Research on machining the hottest double guide lay

Research on the machining of double guide layer involute worm on lathe

the six wire involute worm used in 5327 gear hobbing machine is seriously worn after long-term use. Under the condition that outsourcing cannot be solved, through the efforts of the company's technicians, the machining problem of turning six wire involute worm rod on C ordinary lathe has finally been overcome. Now, the technical theory and machining method are introduced in detail

1 calculation of change gear of lead

5327 the working diagram of the six thread involute worm used by the hobbing machine is shown in Figure 1. The normal section of the worm is an extended involute in the process of "greening" of plastic flexible packaging. To solve the turning of the left and right tooth surface lead of pl=173.02 and pr=166.62, the single change gear method can be preferentially selected. The selection and calculation of change gear are as follows:

i1/i=p1/p, i=a/c, I1=a1/c1

p1=i1p/i= (a1/c1) p/(a/c) =a1 cp/ac1

where: I1 -- transmission ratio of new change gear

i -- transmission ratio of original change gear on machine tool

p1 -- processing lead

p -- nameplate pitch

a -- original driving wheel on machine tool

c -- original driven wheel on machine tool

a1 -- new driving wheel

c1 - New driven wheel

for pl=173.02, after theoretical trial calculation, take: a=42, c=100, a1=45, c1=109, p=176, Then: p1=a1cp/ac1=45 × one hundred × 176/42 × 109=173.001 ≈ 173

lead error of left tooth surface: Δ P=P1-PL=. 02=-0.02

the error on the full length is: -0.02 × 115/173.02=-0.013

for pr=166.62, after theoretical trial calculation,

take: a rubber tensile testing machine does not need a lot of force =42, c=100, a1=33, c1=83, p=176,

then: p1=a1cp/ac1=33 × one hundred × 176/42 × 83=166.609 ≈ 166.61

right tooth surface lead error: dp=p1-pr=166 62=-0.01

error in full length: -0.01 × 115/166.62=-0.007

through the above calculation, it can be seen that the new change gears a1=45, c1=109 and a1=33, c1=83 are used to replace the original change gears a=42 and c=100 on the C lathe respectively to solve the turning of the left tooth surface lead pl=173.02 and the right tooth surface lead pr=166.62. The error is very small, and the two differences are the same in symbols, which has no impact on the tooth thickness of the double lead, especially the quenching and grinding of the part after turning, Therefore, the newly designed two sets of change gears are very suitable for semi finishing

2 thread splitting method of large lead multi thread

thread splitting method is mainly divided into two categories, one is linear splitting method, the other is circular splitting method. Through practice, we have found a new method of dividing lines, that is, dividing lines with the number of gear teeth on the main shaft

in general, the lathe with the number of gear teeth on the main shaft that can be divided by the number of machining lines should be preferred to solve the problem of dividing lines. If the number of gear teeth on the main shaft cannot be divided, the following methods can be used:

in rough turning, the comprehensive method of screw opening and closing nut and small tool holder correction should be used to solve the problem: in order to ensure the accuracy of dividing lines, the method of dividing the number of driving gear teeth of the change gear box should be used in fine turning, Its principle and specific method are as follows:

k/z1=k+a/b, (a/b) × A1=k1+a1/b1

in the formula, K -- multiple of increasing pitch mechanism

z1 -- number of worm heads

k -- integer value of driving wheel rotation

a/b -- fractional value of driving wheel rotation

we can see from the C supplementary turning thread allocation table: when p=176, k=32

for the left tooth surface lead pl=173.02,

z1=32/6=5+1/3, 1/3 × A1=(1/3) × 45=15

that is, when processing the left tooth surface lead pl=173.02, the driving wheel can be rotated for 5 turns and 15 teeth to process the first line: then rotate the driving wheel for 5 turns and 15 teeth to process the second line: the same is true until processing to the sixth line

for the right tooth surface lead pr=166.62,

k/z1=32/6=5+1/3, 1/3 × A1=(1/3) × 33=11

that is, when the lead PR of the right tooth surface is processed = 166.62, the driving wheel can be rotated through 5 turns and 11 teeth to process the first line: then the driving wheel can be rotated through 5 turns and 11 teeth to process the second line: the same is true until it is processed to the sixth line

3 speed reduction methods for processing double lead tapered worm

there are many speed reduction methods. The speed reduction method we choose is to replace the V-shaped pulley of the motor on the lathe, so as to achieve the purpose of speed reduction

4 processing method to ensure that the extended involute tooth groove is a straight line

the extended involute line is divided into "tooth groove straight profile" and "tooth profile straight profile". The six thread involute worm studied in this paper is the "straight tooth profile" in the extended involute line. The "straight profile of the tooth slots" is guaranteed by turning tools and tool rows. Whether manual or mechanical grinding is used, the left and right offset angles should be grinded according to the requirements of the left and right tooth shape angles in the drawing. The two blades should intersect the center line of the tool, and then the grinded turning tool should be installed in the tool row, which is installed on the tool rest. During machining, first check whether the left and right edges of the tool are installed correctly. During operation, the tip of the tool is aligned with the center line of the workpiece. For right-hand threads, the turning tool can be rotated to the left by a spiral rise angle, and the normal section of the tooth shape is processed, that is, the extended involute tooth groove is a straight line (the attached tool arrangement diagram is shown in Figure 2)

figure 2

according to the different thread rotation direction, the two actual working rear angles are also different. For right-hand threads, the rear angle of the left blade of the turning tool is equal to the basic rear angle of the turning tool plus the spiral rise angle, and the actual working rear angle of the right blade is equal to the basic rear angle of the turning tool minus the spiral rise angle. The actual working rear angle is naturally formed when the cutter row rotates a spiral angle

when turning right-hand thread, the left tooth surface is easy to cut, and the right tooth surface is not conducive to cutting because of the gap between the lead screw and the split nut. Therefore, you can turn the left tooth surface to the right tooth surface for turning, but you need to pay attention to the correctness of the tooth shape angle

in order to improve the meshing quality of the machined worm gear pair, the worm can be ground on the lathe

5 turning tool selection and grinding

for the double lead tapered worm, these parameters are beyond the normal thread processing tool, so it is not easy to operate and cut. In order to solve the geometric problems of cutting tools, we take the following measures:

first, the tool tip material is W18Cr4V. Secondly, due to the large module and high finish of the worm, it is divided into rough and finish machining. During fine turning, due to the narrow groove bottom, in order to avoid the two edge turning tool touching the tooth surface of the groove bottom when it is at the bottom of the fine turning groove, the left and right single edge fine turning tools can be selected. The spiral countersunk groove of the cutter is transferred by the grooving cutter at the bottom, as shown in Figure 1. In short, five turning tools need to be selected, namely, a coarse turning tool, a fine turning tool, two left and right single blade fine turning tools, and a slotting tool

(1) during rough machining of rough turning tool (as shown in Figure 3), due to the large machining allowance, when adjusting the whole tool, the tool tip can be appropriately higher than the workpiece center, and the tool tip can be repaired into an arc. For the turning of ordinary threads, the general back angle is 3 ° ~ 5 °, while for spiral parts with large lead and large spiral rise angle, the tool edge is ground into a double back angle, that is, 2 ° ~ 3 ° near the edge and 5 ° ~ 6 ° outside, which can enhance the strength of the tool tip, It is conducive to radial and longitudinal strong cutting, but also increases the heat dissipation area and improves the tool. It is necessary to know the heat resistance and wear resistance of the placement position of the sample, so that it will not collapse under the action of large cutting load and prolong the tool life

figure 3

during rough turning, in order to make the cutter head sharp and easy to cut, an appropriate rake angle can be ground

(2) in order to ensure the accuracy of tooth profile, the rake angle of fine turning tool can be selected as 0 °. As the finish turning allowance is small, the double back corner can not be selected for the back corner of the finish turning tool. In order to improve the smoothness, only use an oilstone to grind two blades slightly. For large lead spiral parts, the rear angle of the left tooth surface can be taken as 5 °, while the actual working rear angle is equal to 5 °+ β L=5 ° +31 ° 28 '=36 ° 28', the rear angle of the right tooth surface should be 3 °, while the actual rear angle is equal to 3 °- β R=3 ° -30 ° 31'=-27 ° 31'(as shown in Figure 4) and set the sample parameters of each experimental situation. The width of the bottom of the tooth groove is narrow. When machining the left tooth surface of this part with the precision turning tool of turning worm, the tool may touch the right tooth surface. When machining the right tooth surface of this part, the tool may touch the left tooth surface. Therefore, when machining the bottom of the tooth groove, the single-sided left and right precision turning tools can be selected (as shown in Figure 5)

figure 4

figure 5

(3) the grooving cutter can be used as a standard cutter. The practice has proved that the processing problem of double lead tapered worm can be solved according to the above method. In addition, it should be noted that the processing method introduced in this paper is suitable for single piece and small batch production. For mass production, gear hobbing can be used for rough processing and special equipment can be used for finish processing