To get the point over regarding the use of Just in Time (JIT) as part of implementing lean manufacturing here is yet another case study for you to read and digest.
I became involved in a project that was already ongoing to help a company to cope with capacity issues. They made “art” products for major retail chains, large framed prints, photo frames and the like.
They had a rather restricted premises space wise and could not yet afford to move elsewhere as profits were not yet as “expected” despite good levels of orders. They had got to the point where they were having to turn orders away as they just did not have the capacity to cope with them. The factory was running on significant amounts of overtime and they were struggling to meet the orders that they had.
They did not make to stock, all production was to order, the customers ordering “large” quantities for delivery to their warehouses where they then split the orders for delivery to the branches.
There were two main areas of production, large high value items which were generally fully hand crafted and low volume and the higher volume (100 – 500 items per order) smaller items (still picture frames of up to a meter square). We concentrated on the higher volume smaller items as this was the main area of concern in the business (not just because it was easier!)
This production line occupied one building with the main assembly line running along the length of the building. The frame being cut to size, and then nailed into the recognizable rectangular frame shape before fitting glass, print, inserts, back plate/stand and then shrink wrapping. The individual components being completed in small cells along the side of the building, such as trimming prints to the correct size on a guillotine.
When I joined this project, the main assembly line had been turned into a flow line producing each item one after another without problem and each sub assembly area had implemented 5S and improved efficiencies at the cell level. But they were still not meeting customer orders, in fact there was felt to have been no improvement at all!
Why was this so? I watched the line for a few hours at the start of production, they started with an empty line as it was the start of the week, as the product progressed along the line it got about half way along the line and was then being placed into boxes as the subassembly that was required at this point was not available. Near the end of the line, operators were taking product out of boxes that had been packed the previous weeks to fit the hangers that had not been in stock when they were run! It seemed that this was a common occurrence, talking to the operators it was rare for a product to reach the end of the line without either a supplier or an internal shortage!
There was no co-ordination between the subassembly stages and the main production lines, the subassemblies built to their weekly schedule as produced by the computer system as did the main production line, but each picked and chosse their order within the week. As to suppliers, they appeared to be a big problem also but no one could quantify the size of the issue.
What was required was a simple system to ensure that the subassemblies built to the order the line was going to run, and that the line only “launched” items for which all subassemblies and purchased parts were available.
One hour later we had a simple white board in place, down the left edge all of the products in the order the line wanted to run, across the top a list of subassemblies and purchased parts. The subassembly areas were instructed to build in the order of this list and to tick the box to show when they were complete. The stores man was instructed to tick the box as product was delivered or if it were in stock to show purchased parts availability. The main line’s job was easy, launch the first product for which every box was ticked!
We started this system before lunchtime that Monday morning, by Wednesday afternoon we had completed each and every product for which there were purchased parts available and matched the best week’s production figures! There was nothing for the line to build due to supplier shortages for the remainder of the week! The operators on the line during previous weeks were filling their time by packing and unpacking unfinished products on the line and cleaning down and setting up multiple times for the same product.
The following week they beat the production record on Tuesday afternoon, everyone in the office appeared to be at one supplier or another trying to resolve issues which were preventing delivery! They again could not produce past Wednesday because of supplier shortages.
Supplier issues were resolved over the following several weeks, and output was roughly doubled through the facility, overdue orders were met and new contracts signed.
Just In Time requires the flow, not just the efficiency of individual cells. The suppliers are as important to your success as your own production, you must include them as part of your process flow for implementation of lean manufacturing to succeed.