Forged Crankshaft Preforming for Volume Distribution

Solution Overview

Problem

Conventional methods for producing forged crankshafts face challenges in achieving a high material yield rate due to insufficient volume distribution in the preforming step, leading to deficiencies in counterweights and excessive flash formation during the die forging process.

Innovation Solution

A method involving multiple preforming steps to distribute the volume of the billet more effectively, including a first preforming step to reduce sectional areas of pin and journal portions, a second preforming step to increase thickness of web equivalent portions, and a final preforming step to shape the crankshaft, minimizing flash formation and improving material distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a conventional single preforming step is used, then the process is simple, but the volume distribution is insufficient leading to deficiencies in counterweights and excessive flash formation

Engineering Contradiction:

Improvevolume distributionVSAvoidpreforming process

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The preforming process is divided into multiple sequential steps (first preforming, second preforming, and final preforming) with each step having specific objectives. The first preforming reduces sectional areas of pin and journal portions, the second preforming increases thickness of web equivalent portions, and the final preforming shapes the crankshaft. This segmentation allows progressive volume distribution control to prevent deficiencies in counterweights and reduce flash formation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The multiple preforming steps perform preliminary shaping actions on the billet before the final die forging. By pre-distributing volume and pre-shaping the workpiece to closely match the final crankshaft geometry, the subsequent die forging requires minimal material redistribution, thereby reducing flash formation and improving material yield rate.

Inventive Principle:

Principle #10Preliminary action

2Loss of substance

If insufficient volume distribution is performed in preforming, then the preforming step is simple, but flash formation increases during die forging

Engineering Contradiction:

Improvematerial yield rateVSAvoidpreforming complexity

Core Design Contradiction:

Loss of substanceVSEase of manufacture

Solution Approach 1:

The preforming process is divided into multiple sequential steps (first preforming, second preforming, and final preforming) with each step having specific objectives. The first preforming reduces sectional areas of pin and journal portions, the second preforming increases thickness of web equivalent portions, and the final preforming shapes the crankshaft. This segmentation allows progressive volume distribution control to prevent deficiencies in counterweights and reduce flash formation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The multiple preforming steps perform preliminary shaping actions on the billet before the final die forging. By pre-distributing volume and pre-shaping the workpiece to closely match the final crankshaft geometry, the subsequent die forging requires minimal material redistribution, thereby reducing flash formation and improving material yield rate.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If conventional preforming is used, then the process is straightforward, but deficiencies occur in counterweight portions

Engineering Contradiction:

Improvecounterweight qualityVSAvoidpreforming steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The preforming steps apply different localized actions to different regions of the billet. The first preforming specifically reduces sectional areas of pin and journal portions while preserving web areas. The second preforming specifically increases thickness of web equivalent portions. This localized quality control ensures proper material distribution in counterweight portions without unnecessarily complicating the entire process.

Inventive Principle:

Principle #3Local quality

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 results in a forged crankshaft with reduced flash and improved material yield rate by ensuring appropriate volume distribution between arm and weight portions, enhancing the efficiency of the forging process.

Implementation Method 1

a heated billet is rolled and subsequently bent

Methodology Applied

Scientific EffectHeating: Heating

Data Source

PatentEP3272439B1Method for manufacturing forged crankshaft

Publication Date: 2020.03.11 NIPPON STEEL CORPORATION

Figure 1A~1B
Figure 2A~2F
Figure 3A~3F

AI summary

A forged crankshaft production method includes a first preforming step, a second preforming step, and a final preforming step. In the second preforming step, an initial blank (23) is pressed by a first pair of dies (40) to be formed into an intermediate blank. The first pair of dies (40) includes web processing parts (42c) to come into contact with portions to be formed into arms and portions to be formed into weights integrated with the arms. Each of the web processing parts (42c) includes an arm processing part (42d) and a weight processing part (42e). The arm processing part (42d) and the weight processing part (42e) form a recessed portion, and the width (Bw) of the open side of the weight processing part becomes greater with increasing distance from the bottom of the recessed portion. Accordingly, in the blank, volume can be distributed between a portion to be formed into an arm and a portion to be formed into a weight integrated with the arm, and the material yield rate can be improved.