What Are The Key Points for Selecting Trapezoidal Lead Screws?

The selection of trapezoidal screw rods requires comprehensive consideration of several key factors. The main selection points are as follows:

1. Load capacity

Axial load: Calculate the maximum axial force (including working load, friction force, inertia force, etc.), ensuring that the stress of the screw rod is lower than the allowable stress of the material to avoid plastic deformation or fracture.

Radial load: If there is a radial force, it is necessary to ensure that the supporting structure can withstand it. Generally, the radial load should not exceed 10% of the axial load.

2. Lead and speed

Lead selection: Select the lead according to the speed requirements. For high-speed scenarios, choose a large lead (such as 20-25mm), while for high-precision or low-speed scenarios, choose a small lead (such as 5-10mm).

Speed limit: The speed of metal nuts is generally not more than 0.05m/s, and that of plastic nuts is not more than 0.5m/s. Avoid overheating or wear due to sliding friction.

3. Precision requirements

The precision of trapezoidal screw rods is usually medium (such as IT7-IT9), suitable for scenarios with low precision requirements. If higher precision is required, a machined with grinding process screw rod should be selected, but the cost will increase significantly.

4. Self-locking property

Trapezoidal screw rods have self-locking property when the pitch angle is less than the friction angle, suitable for vertical installation or scenarios requiring position retention. If high speed or frequent start-stop is required, an additional braking device should be configured.

5. Material and wear resistance

Screw rod material: Commonly used materials include carbon steel (such as 45 steel), stainless steel or alloy steel, choosing corrosion-resistant or high-strength materials based on the environment.

Nut material: For low load, plastic (such as POM) can be selected, for high load, choose brass or bronze, ensuring that the material's wear resistance meets the PV value requirements (pressure × speed).

6. Supporting method and length-to-diameter ratio

Select the supporting method based on the travel and load: For short travel and light load, fixed-free support can be used; for long travel and high load, fixed-support or fixed-fixed support is required. The length-to-diameter ratio should generally not exceed 100 to avoid screw rod bending.

7. Driving torque and efficiency

Calculate the driving torque, considering efficiency (usually 20%-50%), ensuring that the motor can provide sufficient power. Efficiency is affected by pitch and friction coefficient, with a larger pitch resulting in lower efficiency.

8. Environmental adaptability

Consider environmental factors such as temperature, humidity, and dust, select appropriate surface treatment (such as galvanization, chrome plating, Teflon coating) or protective devices to ensure the screw rod operates stably in harsh environments.

When selecting, it is necessary to combine specific application scenarios, through calculation and verification to ensure that the screw rod meets the requirements of load, speed, precision, self-locking property, etc., while also considering cost and maintenance convenience.

Feel free to contact us for more information!