CNC Machinery Online Information

A growing number of manufacturers are now using software to simulate the CNC machining process prior to machining an actual workpiece. The demand for this software has been fueled by the increased use of more sophisticated machine tools such as high speed, 5-axis, multi-headed, and mill/turn machines. Manufacturers benefit from machine simulation by avoiding the expense caused by machine crashes, damaged components, and unprofitable use of their machines while proofing NC programs.

Technology enables improved software. While machine simulation technology has been available since the early 1990s, the software tended to be expensive and inefficient on the computing at that time. Subsequent advances in computing and software technology have enabled CAM software vendors to now offer affordable, robust, and fully integrated machine simulation with their CAM systems.

Tool path verification vs. machine simulation

Tool path verification is useful to verify the accuracy, safety, and efficiency of NC programs, but it does not detect machine-specific problems. This is particularly true where complex five-axis moves or high-speed machining are involved. Simulating the actual machine movement provides greater assurance that an expensive and possibly catastrophic collision will not occur.

Material is expensive. Prices for metallic materials have increased dramatically. “$11,000 is a lot of money,” says Dave Wilhelm, lead programmer at Metalex Mfg. Inc., Cincinnati, OH. That is the cost of just one piece of stock for an impeller manufactured by Metalex. “We cannot take any chances, so every program is simulated before it is sent to the machine,” says Wilhelm.

Metalex specializes in manufacturing complex components often made from difficult-to-machine materials. “Because of the time it takes to receive and prepare the material, the expense is much greater than simply the cost of the damaged material,” adds Wilhelm, further underscoring the importance of detecting problems before an actual part is destroyed.

Rotary axis configurations are complex. Metalex employs several different 5-axis machine configurations. For one particular job it was necessary to mount a 90-degree head onto the spindle of a horizontal machine equipped with a B-axis rotary table mounted on an A-axis trunnion. “With such a complicated configuration, it can be difficult to predict exactly how the machine will move when performing 5-axis cutting operations,” says Wilhelm. “When running our initial NC programs through the simulator we were able to see that our tool path strategy would cause the machine to move the 90-degree spindle to the opposite side of the trunnion which would have caused leverage and travel problems. To our benefit, the software enabled us to modify the tool path strategy to correct the problem without ever putting the program on the machine,” says Wilhelm.

Simulation at work

Optimizing setups: “How the workpiece is mounted on the machine can be critical when performing 5-axis operations. We can simulate different setups to ensure that we achieve optimum machine movement,” explains Wilhelm. Such use of the simulator reduces machine downtime and cycle time.

Automated part handling: To achieve higher efficiency, machines are often equipped with moveable pallet systems, bar feeders, automatic clamping systems, etc. Such systems can cause interference problems. Astro Spar Inc., based in City of Industry, CA, recently installed two high-speed 5-axis machines from Handtmann A-Punkt Automation GmbH, Baienfurt, Germany. The machines are equipped with an A/C style 5-axis head and an automated clamping system. The clamping system allows clamps to be moved to different locations on the workpiece during the machining cycle. Says Astro Spar NC programming manager Don Barnes, “Machine simulation is critical when using the automated clamping system. Without it, a collision could occur with a clamp resulting in serious damage to the machine.”

High-speed machining: The Handtmann PBZ NT used at Astro Spar has a spindle speed of 30,000 and programmed feedrates can exceed 1,000 inches per minute. Says Barnes, “Our machines are used for cutting production parts, not for simulating NC programs. At 1,000 ipm, it would be difficult to stop a collision before it is too late. Therefore, proofing the NC program is handled safely and cost effectively using the machine simulator.”

Astro Spar uses NCL Multi-axis Machining Software from NCCS as its primary CAM system. The NCL software can be equipped with a fully integrated machine simulation product called NCL/MS, which is also available as a standalone system that can be used with other CAM systems.

The NCL/MS software allows users to perform realistic simulation of CNC machines, detect collisions between all machine tool components including axis slides, heads, rotary tables, spindles, tool changers, fixtures, work pieces, cutting tools, and user-defined objects. The software performs both material removal and machine simulation simultaneously with a range of dynamic viewing options and simulation modes.

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