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CNC Upgrades for Improved Machine Tools Faster motion, better accuracy and easier integration. Computer numerical control (CNC) of machine tools has always been about motion control – the increasingly rapid and detailed adjustment of ballscrews, servo motors, gears and spindle systems. Software updates boast larger memories and beefer processing power, but many recent CNC upgrades are about taking existing machine tool hardware and making the afected components more accurate. For example, the new 840D sl CNC from Siemens ( siemens. com ) incorporates the latest version of Sinumerik Operate and its new auto servo-tuning algorithm. Control loop parameters and damping flters are automatically calculated so that machine dynamics are under constant control and all drives automatically adjusted in response. As workpiece mass changes or tools wear, each processing parameter change triggers an optimization response between processing steps, improving precision and productivity. Adapt Jerk Filter Time (AJET) is another feature for the Sinumerik 840D sl that optimizes motion sequences. Drilling patterns, for example, involve sequencing interpo- lation along with fast traverse. AJET recognizes and switches between these diferent phases for maximum available speed and precision. By automatically switching between operating parameters, positioning productivity improves, leading to improved drilling accuracy and turnaround time. As friction is a necessary evil in all machining operations, accuracy is always deteriorating to some point. Sinumerik 4.7 includes new friction compensation for detecting and reducing friction-dependent path deviations due to sliding or static friction. Tolerances are tighter as a result and contour accuracy is higher. By RAY CHALMERS, Contributing Editor RETROFIT BENEFITS Increasingly, CNC upgrades are simpler to integrate and maintain. Retroftting a machine tool to take advantage of the latest CNC advances can be a cost-efective means of achieving higher performance, lower costs and improved accessibility to machining data. A CNC retroft should not be confused with a CNC conversion, where a manual machine is converted into CNC operation. A CNC retroft does not include major upgrades or repairs to the machine mechanics. A CNC retroft replaces the CNC, axes servo motors and drives, spindle motor and drives, and a portion of the asso- ciated wiring and related electromechanical components, according to FANUC America ( fanucamerica.com ). Assuming a machine tool is generally in good shape mechanically, CNC retroftting is typically the lowest-cost solution to improve the machine tool's overall performance. Approximately 20 percent of a machine tool's running costs are due to electrical energy consumption from pumps and drive systems when machining. Servo motors and spindle drives are continuously accelerating and decelerating as they change speed and direction. When accelerating, motors draw energy from the electrical system; when decelerating, kinetic energy is converted back into electrical energy, which must be dissipated. CNC-programmable functions can dynamically turn of both main and peripheral devices when not in cycle, based on an algorithm that considers idle time against the length of time each component needs to restart and achieve full motion. Electricity cost reductions of between 30 and 50 percent in the new hardware can go a long way to justifying retroft costs, the company says. 34