GENERAL MOTION VS. CNC IN MACHINE TOOL APPLICATIONS
Traditionally, CNC has been the control of choice for machine tool applications. However, general motion control (GMC) can be used in many machine tool applications to simplify the overall machine and reduce costs.
The increase of GMC in the machine tool industry is due in large part to the availability of new fieldbuses such as EtherCat. These fieldbuses allow for simple PLC programs to send commands to and from drives in order to set position or velocity profiles for the machine tool.
Additionally, status information is passed to the PLC for user diagnostics. On machines where there are multiple stations, such as inline and rotary transfer machines, the per-axis cost can be reduced as much as 50% due to the hardware cost advantage over CNC.
GMC’s strengths are in non-interpolated axes where repetitive cycles are used. These cycles can have adjustable set-points where the user can make in-process changes based on part size or part changeover. Applications such as drilling, boring, reaming, milling, and material handling, where point-to-point axis moves are used, work nicely with GMC. Additionally, GMC can be used to compliment CNC, where axes are outside of the CNC interpolated path. Such examples of this are tool changers, turrets, live tooling, and pick-n-place units.
At MasterControls, we have over 30 years of experience with General Motion Control, in and out of the machine tool industry. Our experience allows us to determine how to best use GMC and/or CNC in various machine tool applications.