Cnc Rack and Pinion Vs Ball screw

Release Time:2023-02-14

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Both ball screw and rack are transmission tools, which are one of the configurations of laser cutting machines, and are widely used in the industrial field. However, due to their different characteristics, they are used in different ranges. Which transmission should we choose in actual work? As for tools, first of all we have to understand what are ball screw and rack and what are their advantages and disadvantages.

What is CNC rack and pinion

A rack and pinion has a rack bolted to the side of the machine and a pinion, or cog/pinion, meshes with the rack. As the pinion turns, the machine moves, driven by a combination of spur and helical (helical) racks. Racks are also divided into straight toothed racks and helical toothed racks, which are paired with straight toothed cylindrical gears and helical toothed cylindrical gears respectively. The tooth profile of the rack is a straight line instead of an involute, which is equivalent to a cylinder with an infinite radius of the indexing circle. gear. Rack and pinion transmission is a widely used transmission mechanism. This mechanism can not only convert rotary motion into linear motion, but also convert linear motion into rotary motion. It can also be combined with other transmission mechanisms to complete complex functions. As a belt conveyor, it is mainly used as a telescopic device, and the power is meshed with the rack through the gear to realize the forward or backward movement of the frame.

Advantages of CNC rack and pinion

1. The characteristics of large transmission power and high-efficiency gear transmission. Gear transmission is used to transmit motion and power between any two shafts. Its peripheral speed can reach 300m/s, transmission power can reach 105KW, and the gear diameter can range from less than 1mm to more than 150m. It is the most widely used in modern machinery. Mechanical transmission;
2. Long life, stable operation and high reliability;
3. It can ensure a constant transmission ratio, and can transmit the motion between the two shafts at any angle.
4. Rack infinite length, large load (15-20 tons), high speed (120-150m/min)

Disadvantages of CNC rack and pinion

1. The processing accuracy and processing technology requirements are high. If the processing and installation accuracy is poor, the transmission noise will be large and the wear will increase.
2. Manufacturing is more complex
3. Fewer installation options

What is a ball screw?

Ball screw is the most commonly used transmission element in tool machinery and precision machinery. Its main function is to convert rotary motion into linear motion, or convert torque into axial repeated force. It also has high precision, reversibility and high precision. Features of efficiency. Due to its small frictional resistance, ball screws are widely used in various industrial equipment and precision instruments. The ball screw is composed of screw, nut, steel ball, preloader, reverser, and dust collector. Its function is to convert rotary motion into linear motion, which is the further extension and development of Acme screw. The significance of this development is to change the bearing from sliding motion to rolling motion.

Advantages of Ball Screws

1. The ball screw has excellent precision, no friction, and smooth sliding;
2. The friction loss is small and the transmission efficiency is high. Since there are many balls rolling between the screw shaft and the screw nut of the ball screw pair, high motion efficiency can be obtained;
3. High-speed feeding and micro-feeding are possible. Because the ball screw pair uses ball motion, the starting torque is extremely small, and there will be no crawling phenomenon like sliding motion, which can ensure accurate micro-feeding;

Disadvantages of Ball Screws

1. High cost. Due to the high processing precision and low roughness of components such as ball screws and nuts, the manufacturing cost is high. The spiral groove raceway on the screw and nut needs to be ground to form the surface, the process requirements are complicated and the manufacturing is difficult;
2. It cannot be self-locking, especially the vertical screw. Due to the inertial force of its own weight, the moving parts cannot self-lock after the transmission stops, and a braking device is required;
3. The ball screw is prone to bending under long-distance and heavy loads. The ball screw manufacturing and installation precision requirements are high, so the cost is also high; at the same time, it is not suitable for long-distance transmission.

Which is better, CNC rack and pinion or ball screw?

Everyone has a different opinion on which of these two transmissions is the best.
Ball screws are known for being extremely smooth and virtually friction-free. For short-distance precision, ball screws are well suited. That's why we let it handle the Z axis. Their disadvantages include the need for precise alignment, susceptibility to contamination, and the need for increased diameter and weight relative to length (span) to prevent chatter or vibration. This, in turn, requires more gearing or larger motors to compensate for the weight and maintain fast positioning speeds.
Rack and pinion drives are known for their rigidity and unlimited length. The continuous stability of the precision ground helical gear system allows our CNCs to run for extended periods of time. When installed properly, they last for a long time with minimal wear and are virtually impervious to dirt and debris.
In short, the CNC gear hobbing machine is suitable for batch, small batch and single-piece production and processing of cylindrical gears and worm gears, and drum gears with certain parameters can also be used for continuous indexing hobbing with spline hobs and 6 teeth and more than 6 teeth with a length of less than 300 Short splined shaft; rack and pinion is an economical drive, especially for longer strokes over 2m, it is suitable for dirty environments and/or large axial forces, rigidity is equal over the entire length Yes, gears can be milled or ground according to customer requirements. It is also special in that different hardening processes can be realized. Depending on the stresses occurring, soft, nitrided, induction hardened, case hardened and case hardened racks can be selected. Several linear axis transmission methods commonly used in CNC laser cutting machine tools include ball screw, rack and pinion, and linear motor. Ball screw drive is often used in CNC machine tools with medium and low speed and small stroke; rack and pinion drive is widely used, which can realize high speed and large stroke; linear motor is mostly used in CNC machine tools with high speed, high acceleration and special structure.

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