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Thursday, March 25, 2010

Keeping it Simple


We often overcomplicate things at work.  Complicated machines become obstacles to getting the job done.
In one factory, a large, highly automatic machine spun nuts onto threaded nipples.  The operator’s job was mostly to catch defective nut-to-nipple assemblies as they came out of the machine and set them aside for later repair.  If practically all of the assemblies were defective, because the nut had not been spun on straight and had jammed onto the nipple, he shut down the machine, tried to make adjustments to it, and generally ended up calling maintenance.  While maintenance tinkered with the machine, the operator would sit at a workbench and use channel locks to removed jammed nuts from the nipples, so that both parts could be put back into the machine. 
Sometimes, there were so many flawed assemblies, additional workers would be brought to the area, given channel locks and put to work undoing the bad assemblies.
I worked with a team of workers and managers on an improvement project that made this problem go away. We purchased two nut drivers with sockets sized to the nuts in question.  The nut drivers were of the type that activate when you press down on the nut, and stop when you release the pressure.  We mounted these upside down, side-by-side, in the center of a small workbench.  We fashioned some brackets to hold them with the sockets flush with the tabletop, through holes in the center of the workbench.  We had a bin with nuts and a bin with nipples on the workbench. The operator would take two nuts and slide them into the sockets.  He would then take two nipples and briefly press them into the nuts in the sockets. This activated the drivers to spin the nuts onto the nipples.
This simple device created enough nut-to-nipple assemblies, without the waste of a lot of rework.  The work bench was small enough so that the operation could eventually be incorporated into the final assembly process, making what was needed just-in-time, without having to build up batches ahead of time and cart them to the assembly line. The size of the automatic machine would not allow this.
At another plant we worked on an operation in which large metal cabinets were being assembled and welded together.  The designs called for small pieces, most of them no larger than an inch square, to be inserted and welded into place to reinforce corners. These pieces had a dozen or more different shapes, which were stamped out in large numbers at a time in stamping presses.  Hundreds of each part were collected in bins and transported to the welding area, where the bins were stored in racks.  It was important to keep track of the inventory of these small parts, so that the welding area always had some on hand.  In more than one case different parts became mixed in a single bin and had to be sorted.
A member of our improvement team remembered a hand punch that could be fitted with the dies needed for all the variations of these small parts.  We dusted it off and installed the dies. The welders could rotate a dial and hand punch the individual pieces they needed when they needed them, very quickly, out of pieces of scrap metal.  Storage, transportation, inventory tracking all disappeared. There was never a need to wait for a part that had run out.
At another site, we confronted a process in which machined parts had to be dipped in oil to protect them from rust.  The machined parts were put into plastic coated wire baskets specifically designed to hold them.  A dozen parts fit in a basket.  This could be linked to another basket, and then a third, so that all three could be picked up by an overhead hoist and dipped into a large rectangular tank of oil.  Three baskets linked together were so heavy that they hoist was a requirement.
The hoist was needed for other lifting, so, after dipping, the linked baskets would be set down on a conveyor, dripping oil, which fell into a tray under the conveyor.  A couple of times a day a worker with a tractor pulling a wheeled tanker with a vacuum device would come to the tray and suck up the oil.  The oil was now dirty and had to be filtered before it could be returned to the tank. This operation was replicated on several machining lines in the plant.
The improvement team designed and fabricated a small tank with a slanted drain board attached to it. It stood on legs that put it at waist height. This tank held less than a gallon of oil, where the old tank held 50 gallons. A single unit could be placed on a rack directly over the tank. By raising a handle, the machined part could be lowered into the oil. Releasing the handle would raise the part and leave it dripping directly into the tank. The worker would complete a cycle of work and have another machined piece ready for dunking.  He would put the first unit on the drain board and the new part on the rack. He repeated this until he had six parts on the drain board.  By then the first part had drained long enough to be wrapped and packed to go into inventory.
The special wire racks that could be linked together, the overhead hoist, the large tank of oil, the conveyor, the drip pan, the wheeled tanker with the vacuum device and the filtering process were all eliminated. The worker who pulled the tanker around was freed up to do other work.
Managers, supervisors and engineers who want to figure out how to make their plant’s operations more effective, could do worse than identify large operations that process batches and, with the help of a team of workers, ask how the large operation could be eliminated and replaced by something low-cost or no-cost and simple. When designing a new manufacturing or assembly process, always ask how can we keep it simple, while only processing one piece at a time?

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