How to Choose the Right Rack: Tooth Profile, Precision, and Price Analysis

For many customers who are new to rack and pinion transmission systems, a common challenge is: how to select a rack that ensures efficient transmission while remaining cost-effective? Below, we address this question step by step.

Tooth Profile Selection Guide

Choosing the right tooth profile is key to ensuring transmission efficiency and economic performance.

Straight Teeth vs. Helical Teeth

As the names suggest, the main difference between straight and helical teeth lies in their tooth geometry. Straight teeth have a helix angle of 0°, meaning no spiral, which is their most straightforward feature. In contrast, helical teeth have a helix angle of 19°31′42″, giving them a distinctive shape. Both types have specific application scenarios, and the choice depends on the operational requirements and conditions.

Advantages and Disadvantages of Straight vs. Helical Teeth

Straight Teeth:

Simple design, manufacturing, inspection, and assembly.

Lower contact overlap during meshing, leading to relatively higher noise.

Helical Teeth:

Larger overlap during meshing, which reduces noise in high-speed or high-torque applications.

Generates axial forces due to the helix angle, making design, manufacturing, inspection, and assembly more complex.

In summary, helical teeth are commonly used in applications where speed and noise reduction are critical, such as in the laser cutting machine industry.

Price Considerations

Straight teeth are generally more cost-effective due to their simpler manufacturing process. However, at YYC Technology, with over 12 years of experience in the laser cutting machine industry and a broad customer base, the price difference between straight and helical teeth is minimal. In certain product categories, helical teeth may even be slightly cheaper than straight teeth.

Precision and Hardness

Next, let's explore how to choose the appropriate precision and hardness based on actual application needs.

Precision Definition

Precision describes the degree of accuracy of the rack. Standards vary by region and industry. Common international standards include ISO, DIN (Germany), GB (China), and JIS (Japan). Typically, DIN and ISO standards are equivalent.

Precision Levels of YYC Racks

YYC racks define precision levels based on a 1-meter rack length, with the total pitch error (Fp/1000) as follows:

DIN5: Fp/1000 ≤ 0.026

DIN6: Fp/1000 ≤ 0.036

DIN8: Fp/1000 ≤ 0.060

DIN9: Fp/1000 ≤ 0.10

The smaller the DIN number, the higher the precision. DIN5 and DIN6 correspond to grinding level, while DIN8 and DIN9 are precision-milling level. This classification allows YYC racks to meet diverse customer needs, from high-precision applications to cost-sensitive milling-grade applications.

Hardness Definition and Selection

Hardness refers to the material’s resistance to deformation or wear. High hardness is essential for applications with heavy loads. Hardness depends on both the material and processing techniques.

YYC racks use HRC Rockwell hardness standards, with the following ranges:

HRC50°–55°: Carburized and heat-treated.

HRC18°–22°: Tempered treatment.

In conclusion, selecting the right rack requires first determining the required tooth profile, hardness, and precision. For more detailed guidance on modules and calculations, CPTC is ready to provide professional assistance. We look forward to your inquiries!