How to calculate of Power Press calculation

How to Calculate Mechanical Power Press Design Calculation

Mechanical power presses are fundamental in manufacturing processes such as stamping, punching, and forming. Proper design and calculation ensure the press functions efficiently and safely. This article outlines the key calculations involved in designing a mechanical power press.

1. Basic Specifications

Let's consider a mechanical press with the following specifications:

• Power Capacity (Pr): 45 Ton
• Stroke Length (St): 100 mm
• Rated Distance: 3.974 mm
• Stroke per Minute (SPM): 75 SPM

2. Rated Distance Calculation

The rated distance is calculated using the formula:

Rated Distance = (1 - cos α°) × St / 2

Given:

3.974 = (1 - cos 23°) × 50

Thus, α° = 23°.

3. Torque Transmitted by Crank Shaft

The torque transmitted by the crankshaft (Tc) is calculated as follows:

Tc = Pr × sin α°

Substitute values:

Tc = 45 × 10³ × 50 × 10⁻³ × sin 23°

Tc = 879.14 Kg.m ≈ 880 Kg.m

Considering 1.15% safety margin:

Tc = 1015 Kg.m

4. Power Requirement for Motor

The motor power (P) needed is calculated as:

P = (E × Stroke Per Min.) ÷ (60 × 0.8 × 0.8)

Where:

• E = 45 × 10⁴ × 3.974 × 10⁻³
• SPM = 75

P = (3492.77 W) = 3.5 kW ≈ 5 HP (Standard motor size: 3.7 kW).

5. Flywheel Design

The flywheel stores energy and ensures smooth operation. Let's design a flywheel with the following parameters:

• Rim OD: 590 mm
• Rim ID: 390 mm
• Flywheel Speed: 350 rpm (332.5 rpm at 5% fluctuation)

Flywheel energy (E) is calculated as:

E = ½ m [(πdN₁ ÷ 60)² - (πdN₂ ÷ 60)²]

Substitute values:

1015 = ½ m [(3.14 × 0.49 × 350 ÷ 60)² - (3.14 × 0.49 × 332.5 ÷ 60)²]

Mass (m) ≈ 256.9 Kg

6. Clutch Selection and Back Shaft Torque

Clutches control the transfer of energy from the flywheel to the crankshaft. The back shaft torque is calculated as:

Tb = Tc ÷ Gear Ratio

Gear Ratio = 4.66

Thus, Tb = 880 ÷ 4.66 = 188.84 Kg.m

Considering 1.15% safety:

Tb = 236 Kg.m

7. Force Chart

The force chart helps visualize load variations versus crank displacement. In our press:

• The load is constant for displacements between 0 to 4 mm.
• The minimum load produced is 10 tonnes.

Conclusion

Calculating mechanical power press design involves understanding forces, torque, energy, and motor power requirements. Using proper formulas and safety margins ensures efficient and safe operation.