CNC collision avoidance

Technology Update: Machine builders and end users can protect the machine and operators with advanced CNC technologies.


Figure 1: Safe operation and collision avoidance between moving and stationary components on the machine are maintained through constant and real-time 3D monitoring done by the control. An alert can be created anytime a collision is anticipated, shown herCollision avoidance seems intuitive to any machine builder or user, but how it is achieved has changed dramatically in recent years, for the better. Many controls have some alarm mechanism, and the programming of machine limit switches was traditionally a key safeguard. Those didn't always work.

Today, on more advanced computer numerical control (CNC) units, full collision avoidance can be provided for the machine builder and end user, thereby protecting the machine and operator. In the machine design phase, the full cycle simulation is combined with real-time monitoring of all moving and stationary components on the machine. This has particular importance when tombstone fixturing devices, rotary table trunnions, and other hardware are present in the cutting theater.

Planning ahead: Modeling

Figure 2: Builders benefit from the full simulation possible with collision avoidance software, as the controls today can offer full modeling of a cycle, based on an analysis of the tool cutting edges from the tool usage data for machining, as well as theMoreover, on the builder's workstation, an offline PC, and whether working in NX, Catia, or another CAD/CAM design platform, the builder or engineer can define cubes, spheres, cylinders, or STL files to model all machine assemblies and structures relevant to determine full collision avoidance. Plus, it can be done in all operating modes, including JOG/MDI and AUTO, with identifiable selection and deselection programmable, further protecting the machine in the field. Since a full, solid model of the machine is used for all software calculations, this advancement represents a true 3D visualization process of machine motion and cycle characteristics alike. Because this collision avoidance on a virtual machine can created in the design phase, it becomes a useful tool for machine builders as well as fixture and tooling designers. 

Changes in the shop

Figure 3: Gantry, rotary table trunnion, spindle, headstock, and other element positions are all monitored, so the collision avoidance software on today’s CNC can be utilized with any machine tool, up to true 5-axis machines and more. Courtesy: Siemens InIn the shop, using the operating program and HMI on the CNC, users can further identify potential collisions when altering a program, changing a rotary table dimension, resetting a fixture, or simply as the tooling changes. Basic machining areas and limits can be defined by modeling those protected areas. The CNC automatically alerts a potential collision by highlighting the relevant structure of the machine onscreen. Headstock, spindle, rotary table trunnion, tombstone fixturing, or a simple clamp's position can be monitored in this real-time collision avoidance program.

Figure 4: Safe operation and collision avoidance between moving and stationary components on the machine are maintained through constant and real-time 3D monitoring done by the control. An alert can be created anytime a collision is anticipated, shown heThis powerful 3D real-time collision avoidance monitoring can be done on any machine, including a true 5-axis, simultaneous multitasking mill/turn machine with a B-axis and the most sophisticated gantry/rotary table assemblies in the market. All the stationary and moving elements as well as the tool cutting edges are effectively monitored for potential collision. Once again, the affected areas or machine components are quickly identified onscreen during a cycle simulation or in real time.

Human error can also be factored, so the resulting collision that would be caused by a change in a program or a setup error can be anticipated with an alert sent, showing the affected area highlighted onscreen.

- Randy Pearson is a Siemens international business development manager, Siemens Industry Inc., Drives Technologies, Motion Control-Machine Tool Business. Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, mhoske(at)

ONLINE May under this headline has more information and images along with links to other CNC articles.

Key concepts

  • CNC collision avoidance has advanced with software improvements.
  • Modeling platforms warn of conflict before any part is made.
  • On-machine avoidance provides warning when in-shop changes occur. 

Consider this

Would better CNC collision avoidance pay for itself by avoiding operator injury, machine tool damage, or part rework? 

ONLINE extra

Randy Pearson is a Siemens international business development manager, Siemens Industry Inc., Drives Technologies, Motion Control-Machine Tool Business. Pearson, a long-time veteran of the machine tool industry, has a special interest in the many levels of training on CNC machine tools, which he conducts through various seminars, workshops, and classes with machine tool builders and dealers, at vocational/technical schools and on-site at shops, as well as at U.S. Siemens training facilities.

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