A recently installed aba z&b PSM creep feed grinder, said to be the most powerful and largest of its kind, works on undercarriage links for a large piece of earthmoving equipment. But, besides its power and size – 39.4-in. working length, 21.65-in. grinding width, and 21.65-in. grind height – the machine’s efficiency and performance effectiveness come from one CNC.
This one-CNC-controlled grinder replaced a machine with three different processors and operating systems. According to Leonard Cody, president of aba z&b USA Inc., the customer has realized tremendous savings in set up, training, programming and maintenance times as a result of the grinder’s engineering advances.
As the U.S. operation for aba z&b Schleiffmaschinen GmbH, based in Reutlingen, Germany, aba z&b USA rebuilds and field-services existing machines, sells new machines, installs and provides spare parts for aba z&b grinders. The company’s machines are found in other U.S. markets, too, including aerospace, moldmaking, automotive and oil and gas.
On the large one-CNC grinder, a 69-in.-diameter indexing worktable with two workpiece clamping fixtures, each with a qualified surface of 36 in. by 24 in. and load capacity of 4,400 lb, allows simultaneous load/unload and grinding operations. Linear guideways and ballscrew drives are onboard for the main X, Y, and Z axes. A Sinumerik 840D CNC from Siemens Energy & Automation Machine Tool Business, with digital drive and motor that allow free contour programming for interpolation grinding applications, provides overall motion control for the big grinder.
Unlike conventional point-to-point programming, interpolation grinding is done on this machine by transformation orientation or TRAORI, pioneered by Siemens for use in aerospace, automotive and other high-accuracy finishing operations. In essence, the part position, not the machine coordinates, drives the program and its cutting path execution. The result is a higher quality finish, less rework and a marked decrease in time-to-part production.
A Siemens CNC-controlled electro-mechanical drive system runs the grinder’s X-axis longitudinal movement of the wheelhead column. The drive system’s stick-slip-free, high-precision linear guideways provide the highest possible positioning and repeating accuracies.
A variable AC motor and ballscrew move the machine’s grinding wheelhead in the Y-axis vertical. Anti-friction guideways deliver accuracy even in the smallest downfeed increments. The maximum achievable feedrate is 118 ipm. For the grinder’s Z-axis transversal movement of the wheelhead column, there is a Siemens digital AC servomotor package with resolution of 0.000004 in.
The machine’s CNC features PC-based continuous path control, with an integrated Siemens Simatic S7 PLC and Safety-Integrated software for monitoring all feedrates and axis positions.
