Tool Changer Speed Control for Follow-up Delay Prevention
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Solution Overview
Problem
Conventional tool changers of the servo motor driving type experience follow-up delay due to increased frictional resistance in gears when lubricant viscosity decreases, leading to unintended movement and interference with other structures during tool changes.
Innovation Solution
A tool changer with a controller that adjusts the rotational speed of the tool change arms based on calculated differences between command and output values from encoders, reducing speed when increased load is detected to prevent follow-up delay and maintain processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotational speed of the tool change arms is increased to improve productivity, then the tool change time is reduced, but follow-up delay occurs due to increased frictional resistance in gears when lubricant viscosity decreases
Solution Approach 1:
The patent applies dynamics by making the rotational speed of the tool change arms variable rather than constant. The control unit dynamically adjusts the rotational speed based on real-time detection of follow-up delay between the tool change arms and spindle. When follow-up delay is detected, the system reduces rotational speed to prevent interference, and when no delay is detected, it maintains higher speed for productivity. This dynamic speed adjustment resolves the contradiction between maintaining high productivity and preventing positioning errors.
Solution Approach 2:
The patent implements feedback control by using encoders to detect the positional relationship between the tool change arms and spindle, then feeding this information back to the control unit. The control unit calculates follow-up delay based on encoder signals and uses this feedback to adjust the rotational speed command. This closed-loop feedback mechanism ensures that the system can maintain high speeds when safe while automatically reducing speeds when follow-up delay occurs, thus resolving the contradiction between speed and reliability.
2Loss of time
If the rotational speed is maintained at high levels to shorten tool change time, then productivity improves, but the tool change arms may move to unintended positions and interfere with other structures
Solution Approach 1:
The patent applies preliminary anti-action by proactively detecting follow-up delay before actual interference occurs. The control unit continuously monitors the positional relationship between tool change arms and spindle using encoders, and when follow-up delay is detected (indicating potential interference), it preemptively reduces rotational speed. This preliminary detection and counteraction prevents the harmful effect of interference before it can occur, while allowing high-speed operation during safe conditions.
Solution Approach 2:
The system uses real-time feedback from encoders to detect the angular position of tool change arms relative to the spindle. When the feedback indicates that the tool change arms are approaching a position that could cause interference, the control unit automatically adjusts the rotational speed command to prevent reaching that position. This feedback-based control allows the system to maintain high speeds during safe operations while automatically preventing harmful interference.
Data Source
AI summary
A tool changer includes a holding member having a tool change arm disposed thereon, a rotation mechanism rotating the holding member at a first rotation speed in normal and reverse directions, a forward/backward movement mechanism moving the holding member forward and backward at a first forward/backward movement speed, and a controller comparing a first difference as a difference between a command value for the rotation and an output value of an encoder with a first threshold. When the first difference is equal to or greater than the first threshold, a rotational speed of the holding member is chained to a second rotation speed slower than the first rotation speed. Alternatively, when the first difference is less than the first threshold, the rotational speed of the holding member is maintained at the first rotation speed.