Workpiece Shear Cutting With Two-Stage Prebending
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Solution Overview
Problem
Cutting high-strength and brittle materials is challenging due to increased tool loading and wear, leading to poor cut edge quality and rapid tool degradation, as existing methods fail to effectively manage stress and reduce burr and rollover in shear cutting processes.
Innovation Solution
A method involving prebending the workpiece counter to the cutting direction with a stress maximum near the contact surface of the second cutting means, followed by a second prebending in the cutting direction, specifically at the contact surfaces of both cutting means near the cutting location, to distribute stress uniformly and reduce tool loading, using cutting edges with obtuse angles and S-shaped contact surfaces to minimize stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If shear cutting is used on high-strength materials, then cutting speed and productivity are maintained, but tool loading and wear increase significantly
Solution Approach 1:
The workpiece is prebent before cutting to create tensile stresses that facilitate the cutting process. This preliminary action reduces the cutting forces required and decreases tool loading, thereby extending tool service life while maintaining cutting speed
Solution Approach 2:
The method changes the stress state parameter of the workpiece by introducing bending stresses through prebending. This parameter change from unstressed to pre-stressed condition reduces the resistance to cutting, lowering tool wear and extending reliability
2Force
If conventional cutting methods are used on high-strength materials, then cutting forces are high, but this leads to increased tool wear and fatigue
Solution Approach 1:
Prebending the workpiece before cutting creates favorable stress conditions that reduce the actual cutting forces. This preliminary stress introduction makes the material more susceptible to cutting, thereby reducing tool loading and improving durability
Solution Approach 2:
The high strength and brittleness of the material, which normally cause high cutting forces and tool wear, are converted into benefits through prebending. The tensile stresses created by prebending exploit the material's characteristics to facilitate cleaner cutting with reduced forces
3Device complexity
If cutting is performed without prebending, then the process is simple, but stress concentrations occur at the cutting edge leading to poor cut quality
Solution Approach 1:
The prebending step introduces favorable stress distributions before cutting, preventing stress concentrations at the cutting edge. This preliminary action ensures more uniform stress distribution throughout the cutting process, resulting in better cut edge quality
Solution Approach 2:
The cutting process is segmented into two distinct phases: prebending and cutting. This segmentation allows each phase to be optimized independently, with prebending preparing the stress state and cutting executing the separation, thereby improving overall precision
4Force
If small cutting gaps are used to reduce cutting forces, then transverse forces cause gap widening leading to greater rollover and burr
Solution Approach 1:
Prebending creates tensile stresses that reduce the required cutting forces, allowing small cutting gaps to be used without experiencing gap widening. The preliminary stress preparation prevents the transverse forces from causing rollover and burr formation
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 reduces von Mises stresses at cutting edges by up to 40%, minimizes burr formation, and significantly prolongs tool service life by reducing wear and maintaining high cut edge quality, making it suitable for high-strength materials and potentially soft and tough materials with appropriate parameter modifications.
Implementation Method 1
a first prebend is introduced into the workpiece (3) counter to the cutting direction with in particular its stress maximum being situated substantially in the region of the contact surface of the second cutting means (21) at a defined distance from the cutting location
Implementation Method 2
These ensure that the contact with the upper blade cutting edge occurs only when the bending stresses in the metal sheet have already reached very high values. This relieves the load on the cutting edge of the upper blade and earlier crack initiation occurs in the cut region
Implementation Method 3
a second prebend in the cutting direction, in particular for the cutting operation, which is situated in particular both in the region of the contact surface of the second cutting means (21) and the contact surface of the first cutting means (11) in the immediate vicinity of the cutting location
Implementation Method 4
By means of the two prebends, there occurs a reduction or even a suppression of the von Mises stresses at the cutting edges of the cutting device
Implementation Method 5
using cutting edges with obtuse angles and S-shaped contact surfaces to minimize stress concentrations
Implementation Method 6
significantly prolongs tool service life by reducing wear and maintaining high cut edge quality
Data Source
AI summary
The invention relates inter alia to a method for cutting a workpiece, in particular a blank or a component, comprising the following steps: inserting the workpiece into a cutting device, wherein the cutting device comprises a first tool half having at least one workpiece holder and at least one first cutting means, which comprises a first cutting edge and a contact surface, and a second tool half having at least one second cutting means having a second cutting edge and a contact surface, clamping the workpiece by means of the workpiece holder and the contact surface of the second cutting means, cutting the workpiece by means of the cutting means, the workpiece undergoes, prior to cutting, both a first prebending, which is produced substantially in the opposite direction counter to the cutting direction, and thereafter a second prebending in the cutting direction.