Workpiece Clamping Jig With Constant Force to Prevent Distortion

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Solution Overview

Problem

Conventional workpiece fixing jigs cause clamping distortion due to inaccurate positioning of workpiece surfaces and require complex torque wrench operations to maintain consistent clamping force, leading to compromised machining accuracy.

Innovation Solution

A workpiece fixing jig with a clamping mechanism featuring first and second clamping portions that move forward and backward in a direction orthogonal to the base's fixation, utilizing a biasing body like a disc spring to apply a constant clamping force without lifting the jig, ensuring accurate and distortion-free fixation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the workpiece is clamped by pressing against the upper surface of the spacer with the hook clamp, then the workpiece can be fixed on the table, but clamping distortion occurs when the lower surface of the workpiece is not finished with high degree of flatness

Engineering Contradiction:
Improveworkpiece fixation stabilityVSAvoidworkpiece flatness accuracy
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

A lower clamp portion is introduced as an intermediary element between the workpiece and the table. This lower clamp portion contacts the lower surface of the workpiece to provide support, while the upper clamp portion applies clamping force from above. This mediator structure distributes the clamping force and prevents distortion even when the workpiece bottom surface has poor flatness.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The clamping mechanism transitions from a single-point contact system to a distributed contact system by adding the lower clamp portion. The lower clamp portion has a clamping surface that distributes contact across multiple points on the workpiece bottom surface, converting a problematic single-point contact issue into a distributed support system that accommodates surface irregularities.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Reliability

If the clamp bolt is tightened to press the workpiece against the spacer surface, then the workpiece is clamped, but the operation becomes complex requiring special tools such as torque wrench for final tightening

Engineering Contradiction:
Improveclamping force consistencyVSAvoidtightening operation simplicity
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The lower clamp portion is designed to automatically contact and support the workpiece when the workpiece is placed on the table. The clamping force is applied through the lower clamp portion's clamping surface, which self-adjusts to the workpiece position and orientation, eliminating the need for complex torque-controlled tightening operations.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

Instead of applying clamping force from above through the upper clamp portion alone, the invention inverts the approach by having the lower clamp portion apply support and clamping force from below. This inversion allows the clamping mechanism to work with gravity and the natural placement of the workpiece, simplifying the operation.

Inventive Principle:
Principle #13The other way round (Inversion)

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

The solution effectively prevents clamping distortion and stabilizes the workpiece during machining by applying a consistent clamping force, improving machining accuracy and simplifying the clamping process.

Implementation Method 1

utilizing a biasing body like a disc spring to apply a constant clamping force

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP3034233B1Method for fixing a workpiece on a table of a machine tool
Publication Date: 2022.04.13 DMG MORI CO LTD
  • EP3034233B1 patent drawingFigure 1
  • EP3034233B1 patent drawingFigure 2
  • EP3034233B1 patent drawingFigure 3

AI summary

A workpiece fixing jig hardly causing clamping distortion and a workpiece fixing method using the workpiece fixing jig are provided. A workpiece fixing jig 1 includes a base 2 to be fixed on a table, and a clamping mechanism 10 provided on the base 2 for clamping a workpiece. The clamping mechanism 10 includes a first clamping portion 20 and a second clamping portion 30 provided to face each other. At least one of the first and second clamping portions 20 and 30 is configured to move forward and backward with respect to the other along a moving direction and the moving direction is set to a direction intersecting a direction in which the base 2 is fixed on the table. In using this workpiece fixing jig 1, the base 2 is fixed on the table after the workpiece is clamped between the first clamping portion 20 and the second clamping portion 30.