Course "NC NC Process Design for Housing Part"

Introduction

Technology largely determines the state and development of production. Its level depends on labor productivity, economic consumption of material and energy resources, quality of products and other indicators. To further accelerate the development of the machine-building industry as the basis of the entire national economy of the country, it is necessary to develop new technological processes, constantly improve traditional ones and search for more efficient methods of processing and strengthening machine parts and assembling them into products.

An important role in accelerating scientific and technological progress in mechanical engineering is assigned to the training of highly qualified engineering personnel, their mastery of modern methods of manufacturing and control of products, and methods of designing progressive technological processes. Therefore, the graduation by higher educational institutions of engineers in the specialty "Engineering technology, metal cutting machines and tools," as well as the technological training of students in other engineering specialties, are becoming increasingly important.

In the system of education of mechanical engineers, course design according to mechanical engineering technology occupies a special place. This independent work of students is the most important stage of their preparation for graduate design and largely determines the formation of the technological orientation of future engineers .

The purpose of the course project is to consolidate, deepen and generalize the knowledge obtained at the previous stages of the subject study, and acquire practical skills in solving various technological problems of preparing the production of machine parts and developing technological documentation. At the same time, the student must learn to use reference and regulatory literature, GOST, enterprise standards, catalogs and other information materials necessary for conducting coursework and similar developments in production.

Part Processability Analysis

2.1. Qualitative processability analysis

The part is a body made of steel 20 GOST 105088, which has good operational properties.

Machined Part Detail Drawings contain all necessary

information that gives a complete idea of ​ ​ the part, that is, all projections, sections and sections clearly explain the configuration of the part and the method of obtaining the workpiece.

By performing a process analysis of the part design, you can draw the following conclusions: The part has a rational shape. Positive qualities include the absence of abrupt transitions between surfaces, the simplicity of machined surfaces, the unification of features, the absence of sharp edges, and the presence of chamfers. Almost all surfaces are easily accessible and processed by standard cutters and drills, that is, a special tool is not required.

The accuracy of the surfaces is not high. For cylindrical surfaces, high processing accuracy is accepted only for critical areas. Surface roughness is also not high, low roughness is also assigned only to critical surfaces.

The disadvantage is that all surfaces require cutting treatment. This leads to increased labor consumption and overspending on the manufacture of the part.

Nevertheless, we can conclude that in general, the part is technologically advanced in terms of a qualitative parameter, this makes it possible to use high-performance methods for its processing.

Procurement Selection and Design

4.1 Analysis of workpiece production methods

The method of making blanks for machine parts is determined by the purpose and design of the part, material, technical requirements, scale and serial production, as well as cost-effectiveness of production.

To select a workpiece is to establish the method of its production, to outline the allowances for processing each surface, to calculate dimensions and to indicate tolerances for inaccuracy of production.

Since the part material of the steel 20 is not cast, the metal is subjected to pressure treatment as a workpiece.

Rolled products are widely used as blanks and as structural metal for welded products.

Pros: does not require complex equipment to obtain a workpiece. We buy the desired profile and cut off the blank of the required length. Cons: if the part has large step differences, then the rolled stock will have a small material utilization factor (a lot of metal will go into chips); maximum diameter 250 mm.

The blank can be made by forging on hammers. This method is used for parts such as rod with thickening, rings, bushings, parts with holes. It is used for serial and mass production.

Advantages of forging on hammers:

- Allows to obtain high and stable metal quality throughout the cross section;

- Possibility of making large forgings;

- Large forging requires relatively little effort;

- The use of universal machines and in particular universal tools allows you to obtain a wide range of forgings and at the same time dramatically reduce costs.

At the same time, forging on hammers has significant drawbacks:

- low accuracy;

- low performance;

- large blacksmith surges;

- large tolerances and allowances.

Crank hot stamping presses are designed to perform various processes of hot stamping from grade metal: open and closed stamping, hot pressing, etc., in large-scale and mass production conditions.

The disadvantages of stamping on presses: relatively high accuracy of forging, allowances and tolerances, stamping slopes are less than when stamping on hammers, the impact-free nature of the work allows using prefabricated dies, higher reliability in operation.

The disadvantages of stamping on presses: the impossibility of significant redistribution of metal along the axis of the workpiece, a larger number of streams, a more complex design of dies, the need to clean the workpieces from scale, and the high cost of the press.

Since production is small-scale and the diameter of the workpiece does not exceed 250 mm, rolled stock is used as a method of producing the workpiece.

Basic Process Route Analysis

A process route for manufacturing a part refers to a process sequence (or refinement of a process sequence by a typical or group process) with a selection of the type of equipment. At the stage of development of the technological route, allowances and processing modes are not calculated. A rational route is chosen using reference data and guidance materials on typical and group processing methods. Technological routes are very diverse and depend on the configuration of the part, its size, accuracy requirements, and the volume of output. The main principle is to combine the design, technological and measuring bases.

Basic Process:

Operation 005: Turning - Helical

Operation 010: Vertical - Drill

Operation 015: Vertical - Mill

Operation 020: Round Grinding

Operation 025: Locksmith

In the basic version, the production of the part is small-scale. This type of production is characterized by the use of universal equipment and non-progressive machining methods. Often, CNC equipment is also used in processes along with universal equipment. During the manufacturing process, the part is repeatedly moved from one position to another and a rather large number of reinstallations take place in the operations. This affects operational time and increases installation errors. The machining allowance is quite large, so considerable time is needed to remove them, and the cost of the cutting tool is also large.

The basic TP has the following disadvantages: a large number of equipment;

the long time spent moving the workpiece from the machine to the machine; Significant basing error due to frequent rearrangements of the workpiece; reduced processing accuracy; the large number of jobs involved; the greater role of manual labour; application of universal equipment significantly increases the main technological time of workpiece processing (due to multiple transitions).

These disadvantages can be eliminated by proposing to process this part on the turning machining center of the GDM 100/6A model in 2 installations.

Selection of equipment and process equipment

7.1 Selection of metal cutting machines

Equipment selection begins with an analysis of the formation of technological transitions when processing individual surfaces of a part. When developing a technological route for manufacturing a part during the formation of individual operations, the type of equipment used (turning, milling, etc.) is selected, the equipment model is specified taking into account the requirements that should be provided during this operation.

The following factors are taken into account when selecting equipment:

dimensions of the machine working area, which must correspond to the dimensions of the machined part or several machined parts;

The possibility of achieving the required accuracy and surface roughness in the treatment (these factors should be particularly taken into account in finishing and finishing);

compliance of power, stiffness and kinematic data of the equipment with the best operating modes;

providing the required capacity in accordance with the specified volume of the parts release (the equipment capacity is determined based on the analysis of the manufacturing time of the part of the specified quality);

compliance of the equipment with the requirements of safety and industrial sanitation during this process;

compliance of the equipment with the specified volume according to the part manufacturing cost criterion.

As the main process equipment, the turning-turret multi-operation machine with NC model GDM 100/6A was chosen. The machine is designed for full high-performance processing of piece blanks with a diameter of up to 250 mm in semi-automatic mode in conditions of small and medium-sized production.

Accuracy class of semiautomatic P.

On the machine, you can perform the following types of processing: with a non-rotating tool - turning, boring, cutting the ends, cutting the grooves, groove of cones, turning the radial surfaces, drilling, countersinking, unfolding the central hole, threading with a thrower and a ram, cutting the thread with a cutter, turning and thinning complex curvilinear surfaces; with a rotating tool - transverse drilling, countersinking, unfolding, threading with a thrower, screwing of flanges, countersinking of holes, slitting of splines with a disk cutter, milling of key slots, cutting of end slots with a finger cutter, milling of cross flanges.

Processing of complex parts on turning machining centers with high technological capabilities is based on the following principles:

- the least number of operations;

- minimum auxiliary time, taking into account the maximum possible concentration of transitions, the characteristics of machine tools according to the costs of positioning time, auxiliary moves, tool change, etc.;

-operating with optimal allowances and minimum surges.

The expanded technological capabilities of the TOC are due to the use of special turret heads and other structures of holders with a rotating tool. In addition, the spindle of the machine can be programmed to be switched from a rotation mode at a predetermined frequency providing a predetermined cutting speed to a discrete rotation angle positioning mode or to a continuous servo mode with angular position feedback.

It is these design features of the TOC that allow, in addition to the usual turning operations of the non-rotating tool, the external and internal surfaces with a central axis coinciding with the axis of rotation of the workpiece, various other operations of processing holes on the external surface and end, at various angles to the axis of the part. In addition, you can perform various milling operations on the TOC.

7.2. Selection of machine tools

When designing the part processing process, at the same time as selecting the machine, it is necessary to establish what device is necessary to perform the intended operation on this machine. The selection of machine tools is an important stage in the development of the part processing process, since the accuracy of the part processing and the quality of processing depend on the correct basing of the workpiece. In this case, it is necessary to take into account the possibility of maximizing the use of standard and unified devices. As a machine tool at all crossings, we use a three-cap self-centering cartridge included in the machine equipment.