# CAD design and NC machining of the most popular th

2022-08-13
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CAD design and NC machining of three leaf involute rotor profile editor's note: This paper uses CAD technology to modify the three leaf involute rotor profile, and uses CAM technology for modeling, automatic programming and NC machining

I. Introduction

roots vacuum pump and roots blower require that the gas leakage between the two rotors running synchronously and between the rotor and the shell should be small, the volume utilization coefficient should be as large as possible, and the rotor should have good geometric symmetry. These requirements are completed by rotor profile. There are many methods to design the rotor profile, among which the three leaf involute rotor profile is relatively easy to draw. In this paper, cad/cam technology is used to modify the profile of three leaf involute rotor and determine the reasonable machining method

theoretical profile of two and three leaf involute rotor

1. Draw the profile of three leaf involute rotor

theoretical profile of three leaf involute rotor type operation supertest5 measurement and control software drawn by CAXA software. The drawing process is as follows:

(1) take r as the radius, O1 and O2 as the center, and make two circles tangent to P, especially the point of the intermediate optical system or important mechanical components, and T-T is the common tangent. Make a straight line N-N through point P and form a pressure angle with T-T α (this α= 50°）。

(2) take O1 and O2 as the center of the circle, make the circle tangent to the N-N line respectively, and get the involute with radius R. the base circle of the line must be pointed out

(3) divide the circumference of the pitch circle into six equal grades, and the equal points are B, C, D, e, F, g respectively. Unfold the involute from the base circle of the lower rotor, and intersect the N-N line at K1 through point C. With point P as the center and PK1 as the radius, make an arc k1jk2, which is the addendum arc of the lower rotor and the waist profile of the upper rotor

(4) unfold the involute from the base circle of the upper rotor, and extend the tangent hi of the base circle through point K1 to L2. The tooth top of the upper rotor is an arc L1L2 with I as the center and I L2 as the radius

(5) use the symmetry function of CAD to make all the profiles

2. Profile analysis

the addendum and waist of the involute rotor are the same arc, and the involute in the upper and lower rotors is expanded on the base circle of the same size. Theoretically speaking, when one rotor rotates, it will not interfere with the engagement of another rotor

3. Volume utilization coefficient λ

distance from rotor tooth top to rotor center rm=r+p K1. The suction area AK swept by the rotor after one revolution is equal to the difference between the area swept by the rotor RM and the rotor area A

volume utilization coefficient λ Is the ratio of the suction area swept by the rotor to the swept circular area, and the volume utilization coefficient λ Is the efficiency of the suction of the reaction rotor. It can be seen that the smaller the rotor area or the greater the distance RM from the rotor tooth top to the rotor center, the smaller the volume utilization coefficient λ It's big

correction of three leaf involute rotor profile

1. Example

theoretical profile of three leaf involute rotor with an axis distance of 100mm and a pressure angle of 50 °, use the query function of CAD software

2. Correction of three leaf involute rotor profile

to adjust the pressure angle α Reduce it appropriately and increase the addendum radius PK1 appropriately. The purpose of this correction of the profile is to increase the volume utilization factor λ， But when α

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