Accessory is used for processing of hole with diameter of 47 mm near the part Rod

Introduction

A machine tool is an auxiliary tool of production for installing blanks for processing on metal cutting machines.

Depending on the type of machine, machine tools are divided into turning, drilling, milling, boring, grinding, etc. Of the total process tooling, about 50% are machine tools.

With the help of machine tools, three main tasks can be solved:

- basing of machined parts on machines is carried out without reconciliation, which accelerates the installation process and provides the possibility of automatic obtaining of dimensions on tuned machines;

- Increased productivity and easier working conditions for workers through multi-seat, multi-position and continuous processing;

- The processing capabilities of machines are expanded, which allows to perform such processing on ordinary machines or to obtain such accuracy for which these machines are not intended.

Accessories are selected depending on the type of production. In mass and large-scale production, special devices are mainly used. In repetitive production conditions, aggregated devices are used. In small-scale and single-scale production, universal devices are widespread.

The design of devices depends not only on the type of production, but also on the process of manufacturing the part, which provides a close connection between the technologist and the designer at the factory. The theme of this course work is the development of a mechanized machine tool for roughing and finishing of a hole with a diameter of 47mm on a NC vertical milling machine.

Preparation of fixture design assignment

Preparation of the engineering specification is required for a thorough understanding of the initial data for the design, the purpose of the device, the operating conditions of the device, the required operational indicators of the device, the composition of the developed design documentation.

1. The accessory is intended for treatment of hole with diameter of 47 mm near part Rod C63340512 on vertical milling machine with CNC. This device must perform a number of functions: a blank must be installed on it; the workpiece must be fixed; The workpiece must be mechanically clamped.

2. Billet material Steel 45 GOST 105074 having tensile strength = 600 MPa. Billet is made in the form of two-stage shaft, weight of which is 0.64 kg. The length of the workpiece is 407mm. Blank has preformed hole with diameter of 43mm. External cylindrical surface Ø30mm has 9 accuracy and roughness Ra3.2. External cylindrical surface Ø20mm has roughness Ra6.3. We believe that the surface is treated with finishing turning.

3. The hole will be swept by a boring cutter. Material of cutting part of cutter is hard alloy T15K10. The position of the cutter relative to the workpiece is made by adjusting the machine. The hole shall be 47 mm in diameter. Surface roughness shall not exceed Ra2.5. When processing a hole with a diameter of 47mm, it is necessary to maintain a size of 320js11, a deviation from the perpendicular 0.05/100, as well as a deviation from the coaxial T/2 0.25. The annual output of these parts is 6000 pcs. per year. The dilution will be carried out without SOF.

4. This fixture will be installed on a vertical milling machine with NC FP17BS2. The size of the working surface of the machine table is 1600x500 mm. Dimensions of the designed accessory shall not exceed dimensions of the accepted machine table. The number of T-shaped slots of the received machine is 3 pieces, width is 20H7 mm.

Sketch study of machine tool

This basing scheme can be implemented by mounting the preform with cylinders on a support prism with a stop on the end of the prism.

By selecting a method for installing the part and placing the mounting elements in the fixture, we select a clamping device. The fixture clamping device must not change the position of the part in the fixture when it is fixed and allow its displacement on the machine. In our device we use a pneumatic power drive with a two-shoulder straight lever. Due to the long length of the blank, we use two levers. For convenience of blank removal and installation the lever is moved to the side. Clamping force is directed perpendicular to billet axis.

To implement point 6, we use a catcher. When it is installed in the slot, a fit with a gap H8/g6 is used. When the catcher is moved, the end face of the cylinder with diameter of 20 mm moves until it comes into contact with the stop against the end face of the prism. The pneumatic cylinder is switched on and fixes the workpiece, the catcher is retracted.

The accessory is a cast body, on which a prism and a pneumatic cylinder are installed. The pneumatic cylinder is accepted due to the relative ease of manufacture. Also, most enterprises have a pneumatic network, which makes it cheaper and easier to install and maintain. On the machine table, the accessory is fixed by means of two bolts along T-shaped slots of the table.

It is also necessary for the device to set a certain position on the machine table in relation to the longitudinal feeding direction of the table. In this case, the orientation of the devices is carried out with the help of keys along T-shaped slots, the direction of which exactly coincides with the direction of the longitudinal supply of the table. The most widely used are normalized (MN 479063) screwed keys.

After installation of the accessory, hoses of centralized compressed air supply are supplied to it. When assembling the accessory, it is necessary to ensure smooth running of all movable parts of the accessory, during assembly and operation of the accessory use TSIATIM201 lubricant GOST 626774.

The part is fixed and machined as follows:

Billets are installed in prism until stop by end surface against end face of prism.

A catcher is installed to prevent the workpiece from rotating about the x axis.

. Pneumatic cylinder is actuated to clamp blank by means of lever.

The catcher is removed.

The hole is being processed.

The pneumatic cylinder is turned on in reverse direction, the part is taken out.

Conclusion

In this course work, a variant of the device for processing a hole with a diameter of 47mm on a NC vertical milling machine at the part "Rod Ts63340512" with an annual production volume of 6000pc/year was considered.

By calculating the main characteristics of the power mechanism of the accessory, the clamping forces of the accessory, after calculating the strength and accuracy, the most effective accessory was determined. This device is a device with a pneumatic clamp of a part.

Using this device, the proportion of rejected products is reduced.

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