Stepped hole with butterfly spring centering mandrel

Department of Mechanical Engineering, Anhui University of Science and Technology (Huainan 232001) Jiang Zhiming often encounters stepped hole parts as shown in the actual processing. Due to structural limitations, such as the use of a cylindrical (cone) mandrel, an elastic sleeve centering or a liquid plastic centering mandrel, it is inconvenient and it is difficult to ensure accuracy. for

Department of Mechanical Engineering, Anhui University of Science and Technology (Huainan 232001) Jiang Zhiming often encounters stepped hole parts as shown in the actual processing. Due to structural limitations, such as the use of a cylindrical (cone) mandrel, an elastic sleeve centering or a liquid plastic centering mandrel, it is inconvenient and it is difficult to ensure accuracy. To this end, the use of a disc spring centering mandrel can better solve this problem.

Shown is a simplified diagram of one of the gears in a planetary transmission. The tooth surface of the material is carburized and quenched. The hardness of the tooth surface is 58. The internal tooth is a medium hard tooth surface. The hardness of the tooth surface is centered on the right end of the workpiece to clamp the workpiece. Conversely, when the nut 10 is loosened, the disc spring sets 3 and 6 are restored to a free state (the nut 10 does not have to be unscrewed), and the workpiece is removed. The loading and unloading of the workpiece is very convenient. . Mandrel 2. Positioning sleeve 3, 6. Disc spring group 3845HRC.5il20m6, sil30m6 is the mounting bearing, which is the design and assembly standard of the part. Obviously, when the outer circle and the outer tooth surface are ground after heat treatment quenching, it is convenient to position the inner hole and the end surface. Since the inner hole is a stepped hole, it is inconvenient to use an elastic sleeve centering or liquid plastic mandrel centering structure to center. The tolerance of the hole is large. If the machining accuracy of the hole is excessively increased, the measurement and control are inconvenient and uneconomical. When the machining accuracy of the hole is properly increased, the accuracy of the outer circle and the tooth surface is relatively high. For example, the center of the cylinder is centered. In order to ensure the machining accuracy, the mandrel needs to be grouped and matched, and the number of groups is large, and the installation is inconvenient.

After analysis, the part is processed by the disc spring centering mandrel clamping, as long as the design and processing are reasonable, the processing requirements can be ensured, and the installation is convenient.

As an assembly drawing of the fixture. The clamp is mainly composed of a mandrel 1, a positioning sleeve 2, a disc spring group 3 and 6, a spacer sleeve 4, a guide sleeve 8, a nut 10 and the like.

Since the disc spring group 6 requires more axial force than the disc spring group 3 at the same deformation amount, after the workpiece 5 is placed on the mandrel 1, the workpiece 10 is screwed to the mother 10, and the pad 9, the guide sleeve 8, the pad 7, The disc spring group 6 and the spacer 4 first deform the disc spring group 3 so that the end surface abuts against the end surface of the positioning sleeve 2 while the workpiece is centered. Continue to tighten the nut 10, the disc spring group 6 becomes 5. Workpiece 7, 9. Pad 8. Guide sleeve 10. Nut 1 Design of the disc spring group The disc spring is a frustoconical compression spring stamped with a steel plate. It has the characteristics of variable rigidity. According to the ratio of the limit stroke of the disc spring and the thickness of 3, the different disc spring characteristic curves can be obtained. As a centering use, the key is how to improve the centering accuracy, so that the shape curves of the two sets of disc springs are basically the same. The disc spring combination type is a superimposed type to reduce the axial dimension.

When arranged in the manner shown, in the case of the same amount of deformation, the axial force required for the disc spring group 6 should be made larger than the disc spring group and the direction in which it is placed. When the axial force is applied, the disc spring group 3 is first deformed, and the workpiece is pushed toward the end surface of the positioning step to be fitted to ensure the positioning accuracy of the end surface. The inner and outer circles of the disc spring must be machined, and the end faces of the two outermost disc springs should also be flattened.

Figure. The single disc spring can be estimated according to the following formula: - Under the static load, the allowable stress of the disc spring is calculated as follows: - the free height of the single disc spring, mm - the thickness of the single disc spring, mm -The load of the single disc spring, the deformation of the N-single disc spring, mm-auxiliary amount, can be found from the relevant table in the design manual - calculate the stress, /=.75; id, allow 2550~2940MPa stack The total load and total deformation of the combination disc spring are calculated as: a total load, N total deformation, mm - the free height of the combined disc spring, mm - the number of laminated layers h friction factor force is used to consider the influence of friction The frictional force is related to the surface quality, the lubrication condition and the number of laminated layers. Generally, the load per layer increases by about 2%. The number of laminated layers is determined according to the width of the positioning surface, and the number of laminated layers is not too much. In this example, the number of disc spring groups 3 is 6, and the number of disc spring groups 6 is 8. 42~52HRC. The disc springs should all be subjected to strong pressure treatment, and the free twist should be stable after the strong pressure treatment.

2 The main parts are designed to ensure the centering accuracy. The coaxiality of the inner and outer circles of the mandrel 1, the positioning sleeve 2, the spacer sleeve 4 and the guide sleeve 8 is not more than 0.005 mm, and the end face circular runout is not more than 0.005 mm. Both ends of the roughness pad 7 and the pad 9 should be parallel. The quenching hardness of each of the above parts must be higher than the surface hardness of the disc spring. In this example, the hardness is 58~62HRC. The pressing end face and the thread of the nut 10 should be clamped at one time.

In order to avoid the influence of the deformation of the disc-shaped magazine due to excessive deformation, the dimensional accuracy of the positioning hole on the workpiece is not greater than the IT9 level. In this example, the holes 纟limm and 83mm for positioning on the original part are now increased to (4110.1H8 and 83H8, and must be clamped and grounded at one time to ensure the coaxiality requirement.

Disk-shaped pulse-prepared core drilling machine with Hunan Oil Pump Factory (Hengdong 421400) Li Fuxing When we process the threaded bottom hole on the brake disc of the car in batch, due to the high precision of the hole position, the three-point set is adopted. The core drilling fixture has insufficient three-point expansion force and a slight displacement during drilling, so that the hole position does not meet the requirements of the pattern. Later, we improved and designed a disc-shaped expansion-type centering drilling jig to better solve the above quality problems.

The structure of the drilling fixture is as shown in the figure. The centering of the drilling fixture is mainly centered on the lower half of the boss of the drill template 1 and the inside and outside of the disk expansion sleeve 3. The inner hole of the disc expansion sleeve 3 is provided with a taper of 18* and cooperates with the boss half round. The circumference of the disc expansion sleeve 3 is provided with equal expansion grooves. When the upper nut 4 is screwed, the disc expansion sleeve 3 is pulled upward, and by the action of the taper surface, the outer circumference thereof is uniformly expanded outwardly to expand the inner hole of the workpiece. Since the outer circumference of the expansion sleeve and the surface of the workpiece hole are long, the expansion force is large, so it is not easy to loosen, and the processing quality is ensured, and the positioning accuracy can reach about 0.05 mm.

1. Drill template 2. Drill sleeve 3. Disc expansion sleeve 4. Upper * Female 5. Mast 6. Lower nut 7. Workpiece 3) Should be ground after assembly. The method is to first pre-tighten the disc-shaped magazine group (/=0.2/-0.3), and grind the outer circle of the disc-shaped spring group. The tolerance of the outer circle is controlled by h6.

Before the mandrel is used, lubricate between the disc spring sets and between the positioning sleeve and the guide sleeve. In order to ensure the centering accuracy, when the workpiece is removed, the carrier 10 should not be completely loosened, that is, the disc spring group should have a certain pre-tightening force.

The disc spring centering mandrel is used for centering of stepped hole parts, and has the advantages of automatic centering, reliable clamping and convenient use. If the design is reasonable, the disc spring group has a high processing precision, which can achieve higher centering accuracy.

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