Spindle Drive Pressing Force Control via Dynamic Speed Phasing
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Solution Overview
Problem
Existing methods for pressing workpieces with a predetermined force face challenges in achieving high process speed while maintaining accuracy, due to dynamic effects caused by inertia in the drive train components.
Innovation Solution
A method using an electric motor coupled to a forming tool via a screw drive, where the motor is accelerated to maximum speed, then reduced to detect and control the pressing force precisely, with additional measures to account for inertia and vibrations, including model calculations and disturbance observers for improved control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pressing speed is reduced to prevent dynamic effects, then the manufacturing precision is improved, but the productivity deteriorates
Solution Approach 1:
The patent applies dynamics by using a multi-phase speed profile that changes the motor speed dynamically during the pressing process. The motor operates at different speeds in different phases: high speed for approach, reduced speed for contact detection, and controlled speed for actual pressing. This dynamic speed adjustment allows the system to maintain high productivity while ensuring precise pressing force control when needed.
Solution Approach 2:
The patent implements feedback by continuously monitoring the motor current and detecting torque changes. When the forming tool contacts the workpiece, the torque increases, which is detected by the control system. This feedback mechanism allows the system to automatically adjust the speed and apply the predetermined pressing force accurately, achieving both high speed and precision.
2Productivity
If the pressing speed is increased to improve productivity, then the manufacturing precision deteriorates due to dynamic effects
Solution Approach 1:
The system uses dynamic speed adjustment with distinct phases: an acceleration phase at high speed for rapid approach, a transition phase where speed is reduced upon contact detection, and a control phase where the predetermined pressing force is applied. This dynamic approach allows high productivity during the approach phase while ensuring precision during the pressing phase.
Solution Approach 2:
The patent applies preliminary action by detecting the contact between the forming tool and workpiece before the actual pressing begins. The torque increase is detected in advance, allowing the control system to prepare and switch to the predetermined pressing force mode, ensuring both high speed approach and accurate force application.
3Manufacturing precision
If the motor is braked to minimum speed to prevent overreaching, then the manufacturing precision is improved, but the loss of time increases due to vibrations
Solution Approach 1:
The patent applies partial action by braking the motor to a minimum speed rather than complete stop. This partial braking is sufficient to prevent overreaching and maintain pressing force control while minimizing the time loss associated with vibrations. The system operates at this minimum speed just long enough to subside vibrations, then can proceed efficiently.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for increased process speed while maintaining precise control of the pressing force, reducing the risk of overreaching and ensuring accurate achievement of the predetermined pressing force.
Implementation Method 1
A screw drive converts the rotational movement of a drive shaft of the electric motor into a translatory movement of the forming tool
Implementation Method 2
a measuring unit connected downstream of the electric motor detects an increase in pressing force which exceeds a predetermined threshold value
Implementation Method 3
A forming tool which is coupled to an electric motor via a screw drive
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a method for pressing a workpiece (4) with a predetermined pressing force using a forming tool (3) connected via a spindle drive (6) to an electric motor (2), wherein the spindle drive (6) converts the rotational movement of a drive shaft (8) of the electric motor (2) into a translatory movement of the forming tool (3). The method comprises the following method steps: - accelerating the electric motor (2) in the screwing direction to a predetermined maximum rotational speed; - operating the electric motor (2) at maximum rotational speed until the drive shaft (8) of the electric motor (2) has completed a predetermined number of rotations; - reducing the rotational speed of the electric motor (2) to a predetermined reduced rotational speed; - operating the electric motor (2) at a reduced rotational speed until a pressing force increase exceeding a predetermined threshold value is detected by a measuring unit (12) downstream of the electric motor (2); - forming the workpiece (4) while continuously detecting the pressing force by means of the measuring unit (12) until the predetermined pressing force is reached.