Simple Solutions That Work! Issue 6

42 Process consistency is the first step in achieving total quality. A reliable, consistent process begins with reliable equipment. Quality ladlers play an important role in the die casting process as having an incorrectly sized biscuit can cause significant remelt costs. Robotic ladling systems can achieve 99+% accuracy to consistently pour molten metal from a furnace into the shot well of a die casting machine. IMPORTANCE OF REPEATABLE ACCURACY Repeatable accuracy means lower cost of operation. Let’s compare a 60-second cycle operation for 5 days, 20 hours per day, using a 10-pound nominal pour. Ladlers with 10% repeatability for a 10-pound casting: 60 second shot x 20 hours x 5 days = 6,000 shots per week or 60,000 lbs of aluminum. The shot weight variation would be from 60,000 lbs to 66,000 lbs (10% maximum variation) or 6,000 lbs over. Let’s say, however, the excess average is half of that or 3,000 lbs of aluminum per week. The metal saving difference is 2,700 lbs per week. At 50 weeks per year, that’s equal to 135,000 lbs of metal you’ve purchased, inventoried, and melted unnecessarily! And these figures are only for a 10 pound casting! What is this costing your company? One die caster stated that a biscuit 1” longer than needed (on a 2-1/2” diameter sleeve) costs about $50,000 a year (per machine) in remelt costs. 99+% can be achieved by controlling the ladle cup spill off angle with a servo motor and servo drive. One revolution of the ladle cup is divided into almost 2 million parts (1,966,000 to be exact). What this means is that the cup spill off angle can be controlled to 2 millionth of its rotation and it’s this repeatability of the spill off angle that achieves the ladlers’ shot size repeatability (see Figure 1). IMPORTANCE OF LADLER DESIGN Direct Drive Systems The gearbox is either a ground helical gear set or a Cone Drive double- enveloping gear set where the worm is manufactured in an hourglass configuration and wraps around the wormwheel (see Figure 2). Either provides low backlash and extremely long life. The brushless servo motors are directly coupled to the gearset reducing service drive train problems and improving mechanical response to the servo motors. The output shaft of the ladler linkage arms is a large, one-piece shaft, which goes completely through the gear box. The positioning encoder, motor, and gearbox are giving direct drive without use of pulleys, belts, or cams. Heavy Duty Support Arms On larger models (more than 50 pounds of metal), the entire arm assembly can be supported by a large housing with double opposed tapered roller bearings (see Figure 3). TROY TURNBULL President INDUSTRIAL INNOVATIONS ARTICLE TAKEAWAYS: • Quality ladlers can achieve 99+% repeatable accuracy • Repeatable accuracy means lower cost of operation • Robotic ladlers offer: servo motors & drives, heavy-duty support arms, LCD operator stations, no dunking probes and die cast or ceramic ladle cups SYSTEMS INTEGRATION Figure 1 Shot weight variations Figure 2 Direct drive systems Figure 3 Heavy duty support arms SHOT SIZE REPEATABILITY IN DIE CASTING SAVES MONEY