Introduction
The crankshaft is one of the indispensable parts of an internal combustion engine to transform linear motion into rotary motion. The crankshaft is utilized in motor vehicles, motorbikes, ship engines, and industrial machinery for efficient energy transfer from pistons to the drive system. Since it plays a crucial role, crankshaft manufacturing involves careful engineering and a series of processing steps. Herein, this blog is presented after proper discussion with Top Crankshaft Manufacturers, with the crankshaft manufacturing process presented step by step, i.e., material, process, machining process, and quality control processes.
Materials Used to Manufacture Crankshafts
There has to be a material that is available and will offer strength, wear, and durability. The crankshaft has to be temperature-variable, cyclical loading, and stress-resistant. The most widely used ones are as follows:
- Cast Iron: Cast iron crankshafts are suitable for wear-resistant, low-cost applications but not very durable in relation to steel crankshafts
- Forged Steel: Durable and with better fatigue life, forged steel crankshafts are appropriate for heavy-duty and high-performance engines.
- Billet Steel: As single pieces of steel, billet crankshafts are used mostly in racing and high-performance applications without any compromise in strength but at extra costs.
Crankshaft Manufacturing Processes
The three important processes used to manufacture crankshafts include forging, casting, and machining a billet. They differ in terms of their benefits and are applied based on application, levels of performance to be achieved, and amounts to be manufactured.
1. Casting Process
Description:
Molten metal is fed into the mould so as to obtain the desired final crankshaft form. The casting process is cheaper and can be utilized in the mass production of large lots.
Steps involved:
- Pattern and Mould Preparation: The mould is prepared with the shape of the crankshaft as required by metal or sand.
- Molten Metal Pouring: The alloy (steel or iron) in the desired shape is melted and poured into the mould.
- Solidification and Cooling: Metal is cooled and allowed to solidify, adopting the shape of the crankshaft.
- Shakeout and Cleaning: The casting is shaken out from the mould and cleaned of excess material.
- Shakeout and Cleaning: The casting is shaken out from the mould and cleaned of excess material.
- Heat Treatment: Heat treats the crankshaft for improving mechanical properties.
- Machining: Machining for acquiring the wanted end shape and surface finish.
Advantages:
- Inexpensive to mass-produce
- Able to create intricate shapes
- Medium mechanical properties
Disadvantages:
- Poor compared to crankshafts produced by the forging process
- Susceptible to casting flaw of porosity
2. Forging Process
Description:
Forging is the best process for crankshafts for high performance because it hardens and increases durability.
Steps Involved:
- Billet Preparation: Steel billet is subjected to malleable temperature.
- Forging: Hot billet is forced into die and pressed with enormous force to achieve crankshaft shape.
- Trimming and Flash Removal: Excess flash material is trimmed by cutting.
- Heat Treatment: Heat-treated forged crankshaft is heated to provide hardness and life in fatigue.
- Machining: Machining is performed at a high level of accuracy to achieve correct sizes.
- Grinding and Polishing: Journaling is ground and polished to achieve high polish.
Advantages:
- Harder and longer-lasting than cast crankshafts
- Improved fatigue life and impact
- Better grain structure for application performance
Drawbacks:
- Higher cost of manufacture
- Need for specialty machine
3. Billet Machining Process
Explanation:
The billet crankshafts are made from a single piece of the finest-grade steel and thus are the strongest and most accurate form of crankshaft.
Process Involved
- Material Selection: The suitable steel billet is chosen.
- CNC Machining: The profile of the crankshaft is machined on computerized machines from the billet.
- Heat Treatment: Hardening operations are employed for enhancing mechanical properties.
- Grinding and Polishing: Smooth journal surfaces are created through meticulous grinding.
- Balancing: Dynamically balanced to avoid vibration.
Advantages:
- Very strong and robust
- Suitable for high-performance applications
- Real dimension accuracy
Disadvantages:
- Extended and costly operation
- Not suitable for mass production
Machining and Finishing Operations
After the main forming operation (forging, casting, or machining of the billet) is finished, the crankshaft undergoes a series of finishing and machining operations to achieve the desired specificatio
1. Rough Machining
The initial machining operation removes excess material to achieve the crankshaft close to finished dimensions.
2. Turning
Connecting rod journals and main crankshaft journals are turned on lathes.
3. Grinding
Precise grinding for precise sizing and surface finishing of bearing surfaces is employed.
4. Oil Hole Drilling and Drilling
Lubrication, an anti-friction and anti-wear substance, is provided through drilled oil holes.
5. Heat Treating
The crankshafts are nitrided or induction heat-treated to make them surface-harder and more surface wear-resistant.
6. Balancing
Dynamic balancing is conducted to reduce the vibration to such levels that a smooth engine run could be ensured.
7. Polishing and Superfinishing
Surface finishing operations enhance surface smoothness, minimize friction, and promote performance.
Quality Control Steps
Manufacturing of crankshafts involves rigorous quality inspections to ensure reliability and stability. Important quality control measurements are:
● Magnetic Particle Inspection (MPI): It inspects surface defects and cracks.
● Ultrasonic Testing (UT): Internal defects are detected.
● Hardness Test: Checks for proper hardness of material. Dimensional Inspection: Verifies critical dimensions on coordinate measuring machines (CMMs). Fatigue Testing: Cyclic load capacity is tested. Microstructure Analysis: Ensures the grain structure of the material for homogeneity.
Conclusions
Manufacturing of the crankshaft is a process right from material choice to precise machining and quality inspection. Depending upon the application, an enterprise chooses to machine from a casting, to machine from forging, or to machine from a direct billet, each with its own strengths. With advances in CNC machining technology and materials sciences, the crankshaft is improved with enhanced engine power and efficiency. For engines that are used for racing or non-military use, the manufacturing process creates crankshafts with stress resistance during full-load operation.
Also Read: Top Sustainable Material Handling Equipment Choices for Eco-Friendly Operations
