Machine Tool Axis Collision Mitigation by Braking and Unlocking
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Solution Overview
Problem
Existing methods for mitigating accidental collisions in machine tools, such as wire electrical discharge machines, often result in significant damage due to the rigidity of the machines and considerable colliding masses, with emergency braking techniques not adequately addressing the severity of the impact.
Innovation Solution
A method that identifies the collider axis and a parallel or orthogonal axis, then applies emergency actions such as braking, unlocking, or stepping away to reduce the collision force by decoupling mass and reducing collision stiffness, utilizing a rules table for specific axis combinations and incorporating strain or force monitoring circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If emergency braking is executed by inverting motor current to maximum extent, then the braking force is improved, but the collision damage remains severe due to machine rigidity and considerable colliding masses
Solution Approach 1:
The invention segments the machine tool axes into independent controllable units, identifying specific collider and concordant axes separately. This allows targeted braking of the collider axis while independently controlling the concordant axis, rather than applying uniform emergency braking to all axes. The segmentation enables precise control of collision dynamics to reduce impact damage.
Solution Approach 2:
The invention dynamically adjusts the control strategy based on real-time axis status. By determining whether axes are moving or resting at the moment of collision, the system applies different actions (braking for moving axes, unlocking or stepping away for resting axes). This dynamic response optimizes collision mitigation by adapting to the specific collision scenario rather than applying a fixed emergency braking pattern.
2Manufacturing precision
If the machine tool is built to be rigid, then the manufacturing precision is improved, but the collision damage increases due to inability to absorb impact
Solution Approach 1:
The invention segments the rigid machine structure into independently controllable axis systems with separate monitoring and control. By identifying specific collider and concordant axes and applying targeted actions to each, the system can protect against collision damage while maintaining the overall rigidity needed for manufacturing precision. The segmentation allows the rigid structure to be preserved for precision work while adding intelligent control layers to mitigate collision risks.
3Reliability
If emergency stop circuitry is activated, then the power supply is cut off, but the collider is not braked and collision may be much harder
Solution Approach 1:
The invention merges the emergency stop function with active braking control. Instead of using emergency stop circuitry alone (which only cuts power), the system combines it with motor current inversion braking. This integration ensures that when a collision is detected, both the power supply is cut off for safety shutdown AND the collider axis is actively braked to reduce collision force, addressing both safety and impact mitigation requirements simultaneously.
Data Source
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AI summary
The present invention is directed to a method for mitigation of the damages in case of accidental collisions in a machine tool comprising a computer numerical control (CNC) and a plurality of axes, wherein the occurrence of collisions is monitored, comprises: identifying a first axis being an axis at which a collision is first detected, identifying a second axis being an axis parallel to said first axis, and determining if both or one or none of the axes are resting. If both are resting unlocking the first axis or both axes. If the first axis or second axis is not resting, then the moving axis is defined as the collider, and said moving axis is braked, and simultaneously the resting axis is unlocked or stepped away or heldin position. If both axes are moving, defining a collider axis based on said identified first axis at which a collision has been first detected, braking said collider axis and simultaneously unlocking or stepping away the axis parallel to said collider axis.