Improve nesting strategies; reduce hit counts
by Peter Visser
There seems to be a disconnect between how companies find ways to save on production costs in their turret departments. Along my travels to sheet metal fabrication shops I constantly hear two things.
The first is that the production manager of a company has an agenda to get more throughput out of his machine or shop, without spending more money from the budget. The second thing I hear is that the purchasing department wants to cut costs through less spending. Unfortunately, many times these two things cancel each other out. Companies need to create better communication between these two departments to determine what their “real” cost is once a job is complete.
Shops can do a simple analysis of the cost of the tools versus the money it will save in creating higher production yields. Managers and fabricating shop planners forget that these things are affected by better programming and punching parts through the purchase of “special shapes,” throughput, or “green light time,” greater return on investment (ROI), and reduced expenses from operations (REFO). Many forget they can cut machine cycle time down drastically, which means they can produce more parts per day, per month, and per year. This is where they can increase their sales and capacity.
At almost every company I visit each year the manager will say the shop needs another machine to keep up with demand. Upon investigation of the parts punched on the floor, I typically see most of the parts being produced with at least 30 to 50 per cent more tool hits than necessary. I also see machines being run on the slowest speeds, due to incorrect tool selections, dull tools, and fatigued springs. Most shops are only running at 50 to 60 per cent of their potential capacity, not to mention that the next machine down the line is waiting for parts (“bottlenecks”).
I haven’t found many shops that measure their savings versus final cost by using special shape tools; maybe less than 20 per cent of shops utilize this philosophy to its fullest potential. Special shapes enable customers to nest parts together and use common lines to reduce hit counts. If I were to “nibble” a 6.000 in. circle with a small round punch, it could take approximately 500 hits, not to mention the “scallop” that would have to be removed from the parts, which of course is a unnecessary secondary operation. If I were to produce the same feature with a special shape, I could cut the same feature in about ten hits. The average machine has a hit rate (depending on material thickness) of about 300 hits per minute. By purchasing a special shape, it would reduce almost two minutes per part, which means that it is possible to reduce a whole day’s work over the course of punching a few hundred parts. You can now start to imagine how many more days could be taken back each year just by spending under $500 in tooling.
The average turret costs a company about $50 an hour to run. Imagine saving hundreds, even thousands of hours a year in production; this can translate easily into five or even six figure savings each year (REFO). As well, companies now have the ability to produce more parts per year, which could mean the average sheet metal shop could produce millions of dollars more worth of product each year. This also allows companies to take the savings and invest it in other equipment and tooling for even more increased profits and reduced manufacturing costs. SMT
Remember, time is money.
Peter Visser is a sales engineer with Mate Precision Tooling.