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论老子

道,领导也。领导必需要不断呼唤,教导下属以及以身作则。下属的过和错皆因领导懒惰。

 
 
 

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Chapter 17: Waste of waiting  

2012-06-24 12:09:24|  分类: Buffer Mentality |  标签: |举报 |字号 订阅

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In Eastern Wire, pieces of steel wires are welded together at 90 degrees to one another to form a piece of weld mesh. The size of the largest piece of weld mesh measures 2.4 meters by 6 meters. Depending on whether the piece of mesh is meant for a part of the civil works or building structures (such as a beams, columns, walls or staircases), the welded mesh could vary from as small as 0.6 meter by 1.2 meter and all the way up to the largest pieces of 2.4 meter by 6 meter. As many as thirty different kinds of weld meshes of varying sizes make up one job order.

Weld meshes from a typical job order are welded by several welding machines of which each machine is dedicated to weld meshes of a fixed diameter ranging from 6 mm, 7 mm, 8 mm, 10 mm, 12 mm and 13 mm.

Three quarter of the factory space was being used up to hold the weld meshes and to stage them together but segregated by job order number. Each job order was then loaded onto a truck that delivers it to the construction site. At any one time, there were more than 45 job orders stacked all over the factory.

The General Manager was screaming for space. Without adding more space to the factory, output would be severely constraint to 2,800 tons per month. The Group General Manager from the parent company, NatSteel Ltd, could not accept this. I was asked to go down to help him increase the factory’s output without adding any factory space which in the first place was already impossible. Its two neighbors were not willing to sell their factory space to Eastern Wire.

I observed the factory for half a day. I noticed wire cutting machines were placed at the front-end. Cut wires were hoisted away from the wire cutting machines and placed on the floor occupying about 2,000 square feet. When needed, the cut wires were hoisted from the floor and onto the cross wire feeder of the welding machines. A single over-head crane was used for this purpose.

Quite similar to Eastern Steel Services, the main problem lay with finding the right bundle of cut wires. Waiting time for the crane to move over to hoist the cut wires on the other hand was frequent and was long. In other words, the waste of waiting became the bottleneck that caused the welding machines to be idled for a substantial amount of time.

A quick estimation indicated about 25% losses in productivity was due to waiting. The solution to cut down the waiting time for hoisting cut wires was implemented in the form of restricting the number of bundles of cut wires on the shop floor to the minimum. Wires were cut in accordance with the Just-In-Time principle. Searching for the bundle of cut wires became so easy that the waste of waiting became negligible overnight.

Over at the back-end of the factory lay weld meshes of varying sizes. One over-head crane was in operation hoisting the weld meshes away from the welding machines and stacking them onto the factory floor. The same over-head crane was later called upon to hoist these weld meshes placed on the floor onto delivery trucks.

For almost 40% of the time, the welding machines were seen to be idling, waiting for the over-head crane. They were forced to idle because they have completed welding one type of weld mesh and needed the service of the over-head crane to hoist these finished weld mesh away. Without clearing away the completed weld meshes from the output end of the welding machines, new meshes couldn’t be welded.

They were not supposed to be mixed up different bundles of welded meshes together into a batch and therefore, were forced to remove the welded meshes away each time a bundle of them is completed. The root cause of the low productivity is obviously due to waiting time wasted in queuing for the service of the over-head crane.

A quick study showed that it was not a good idea to install another over-head crane. The service turn-around time of two over-head cranes crossing each other paths would improve by about 40% only. That was insufficient to raise the productivity much.

In addition, the hoisting cycle time for over-head cranes was found to be too slow. It had to lift up the weld meshes to a height of at least three meters well above the height of workers moving around the factory floor and then move the weld meshes laterally across the factory floor to the designated position. Several solutions were finally adopted.

A roller conveyor Figure was specifically designed to withdraw the freshly weld mesh from the welding machine. Upon shearing to form a complete weld mesh, the finished weld mesh is rolled off onto a scissor Figure with the latest piece of weld mesh lying on top. Upon completing welding the wire meshes of a particular type, all the weld meshes are bundled together and tagged.

The overhead crane is called over to hoist them away and placed at the back-end of the factory floor. The over-head crane was dedicated to hoist completed weld meshes away from the scissor Figures. These reduced the waiting time for the over-head crane to a negligible level. The welding machines were no longer idle due to waste of waiting.

Over at the back-end of the factory, instead of using the over-head crane to hoist the weld meshes onto trucks, two forklifts were used to transport the weld meshes away to the sorting yard. This immediately freed up the overhead crane from being used to hoist the weld meshes onto a truck that transports them out to the sorting yard.

The forklift has replaced the use of both the over-head crane and a truck for this purpose. With the mere introduction of widely available fork lifts, the productivity of the welding machines increased by more than one-third. The waste of waiting due to a congested overhead crane was almost totally eliminated.  

 

Figure 17-1: Mechanization of retrieval of welded meshes



A piece of equipment could be idled due to waiting for auxiliary services. Such productivity loss can be easily recovered once the cause of waiting was eliminated.

 

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