The quality of gear produced is as much dependent on the quality of gear lank used as on the accuracy of the machine used for teeth cutting. The locating surfaces should be selected and maintained throughout the manufacturing processes.
Gear blanks may be either of the following two types: (a) Shaft type having centers, and (b) Cylindrical blanks with round bores with or without keyway or with splined bores.
Shaft type blanks are usually mounted between centers during all the operations. Therefore, to get accurate gears, the centers should not be damaged during material movement, and they should be cleaned while mounting on the machine as well. A typical shaft like component is shown in second Figure.
In this case, the locating surfaces are the cone-surfaces C and D of the centers. The first requirement is that these centers should be in line so that you get proper contact on the locating surfaces. These cone surfaces should be smooth, and used for manufacturing both the mounting surfaces A and B as well as for tooth cutting. Gear outer surface E also should be produced in the same operation like the operation of producing surfaces A and B, and it (surface E) can be consequently used for dialing when mounted on the gear-cutting machine to check the accuracy of mounting.
Cylindrical blanks can be of two types, namely, (a) Blanks having round bore with or without keyway, and (b) Blanks having splined bore. Fig2 For this, normally the bore (Surface A) and the face (Surface B perpendicular to it are the locating surfaces, as shown in the first figure.
. The requirements of the blank are the following :
(a) Surface B should be at right angles to surface A. For very accurate gears, face runout of surface B required will vary from 5 (0.002”) to 25 m (0.001”) depending on the accuracy required. For very accurate gears it can be 5 m. for normal accuracy gears (such as DIN 7 Class) it can be 10-12 m.
(b) The bore A should also have close tolerance so that while it is mounted on the machine, there is minimal play between the bore and the mounting mandrel. This will reduce pitch errors generated due to the blank runout. It may, therefore, be necessary to green grind the cylindrical blanks for bore A and face B to achieve the necessary accuracy for process purposes though it may not be required for actual operation of the gear.
(c) Face C is kept concentric with respect to the locating surface A so that it can be used for initial dialing on the gear-cutting machine.
The tooth cutting processes can be divided into two types, namely, form machining and tooth generation process.
Gear blanks may be either of the following two types: (a) Shaft type having centers, and (b) Cylindrical blanks with round bores with or without keyway or with splined bores.
Shaft type blanks are usually mounted between centers during all the operations. Therefore, to get accurate gears, the centers should not be damaged during material movement, and they should be cleaned while mounting on the machine as well. A typical shaft like component is shown in second Figure.
In this case, the locating surfaces are the cone-surfaces C and D of the centers. The first requirement is that these centers should be in line so that you get proper contact on the locating surfaces. These cone surfaces should be smooth, and used for manufacturing both the mounting surfaces A and B as well as for tooth cutting. Gear outer surface E also should be produced in the same operation like the operation of producing surfaces A and B, and it (surface E) can be consequently used for dialing when mounted on the gear-cutting machine to check the accuracy of mounting.
Cylindrical blanks can be of two types, namely, (a) Blanks having round bore with or without keyway, and (b) Blanks having splined bore. Fig2 For this, normally the bore (Surface A) and the face (Surface B perpendicular to it are the locating surfaces, as shown in the first figure.
. The requirements of the blank are the following :
(a) Surface B should be at right angles to surface A. For very accurate gears, face runout of surface B required will vary from 5 (0.002”) to 25 m (0.001”) depending on the accuracy required. For very accurate gears it can be 5 m. for normal accuracy gears (such as DIN 7 Class) it can be 10-12 m.
(b) The bore A should also have close tolerance so that while it is mounted on the machine, there is minimal play between the bore and the mounting mandrel. This will reduce pitch errors generated due to the blank runout. It may, therefore, be necessary to green grind the cylindrical blanks for bore A and face B to achieve the necessary accuracy for process purposes though it may not be required for actual operation of the gear.
(c) Face C is kept concentric with respect to the locating surface A so that it can be used for initial dialing on the gear-cutting machine.
The tooth cutting processes can be divided into two types, namely, form machining and tooth generation process.
2 comments:
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