Quality Magazine: December 1998 Case Studies -
[Cached Version]
Published on: 12/1/1998
Last Visited: 7/22/2001
At the bottom position , explained Charles Tellas , president and owner of Milan Screw Products , Milan , MI , maybe a drill will come in.The carrier indexes.Perhaps in the next position , a part is machined on the outside a little bit.It goes through six stages. [ At ] the last stage , the end of the bar of material is cut , and it's a precision screw- machine part..
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We would inspect the tool visually to determine its condition , remembered Tellas.It usually would be predictable , given a particular grade of steel , and a particular operation , but there are occasional variations in the way the tool was ground , or sometimes hard spots in the steel , sometimes weaknesses in the tool , that would cause the tool to fail early.The problem with that is , oftentimes when a drill fails in steel , it can produce a lot of heat , which could lead to a fire..
Although this particular machine never started a fire , other drill machines in the facility had.The possibility was there for the screw machine , which at times in its production sequence generated intense heat.Milan Screw Products had also just finished completion in 1997 of a new 37 , 000-sq.-ft. facility.
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We needed something simple , and eventually what we would like to do is work on lights-out operation , said Tellas.Ideally , the plant would run itself at night , controlled by programmable logic controllers ( PLC ).I have a vision of our people coming in and working eight hours , stocking the machines , going home , and letting the machines run by themselves for four hours , then having the next shift come in..
Rather than waiting to be approached by vendors , Milan Screw Products approached another company , Promess Inc. , with its idea of a screw machine monitor.Promess Inc. manufactures sensing devices and electronics , and is based in Brighton , MI.We knew they had experience in measuring , Tellas explained.They had experience checking for the tool condition on particular machining operations.We went to them with this idea..
What Promess developed was a sensor system within the screw machine itself.A strain gage is mounted in the drill holder and measures the thrust of the drill throughout operation.If the gage detects no thrust , it relays to the screw machine's PLC that a tool isn't present , and the machine is stopped.
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Certainly the confidence level has increased , noted Tellas.We're not necessarily looking for that increase in tool life ; it's to prevent those catastrophic failures..Before the monitor , the drill experienced frequent failures.After the monitor , the screw machine has shut down only twice.Without the monitor , the drill would have continued , and ruined the parts.
Implementation went with few hitches.
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When someone's here , Tellas explained , they can see , hear , smell-they can get some indication something's wrong.If no one's here , something very costly could happen..The screw-machine monitor is in place to prevent that something from happening.-Samantha Hoover.
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