Case History #3 Maximizing Part Flow Through FMS While Maintaining Top Quality

CASE HISTORY

 

COMPANY :
Spirax Sarco, Inc.
Blythewood, S.C.

 

PROBLEM:
Maximize part flow through FMS while maintaining top quality

 

SOLUTION:
Work holding systems custom-designed to hold multiple parts securely.

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United-Kingdom-headquartered Spirax Sarco Engineering Ltd. is a world leader in the control and efficient use of steam and other industrial fluids. Its South Carolina-based U.S. unit specializes in the manufacturing of steam pumps and condensate recovery equipment.

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Facing global competitive pressure, the operation continually seeks ways to boost its throughput while maintaining top quality. The plant machines a wide variety of components in cast iron, cast steel, and stainless steel, with the volume of some parts exceeding 600 pieces. To maximize efficiency, senior manufacturing engineer Al Chapman said, “We run a demand flow technology, a just-in-time system.” Key operations employ tool breakage detection and tool life management systems to permit running a third untended shift each day. Machining parameters are aggressive as well. Silicon nitride milling tools are run at cutting speeds in the area of 3500 sfm and feed rates of 100 ipm. Drilling takes place at an average 50-60 ipm, and rigid tapping at 90 – 120 ipm. Finally, part tolerances can be tight, ranging from +/- plus or minus 0.005″ to +/- 0.0008.”

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The combined demand for high volume, speed and accuracy place tough requirements on work holding equipment. “The fixturing must accommodate the maximum amount of parts, within the work envelope of the machine, and hold them securely enough to be able to withstand our feed rates in milling, drilling, and tapping,” Chapman said.

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The first step in maximizing work holding potential, Chapman said, is to “look at the machining envelope: How big of a fixture can I put inside this machine? I want as many parts on that cube, hexagon, octagon, or flat face tombstone as can fit inside the axial stroke limits of that machine. ”

 

To develop its work holding equipment, Spirax Sarco has worked for more than 25 years with Royal Machine and Tool Corp., Berlin, Conn. Chapman said about 80 percent of the work holding equipment Royal supplies to Spirco Spirax is hydraulically activated, with the rest operated manually. Volume determines which method is applied; any part made in numbers over 100 a month is held hydraulically.

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Royal Machine Sales Manager Bernie McAloon said his company works in partnership with Spirax Sarco. “They come to us and say we’d like to put as many parts as possible on the machine. We work closely with their engineers regarding the best way to approach the work piece and the order of operations.”

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Chapman emphasized the importance of clamping as many parts as possible on each fixture. In some instances, he said, “Royal has upped some fixtures that only held two or four parts per cycle to as many as 24 parts per cycle.” The difference, Chapman said, is between “machining four parts in 12 minutes, or 24 parts in 32 minutes. Whenever you go from four parts to 24, you basically are amortizing all of your tool changing. So, where previously every four parts you had to change a tool, now, every 24 parts I index to the next tool.” The time saved in tool indexes is significant, as is the time no longer spent switching pallets in and out of the machine.

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Spirax recently replaced three vertical pallet pool machining centers with a new Toyoda flexible manufacturing system consisting of two machining centers and 44 pallets delivered by a rail-guided vehicle.

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Royal’s McAloon said to help Spirax Sarco get the new FMS up and running, “we did the fixtures right away,” noting that the work also included modifying some older fixtures for use in the new machines.

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