Forged Crankshaft Preform Shaping for Material Utilization
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Solution Overview
Problem
Existing methods for manufacturing forged crankshafts for straight-6-cylinder engines face challenges in achieving high material utilization and dimensional accuracy, particularly due to the generation of excessive flash and instability in arm contour shapes, limiting the crankshaft's strength, stiffness, and shape complexity.
Innovation Solution
A forming apparatus and method that preprocess a preform blank to create a blank for finish forging, with specific configurations of journal and crank pin dies to reduce arm thickness, increase eccentricity, and control movement to prevent flash formation, allowing for high material utilization and accurate shaping of crankshafts with complex shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional block forging and finish forging are used to manufacture forged crankshafts, then the crankshaft can achieve high strength and stiffness, but excessive flash is generated leading to low material utilization
Solution Approach 1:
The patent applies preliminary action by performing preforming operations (roll forming and bending) before the main block forging and finish forging steps. The preforming creates an intermediate blank with a shape closer to the final crankshaft geometry, which then requires less material removal and flash generation during the subsequent forging operations. This sequential preparation reduces the harmful flash effect while maintaining the desired crankshaft properties.
Solution Approach 2:
The manufacturing process is segmented into multiple distinct stages: roll forming to create a reduced cross-section blank, bending to form the crankshaft contour, block forging to establish the basic shape, and finish forging to achieve the final precision geometry. This segmentation allows each stage to optimize for its specific function, with preforming stages preparing the material to reduce flash in the final forging operations, thereby improving material utilization.
2Manufacturing precision
If conventional forging methods are used, then the crankshaft can be manufactured with standard processes, but the arm contour shape shows instability and low dimensional accuracy
Solution Approach 1:
The preforming operations (roll forming and bending) are performed in advance to create a blank with predetermined geometry that closely matches the final crankshaft shape. This preliminary shaping ensures that the arm contours are established early in the process with high dimensional accuracy, and subsequent block forging and finish forging operations maintain this stability rather than introducing variations, thereby resolving the contour instability problem.
Solution Approach 2:
The patent employs dynamic control in the finish forging step, where the lower die is designed to be movable rather than fixed. This allows the die to adapt to material flow during forging, ensuring uniform pressure distribution and consistent arm contour formation. The dynamic lower die mechanism maintains dimensional accuracy and contour stability throughout the forging process, preventing the instability that would occur with rigid fixed dies.
3Adaptability or versatility
If simple crankshaft shapes are used, then the manufacturing process is easier, but complex shapes with balance weights cannot be achieved
Solution Approach 1:
The preforming stage includes bend forming operations that create complex crankshaft contours and arm geometries before the forging process. This preliminary formation of complex shapes allows the subsequent block forging and finish forging to focus on densification and precision shaping rather than creating the overall geometry, making it feasible to manufacture complex crankshafts with balance weights while maintaining manufacturing efficiency.
Solution Approach 2:
The manufacturing process is divided into specialized stages: roll forming for cross-section reduction, bending for contour formation, block forging for basic shape and density, and finish forging for final precision. This segmentation allows each operation to be optimized for its specific function, enabling the production of complex crankshaft geometries with balance weights without excessively complicating the overall manufacturing process.
4Loss of substance
If roll forming and bending are added as preforming steps, then material utilization improves, but the device complexity increases
Solution Approach 1:
The manufacturing process is segmented into distinct operational stages, each performed by specialized equipment optimized for its function. Roll forming equipment is dedicated to cross-section reduction, bending equipment to contour formation, and forging equipment to shape finalization. This segmentation improves material utilization by ensuring each stage performs its specific function efficiently, while the modular nature of separated equipment keeps individual device complexities manageable despite the increased overall process complexity.
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 enables the production of forged crankshafts with high material utilization and dimensional accuracy, capable of achieving complex shapes and balance weights, while minimizing flash and ensuring the strength and stiffness required for straight-6-cylinder engines.
Implementation Method 1
a billet 2 shown in FIG. 1(a), which has been previously cut to a predetermined length, is heated by a heating furnace
Implementation Method 2
the billet 2 is rolled and reduced in cross section by grooved rolls, for example, to distribute its volume in the longitudinal direction
Implementation Method 3
the rolled blank 103 obtained by the roll forming is partially pressed in a press in a direction perpendicular to the longitudinal direction to distribute its volume
Implementation Method 4
the bent blank 104 obtained by bending is press forged with a pair of upper and lower dies
Implementation Method 5
the block forged blank 105 obtained by the block forging is further processed by press forging the block forged blank 105 with a pair of upper and lower dies
Data Source
AI summary
In a forming apparatus, movable journal dies and stationary journal dies hold and retain rough journal portions of a preform blank therebetween, and movable crank pin dies contact rough crank pin portions thereof, and in this state, the movable journal dies and the movable crank pin dies are moved axially toward the stationary journal dies and the movable crank pin dies are moved in a direction perpendicular to an axial direction. With this, rough arm portions are axially compressed to reduce their thickness to that of arms of a forged crankshaft, and the rough crank pin portions are pressed in the direction perpendicular to the axial direction to increase an amount of eccentricity to that of the crank pins of the forged crankshaft.