Forged Crankshaft Preforming to Reduce Weight and Yield Loss
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Solution Overview
Problem
Conventional methods for producing forged crankshafts with reduced weight and sufficient stiffness face challenges in forming recesses on the journal-side surface, requiring significant force and complex mechanisms, and do not effectively address weight reduction while minimizing yield loss due to excessive flash generation.
Innovation Solution
A method involving a preforming step to create a preformed blank with excess projecting portions, followed by a die forging step using a second die to increase the thickness of the crank arm side portions and form a recess, and a trimming step to remove flash, allowing for the production of a forged crankshaft with reduced weight and sufficient stiffness without requiring excessive force or complex mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a recess is formed on the journal-side surface of the crank arm to reduce weight, then weight reduction is achieved, but significant force and complex mechanisms are required
Solution Approach 1:
The preforming step creates excess projecting portions on the crank arm before die forging, preparing the material distribution in advance. This preliminary action allows the subsequent die forging to simply redistribute the material to form the recess, avoiding the need for complex punching mechanisms while achieving weight reduction through the recess formation
2Ease of manufacture
If conventional die forging is used to form the crankshaft, then the crankshaft structure is formed, but excessive flash is generated resulting in yield loss
Solution Approach 1:
The preforming step pre-distributes the material volume along the longitudinal direction and creates the basic crankshaft shape with excess projecting portions. This preliminary shaping reduces the amount of material that would otherwise flow out as flash during die forging, thereby minimizing yield loss while still achieving the required crankshaft structure formation
Solution Approach 2:
The excess projecting portions are created at specific locations on the crank arm where material is needed. During die forging, this localized material distribution control ensures that material flows only where required to form the recess and thick side portions, rather than generating excessive flash around the entire crankshaft periphery
3Strength
If the side portions of the crank arm are made thick to ensure stiffness, then stiffness is improved, but weight increases
Solution Approach 1:
The recess is formed specifically on the journal-side surface of the crank arm while maintaining thick side portions at the locations where stiffness is required. This localized material redistribution allows weight reduction through the recess without compromising the structural stiffness provided by the thick side portions
Solution Approach 2:
The preforming step creates excess projecting portions that are strategically positioned to allow subsequent die forging to form the recess while preserving material at the side portions. This preliminary material distribution enables the final structure to have both weight reduction and sufficient stiffness simultaneously
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 method enables the production of forged crankshafts with reduced weight and maintained stiffness, improving yield by minimizing flash formation and simplifying the process, while avoiding the need for high force application and complex mechanisms.
Implementation Method 1
a preforming step of forming a preformed blank with no flash... a die forging step of forming a forged blank with flash by pressing the preformed blank
Implementation Method 2
by the first dies the excess projecting portions of the crank arm are deformed so as to increase the side portions of the crank arm in thickness
Data Source
AI summary
A method for producing a forged crankshaft includes: a preforming step of forming a preformed blank with no flash, the preformed blank including a shape of the crankshaft, wherein the crank arm have excess projecting portions at an outer peripheries of side portions of the crank arm near the crank pin; a die forging step of forming a forged blank with flash by pressing the preformed blank with a pair of first dies; and a trimming step of removing the flash from the forged blank. In the die forging step, while a second die is abutted against a journal-side surface of the crank arm and holds the surface, the excess projecting portions of the crank arm are deformed by the first dies so as to increase the side portions of the crank arm in thickness.