How To Select A Trapezoidal Screw for Heavy-load Scenarios?

When choosing a trapezoidal screw for heavy-load scenarios, the following key factors should be considered comprehensively:

1. Load capacity

Based on the actual load size, select the screw diameter and material that can withstand the maximum axial force. Generally, the load should be calculated and an additional 1.5-2 times safety margin should be added to ensure that the screw does not deform or break under long-term heavy load.

High-strength alloy steel materials such as 45 steel quenched and tempered or higher-strength materials should be preferred to increase the bearing capacity.

2. Pitch and self-locking property

If a self-locking function is required (such as vertical lifting to prevent the load from falling back), choose a screw with a smaller pitch, so that the helix rise angle is less than the friction angle, ensuring reliable self-locking after power failure. Generally, a pitch angle of less than 3° provides better self-locking effect.

If speed requirements are high and no self-locking is needed, the pitch can be appropriately increased, but attention should be paid to the fact that increasing the pitch will reduce the transmission efficiency.

3. Precision requirements

If the positioning accuracy requirement is not high (within ±0.1mm), a conventional precision grade (C7-C10) trapezoidal screw can be selected, which has a lower cost.

If higher precision is required, a trapezoidal screw processed by grinding can be chosen, with a precision of up to C5-C7, but the cost will increase accordingly.

4. Speed and speed limit

Trapezoidal screws have low rotational speed and linear speed due to sliding friction. Generally, the linear speed does not exceed 1m/min and the rotational speed does not exceed 300rpm. The appropriate pitch and diameter should be selected based on the actual operating speed to avoid increased wear or heating due to high speed.

Calculate the critical speed to ensure that the actual operating speed does not exceed 75% of the critical speed to prevent resonance or vibration problems.

5. Lubrication and maintenance

Choose a suitable lubrication method for heavy-load scenarios, such as using high-viscosity lubricating grease or solid lubricants to reduce friction and wear.

Consider the convenience of maintenance for the screw, choose a design that is easy to disassemble and replace the nut, to facilitate regular inspection and replacement of worn components.

6. Installation and support

Ensure that the screw is firmly supported at both ends during installation to avoid bending or deformation due to cantilever or eccentric load. Fixed-support or fixed-free support methods can be chosen based on the actual installation conditions.

If the screw is long, consider adding intermediate supports or using decoupling structures to reduce axial bending torque. Summary: In heavy-load scenarios, the selection of trapezoidal screws should focus on load capacity, self-locking property, precision, rotational speed, and lubrication maintenance. Based on specific application scenarios and installation conditions, select the appropriate diameter, pitch, material, and precision grade of the screw to ensure stable operation and long-term reliability of the equipment.

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