Press Machine Screw Shaft Co-Rotation Prevention
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Solution Overview
Problem
The existing press machine designs face challenges in preventing co-rotation of the screw shaft and stabilizing the bottom dead center position of the upper tool, particularly when the workpiece is bent using the self-weight of the ram, leading to variations in the bottom dead center position and difficulties in bending the workpiece as scheduled.
Innovation Solution
A press machine with a drive mechanism that includes a screw shaft or nut connected to a movable member, which can be rotated by a drive unit to contact or retract from the end of the screw shaft or nut, eliminating the gap between the screw shaft and ram, and utilizing inclined surfaces for enhanced friction to prevent co-rotation, along with a piezoelectric element for precise movement control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a co-rotation prevention mechanism is used to prevent the screw shaft from rotating during bending, then the co-rotation is prevented, but a gap forms between the screw shaft and ram, causing the bottom dead center position to vary
Solution Approach 1:
A movable member is introduced as an intermediary element between the screw shaft and the ram. This movable member can contact the end of the screw shaft to prevent co-rotation while allowing the screw shaft to rotate freely during approach and return operations. The movable member acts as a mediator that enables co-rotation prevention only when needed, without creating a permanent gap that would affect positioning precision.
Solution Approach 2:
The movable member is designed to dynamically change its state between contacting and non-contacting the screw shaft. During bending operations, it contacts the screw shaft to prevent co-rotation. During approach and return, it retracts to allow free rotation. This dynamic behavior resolves the contradiction by adapting the co-rotation prevention mechanism to the specific operational phase.
2Manufacturing precision
If the ram is lifted to cause contact with the screw shaft to eliminate the gap, then the bottom dead center position is stabilized, but a high-output hydraulic mechanism is required, making downsizing difficult
Solution Approach 1:
The movable member is designed to automatically contact or retract from the screw shaft based on the operational phase without requiring external hydraulic intervention. The system uses the existing mechanical structure and forces already present in the press machine to achieve the contact/retract cycle, making the system self-sufficient and eliminating the need for additional high-output hydraulic mechanisms.
Solution Approach 2:
The unnecessary high-output hydraulic mechanism is extracted from the system. Instead of using a complex hydraulic system to lift the ram for contact, the invention uses a simpler movable member that can be actuated by the existing machine structure and operational forces, thereby simplifying the overall system while achieving the same positioning stability.
3Reliability
If the co-rotation prevention mechanism causes contact between the screw shaft end and ram, then co-rotation is prevented, but when the workpiece is bent by self-weight of the ram, the gap remains and co-rotation cannot be prevented
Solution Approach 1:
The movable member dynamically adapts its contact state based on the bending operation type. When the workpiece is bent by the self-weight of the ram, the movable member remains retracted to allow free rotation. When active pressing is required, the movable member contacts the screw shaft to prevent co-rotation. This dynamic adaptability resolves the contradiction between co-rotation prevention and operational flexibility.
Solution Approach 2:
The system incorporates feedback control where the controller detects the bending operation type and adjusts the movable member's position accordingly. This feedback mechanism ensures that the movable member contacts the screw shaft only when co-rotation prevention is needed, while allowing free rotation during self-weight bending operations, thus maintaining both reliability and versatility.
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 solution effectively prevents co-rotation of the screw shaft, stabilizes the bottom dead center position of the upper tool, and ensures reliable machining of the workpiece, even when the load required is close to the self-weight of the ram, thereby reducing defective products and improving production efficiency.
Implementation Method 1
a piezoelectric element for precise movement control
Implementation Method 2
utilizing inclined surfaces for enhanced friction to prevent co-rotation
Data Source
AI summary
A press machine includes a drive mechanism that moves at least one of an upper tool and a lower tool and machines a workpiece placed between the upper and lower tools. The drive mechanism includes a first drive source that rotates a screw shaft serving as an advance-retract component and a second drive source that rotates a nut connected to the screw shaft. A structure including the upper tool and lower tools includes a casing supporting the screw shaft such that the screw shaft is rotatable, a movable member that is movably formed in the casing and can contact an end of the screw shaft or retract therefrom, and a drive unit that moves the movable member.