Advantages and applications of rack and pinion transmission

The gear rack transmission structure consists of gears and racks, which are also divided into straight and helical teeth and are widely used in factory automation. Among them, laser cutting machines, gantry trusses, and the seventh axis are widely used by us, with advanced technology and rich selection experience. Gear and rack have their own advantages in transmission, so what are the advantages of gear and rack transmission?

The gear has a large load-bearing capacity, high transmission accuracy, up to 0.1 millimeters, can extend infinitely long, and can have a high transmission speed. However, its disadvantages include poor machining and installation accuracy, high transmission noise, and high wear. Usage: Layout steel plates, glass CNC cutting machines, and construction elevators can reach a height of up to 30 floors. The synchronous belt has a large load-bearing capacity. If the load is large, the belt should be widened. The transmission accuracy is high, and the transmission length should not be too large. Otherwise, significant elastic deformation and vibration should be considered, and larger transmission distances are particularly unsuitable for precise positioning and continuous motion control, such as the larger XY axis layout of CNC equipment, but it can be used for short distance transmission from servo motors to transmission gears or from servo motors to screws. Advantages: Short distance transmission speed can be very high, with low noise. Typical use: Small CNC equipment.

(1) The ordinary trapezoidal screw can lock itself, which is the biggest advantage, but the transmission efficiency is low, far lower than the above two, so it is not suitable for high-speed back and forth transmission. The disadvantage is that the transmission gap is large and the return accuracy is poor after a long time, making it more suitable for use in vertical transmission.

(2) Ball screws cannot be self-locking, have high transmission efficiency, high accuracy, and low noise, and are suitable for high-speed back and forth transmission. However, when the horizontal transmission span is large, the maximum speed and self weight sag deformation should be considered. Therefore, the transmission length should not be too large. Either switch to rotating nuts, but not too long, or use gears. Typical applications: CNC machine tools, small CNC cutting machines.

What are the differences between rack and pinion applications?
In long-distance heavy-duty linear motion, the screw may have insufficient rigidity, which can lead to machine vibration, shaking, and other situations. In severe cases, the screw may bend, deform, or even break, etc; However, the rack will not have this situation. The rack can run infinitely long and at high speed without affecting the accuracy of the rack (of course, this is related to assembly and bed accuracy). The screw cannot achieve this, but in short distance linear motion, the accuracy of the screw is significantly higher than that of the rack. In addition, in terms of structural design of the dryer, rack and gear transmission are relatively simple. Anyway, everyone has their own strengths and weaknesses. Therefore, the screw market and the rack market will not affect each other.

In long-distance heavy-duty linear motion, the screw may have insufficient rigidity, which can lead to machine vibration, shaking, and other situations. In severe cases, the screw may bend, deform, or even break, etc; However, the rack will not have this situation. The rack can run infinitely long and at high speed without affecting the accuracy of the rack (of course, this is related to assembly and bed accuracy). The screw cannot achieve this, but in short distance linear motion, the accuracy of the screw is significantly higher than that of the rack. In addition, in terms of structural design of the dryer, rack and gear transmission are relatively simple. Anyway, everyone has their own strengths and weaknesses. Therefore, the screw market and the rack market will not affect each other.

When the number of teeth of a standard external gear increases to infinity, the base circle and other circles on the gear become parallel straight lines, and the involute tooth profile on the same side also becomes parallel oblique straight tooth profile, which is called a rack. Compared to gears, racks have the following two characteristics:

(1) Due to the straight tooth shape of the rack, the normal of each point on the tooth profile is parallel. And because the rack is translated during transmission, the speed and direction of each point on the tooth profile are the same, so the pressure angle at each point on the rack is equal, equal to the tooth profile angle, with a standard value of 20 °.

(2) The pitch on each straight line parallel to the tooth crest is the same, and the modulus is the same standard value. The straight line with tooth thickness equal to the width of the tooth slot and parallel to it is called the centerline, which is the reference line for determining the dimensions of each part of the rack.

However, during the stamping process, as the stamping stroke is the working stroke, the return process is not the working process. When processing the workpiece and returning, we should try our best to meet the restoration time of the workpiece. Therefore, it is necessary to meet the emergency port characteristics of this mechanism. However, gears cannot meet the characteristics of emergency ports, cannot improve the stamping efficiency of workpieces, and the motion form of rack and pinion machining does not comply; Then exclude the handling method for this process.

Source: Shenzhen Weidong Automation