Spindle Axis Control for Tapping Cycle Time Reduction
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Solution Overview
Problem
In machine tools performing synchronized operations of spindle and feed axes during tapping processes, the cycle time is often limited by the acceleration capacity of the spindle axis, and deceleration at maximum capacity is hindered by mechanical losses in the drive source, making it difficult to achieve efficient deceleration.
Innovation Solution
A controller is configured to control the spindle axis with a numerical control section that prepares spindle-axis commands based on a tapping program, including a maximum rotation speed and total rotation amount, and a spindle-axis control section that performs accelerated rotation at maximum capacity using the maximum permissible current, followed by deceleration at a positioning deceleration higher than the maximum acceleration to compensate for mechanical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the spindle axis is controlled to maximize acceleration capacity using maximum permissible current, then the cycle time is reduced, but the deceleration capacity is limited by mechanical losses in the drive source
Solution Approach 1:
The patent applies inversion by controlling the spindle axis to decelerate in the opposite direction of conventional control. Instead of simply reducing power during deceleration, the system applies regenerative braking by converting the kinetic energy of the decelerating spindle into electrical energy, which is fed back to the power supply. This allows the spindle to decelerate at maximum capacity without being limited by mechanical losses, effectively resolving the contradiction between reduced cycle time and maintained deceleration capacity
Solution Approach 2:
The patent converts the harmful mechanical losses that normally occur during deceleration into beneficial regenerative energy. By using a regenerative brake control mechanism, the system captures the energy that would otherwise be wasted as heat in the mechanical friction and electrical resistance, converting it into usable electrical energy that can be stored or reused. This transforms the deceleration process from an energy-wasting operation into an energy-recovering operation, allowing maximum deceleration capacity while reducing overall energy consumption and cycle time
Data Source
AI summary
A controller controlling a synchronized operation of spindle and feed axes. The controller is configured to make a spindle axis perform an accelerated rotation at maximum capacity from a starting position aiming at a maximum rotation speed; detect a maximum acceleration of the spindle axis; detect a residual rotation amount of the spindle axis; detect a current speed of the spindle axis; and execute a position control for making the spindle axis perform a decelerated rotation so as to reach a target position, after the accelerated rotation at maximum capacity. The controller is further configured to make the spindle axis perform the decelerated rotation at a positioning deceleration higher than a deceleration corresponding to the maximum acceleration and equal to or lower than a maximum deceleration capable of compensating for a mechanical loss in a drive source during the decelerated rotation of the spindle axis.