Cost Breakdown to producing open die forged screw rotors with large diameter

Producing open-die forged screw rotors with large diameters (e.g., 580mm) involves a series of complex and high-precision processes, each of which incurs specific costs. The cost breakdown can vary depending on the material used, production volume, tolerances, and the machining complexity of the rotor. Below is a general cost breakdown for producing large-diameter screw rotors using open-die forging, which is a custom and often low-to-medium volume manufacturing process:

1. Material Costs

Material Type: The cost of the material depends on the alloy chosen. High-strength steels such as 42CrMo4, 17CrNiMo6, or AISI 4140 are commonly used for screw rotors.

• Material Cost per kg: The cost of steel alloys typically ranges from $3–$7 per kg, depending on alloy grade and market conditions.

• Weight of Rotor: For large-diameter screw rotors (e.g., 580mm), the weight can range between 100kg–300kg or more, depending on the thickness and complexity of the rotor.

• Example: For a rotor weighing 200kg and a material cost of $5 per kg, the material cost would be $1,000.

Cost Estimate:

• Material Cost = Material cost per kg × Weight of rotor

• Example: $5/kg × 200kg = $1,000

2. Pre-Forge Preparation

Billet/Bar Inspection and Cutting:

• Billet cost: Additional costs are associated with cutting the billet to size and inspecting it for defects before forging.

• Cost per unit of billet: This typically ranges from $50–$200 depending on the size and type of billet.

• Cutting and handling: Labor and machine time for cutting and preparation.

Cost Estimate:

• Billet cost: $200–$500 depending on the size.

• Preparation cost: Additional $100–$200 for cutting, cleaning, and preparation.

3. Open-Die Forging

Equipment Costs:

• Forging Press/Hammer: The cost of using hydraulic presses or mechanical hammers for open-die forging. This typically involves large, expensive machinery, often requiring custom setups.

• Press usage rate: A typical forging press might cost between $500–$2,000 per hour to operate, including energy consumption, maintenance, and amortization of equipment costs.

Labor Costs:

• Forge operator labor cost: Skilled operators are needed for each stage of the forging process. This could cost $50–$100 per hour depending on location and experience.

• Total forging time: Depending on complexity, forging a large screw rotor could take anywhere from 6 to 20 hours.

• Total labor cost for forging: $500–$2,000, depending on the duration of the operation and labor rates.

Additional Costs:

• Die Wear and Maintenance: Open-die forging can cause wear on the dies, especially for large parts. Die costs and replacement can range from $500–$3,000 for custom dies, depending on the complexity and material used.

• Energy Costs: High energy consumption for heating and forging can add significant costs, ranging from $200–$1,000 per forging operation.

Cost Estimate:

• Forge Equipment and Labor: $2,000–$10,000 per rotor

• Die costs and energy: $1,000–$3,000

4. Heat Treatment

Furnace Costs:

• Heat treatment equipment (e.g., induction or batch furnaces) can be expensive, especially for large parts. The cost per cycle might range from $500–$2,000, depending on the size and complexity of the part.

• Heating and cooling times: Heat treatment of large-diameter parts takes longer due to the mass and requires controlled cooling, which can increase energy costs.

Labor and Supervision Costs:

• Heat treatment is a high-skill process, and operators must monitor temperature profiles and adjust as needed. Labor costs range from $50–$100 per hour.

Cost Estimate:

• Heat Treatment Equipment and Labor: $1,000–$3,000 per rotor

5. Machining and Surface Finishing

CNC Machining:

• CNC Turning/Milling: The process of machining large screw rotors is labor- and machine-intensive. CNC machines charge an hourly rate of $100–$250 per hour depending on machine complexity and part features.

• Machining time: Machining time for large rotors can take anywhere from 15 to 50 hours, depending on the size and complexity.

• Cost Estimate for Machining: For 50 hours of CNC machining at $150 per hour, the machining cost would be $7,500.

Surface Finishing:

• Grinding/Polishing: Fine grinding and polishing for smooth surfaces and critical features can take additional time. This process is generally $50–$100 per hour.

• Time for Finishing: 5–15 hours, depending on the quality required and part size.

Cost Estimate:

• Machining Cost: $7,500–$15,000 (depending on complexity)

• Surface Finishing: $500–$2,000

6. Inspection and Testing

Dimensional Inspection:

• CMM (Coordinate Measuring Machine) or Laser Scanning costs are typically $100–$200 per hour.

• Time for Inspection: It may take 4–10 hours to thoroughly inspect the rotor, including using 3D scanning or CMM.

• Cost Estimate: $500–$2,000 per rotor for full inspection.

NDT (Non-Destructive Testing):

• Methods like ultrasonic testing, magnetic particle inspection, and dye penetrant inspection may be employed to detect internal or surface defects.

• NDT Cost: For large parts, the cost of NDT services ranges from $500–$2,000 depending on the testing methods used.

Cost Estimate:

• Inspection and NDT: $1,000–$3,000

7. Balancing and Final Testing

• Dynamic Balancing: For screw rotors, dynamic balancing is crucial. The cost of balancing can range from $300–$1,500 per rotor, depending on the machine and complexity.

• Functional Testing (if applicable): If the rotor is part of a larger system, it may require performance testing, which can add $500–$3,000 depending on the testing method and equipment.

Cost Estimate:

• Balancing and Final Testing: $1,000–$4,000

8. Packaging and Shipping

• Packaging: Custom crates, protective materials, and shipping preparation can add significant costs, especially for large and heavy parts.

• Shipping: Depending on the destination, international shipping and freight charges can range from $500–$3,000, especially for large, heavy items that require special handling.

Cost Estimate:

• Packaging and Shipping: $500–$3,000

Total Estimated Cost Breakdown

Here’s an estimated cost breakdown for producing a single open-die forged screw rotor with a large diameter (e.g., 580mm):

Total Estimated Cost for One Rotor:

$14,700 – $87,500 (Depending on complexity, material, labor, and additional features)

Factors That Influence Cost:

• Material Choice: Higher-end alloys will increase material costs.

• Complexity: The more intricate the rotor’s design (e.g., multiple grooves, special profiles), the higher the machining and inspection costs.

• Quantity: Larger production runs reduce the cost per part due to economies of scale, especially for die use, machine setup, and labor.

• Tolerances and Surface Quality: Tight tolerances and high-quality finishes demand more time in machining and inspection, increasing costs.

• Heat Treatment and Testing Requirements: If specialized heat treatment or rigorous testing (e.g., pressure tests, functional testing) is required, this will add to the cost.