Magnetic Chuck Workrests for Low-Distortion Annular Grinding

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Solution Overview

Problem

Thin annular workpieces are prone to radial deformation during grinding due to their lack of stiffness across their diameter, making it challenging to secure them without causing distortion, especially when using existing workholding methods like scroll chucks or magnetic faceplates.

Innovation Solution

A workpiece holding assembly for a grinding machine that includes a magnetic chuck, a chuck drive for rotating the chuck, and separate sets of workrests configurable to engage with the outer and inner circumferential surfaces of the workpiece, allowing for precise and robust restraint during grinding without reconfiguring the machine.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If magnetic faceplates or chucks are used to hold the workpiece, then the workpiece can be securely held during grinding, but the magnetic force may cause radial deformation of the thin annular workpiece

Engineering Contradiction:

Improveworkpiece holding securityVSAvoidworkpiece radial deformation

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The workholding system is segmented into multiple independent workrests (first and second sets) that can be selectively engaged. Each workrest provides localized support at specific positions around the workpiece circumference, distributing the holding force and preventing concentrated radial deformation while maintaining secure workpiece positioning during grinding operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Workrests serve as intermediary elements between the magnetic chuck and the workpiece. These workrests provide mechanical support and contact points that distribute the magnetic holding force, preventing direct transmission of concentrated magnetic pressure to the thin annular workpiece that would cause radial deformation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If cutting forces are limited to avoid workpiece break free, then workpiece distortion is minimized, but machining cycle time increases

Engineering Contradiction:

Improveworkpiece distortionVSAvoidmachining cycle time

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The workrests are positioned and configured in advance to provide preliminary support and restraint against grinding forces before the actual grinding operation begins. This preliminary positioning prevents workpiece movement and distortion during machining, allowing higher cutting forces to be applied without risking workpiece break-free or excessive deformation.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The workholding system is designed to be dynamically adaptive, with workrests that can be selectively engaged or disengaged based on the specific grinding operation. This dynamic configuration allows the system to provide maximum restraint when needed while maintaining flexibility for different machining scenarios, optimizing both precision and productivity.

Inventive Principle:

Principle #15Dynamics

3Manufacturing precision

If the workpiece is reconfigured or removed between grinding outer and inner circumferential surfaces, then machining accuracy can be maintained, but time is lost

Engineering Contradiction:

Improvemachining accuracyVSAvoidcycle time between grinds

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The workholding assembly is designed with universal multi-functionality, where the same magnetic chuck and workrest configuration can accommodate and support the workpiece for both outer and inner circumferential surface grinding operations. The workrests are positioned to provide appropriate support for different grinding scenarios, eliminating the need to reconfigure or remove the workpiece between operations.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The workpiece remains continuously held and supported throughout the entire machining process, including during transitions between grinding outer and inner surfaces. The workrests maintain continuous engagement with the workpiece, providing uninterrupted support and positioning, which eliminates idle time for workpiece removal and reconfiguration while maintaining machining accuracy.

Inventive Principle:

Principle #20Continuity of useful action

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 assembly enables precise and robust restraint of the workpiece during grinding, minimizing distortion and cycle time, and allowing for the use of super-abrasive grinding wheels on both outer and inner surfaces, even under high grinding forces.

Implementation Method 1

a magnetic chuck for holding a workpiece

Methodology Applied

Scientific EffectMagnetic force: Magnetism

Data Source

PatentUS12318887B2Workpiece holding assembly for a grinding machine and grinding methods

Publication Date: 2025.06.03 FIVES LANDIS

AI summary

A workpiece holding assembly comprises a magnetic chuck, and first and second separate sets of workrests for engaging with the outer circumferential surface of an annular workpiece. The workrests are configurable such that when the outer circumferential surface of the workpiece is ground with the chuck rotating in one direction, the outer circumferential surface is only urged in contact with the first set of workrests, and when an inner circumferential surface of said workpiece is ground with the direction of rotation of the chuck reversed, the outer circumferential surface is only urged in contact with the second set of workrests. Grinding methods using such a workpiece holding assembly are also described.