Centring Grinding Actuator Current Control
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Solution Overview
Problem
Existing grinding technologies face challenges in efficiently grinding workpieces without overloading the grinding tool or causing shape defects, particularly when dealing with non-round geometries, due to issues with feed rate control and the use of mechanical solutions like cam disks and springs, which lead to inefficiencies and potential quality defects.
Innovation Solution
A method that uses an actuator with a current regulator to control the feed force by comparing the desired and actual directions of movement, reducing the actuator current when deviations occur, thereby optimizing the feed force and preventing overloading, and employing a PI or PID transmission element to adjust parameters for different geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high feed rate is used to increase productivity, then the grinding process becomes faster and more efficient, but the grinding tool may be overloaded and the workpiece may burn or develop shape defects
Solution Approach 1:
The patent implements a control method that continuously monitors the actual direction of movement of the feed movement and compares it with the desired direction. When a deviation is detected (indicating potential tool overload or workpiece resistance), the system automatically reduces the actuator current limit, thereby reducing the feed force. This closed-loop feedback mechanism allows high feed rates to be maintained while preventing tool overload and workpiece damage by dynamically adjusting the feed force based on real-time conditions.
2Force
If spring preload is used to adjust grinding force, then the grinding force can be controlled, but the spring preload increases when grinding non-round geometries causing corner depressions
Solution Approach 1:
The patent replaces the mechanical spring-based force adjustment system with an electronically controlled actuator system. Instead of using springs that passively apply force and cannot be dynamically adjusted, the system uses an actuator with electronic current control. The control method monitors the actual vs. desired feed movement direction and dynamically adjusts the actuator current limit, thereby precisely controlling the feed force. This electronic control system eliminates the corner depression problem because it can reduce feed force on demand without the cumulative preload effect of springs.
3Reliability
If safety distances are programmed to prevent tool overload, then the grinding tool is protected from overloading, but the processing time increases due to reduced feed rates
Solution Approach 1:
The patent replaces passive safety distances with an active feedback control system. Instead of pre-programming conservative feed rates and safety distances that slow down the entire process, the system continuously monitors the actual feed movement direction and compares it with the desired direction. When the workpiece or tool shows resistance (indicated by direction deviation), the system automatically reduces the actuator current limit to prevent overload. When no resistance is detected, the system maintains high feed rates. This dynamic adjustment eliminates the need for conservative safety margins while maintaining tool protection.
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 faster and more efficient grinding processes with reduced risk of overloading and shape defects, eliminating the need for safety distances and improving workpiece quality by dynamically adjusting the feed force based on real-time conditions.
Implementation Method 1
using an actuator (34) to generate a relative feed movement (V) between the grinding tool (G) and the workpiece (L)
Implementation Method 2
the actuator (34) being integrated in a position control circuit (40) with a current controller (48) for an actuator current (I) which determines a feed force (FV) of the actuator (34)
Implementation Method 3
The edge of the lens is then machined in a defined relationship to the optical axis of the lens... this is done by means of a grinding process
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates in particular to a method for centring grinding of workpieces such as optical lenses by means of a grinding tool using an actuator (34) for generating a relative advancing movement between the grinding tool and the workpiece, wherein the actuator is integrated in a current regulator (48) for an actuator current which determines an advancing force of the actuator in a position control loop (40) which is run through using a predetermined control cycle. In the method, for each control cycle: (i) a desired direction of movement (Rsoll(n)) of the advancing movement and an actual direction of movement (Rist(n)) of the advancing movement are ascertained; then (ii) the ascertained actual and desired directions of movement are compared to one another; and finally, (iii) when the comparison results in a deviation between the actual and desired directions of movement, a predetermined current limit (ISollmax) for the actuator current emitted via the current regulator is decreased in a defined manner in order to reduce the advancing force of the actuator. As a result the advancing movement and material machining can be carried out quickly and efficiently without overstressing the tool or workpiece.