When selecting a linear actuator, one of the first mechanical questions you will face is: “Should I use a Trapezoidal (Lead) Screw or a Ball Screw?”
While Ball Screws are often marketed as the “high-end” option, AKT Motor’s HSL Series utilizes precision Trapezoidal Screws (also known as Acme screws). Why? Because for the vast majority of precision automation, medical, and laboratory applications, trapezoidal screws actually offer superior benefits in terms of cost, noise, and stability.
Here is a detailed comparison to help you decide.
1. The Fundamental Difference: Sliding vs. Rolling
- Trapezoidal Screws (AKT HSL Series): These rely on Sliding Friction. The nut slides along the threads of the screw. It is similar to a standard bolt and nut but manufactured with much higher precision.
- Ball Screws: These rely on Rolling Friction. The nut contains recirculating steel balls that roll between the nut and the screw threads, acting like a ball bearing system.
2. Why Choose Trapezoidal Screws (AKT HSL)?
Our Linear Stepper Motors (NEMA 8 to NEMA 23) are designed with high-quality stainless steel trapezoidal screws. Here is why this is the preferred choice for many industries:
- Self-Locking Safety: As discussed in our previous guide, trapezoidal screws create friction. This means they can hold a vertical load in place when power is cut (depending on the lead). Ball screws have almost zero friction and will always back-drive, causing loads to crash without a brake.
- Quiet Operation: Ball screws can be noisy due to the sound of metal balls recirculating inside the nut. In contrast, the sliding action of a trapezoidal screw is smooth and nearly silent, making it ideal for medical analyzers and hospital equipment where noise is prohibited.
- Cost-Effectiveness: Manufacturing a precision ball screw is expensive. A trapezoidal screw linear actuator provides excellent positioning accuracy (often down to 0.005mm) at a fraction of the cost.
- Compact Nut Design: The nut on a trapezoidal screw takes up very little space. A ball screw nut requires bulky return channels for the balls, which often won’t fit in compact NEMA 8 or NEMA 11 designs.
3. When is a Ball Screw Better?
We value transparency. There are specific scenarios where a ball screw might be necessary (though they typically require a different type of actuator):
- Continuous High-Speed Duty: If your machine runs 24/7 at high speeds, the friction of a trapezoidal screw will generate heat. Ball screws run cool due to low friction.
- Heavy Industrial Loads: For moving hundreds of kilograms on a large CNC mill, the efficiency of a ball screw (90%+) is required to minimize motor size.
4. Efficiency and Life Expectancy
A common myth is that trapezoidal screws wear out quickly.
- Reality: When properly lubricated and used within their rated load, the life of an AKT linear stepper motor screw is excellent.
- Efficiency: While a ball screw is ~90% efficient, a trapezoidal screw is typically ~40-60% efficient. This simply means you need to size your stepper motor with enough torque to overcome the friction—which is exactly why we offer high-torque motors like the 57HSL Series.
Conclusion
Don’t overpay for a ball screw system if you don’t need one.
For applications requiring silent operation, vertical holding capability, compact size, and high precision (such as syringe pumps, 3D printers, and laboratory stages), the Trapezoidal Linear Stepper Motor from AKT Motor is the engineered solution of choice.