Elimination of transmission gear clearance in CNC machining feed system
by：QY Precision 2020-03-29
The transmission gear in the feed system of the CNC machining machine tool must eliminate the transmission gap between the phase meshing gears as much as possible. Otherwise, the motion will lag behind the command signal after each reverse of the system, which will affect the machining accuracy.
There are two common methods for eliminating the gap between transmission gears in CNC machining machine tools. 1.
Rigid adjustment method is an adjustment method that cannot automatically compensate the tooth side clearance after adjustment. Therefore, the perimeter tolerance and tooth thickness of the gear should be strictly controlled, otherwise the flexibility of transmission will be affected.
This adjustment method is relatively simple in structure and has good transmission stiffness.
Elimination of transmission gear clearance of CNC machining feed system (1)Eccentric shaft adjustment method as shown in Figure 6-
As shown in 10, gear 1 is installed on the eccentric shaft sleeve 2. Adjusting the eccentric shaft sleeve 2 can change the center distance between gear 1 and gear 3 to eliminate the gap. (2)The axial gasket adjustment method is shown in Figure 6-11a)
As shown, a pair of meshing cylindrical gears, if their pitch diameter is made into a smaller taper along the axial direction of the gear, change the thickness of the gasket 3, the axial relative positions of Gear 2 and Gear 1 can be changed to eliminate tooth side clearance. Figure 6-11b)
As shown in the figure, add a gasket 2 between the two thin helical gears 3 and 4, change the thickness t of the gasket, and the spiral lines of the thin Gears 3 and 4 will be misplaced, in this way, the thin gear 3 and 4 are respectively attached to the left and right sides of the gear slot of the wide helical gear 1, thereby eliminating the flank clearance.
Elimination of transmission gear clearance of CNC machining feed System 2.
Flexible adjustment method flexible adjustment method is an adjustment method that can still automatically compensate the tooth side clearance after adjustment.
This method generally uses adjusting the pressure of the pressure spring to eliminate the tooth side clearance, and can also maintain non-gap meshing when the tooth thickness and perimeter of the gear change, however, the structure of this adjustment method is more complicated, the axial size is large, the transmission stiffness is low, and the transmission stability is also poor. (1)The axial pressure spring adjustment method is shown in Figure 6-
As shown in 12, two thin helical gears 1 and 2 are set on the shaft 6 with keys 4, and the axial pressure of the pressure spring 3 is adjusted with nut 5, the left and right tooth surfaces of the thin gear 1 and 2 are respectively attached to the left and right tooth surfaces of the gear slots of the wide helical gear 7 to eliminate the flank clearance.
The spring force needs to be adjusted properly, the gap cannot be eliminated if it is too loose, and the wear of the gear will be accelerated if it is too tight. (2)The circumferential spring adjustment method is shown in Figure 6-
As shown in 13, two thin Gears 1 and 2 with the same number of teeth are engaged with another wide gear, and gear 1 can rotate relatively on Gear 2.
Each gear end face is evenly equipped with four threaded convex ears 3 and 8 respectively, and the end face of gear 1 has four through holes, from which convex ears 8 can pass through, spring 4 is hooked on adjusting screw 7 and 9 convex ear 3 respectively.
Rotating nuts 5 and 6 can adjust the pulling force of spring 4. The pulling force of spring makes the thin Gears 1 and 2 dislocated with each other and stick to the left and right tooth surfaces of the wide gear groove respectively, eliminate tooth side clearance.