Screwdriving Torque-Based Speed Changeover for Shorter Cycle Time
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Solution Overview
Problem
Conventional screwdriving tools face challenges in achieving short cycle times while maintaining the required torque for screw tightening, as rapid deceleration of motor drives often results in excessive torque overshoot or prolonged cycle times due to the inability to quickly stop high rotational speeds.
Innovation Solution
The method involves driving a screw at a rapid speed, detecting torque, and transitioning to a creep speed before head contact, utilizing the torque curve to determine the changeover time, ensuring the screw is driven at a lower rotational speed until the desired tightening torque is achieved, with a torque detection device and controller managing the motor drive to optimize the screwdriving cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotational speed for screwing in the screw is reduced to avoid torque overshoot, then the tightening torque can be maintained, but the cycle times are lengthened in an undesirable manner
Solution Approach 1:
The system performs preliminary detection of the torque curve during the rapid speed phase to identify the triggering torque threshold before head contact occurs. This advance detection allows the control system to prepare for the speed transition, enabling seamless switching from rapid to creep speed without interrupting the overall tightening process timing.
Solution Approach 2:
The invention implements dynamic speed adjustment by transitioning from a fixed rapid speed to a variable creep speed based on real-time torque detection. The motor drive dynamically modifies its operational parameters during the screwdriving process, adapting the rotational speed according to the detected torque curve characteristics and the determined changeover time.
2Productivity
If faster-running motor drives are used to reduce cycle times, then productivity increases, but the motor drives cannot be stopped quickly enough to avoid torque overshoot
Solution Approach 1:
The system continuously monitors the torque curve during the rapid speed phase and uses this feedback to determine the optimal changeover time. The torque detection device provides real-time information about the screwdriving process, allowing the control system to identify when to transition from rapid to creep speed based on the actual torque characteristics rather than relying on pre-programmed timing.
Solution Approach 2:
The invention replaces the conventional mechanical approach of simply reducing motor speed with a sophisticated control system that uses torque detection and dynamic speed adjustment. Instead of relying on mechanical braking or simple speed reduction, the system uses electronic control to modulate the motor drive based on real-time torque feedback, substituting mechanical simplicity with electronic intelligence.
3Measurement precision
If sensor-based detection of head contact time is used to stop rotational motion, then the tightening process can be controlled, but the abrupt deceleration from high rotational speeds causes excessively high torques
Solution Approach 1:
The system performs preliminary detection of the torque curve during the rapid speed phase to identify the triggering torque threshold before head contact occurs. This advance detection allows the control system to prepare for the speed transition, enabling seamless switching from rapid to creep speed without interrupting the overall tightening process timing.
Solution Approach 2:
The invention changes the operational parameters of the motor drive by transitioning from a high rotational speed regime to a low rotational speed regime. This parameter change is timed based on the detected torque curve, allowing the system to maintain precise torque control during the critical head contact phase while minimizing torque overshoot.
Data Source
AI summary
A method for producing a screw connection having a screw that is set in rotational motion with a screwdriving head of a screwdriving tool. The screwdriving head has a motor drive for creating the rotational motion of a screw receptacle of the screwdriving head. The screw is driven into at least one mating part of the screw connection in a rapid speed. A torque is detected with which the screw is driven. The rapid speed with a higher rotational speed is changed to a creep speed with a lower rotational speed at a changeover time. The changeover time is determined as a function of the detected torque during screwdriving at rapid speed. The screw is further driven at the creep speed until a head contact time when a head of the screw makes contact on the mating part.