Eccentric Clamping Device for Tool Positioning Accuracy

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Solution Overview

Problem

Existing tool units face challenges in achieving simple, reliable, and repeatable tool positioning with high accuracy during clamping, particularly in spindle-based systems, which affects the efficiency and precision of operations like drilling and milling.

Innovation Solution

A tool unit design incorporating an eccentric clamping device with a spindle mounted in a housing, featuring an eccentric shaft actuated by a special assembly that includes a segment collet and an actuation element, allowing for precise control of the clamping bolt through a toggle mechanism, enhancing repeatability and handling ease.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If an eccentric clamping device is used to clamp tools in a spindle, then the clamping force and repeatability of tool positioning are improved, but the complexity of the clamping mechanism increases

Engineering Contradiction:
Improvetool positioning accuracyVSAvoidclamping mechanism complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The actuating element is received within a retaining element that is integrated into the housing structure. The eccentric shaft is nested within the spindle assembly, and the segment collet is positioned within the tool holder. This nested arrangement reduces overall complexity by eliminating separate mounting structures and reducing the number of external components.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The eccentric clamping device is designed to be self-actuating through the eccentric shaft mechanism. When the actuating element is moved, it automatically engages the eccentric shaft which then self-generates the clamping force through its eccentric geometry, eliminating the need for additional actuators or complex control mechanisms.

Inventive Principle:
Principle #25Self-service

2Reliability

If a segment collet is used with the eccentric clamping device, then the repeatability of tool clamping is improved, but the device complexity increases

Engineering Contradiction:
Improveclamping repeatabilityVSAvoidclamping device complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The collet is divided into multiple segments that can independently move radially. Each segment is equipped with clamping lobes that engage the tool shank. This segmentation allows the collet to progressively close around the tool with high repeatability while maintaining a relatively simple overall structure, as each segment operates independently rather than requiring a complex multi-component system.

Inventive Principle:
Principle #1Segmentation

3Ease of operation

If the actuating element is received in a retaining element integrated in the housing, then the handling ease is improved, but the housing structure complexity increases

Engineering Contradiction:
Improveactuation easeVSAvoidhousing structure complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The retaining element is merged with the housing structure, forming an integrated assembly. The actuating element is received directly in the retaining element which is part of the housing, eliminating the need for separate mounting brackets or external retention structures. This merging simplifies the overall housing structure while maintaining ease of operation.

Inventive Principle:
Principle #5Merging (Combining)

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 provides a tool unit with improved repeatability and accuracy in tool positioning, ensuring reliable clamping and efficient operation by leveraging the eccentric clamping mechanism to enhance the clamping force and precision of tool engagement.

Implementation Method 1

The eccentric shaft (151) can be actuated by means of an actuating element (51) of an actuating assembly (40) mounted in the housing (10). The eccentric shaft (151) has a pivot axis (75) and an eccentric section (161) with at least one active eccentric center (163).

Methodology Applied
Scientific EffectEccentric mechanism: Eccentric

Implementation Method 2

The eccentric clamping device has an eccentric shaft (151) mounted in the spindle (80), which can be actuated through the housing (10) to actuate the segment collet (120).

Methodology Applied
Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentEP2646188B2Tool assembly with eccentric clamping device
Publication Date: 2019.11.06 BENZ GMBH
  • EP2646188B2 patent drawingFigure 1~2
  • EP2646188B2 patent drawingFigure 3
  • EP2646188B2 patent drawingFigure 4~5

AI summary

The invention relates to a tool unit comprising at least one drivable spindle arranged in a housing, wherein the spindle has a tool holding fixture with an integrated eccentric clamping device and wherein the eccentric clamping device has an eccentric shaft which at least at one end bears an actuating adapter. For this purpose, an actuating assembly comprising a holding element, an actuating element and a restoring spring is arranged in the housing. The actuating element is movably mounted in the housing and/or in the holding element. The pivot axis of the eccentric shaft lies at least approximately in a plane in which the centre line of the actuating element also lies. The actuating element has an end-face structure that is located in the interior of the housing and suitable for coupling onto the actuating adapter. The present invention develops a tool unit which has a device for tool clamping that is distinguished by easy and reliable handling with a high repeat accuracy with respect to the tool positioning.