Issue link: https://industrialengineer.epubxp.com/i/826827
June 2017 | ISE Magazine 43 Part of the installation is getting the machine to work right. The large machine with all the bells and whistles may take months to debug. The maker's claims on the rated capacity of the machine are generally like the mileage claims of the automaker. Some- body somewhere under some conditions achieved the claimed result – maybe – but not this owner. This owner finds that all too often the machine must be tweaked and coaxed to get it to make products, and so much time is lost in fussing with the machine that it produces far less than the manufacturing engineer expected or hoped for. Manufacturers also have to be cognizant about how their equipment and systems respond to downtime. Are smaller ma- chines easier to install, move, debug and run at rated capacity? Generally, yes. There are still more disadvantages of large equipment. When a given class of parts is made on one large machine, a breakdown totally halts production of that class of parts. With several small machines, when one goes down the rest can keep producing. With a bit of overtime on those still running, all schedules may be achievable while the broken machine gets fixed. Downtime didn't necessarily result in late customer deliver- ies in yesterday's factory, loaded as it was with buffer stock. In the modern lean plant, however, lack of buffer stock places a premium on every work center meeting daily schedules. Therefore, some machine capacity needs to be available for use in each process. Since small machines are generally not so complicated, the operator may be able to learn how to do all of the preventive maintenance, along with some simple repairs. Operator-cen- tered preventive maintenance and a sense of machine "own- ership" on the part of the operator are central to the "total productive maintenance" (TPM) concept. TPM, in turn, is (along with total quality) a key to lean production. Rationale: Remove main sources of output variability – uncertain ma- chine uptime and uncertain quality – in order to slash buffer stocks. This brings the discussion into the mainstream of reasons for the lean preference for smaller machines: Fast reaction. Think about it. Small machines may be dispersed. Each machine of a given type may be installed at the point of use so that the work need not traverse the plant to find the next process. Production lines or group-technology cells (two ways of saying about the same thing) are formed when machines are placed at points of use. Close positioning of feeder machines to user machines shrinks the amount of inventory in transit – and the size of the economical unit load and handling equipment as well. We may be able to get by with chutes instead of con- veyors, hand carry instead of dollies, carts instead of forklift trucks, small conventional shelves instead of automated storage and retrieval systems, and so forth. Each of several small machines can be assigned to work on a different size model of the product. That way, small amounts of each product are made at frequent intervals – just-in-time or nearly so. The large machine can only work on one variety of the product at a time. With small machines, setups or setup times may be reduced. Setups are eliminated when each machine of a given type is dedicated to making just one type of part. Setup times are sometimes less with small, simple machines than with larger ones of the same kind. With less time spent setting up, smaller lot sizes or repetitive production – lean ideals – are justifiable. Smaller can be beautiful Lean production means making only what is needed at the next process. Somewhere in the manufacturing chain there is a process that operates one at a time. That process attempts to pull just one piece at a time from the previous process. If the previous process is a large machine that makes six at a time, then the machine is a lean obstacle. Also, if the previous process is so distant that a container or transport device holding six must be used (for the sake of handling economies), then the distance is an obstacle. Often the distance obstacle is really a large-machine obsta- cle: Where there is just one large machine, it cannot be located at several places at once. That is, it cannot have several points of use. It may be at some considerable distance from some of the processes that use its output. What we are seeking is zero delay time and 100 percent value-added time. Large machines are likely to make larger quantities than can be used right away at the next process. Large machines also are often geographically removed from the previous or next process, and their size and demanding installation features may make them hard to move to the right place when conditions change. For these reasons, in select- ing equipment we need to give much more consideration to multiple small machines instead of the largest machine in the catalog. Richard J. Scho berger is director of Global Lea ess Studies a d the World Class by Pri ciples i ter atio al be chmarki g project. He has authored 15 trade or textbooks, i cludi g Japanese Manufacturing Techniques, World Class Manufacturing a d his latest, Best Practices in Lean Six Sigma Process Improvement: A Deeper Look. His 200-plus articles have appeared i ide ra ge of peri- odicals. After eight years as a practici g i dustrial e gi eer, he joi ed the U iversity of Nebraska faculty, becomi g George Cook (chaired) Professor a d later affiliate professor i a ageme t scie ce at the U i- versity of Washi gto . He was a recipie t of the Shi go Prize, the British I stitutio f Productio gi eers' I ter atio al Award i Ma ufacturi g Ma ageme t a d the IIE Productio d I ve tory Co trol Award.