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Wasted production hours.

Wasted production hours

There are a total of 8760 hours in a year. How many of these are used productively in metalworking shop operations? In machining operations, it is generally understood that money is made only when a tool is cutting metal. But many other support activities take place that keep the tool out of the cut. Setups, workpiece loading and unloading, tool changing and maintenance, movement of material to and from the machines, all let the tool cut metal only 50 percent of the time--at best. And all machine spindles in the shop are not running all the time--far from it.

The idea that a lot of production hours are being wasted may not occur to someone running a single-shift machining operation. Actual machining-time costs are recovered by an hourly rate. To this direct cost, an overhead rate or burden, is tacked on to cover most of the indirect support costs that accounting has no way to pin down. If business picks up, a second shift is added, but the same conditions exist regarding idle spindle time.

This month's cover story deals with untended machining-center operations. In preparing material for this article, we talked to a number of machine tool experts about what is needed to operate such machines unmanned for extended periods of time. We not only learned what it takes, but--more importantly--what benefits can be expected.

The consensus is that untended operation maximizes machine tool utilization. The experience and intelligence of a trained machinist is built into hardware controlled by sophisticated software able to cover every eventuality that a machine operator would encounter. The technology is available now to do this. Sensing devices needed to read what the machine and tools are doing are well developed. The software that must interpret and react to what is sensed is also available.

The problem lies with potential users who fail to recognize what is needed to apply this technology to its greatest advantage. For one thing, it is necessary to stop looking at machine-tool output in terms of parts per hour and begin considering production potential on an annual basis. Specifically, how to use the 8760 hours in a year more productively when machining prismatic parts on machining centers.

Traditionally, a one-shift manufacturing operation accounts for 2000 hours, based on a 40-hour week, 50 weeks per year. Four-thousand more hours can be divided up between 40-hour, 5-day second and third shifts. That leaves 2760 hours for weekends and holidays when nothing is happening in the shop. The whole premise of untended operation is that you can run production on weekends, holidays and second and third shifts on the same machine. Productivity can be doubled or tripled with no additional capital expense and no added support costs.

None of this comes easy, however. It takes a lot of effort such as getting the part program exactly right, minimizing setups, minimizing the number of tools needed by taking a critical look at workpiece design, and optimizing process steps. Yet, these are the very same things that will greatly improve productivity in manned operations-things that companies should be doing all along.

Untended operation is not the type of technology that you can simply go out and buy. You must study it, learn it, use it, and make it work for you. There is a considerable investment in time and money, but the payoff is the ability to use production hours that are now wasted. No one should be guilty of wasting time.
COPYRIGHT 1989 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989 Gale, Cengage Learning. All rights reserved.

Article Details
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Author:Green, Dick
Publication:Tooling & Production
Article Type:editorial
Date:Apr 1, 1989
Words:580
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