Inner hole surface processing method and processing plan (in)

There are mainly three ways to boring a boring machine:

(1) The boring machine spindle rotates the arbor and boring tool, and the work table drives the workpiece to perform the longitudinal feed movement, as shown in Fig. 7-12. The bore diameter of this type of boring is generally less than about 120mm. Fig. 7-12a shows an overhanging arbor, which should not be extended too long to avoid excessive bending deformation. It is generally used for boring holes with smaller depths. The cutter bar shown in Fig. 7-12b is longer and is used to cut the coaxial hole system with the two walls farther apart from each other. In order to increase the rigidity of the arbor, the other end of the arbor is supported in the guide pedestal of the rear column of the trampoline.

(2) The boring machine spindle rotates the arbor and boring tool and performs longitudinal feed motion, as shown in Fig. 7-13. In this way, the length of the overhang of the main shaft is continuously increased and the rigidity is weakened. Generally, it is only used to cut short holes of a short length.

In the above two boring methods, the size and tolerance of the hole diameter are ensured by adjusting the protruding length of the cutter head, as shown in Figure 7-14. Need to be adjusted, tested and measured, after the qualified aperture can be officially boring, and its operating technology requirements are high.

(3) The rotary table of the boring machine drives the boring knife to rotate, and the work table drives the workpiece to perform the longitudinal feed movement.

The trampoline leveling disc shown in Fig. 7-15 can be moved up and down with the headstock and can perform its own rotary motion. Radial tool holders in the middle can perform radial feed movements and can be in any desired position.

As shown in Fig. 7-16a, the radial tool holder is used to make the boring tool in the eccentric position, so that the large hole can be bored. Holes of Φ200mm or more are used for this boring method, but the holes should not be too long. Fig. 7-16b is a boring inner groove. The rotary disk drives the boring tool to rotate, and the radial tool holder drives the boring tool to perform a continuous radial feed motion. If you extend the tip beyond the end of the shank, you can also boring the end of the hole.

Boring machines are mainly used to cut support holes, inner grooves, and hole end faces of large and medium-sized brackets or boxes. Boring machines can also be used for drilling, reaming, reaming, milling, and milling planes.

3. Milling machine bore

The boring hole in the horizontal milling machine is the same as that shown in Fig. 7-12a. The boring bar is installed in the spindle taper hole of the horizontal milling machine to make a rotary motion. The workpiece is mounted on the workbench to make a horizontal feed motion.

4. Floating boring

As mentioned above, single-edged boring tools are used for the boring of lathes, boring machines, and milling machines. In the batch or mass production, for the hole with large hole diameter (>Φ80mm), long hole depth and high precision, it can be finished with a floating boring tool.

The adjustable floating boring block is shown in Figure 7-17. During adjustment, loosen the two screws 2 and turn the screws 3 to adjust the radial position of the block 1 to match the diameter and tolerance of the bore. The floating boring tool for turning the workpiece on a lathe is shown in Figure 7-18. In operation, the arbor is fixed on the square tool holder, and the floating boring knife is installed in the rectangular hole of the arbor, and is automatically centered by the balance of the radial cutting forces of the two blades, so that the knife block can be eliminated. Installation error caused by the aperture error.

Floating boring is essentially equivalent to reaming, and its machining allowance and achievable dimensional accuracy and surface roughness values ​​are similar to those of reaming. The advantage of floating boring is that it is easy and stable to ensure the quality of processing, and the operation is simple and the productivity is high. However, it is not possible to correct the positional error of the original hole, so the positional accuracy of the hole should be guaranteed in the previous process.

5. Boring process features

Single-edge boring boring has the following features:

(1) The adaptability of boring is strong. Boring can be performed on the basis of drilling, casting and forging holes. Achievable wide range of dimensional tolerances and surface roughness values; except for small and deep holes, holes of various diameters and various construction types can be cut, as shown in Table 7-1. .

(2) Boring can effectively correct the position error of the original hole, but because the diameter of the boring bar is limited by the hole diameter, its rigidity is generally poor, and it is easy to bend and vibrate. Therefore, the control of boring quality (especially slender holes) is not as good as Reaming is convenient.

(3) The productivity of boring is low. Because boring requires multiple cutting passes with smaller depth of cut and feed to reduce the bending deformation of the arbor, and the boring and boring need to adjust the radial position of the boring burr on the arbor in the boring machine and the milling machine. The operation is complicated and time-consuming.

(4) Boring is widely used for hole machining of various parts in single small batch production. In mass production, boring the bearing holes of the bracket and the box requires a die.

V. Lacon

Lakong is a highly efficient finishing method. In addition to broaching round holes, it is also possible to broach through holes and inner keyways of various cross-sectional shapes, as shown in Figure 7-19. The broaching round hole can reach the size tolerance grade IT9~IT7, and the surface roughness value is Ra1.6~0.4μm.

1. Broaching can be seen as planing by a number of planers arranged in order of height, as shown in Figure 7-20. The structure of the round hole broach is shown in Figure 7-21. The function of each part is as follows:

Handle The broaching tool holder holds the broach.

neck The diameter is the smallest. When the broaching force is too large, it is generally broken here, which is convenient for welding repair.

Transition cone Guide the broach into the hole being machined.

Leading part Ensure that the workpiece smoothly transitions to the cutting part, and at the same time check whether the aperture before pulling is too small, so as not to overload the first blade and damage it.

Cutting section Including coarse and fine teeth, the main cutting work.

Calibration section To calibrate the tooth, its role is to correct the aperture, repair hole wall. When the diameter of the cutting tooth is reduced, the first few calibration teeth are ground into cutting teeth.

Follower When the broach teeth are cut away from the workpiece, the workpiece is prevented from sagging and scratching the machined surface and damaging the teeth.

The horizontal broaching machine is shown in Figure 7-22. The bed is equipped with a hydraulic drive cylinder. The right end of the piston rod is equipped with a follower bracket and tool holder to support and hold the broach. Before work, the broach is supported on the rear bracket of the roller and broach, and the workpiece is penetrated by the left end of the broach. When the tool holder holds the broach to the left and moves in a straight line, the workpiece rests on the “support” and the broach can finish the cutting process. The straight movement of the broach is the main movement, and the feed movement is accomplished by the amount of increase of each tooth of the broach.

(1) The broaching round hole is shown in Figure 7-23. The broaching hole diameter is generally 8~125mm, and the aspect ratio of the hole is generally not more than 5. Pre-cutting generally does not require precise pre-machining, drilling or roughing can be broached. If the end face of the workpiece is not perpendicular to the hole axis, the end face is pressed against the spherical gasket of the broaching machine. Under the action of broaching force, the workpiece rotates slightly together with the spherical surface washer so that the axis of the hole is automatically adjusted to the direction of the broach axis. Consistent, avoid breaking broach.

(2) Broaching the inner keyway is shown in Figure 7-24a. The keyway broach is flat and the upper part is a knife. The correct position of the workpiece and broach is ensured by the guide element. The cylinder 1 of the broach guide element (Fig. 7-24b) is inserted into the hole of the broaching end, the cylinder 2 is used for placing the workpiece, and the slot 3 is for positioning the broach.

2. Broaching process features

(1) When broaching, the broach multi-teeth works at the same time, and rough finishing is completed in one stroke, so the productivity is high.

(2) The broach is a fixed-size cutter, and there are calibration teeth for calibration and light repair; the broaching adopts hydraulic system, the transmission is stable, and the broaching speed is very low ( = 2~8m/min), the cutting thickness is thin, no built-up edge is produced, so the broaching can obtain higher processing quality.

(3) The broaching tool is complicated to manufacture and costly. A broach can only be used for a size hole or a key groove. Therefore, broaching is mainly used for mass production of mass production or styling products.

(4) The broaching cannot process step holes and blind holes. Because of the working characteristics of the broaching machine, holes in some complex parts are not suitable for broaching, such as holes in the box.

Six, grinding hole

Grinding is one of the finishing methods for the holes. The attainable dimensional tolerance grade is IT8~IT6, and the surface roughness value is Ra0.8~0.4μm.

Grinding can be done on an internal cylindrical grinding machine or a universal cylindrical grinding machine, as shown in Fig. 7-25. Using a grindstone with an internally recessed taper on the end can grind the hole and the shoulder in the hole in a single clamping, as shown in Figure 7-26.

The grinding hole has the following disadvantages compared to the grinding circle:

(1) The surface roughness of the grind hole is generally slightly larger than that of the cylindrical grinding, because the rotational speed of the commonly used internal grinding head generally does not exceed 20000 r/min, while the diameter of the grinding wheel is small, and the peripheral speed is difficult to reach the cylindrical grinding. 35~50m/s cut.

(2) Control of grinding accuracy is not as convenient as grinding of cylindrical wheels. Because the contact area between the grinding wheel and the workpiece is large, the heat generation is large, the cooling condition is poor, and the workpiece is easy to burn; in particular, the axis of the grinding wheel is slender and poor in rigidity, and it is easy to cause bending deformation and cause internal conical error. Therefore, it is necessary to reduce the depth of grinding and increase the number of light-grinding strokes.

(3) Lower productivity. Because the diameter of the grinding wheel is small, the wear is fast; and the coolant is not easy to wash away the crumbs, and the grinding wheel is easy to be clogged, requiring regular dressing or replacement so that the auxiliary time is increased. In addition, the reduction in the depth of grinding and the increase in the number of light mills also have an effect on productivity. Therefore, grinding holes are mainly used for high-precision holes that are not suitable or impossible to make boring, reaming, and broaching, and the finishing of hardened holes.

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