Modern Machine Shop

FEB 2018

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In some cases, large gaps between green time were due to manual machine loading. This is one reason why the shop purchased its first two subspindle lathes with bar feeders and parts conveyors to enable long stretches of unattended operation. Integrating these machines had an immediate impact for certain higher-volume jobs that could be processed from 3-inch-diam- eter barstock or less, which is the capacity of the machines' subspindles. In one case, a job ran over an entire weekend, only requiring an operator to come in two hours each day to check on the two machines, resulting in a productivity index of approximately 10. "Adding an automated process such as this to gain uninterrupted green time sounds like common sense, but when you're encountering a f lat-screen monitor each day that shows all The machine-monitoring data is imported into a spreadsheet to calculate the monthly produc- tivity index for the entire shop. The productivity index com- pares the number of machine run hours to payroll hours. This ratio was low when the shop started collecting this data in 2015, but now typically ranges from 1.2 to 1.4 thanks to automating some processes and reducing cycle times by modifying programs and using new cutting tool technology. The addition of new equipment and other process improvements has pushed monthly machine hours over 5,000 today. this data, you become more apt to do something about the yellow interruptions," Mr. Tumanic says. "It spurs you to make changes to minimize the gaps in machine uptime." Examining the index also served to balance cells. The turning centers in the shop are located in one aisle with identical machines facing each other, so one operator can more easily tend both machines. In fact, each time the shop purchases new turning centers, it purchases two at a time for that reason. For the cells with chucker turning centers running one part number, one turning center performs machining on side A of the part, and the other machines side B. By closely looking at the amount of interrupted production for each side due to part loading, the shop was able to better balance the cells. For example, if the cycle time for side A is 10 minutes and side B is 5 minutes, the shop might work to improve the performance of machine A; take features produced on machine A and have machine B produce them; set up both machines to run side A and then once completed, set up both to run side B; or, if the volume was sufficiently high, set up four machines with one pair machining side A and the other pair machining side B (each cell would start and end at a different time). MMS FEBRUARY 2018 82 mmsonline.com MACHINE MONITORING 2014 TOP SHOPS WINNER Not surprisingly, J&R Machine was the 2014 Top Shops Honors Program winner in the shopfloor practices category. This year's survey is now online. Participate, and perhaps you can be an Honors Program winner, too. survey.mmsonline.com/topshops

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