Tool for milling key slot, shaft fabrication - drawing

Contents

Summary

Introduction

Purpose and Specification for Fabrication

Evaluation of Constructability

Workpiece Manufacturing Process

Definition of tolerances and limit deviations

Determining the Size of a Bar

Setting of heating and cooling mode

Forging operation

Forging Process

Part pretreatment processes

Part machining process

Selection of machine tools

Machining

Final heat treatment

Calculation and design of machine tool

Machine Tool Design

Calculation of fixture capacity

Description of device and operation of accessory

List of literature used

Summary

In the course project, the process of making the shaft was developed. The workpiece production method is selected. The processes of thermal and mechanical treatment of the shaft are designed. Also, the structure of the device for attachment of the shaft during cutting of the key slot is described.

Pages 18, Figures 13, Tables 6.

Introduction

The shaft part is an integral part of the guillotine scissors drive and serves to transmit torque.

During operation, the part is subjected mainly to dynamic loads associated with torque transmission.

This part belongs to the shaft class. All surfaces of the part have access to machining, it is possible to multithreaded productive machining on automatic and semi-automatic machines. The specified accuracy of the part surfaces corresponds to the economic accuracy of the equipment. The part material, steel 45, is easily treated with a blade and abrasive tool. With the thermal treatment of such steel, it is possible to obtain the necessary structure and hardness. The shaft has a small number of stages with a slight difference in their diameters, so this part is made of piece blanks. Shaft surfaces having different roughness parameters and treated to different degrees of accuracy. Part has increasing diameters of steps. Treated and unprocessed surfaces are clearly distinguished.

The choice of overall dimensions, configuration, parameters of accuracy of production of individual surfaces of a part and material of a part is dictated by the dimensions of the article, which includes the manufactured part, the working conditions of the part in the unit and its functional purpose.

Evaluation of Constructability

The development of technological processes is the main section in the technological preparation of production .

The technological process being developed should be progressive, ensuring increase of labor productivity and quality of parts, reduction of labor and material costs for its implementation, reduction of harmful effects on the environment.

The process is developed on the basis of existing standard or group process. Initial information is required in process development.

To develop the part processing process, it is necessary to preliminary study its design and functions performed in the assembly, mechanism, machine, analyze the processability of the design and check the drawing. The working drawing of the part shall have all the data necessary for a comprehensive and unambiguous understanding during the manufacture and control of the part, and comply with the current standards.

Workpiece Manufacturing Process

The represented part is of the Shaft type by its type.

Shafts are smooth, stepped and with flanges at the ends. The most common stepped shafts have a thickening at the middle or at one end.

Shafts whose length does not exceed twelve times the average diameter are considered rigid.

Shafts are mainly made of structural and alloyed steels, which are subject to requirements of high strength, good workability, low sensitivity to stress concentration, as well as increased wear resistance. These requirements are met steel of brands 35,40,45,45G, 40XH, etc.

Billets of stepped shafts are stamped on hammers and presses, made on rotary forging machines and on MCC by landing method.

Billets of stepped shafts are often obtained by cutting hot-rolled rods, they are used in single production, as well as in mass production in the manufacture of shafts with a small difference in the diameters of the stages. Method of obtaining blanks is selected by comparing total production costs of blanks.

The starting material for forged blanks is round rolled stock. Due to the fact that the curvature of the rolled stock and forgings reaches 5 mm/m, the blanks are often adjusted to reduce machining allowances. Straightening reduces curvature of blanks to 0.5 mm/m.

The workpiece of the shaft of the guillotine scissors can be obtained by cutting hot rolled stock or stamping on hammers. It is convenient and advantageous to fabricate a rolled stock in that the diameter of the rolled stock corresponds to the calculated dimensions of the stock, which in turn is advantageous because we have to cut the rolled stock rod into pieces and start the forging process. Steel hot-rolled round steel 45 according to GOST 259088 is used as the initial workpiece.

Setting of heating and cooling mode

The main factor determining the temperatures of the beginning and end of hot deformation is the chemical composition of the alloy and its physical properties.

A two-chamber furnace is used to heat the carbon steel 45. We choose hot-rolled round of ordinary accuracy. The carbon monoxide will be approximately 1.4% by weight.

When forging rod blanks, it is necessary to solve two problems:

- giving the workpiece the specified shape and dimensions of forging;

-Gets the required properties.

An optimal thermal forging regime should facilitate a successful process in which the harmful effect of heat is limited as far as possible and high forging quality is ensured. Therefore, the thermal mode is developed for each steel, taking into account the initial structure of the metal, the volume and the ratio of the dimensions of forging and the purpose of forging.

Heating and cooling mode includes:

- metal heating before forging;

- metal cooling during forging;

- cooling of metal after forging.

The speed of the forging process generally allows for a period of time determined by the cooling of the metal.

One of the main tasks in the development of the thermal forging process is to determine the temperature range. By temperature interval is meant the interval between the temperature of the end of heating and metal and the temperature of the end of deformation. Temperature of metal heating end exceeds temperature of metal deformation beginning by value of temperature loss during metal transfer from heating device to punching mechanism.

The temperature of the metal heating end is 100 250 0 less than the melting point of the metal.

According to the reference data we accept:

- temperature of metal heating end 1200 0С;

- forging end temperature is 850 0С.

The approximate heating time of the preform at a single location in the furnace is 22.5 minutes, at a furnace working space temperature of 1300 0C and a heating temperature of 1200 0C.

The correct heating mode ensures that the metal is heated to the required temperature in the minimum possible time. In this case, the temperature should be equal throughout the entire section of the workpiece. The quality of the obtained forging and its properties depend on the uniformity of the temperature distribution along the section of the workpiece and optimally in value, labor productivity and safety of the performed works.