or supermarket inventory system for use in the presses. The finishing cell receives no scheduling instruction, the cell simply processes the products that are outputted from the rubber press in the order they are received.
Any of the operators in the cell that get ahead of the rubber press will go to the rubber press area to help there. The future state scheduling system is much simpler and less time consuming than the current state system. The added time can be dedicated to better scheduling of out of the ordinary orders, outside vendors, expediting activities, and training. Simpler scheduling should lead to less scheduling mistakes and allow for better control over an order. Currently, a job is only being worked on by one operation, thus every operation is working on different jobs at the same time. It is difficult to manage so many jobs all at once leading to mistakes and oversights; often the wrong jobs are being done at the wrong time. In the future state, only a few select jobs will be worked on at any given time; most of the time the press and the cells will be working concurrently on the same job.
Supervisors and production leads can now concentrate on the few jobs at hand instead of managing many jobs all at once. Lastly, quality checks are done at operations that pose a high probability of unconformity. The quality checks focus on finding errors. Operating in a batch mode, quality checks are critical because if not caught, large quantities of parts go through several operations before the error is discovered leading to large quantities of scrap or rework. In the future state, quality checks do not need to be done as frequently and the consequences of an error are minimized. In one piece or small batch production, parts flow quickly through several processes in small numbers. Producing in large batches creates a high risk of loss; producing in a one piece or small batch mode has little risk and is easy to correct.
A common problem in producing modular rubber screen panels is having the frames made correctly. A high number of variations in frames and print errors lead to incorrect frames that inspections often do not detect. Often, incorrect frames are not discovered until the pressing operation. The future state map shows that frames are inventoried in a first-in-first-out system before the pressing occurs.
This creates quantities of frames that could be potential scrap that will not be discovered until pressing. The future state does address this problem. Frames are queued in quantities to ensure that the press does not have to wait for upstream operations. This introduces the risk that the entire batch in the queue could possibly be unusable.
However, the risk is minimized by the fact that the queued quantities are only the amount that can be pressed in one day or shift and not the entire order quantity (Lacerda, 1720)A current state map was created and analyzed for potential areas of improvement. Lean manufacturing techniques were used to create a future state map that would reduce lead-times and increase throughput. The future state map suggests that a 66% lead-time reduction could be achieved, mainly through eliminating large batch production and using cellular manufacturing. In addition, a 20% increase in throughput could be realized by focusing on the scheduling of the rubber press, a controlled bottleneck.
Value stream mapping has proven to be an excellent tool to analyze a manufacturing process. The current state map helped identify areas of potential improvement while the future state map suggested ways to reduce lead-times and increase throughput. Therefore, the value stream mapping is an effective tool to suggest ways to reduce lead-times and increase the throughput of a manufacturing process. The current state map laid out the manufacturing process while the timeline comparing value added and non-value added times clearly showed large amounts of wastes contributing to long lead-times.
Many times process improvement efforts will focus on reducing set up times or increasing machine and operator efficiencies. The current state map shows that most of the waste in the process contributing to long lead-times is in the non-value added times while the product waits in the queue. Large reductions in lead-times can be achieved just by reducing the time that the product waits in the queue. In the future state, no new machines were purchased nor were operators expected to work faster or harder; only procedures and layouts were changed to allow the product to flow more smoothly through the manufacturing process.
Increased throughput was achieved through careful scheduling of a controlled bottleneck. Ensuring that the bottleneck is producing at its maximum realistic capacity ensures the highest throughput potentials of the manufacturing system (Bhamu, 940)