Course project "Development of casting production process"

Contents

Introduction

Analysis of input data and selection of technology

Source Data

Part Constructability Analysis

Selection and justification of casting method

Process Part

Define the casting position in the mold, model connector plane, and shape

Machining Allowance

Selection of rod manufacturing method

Selection of the mold manufacturing method

Select Options

Runner System Selection and Calculation

Design development of the model kit

Select Mold Material

Process sequence of mold and rod manufacturing

Mold preparation and filling, casting cooling

Knock out castings and remove rods

List of used literature

Introduction

The manufacturing process of the casting should ensure good quality of the part and at the same time should be advantageous in these production conditions.

It is necessary to take into account not only the cost of manufacturing the casting, but also the wrapping and the cost of cutting. Therefore, the cutting allowance should be reduced and, if possible, completely eliminated. When designing the molding process, care should be taken to simplify the process as much as possible, using the main and auxiliary equipment in the workshop.

The design of the casting manufacturing process includes the development of:

1) Casting drawings as per part drawing

2) process documentation for the designed process.

Analysis of input data and selection of technology

Source Data

Casting "Case" is cast from gray cast iron of SCh20 brand in accordance with GOST 141285 weighing 6.6 kg. The thickness of the casting walls is 10 mm.

The casting length is 200 mm, the diameter of the middle part is 64 mm. The part is machined: 9 holes are drilled, part of the surface is drilled to obtain a given purity and size, subjected to turning and milling, the rest is obtained by casting.

Mechanical properties and the recommended chemical composition of SCh20 the following:

Tensile strength 200 MPa

Hardness 170-241NV

Carbon 3.33.5%

Silicon 1.42.4%

Manganese 0.71.0%

Phosphorus 0.30.6%

Sulphur 0.080.15%

Plate graphite cast iron is a good casting alloy. Due to its high casting properties, castings can be obtained from it without profit.

Analysis of workability of a part design from the point of view of its compliance with the requirements of casting technology.

The cast part must be not only sufficiently strong and reliable during operation, but also technological in manufacture, i.e. most easily feasible in specific production conditions with minimal costs for the manufacture of the casting and its further processing.

The phenomena occurring in the manufacture of castings: the interaction of metal or alloy with medium and shape, shrinkage, the formation of shrinkage defects, gas shells, porosity, casting stresses - can have a significant impact on the quality of castings and finished parts.

Given these factors, the part to be constructed can be considered to be quite technological, since the following basic principles are observed:

1). The casting does not have mutually perpendicular machined planes that could create areas that are difficult to fill during molding;

2). The structure does not have single-sign rods;

3). The casting has the same wall thickness;

4). There are no abrupt transitions during conjugation of walls;

5). There is a plane on which a simple connector of the model and form can be made;

6). Grey cast iron has good fluid flow;

7). Grey cast iron has a slight shrinkage, about 1%.

Selection and justification of casting method.

The choice of the casting method depends mainly on the type of alloy, the size and configuration of the part, the type of production, the required accuracy of the dimensions and quality of the casting surface, the nature of the subsequent machining.

The first place is put forward the technical and economic efficiency of their production.

The selected technological process should ensure high labor productivity, the most economical consumption of materials, the simplicity of manufacturing model tooling and its durability, the minimum cost of cast parts.

In our case, the production of casting is serial in nature (15 thousand pieces per year), the method of production is casting into single sand forms.

Castings are usually made by casting into sandy raw, dried, chemically hardening and dry forms.

The most economical method of making castings and in raw forms is, since in this case no area is required for installing drying units and storing molds before drying and additional fuel consumption. Compared to other methods, the cycle of casting production is significantly reduced and its cost is reduced, therefore, we prefer raw molding.

Mold is manufactured on semi-automatic moulding machines and molds are poured on casting conveyor.

Process Part

2.1. Defines the casting position in the mold, model parting plane, and shape.

Selecting the plane of the model connector and shape decisively affects the manufacture of the model, mold and rods. It is also important for the dimensional accuracy of castings, the purpose of allowances and base surfaces for machining.

Considering possible options for the purpose of the model and shape connector, it is necessary to take into account not only the probability of defects, but also the labor-intensive production of molds, which is especially important when mass production of castings.

In the manufacture of the case, the horizontal surface of the connector is applicable, which allows you to gain an advantage in reducing the volume of rod work and reduces the possibility of shear of the rods.

The cast height in the mold will be 110 mm.

2.2.Accesses for machining.

Machining allowances are provided on all surfaces to be machined. The amount of allowance for mechanical processing depends on: the casting material, the molding method, the position of the casting surface in the mold when it is poured, the complexity and size of the casting. So the allowance on the upper surfaces of the casting should be greater than the allowance on the lower and side surfaces, since slag, particles of the molding mixture and gas inclusions accumulate in the upper parts of the casting.

The amount of machining allowances for grey cast iron castings is regulated by GOST 2664585. For our casting as per Table 2.4 [1] let us accept:

Nominal size, mm allowance, mm

Ǿ45 3

Top 4.5

Bottom, side 3.5

The basis for assigning the allowance for machining is its nominal size. The nominal dimension is the distance between two opposed machined surfaces or the distance from the mounting base surface to the machined surface.

GOST s and normals provide for the largest values ​ ​ of mechanical machining allowances, which can be reduced based on production conditions.

Large allowances are unprofitable, as they increase the weight of the casting and increase the cost of processing it. But too small allowances are also unprofitable, since they can lead to increased scrapping of products and to rapid wear of the tool working on the casting crust.

2.4. Select a method for making the mold.

Machine molding is mainly used in mass production and mass production. For the production of castings, the Hull uses semi-automatic machine molding with shaking and additional pressing, which allows you to make shapes in supports with a size of 850 × 650.

2.5. Select options.

The dimensions of the supports are set after selecting the position of the model in the form, the surface of the connector of the form, as well as choosing the size, dimensions and configuration of the rod signs.

The dimensions of the supports are determined by the dimensions of the models, the location of the sprue system and the necessary distances between them and the walls of the supports, as well as between the models and the upper and lower edges of the supports. This layer must be strong enough not to break down under the pressure of liquid metal when pouring the mold. In addition, the mold must withstand tremors during its assembly and transportation.

From the top of the model to the top of the leg - > 60 mm,

From the bottom of the model to the bottom of the support - > 60 mm,

From model to support wall - > 30 mm,

Between models

Between model and slag trap > 55mm.

Considering the overall dimensions of the casting and the above, we accept the following arrangement of castings in the form - 4 pieces. The maximum number of molds in the mold allows you to reduce the number of molding machines and the volume of the molding mixture.

The dimensions of the supports obtained by calculation are rounded to the nearest dimensions according to GOST 213375. For cast poles, we choose the lower support with a size of 850 × 650 × 120, the upper support with 850 × 700 × 120.

We accept the molding machine 253.

Standard sizes of centering and guide bushings are regulated by GOST 1501969.

2.7. Design development of the model kit.

The model set must meet the following main requirements: to ensure the production of a cast of a certain geometric shape and size, to have high strength and durability, to be technological in manufacturing, to have a minimum cost taking into account repair costs, to maintain dimensional accuracy and strength for a certain time of operation.

Molding slopes are regulated by GOST 321257 for external and internal surfaces of models.

For the manufacture of models, we choose gray cast iron ChC20, which during machine molding withstands up to 100,000 removals.

Gray cast iron slabs CH 15 are used as model slabs.

2.8. Selects the mold material.

Moulding mixtures of various composition and properties are used to produce single molds.

The composition of the mixtures depends on the nature of casting, the kind of alloy, the purpose of the mixture and can be classified:

1). By the type of alloy;

2). According to the moulding method;

3). By appointment.

For machine molding in raw, we will use a single sandy-clay molding mixture.

Main components of single moulding mixture (Table 2.19. [1]):

Recycle mixture 91-94%

Quartz sand 5-6%

Carbon-bentonite emulsion 1.03.0%

Starch 0.020.05%

Blend Properties:

Humidity 3.23.8%

Compression strength 6888 kPa.

2.9. Process sequence of mold and rods manufacturing.

2.9.1. Process sequence of mold manufacturing.

Molding technology includes the following operations in their sequence:

The bottom model is mounted on the model plate.

We install the lower support on the model plate with the model.

The model surface is wetted with a mixture of kerosene and fuel oil and sprinkled with graphite.

The mold is packed with a molding semiautomatic 253.

Manually vent needles make ventilation inclines and vent when moulding the upper support.

The support is turned by 180 °.

The shape print is checked if finishing is required - finished.

Top models are mounted on the top model plate.

Repeat paragraphs 3-7.

We install the rods in the lower half-mold.

We collect forms.

Forms are filled.

2.9.2. Procedure for production of rods.

The rods are made by hand. Half of the vertically detached rod box is blown and sprayed with a separation mixture. Then box is packed with rod mixture and compacted by hand. They make ventilation knuckles. The rods are installed on a drying plate and dried in a certain mode (200 ° C, 1-2 hours). The dimensions of the rod are checked according to a template, and the quality of the surface is also controlled. The final step is the application of refractory coatings.

2.10. Preparation and filling of mold, cooling of casting .

2.10.1. Mold preparation, rod installation.

Check of the mould is performed visually. If defects are detected, the shapes are corrected with a lancet ironing. Prior to assembly, mold cavity is blown with compressed air to remove mixture and foreign bodies from them.

Before the rods are installed, they are controlled by external inspection, measuring tool or devices. The rods are placed manually.

2.10.2. Select a bucket to fill the shape, and how to fill it.

Ladle is used for transportation of liquid metal and casting of molds. It is a steel casing whose inner walls and bottom are lined with refractory material.

The thickness of the lining layer is 6580 mm. The ladle is heated to 500700 ° C prior to use.

By design, we choose a teapot ladle. When pouring, we will use a 200 kg teapot ladle.

The temperature of cast iron at the outlet from the furnace is 1380 ° С.

2.10.3. Duration of mold castings cooling.

The regulation of the cooling time of molds is dictated by the need to ensure complete solidification, excluding the formation of some shrinkage defects, to obtain the required structure of the metal of the molds.

Cooling time depends on casting weight and cooling conditions. For these castings, the cooling time on the conveyor will be from 0.15 to 0.4 hour.

2.11. Knocks out castings and removes rods.

The labor intensity of these operations is more than a third of the labor intensity of the entire process of manufacturing castings.

We knock out castings and remove rods on knock-out grates, with a lifting capacity of up to 1 t. To clean castings from rods and burning, we use crushing chambers.