SOUTHLAND CNC MORE THAN DOUBLES OUTPUT WITH IMPROVED FIXTURING Hydraulic workholding yields high accuracy on machined cast parts Southland CNC (Cornelia, GA) is a tier-two supplier to the automotive industry, providing machined aluminum sand-cast components to all three American and the six largest foreign auto manufacturers.The company, which was started 19 years ago in President/Owner Keith Armour’s garage on a single machine, has now grown to 30 employees using 21 high-capacity machining centers. Southland machines a variety of parts that includes production runs of very high volumes and other production runs of relatively low volume. Southland uses dedicated hydraulic clamping fixtures on Okuma Howa vertical machining centers for its high volume production runs, because these fixtures greatly decrease production time, which makes the fixturing highly cost effective.The dedicated hydraulic fixtures also provide clamping pressure that is consistent and repeatable, which improves machining accuracy. According to Keith Armour, the typical tolerances are held to 20 microns true position, with critical dimensions to +/- 6 microns, which he credits largely to the hydraulic fixturing supplied by Southland’s longtime supplier, Advanced Machine & Engineering (AME) of Rockford, Illinois. Because low volume production runs do not justify dedicated fixturing, Southland uses manual fixturing for its adaptability and lower cost of acquisition, when appropriate. Southland currently has four horizontal machining centers that use hydraulic tombstone fixturing, and three vertical machining centers that use hydraulic tombstone fixturing, all designed and built by AME.These fixtures are dedicated to high volume production of single parts or single families of parts. Southland chose AME to provide its first tombstone hydraulic fixture because the fixturing solution was competitively priced and specifically designed by AME engineering to fit Southland’s production needs.Delivery, which was very important to Southland’s production scheduling, was significantly better than any other designer/supplier, according to Armour. The first AME fixture specifically replaced the customer-supplied fixturing Southland had been using, which Southland determined was not providing the efficiency needed to meet cost and schedule goals for the high volume production run. The advantages provided by the AME-designed fixture included reduced load/unload time, reduced cycle time, reduced scrap rates, and error-free loading. The initial application of the fixture reduced Southland’s cycle time by over 50 percent, which allowed Southland to meet the high production volume without additional machines. On one bearing plate for a supercharger assembly, according to Keith Armour, production has gone from 50 units to 110 units per day with the same superior tolerances and a 1.67 Cpk, critical to the Six Sigma conformity for its major automotive customers. The fixture, which provides automatic clamp and release, is designed with locating dowels to assure error free handling. Each component to be machined is handled only twice, once as it is loaded into the fixture, and a second time as it is unloaded.Because the fixture is a windowed fixture, the component is completely machined on all four sides without additional handling. On the vertical machining centers typically, a second loading pallet is used to mount workpieces while another fixture is running in the machine. This further enhances Southland’s throughput. Keith Armour states that the AMEproduced fixturing has been very reliable. One fixture has been in operation 20 hours a day, five days a week for more than seven years without a single problem. Because of this reliability, and because of the cooperation and innovation AME has provided, Southland added a second fixture used on the vertical machining centers, plus a fixture dedicated to horizontal machines. “The fixture configurations we designed for Southland include cast tombstones as well as welded tombstones. Depending on the intended use for the fixtures, they Were provided with external surface mounted hydraulics, as well as internally cored hydraulics,” according to AME Fixturing Group Manager Alvin Goellner. On one particular part, a bearing plate for a supercharger, the part is aluminum sand-cast, measures 8-inch long x 4-inch wide x 1-1/2- inch deep. A two-operation part per side, the workpieces are loaded in less than 20 minutes on a second fixture, using the secondary pallet on the VMC. Southland produces approximately 30,000 of this part annually for a Tier One supplier to Jaguar, BMW and Mercedes. As Keith Armour explains, “The fixture was designed specifically for this part, though it’s flexible enough to allow us to use it for other jobs.AME had a very short turnaround time, plus their knowledge of work holding and the components they selected were all first-rate. We have experienced zero downtime because of the fixturing they supplied us for this particular part. Although we tweak the rest pads for enhanced accuracy, that’s normal with the machining centers we use.” He further noted the design and development work was done via CAD drawings and the completion of the entire project was done on schedule and at the quoted price. “When we began to go from 50 parts per day to 110 or better, with absolutely no loss of accuracy and finish quality, we knew we’d made a wise choice,” says Armour. All accuracies are checked on the in-house CMM at Southland for verification. Advanced Machine & engineering 2500 Latham Street Rockford, IL 61103 (815) 962-6076 www.ame.com email@example.com
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