Milling Path Phase Synchronization for Uniform Surface Finish

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Solution Overview

Problem

Milling processes often result in irregular surface structures due to asynchronous spindle position and feed rate, leading to uneven surface quality and potential defects in products like injection molding.

Innovation Solution

Control the speed and phase position of the spindle along the machining path by varying spindle speed and feed rate, ensuring synchronized phase positions across adjacent paths, which can be achieved through precise control of a position-controlled electric motor and angular position determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If constant spindle speed is used during milling, then the machining process is simple to control, but the surface quality becomes uneven due to asynchronous spindle position and feed rate

Engineering Contradiction:
Improvecontrol simplicityVSAvoidsurface quality
Core Design Contradiction:
Ease of operationVSManufacturing precision

Solution Approach 1:

The patent applies dynamics by transitioning from constant spindle speed to variable spindle speed that is synchronized with the feed rate. The spindle speed is dynamically adjusted along the machining path to maintain a constant relationship between spindle rotation and tool engagement position, thereby achieving uniform surface quality while keeping the control system manageable through coordinated motion control.

Inventive Principle:
Principle #15Dynamics

2Measurement precision

If feed rate is varied during machining, then positioning accuracy is improved, but the spindle position and path feed become asynchronous, causing random phase positions

Engineering Contradiction:
Improvepositioning accuracyVSAvoidphase position synchronization
Core Design Contradiction:
Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the spindle speed parameter in response to feed rate variations. When the feed rate changes during machining, the spindle speed is proportionally adjusted to maintain the synchronization between spindle rotation and tool engagement position. This ensures that phase positions remain consistent across adjacent milling paths while allowing flexible feed rate control for precise positioning.

Inventive Principle:
Principle #35Parameter changes

3Manufacturing precision

If spindle speed is controlled to maintain phase position, then surface uniformity is improved, but the control system complexity increases

Engineering Contradiction:
Improvesurface uniformityVSAvoidcontrol system complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies feedback by continuously monitoring the relationship between spindle speed and feed rate, and automatically adjusting the spindle speed to maintain constant phase positioning. The control system uses the programmed feed rate as feedback to dynamically calculate and adjust the required spindle speed, ensuring uniform surface quality without requiring overly complex control architecture.

Inventive Principle:
Principle #23Feedback

Data Source

PatentEP3821307B1Milling method
Publication Date: 2023.08.30 EXERON
  • EP3821307B1 patent drawingFigure 1~2
  • EP3821307B1 patent drawingFigure 3~4
  • EP3821307B1 patent drawingFigure 5~6

AI summary

The invention relates to a method for machining a workpiece by means of a milling tool arranged on a rotatable spindle, the spindle being moved relative to the workpiece or the workpiece being moved relative to the spindle along a machining path and, at the same time, the spindle rotating about a spindle axis. In said method, an improvement in the surface quality is achieved by controlling the rotational speed and/or the phase position of the rotation of the spindle along the machining path, the machining path comprising linear parallel tracks and the phase position of the spindle along the machining path being substantially the same on adjacent tracks, the phase position being controlled by varying the rotational speed of the spindle and/or the advancing speed of the spindle relative to the workpiece along the machining path.