Flexible Unattended Machining Helps Improve Part Quality And More

V&L Tool, Inc. (Waukesha, Wisconsin) prides itself in staying current with evolving machine tool technology. The company designs and manufactures tables and diagnostic imaging systems, as well as parts for x-ray, CT, MR and ultrasound systems.

In its desire to use new methods, the shop looked for a product that would increase tool life, improve part quality and decrease changeover time. It found the One-Touch flexible manufacturing system (FMS) from Okuma (Charlotte, North Carolina) and became the first to own one. The Okuma One-Touch FMS automates horizontal machining centers to create a hands-free, unattended manufacturing system. Up to four machines can be configured with either a multi-level stacker crane or a single-level Rail Guided Vehicle (RGV) to offer up to 250 pallets of workpieces. One-Touch FMS provides the flexibility to run small lot parts on demand.

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The One-Touch FMS works like this: The FMS operator programs the pallet scheduling, pallet code and the machining priority level. Once the pallet scheduling is entered, the RGV loads pallets from the pallet pool buffer station to the fixturing stations.

Next, the operator sets the workpiece onto the pallet at the fixturing station. The pallet is then moved to the specified machine, ready for machining. When machining is complete, the pallet can be moved through an optional wash station, then back to the buffer station for storage.

According to Marty Pierson, the One Touch FMS setup machinist, setup processes used to be time consuming. "Before the FMS came online, we used a double-pallet machine to make these parts," says Mr. Pierson. "Now we have no more repeat setup time. Once we're set up to make a part, we're done. We save about nine days setup time every year, gaining 72 hours that can be used to produce parts."

"With this new Flexible Manufacturing System, tooling savings are significant," says V&L president Gerry Schaefer, "Tools have longer life and cost less to maintain. It usually takes from 30-70 tooling changes to make one part. Now, one tool installed in the FMS works to create many different parts."

V&L's current FMS has 150 tools, but soon Mr. Schaefer plans to upgrade to a 400-tool capacity. According to Mr. Schaefer, the automated Okuma tool probe detector will check to see if any tools are broken or misaligned. If the tool is not the proper configuration, the detection system will alert personnel to the needed adjustment. This prevents specification deviations and abnormal tool wear.

According to Mr. Schaefer, a typical parts run for V&L would be a 2- by 2-foot medical diagnostic imaging component. Okuma guarantees the NIX-60 BB will hold 0.0002 tolerance in the X and Y axes. Made from aluminum sandcasting, the component is hog-milled using a high helix carbide end mill tool to mill the contours of the component. Then the component would be spot- or center-drilled to ensure proper alignment.

Next, depending on the size of the threaded hole needed, the component will be tapped for the smaller holes or, in the case of this component, a 1.25-inch, twelve-pitch hole will be thread-milled for speed and precision. One-inch holes are then bored in the component using Kaiser Technara boring heads for close tolerance resilience at 0.0002 inch. Finally, the component is reamed at speeds running up to 10,000 rpm, with feeds up to 90 ipm. The size of parts runs may vary from 25-50 parts per run.

"Since adding the FMS, the quality of the parts has improved," explains Mr. Schaefer. "Often a tooling fixture change could cause the first part made to fall short of tolerances as we adjust to specifications. Now with the FMS, we don't have to change the tooling fixture once we've set up. We save so much time on setup that productivity has increased, both throughput and output."

The FMS has the capacity to run a total of four machines. Mr. Schaefer runs one MX-60HB for now, chosen because of its size and capacity.

"I envision getting an N4X-40, an MX-50 and another MX-60 for this FMS setup," Mr. Schaefer says. "Right now, we have a pallet storage and handling capacity of 20 pallets on two levels, but this system will expand up to 100 pallets."

Typically, changeover on parts takes from two to 12 hours setup time and is performed two times per week on a regular machine. "However, with the Okuma One Touch FMS, you never need to change over," explains Mr. Schaefer. "Once you set it up, it's always ready to go."

With the flexibility and convenience the FMS offers, V&L hopes to increase its current customer base. With plans to further vertically integrate its in-house operations, Mr. Schaefer envisions continuing V&L's ability to design, machine, assemble and test the components it produces.