Main Spindle Feed Control for Brittle Material Machining
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Solution Overview
Problem
Machine tools struggle with achieving high surface quality and process reliability when machining brittle or inhomogeneous materials like glass, ceramics, and fiber-reinforced plastics due to excessive cutting forces, leading to cracks, chipping, and tool damage, especially when working with inclined surfaces.
Innovation Solution
A machine tool equipped with a main spindle that uses a screw-and-nut gearing system, combined with an electromagnetic feed device, to control and limit axial and tangential forces, allowing for automatic withdrawal of the tool when resistance is met, thereby preventing damage and improving machining quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional machine tools with direct drive systems are used, then high cutting forces can be applied to improve productivity, but cracks and chipping occur in brittle materials reducing manufacturing precision
Solution Approach 1:
The patent applies dynamics by making the feed force controllable and adaptable during machining. The electromagnetic feed device allows the feed force to be dynamically adjusted based on machining conditions, enabling high productivity when materials are easy to machine and low feed force when machining brittle or inhomogeneous materials to prevent damage while maintaining acceptable productivity
Solution Approach 2:
The patent changes the parameter of feed force from a constant high value to a variable parameter that can be adjusted in real-time. By monitoring cutting forces and adapting the feed force accordingly, the system maintains high productivity during normal machining while preventing cracks and chipping in difficult materials through parameter adaptation
2Productivity
If high feed forces are applied to maintain productivity, then machining efficiency improves, but tool damage and workpiece cracks increase reducing reliability
Solution Approach 1:
The patent implements feedback by monitoring cutting forces during machining and using this information to adjust the feed force. The sensor system detects changes in cutting conditions and feeds this information back to the control system, which then adapts the feed force to maintain productivity while preventing tool damage and workpiece cracks, thereby improving process reliability
Solution Approach 2:
The system transitions from static high feed force to dynamic adaptive feed force control. The electromagnetic feed device enables real-time adjustment of feed force based on actual machining conditions, maintaining high productivity when possible while automatically reducing force to prevent damage, thus improving reliability without sacrificing overall efficiency
3Productivity
If the tool enters the workpiece at high speed to improve productivity, then machining throughput increases, but breakage of sensitive workpieces occurs reducing manufacturing precision
Solution Approach 1:
The patent applies preliminary action by reducing the feed force specifically at the entry zone before the tool fully engages the workpiece. The control system detects the entry phase and automatically reduces feed force to prevent breakage of sensitive workpieces, then can increase feed force again once the tool is properly engaged, thus maintaining high throughput while ensuring precision at the critical entry zone
4Reliability
If sensor-based control systems are used to monitor cutting forces, then workpiece damage can be detected, but the inertia of controls causes delayed response leading to damage occurrence
Solution Approach 1:
The patent replaces the mechanical sensor-based control system with an electromagnetic feed device that can be controlled more rapidly. The electromagnetic actuation allows for faster response times compared to mechanical systems, reducing the delay between detecting excessive cutting forces and responding by adjusting feed force, thus minimizing the time loss while maintaining damage detection capability
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 enables excellent machining results, including drilling fine holes in thin inclined glass plates without chipping or fractures, by instantly adjusting the tool's direction to avoid excessive resistance, thus enhancing the machining process for difficult materials.
Implementation Method 1
a preferably electromagnetic feed device configured to exert on the main spindle a force acting along the axis of rotation
Data Source
AI summary
A machine tool (10) for machining workpieces (18) has a main spindle (12) which carries a tool holder (14) at its end and is mounted in such a way that it can rotate about an axis of rotation (22) and can move along the axis of rotation (22). A preferably electromagnetic feed device (32) is also provided, which exerts a force (FZ) acting along the axis of rotation s on the main spindle (12). A screw gear (52), which connects a drive (20) for driving the main spindle to the main spindle (12), drives the main spindle (12) in rotation and simultaneously moves it along the axis of rotation (22). The screw-and-nut gearing (52) has a thread (64, 66a, 66b) formed on a first component (54) and a cam (70a, 70b) formed on a second component (12) that cooperates with the thread (64, 66a, 66b). One of the two components (54) is rotated by the drive (20) via a drive gear (57) and is immovably mounted along the axis of rotation (22). The other of the two components is the main spindle (12).