Lathe by Vertical Sliding Table Rotation Method

Figure 10-7

In addition, for the keyway, the symmetry of both sides of the groove must be checked with the shaft centerline. This requirement can be checked with a gauge (Figure 10-8). After reaching the gauge in position 1, if the gap is even, lift it out. Turn the gauge 90 0 and place it in position 2. If the keyway is symmetrical, the contact between the gauge and the groove is even. Then push the gauge along the shaft to check along the length. If the gap is even, the keyway is parallel.

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Checking the parallelism of the keyway and spline with the shaft centerline can be done by placing the shaft collar on two short V-blocks, and placing the dial indicator foot against the side of the keyway and spline (Figure 10-9) and measuring at two positions.

Figure 10-8 Figure 10-9

Question

Question 1. List the tools for machining flat keyways and semi-circular keys.

Question 2. Describe the principle of key processing by the shaping method and the blanking method.

Question 3. State the methods of checking keyways.

Introduce:

CHAPTER 11 : PROFILE PROCESSING

Chapter code: MH 21 - 11

“ Profile surface machining ” is a complex technology, when cutting the cutting force is very large, so the worker must have other cutting processing skills. The profile surfaces on the details are mainly used to create beautiful shapes, or handles, and are rarely used for assembly .

Target :

- Recognize the methods of machining shaped surfaces;

- Describe the principles of shaping motion of shaping processing methods;

- Practice discipline, perseverance, carefulness, seriousness, initiative and positivity in learning.

Content :

1. Concept, technical requirements.

On a detail, the detail surface has a generating line that is not parallel to its axis, that detail surface is called a forming surface.

- The facial contour has a regular curve that is not broken;

- The shaping surface must ensure surface smoothness.

2. Method of machining shaped surface

Target :

- Recognize the methods of shaping on lathes using lathe tools;

- Describe the principle of the knife and the details when processing;

- Have a positive self-discipline in learning .

2.1. Machining with shaping knife .

Normally, the workpiece performs a circular motion to create a cutting motion, the tool performs a translational motion (S), to ensure that the cutting process is continuous. S = S ng + S d . If the tool feed S ng = 0 then S = S d we get a smooth cylindrical surface .

If S d = 0 then S = Sng , that is the case of turning the oil surface or cutting off. If S ng # 0, S d # 0 then S = S ng + S d , that is the case of turning the shaped surface (figure 11-1)

horizontal

Figure 11-1

Figure 11-1 Forming by moving the tailstock in the horizontal direction

From there there are two convenient shaping methods:

Horizontal feed shaping ( S d = 0 ) :

In this case the workpiece rotates, the tool only performs a forward motion.

horizontal, the cutting edge of the knife has the shape of the part's generating line and must lie in a horizontal plane passing through the center of the part. This method is only applicable when the forming surface has a length less than 60mm. If the forming surface has a length greater than 60mm, the cutting edge will be long, difficult to manufacture accurately, large cutting force can easily cause vibration, people often take Sng = 0.01 - 0.1 mm/rev.

If the length of the shaped surface is less than 60mm. Usually shape it with a shaping knife (figure 11-2)

Figure 11-2 Forming with a shaping knife

If using a horizontal feed lathe fixture, non-rotating parts can be machined.

Forming by combining horizontal and infeed motions

vertical :

This method not only processes round shaped surfaces but also

also capable of machining eccentric surfaces, internal and external spherical surfaces.

When the length of the forming surface is large, a shaping lathe should not be used because the shape of the tool is complex, the cost is high due to difficult manufacturing, and vibration when cutting.

If the surface has a straight generating line, use a disc milling cutter (Figure 11-3). The accuracy of the forming surface depends on the accuracy of the forming cutter (circular milling cutter, gear forming milling cutter).

Figure 11-3. Milling grooves with a disc milling cutter

Formed holes in mass production are machined with a boring tool (Figure 11-4).

The shaped surface after quenching can be processed with a shaped grinding stone. The grinding stone surface is corrected with a copying jig, ensuring high processing accuracy (Figure 11-5).

Figure 11-5 Figure 11-4

The profile surface can be milled by the following methods:

Forming milling with a shaping cutter : Can process forming grooves with straight generating lines such as processing rectangular grooves, circular grooves, keyways, gill grooves and machining gears. Because the cutting speeds of the points on the cutting edge are not the same, the cutter wears unevenly, making it difficult to manufacture, the cutting speed is not high, leading to low productivity. Machining accuracy depends on the precision of the cutter manufacturing, the mounting method and the accuracy of the surface used as a reference.

2.2. Forming by copying fixture.

2.2.1. Forming turning (Figure 11-6)

after:

Figure 11-6. Turning by rotating the longitudinal slide table

Cone turning, in addition to using a shaping knife, can also use other methods

Cone turning by moving the tailstock horizontally. When turning a cone

has a mounting length of 2 center points to perform horizontal movement.

interval (h) figure 11-1. Formula for calculating (h )

Forming turning uses a copying mechanism (figure 11-7,8). When changing different templates, different circular shaped surfaces can be machined. Using a copying fixture, spheres, cams, and discs can be machined.

Figure 11-7. Forming with a copy template

Figure 11-8. Forming with closed template

2.2.2. Forming milling (Figure 11-9)

Milling according to the copy template, on the fixture using a conventional milling cutter (figure 11-9) the copy fixture has a rotary table.

The nature of copy milling is that in addition to the cutting motion caused by the rotating tool, two feed motions are also required: (the longitudinal feed motion Sd performed by the machine table and the transverse feed motion Sng performed by the tool head).

by the roller or cutter head always in contact with the template surface by the pressure of the spring or the load of the counterweight.

The accuracy of the machined object depends on the accuracy of the template, the template on the movement of the machine and other auxiliary mechanisms. Normally, to reduce the machining error, the template is made larger than the surface to be machined.

+ Each rotating cutting piece has 3 to 4 cutting blades manufactured according to standards and then clamped tightly to the knife head. After the cutting blade wears out, the rotating cutting piece can be easily rotated to use other cutting blades. When all the cutting blades are worn out, a new rotating cutting piece can be quickly replaced, thus shortening the auxiliary time.

+ In case of using specialized machines, it is possible to process many different surfaces at the same time with many knives.

2.3.Processing the shaped surface on a specialized machine .

The shaped surface can be machined on a special copy machine, by using templates and samples with a similar profile to the shaped surface to be machined. Through the probe that is always pressed against the sample, it guides the tool or part to move according to the profile and sample to create the shaped surface. This method is often used on lathes or copy milling machines.

Figure 11-9. Copy milling fixture

Question

Question 1. Describe the principle of machining a shaped surface with a shaping knife. Question 2. Describe the principle of machining a shaped surface with a copying jig.

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