ONE PIECE FLOW….OPF
Ashok Puri
Director and India Head
Kaizen Institute India
In the current economic scenario, the manufacturing companies have no choice but to tighten their belts. They have to apply all their intelligence to make their manufacturing systems highly efficient and productive. In other words they have to adopt the lean manufacturing practices.
Lean Manufacturing is an approach for building the variety of products customers require, profitably. Lean Manufacturing makes companies more profitable and really competitive by helping them reduce wastes that typically add to cost and the Lead time of the manufacturing process. Waste in this sense means any element of a process that adds cost without adding any value to the product. Eight types of wastes have been addressed in Lean manufacturing.
One piece flow ,OPF, in a cellular form, is a major building block of Lean manufacturing. OPF is the state that exists when products move thru the mfg. process one unit at a time, at a rate determined by the needs of the customer. And the opposite of the OPF is Big lot production, which is usually practiced in most of the mfg. companies.
Big Lot production lowers company’s profitability in many ways.
…The lead time between the client’s order and the delivery of the products is longer.
…More labour, energy, storage space, logistical support is required.
…Products have a chance to get damaged or deteriorate.
Whereas , OPF helps in solving many problems…
…Products flow faster to the customers with les delays.
…Less resources for storage and transport are required.
…Minimum risk of damage ,deterioration and obsolescence.
…many other problems are exposed that can be addressed
OPF is an ideal state. However in daily operations it may not be always possible or desirable to process one at a time. The important thing is to promote a continuous flow of products, with least amount of delay and waiting.
Why OPF will not work in many companies is briefed below…
1. It is not possible to get needed materials in quantity, in quality or in time.
That’s right. Fix this first. If you can’t seem to get this issue the attention it needs, implement one piece flow anyway, watch the line stop, make the problem visible so that you get the attention and resources needed to fix the problem.
2. We have a problem of unreliable equipment that may break down, causing downstream processes to run out of parts. …use the same logic as in 1 above
3. Our people will not agree and will resist this change. So what? That’s what education is for. If the leaders don’t understand and believe in OPF enough to take the time to remove resistance through education, don’t bother with one piece flow. This is a weak excuse. We need to learn about motivational techniques , practice them and then address this issue as you would a speed bump in the road.
4. Our people are incompetent and not cross trained to do more than one or two limited tasks. Is it fair on your part for limiting people’s potential to learn and develop to their fullest. Take “boring part ” out of work by giving people variety, and watch morale soar. People are not motivated to learn new things, how can you say? Stop undermining your people.
5. Real Long changeover times prevent us from doing OPF. If you are really trying to run one piece lot sizes through 1,000 ton stamping presses, bravo, and see 1 above. Flow one at a time wherever you can. In practice you will find that this is more often than not. When changeovers do present a genuine barrier to OPF, reduce the changeover time continuously, all the while reducing lot sizes to approach OPF.
6. There is too much distance between processes to move one at a time. Is it that big a problem ??
7. The process produces defects/reworks that will stop the line too frequently if we have no bufferstocks. See 1 above.
8. Process cycle times are unstable or variable, creating imbalance between opeators. The first step is to examine your process cycle times through direct process observation, break the work into smaller work elements, take out waste, and recombine them. If chronic variation is still above the 5% to 10% range, see 1 above. If it’s predictable variation, this is only really a problem if you are trying to maximize the utilization of the man-hour, which may result in greater waste such as overproduction, inventory, transportation, defects and processing which adds no value. You can proceed with OPF and kaizen implementation.
9. Our machines are not designed for OPF. This is quite true, even in our daily lives. A washing machine is a good example. Need to wash one pant? You have to wait until you have close to a full load or you waste water and energy. So we batch our dirty clothes. The same is true with a dryer. You don't dry one wet pant in the machine, but you might hang it up to dry if you don't need it dry right away. Disciplines like 3P (Production Preparation Process) exist to create OPF equipment. If you cannot get equipment planners and designers involved early enough to keep bringing in batch equipment, see 3 above. Failing that, you can manage by deploying SWIP to some kind of a flow through batch processes.
10. We have occasional work that interrupts the process. There is something in Lean Mfg. called the Water Spider or Mizusumashi which acts as a line support function to handle relief work and recurring-but-not-every-cycle tasks such as moving materials in, moving finished goods out, building another cardboard box when the previous one has been packed full of finished product. When it is not practical to have a Water Spider, you can have foremen or team leaders help in these areas. Failing that, create Standard Work to reflect the changing work sequence and work balance every so many pieces for these types of recurring tasks.
We need to seriously address each of these ten reasons and see that the OPF is really implemented to our competitive advantage. And you try neglecting them ,you will have ten reasons for Poor cash flow and may be Ten reasons for Long Lead Times too.