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Production Engineering - 1

Dr: Soheir Backar

Production process

Manufacturing process

Material Parts of product

Assembly Final product

Storage

Transportation

Forming Machining

Factory planning Quality control

Measurements

Required specifications (shape, dimensions)

Design

Selected according to material, shape, dimensions, cost,..

PE 011 Production technology

PE 123 Production engineering - 1

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Coarse contents:

Casting

Metal forming

Metal cutting

Welding process

Measurement and inspection

Week Date Lectures

1 11-10 Introduction + Sand Casting

2 18-10 Sand casting

3 25-10 Special casting processes

4 1-11 Bulk metal forming

5 8-11 Bulk metal forming + Quiz

6 15-11 Sheet metal forming

7 22-11 Mid year exam

8 29-11 Sheet metal forming

9 6-12 Machining processes

10 13-12 Machining processes

11 20-12 Measurement and inspection + Quiz

12 27-12 Welding techniques

13 3-1

14 10-1 Final exam

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Semester work (Sheets + reports) +Quizzes

15%

Mid term exam 15%

Final exam 70%

References: - E. Paul Degarmo, J T. Black, Ronald A. Kohser, “ Materials and processes in manufacturing”, John Wiley & sons, Inc., 2003.

-R. L. Timings, “ Manufacturing Technology”, Addison Wesley Longman, 1998.

-Hassan El-Hofy, “Fundamentals of Machining Processes”, Taylor & Francis, 2007.

-Helmi A. Youssef & Hassan El-Hofy, “Machining Technology”, Taylor & Francis , 2008.

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Manufacturing processes

Machining Processes

Forming Processes

Metal in liquid state Metal in solid state

Casting processes

Sand casting Special casting process

Bulk metal forming

Sheet metal forming

Short Introduction to Casting 7

Casting Meaning:

Melt metals

Force liquid into

hollow cavity

Cool / Solidify

Remove

Finish

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- Simple process. - Produce complex shapes with internal cavities or hollow sections. - Produces near net shape parts (less machining required)

Main advantages of casting process:

- Can utilize brittle materials. - Produce products as a one part.

- Can produce very large parts with high weights.

- The least expensive process.

Short Introduction to Casting 9

Expendable molds:

Sand Shell Investment Carbon dioxide

-Low production numbers.

- Lower molding cost.

Short Introduction to Casting 10

Permanent mold:

Permanent mold Centrifugal Die casting

-Molds made of metals that maintain their strength at high temperatures (higher cost). -Higher production rates.

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Classification of Metal casting processes:

Sand casting (expendable mold)

Special casting processes

-Gravity die or permanent mold -Die casting -Hot chamber -Cold chamber

Centrifugal casting -True centrifugal -Semi centrifugal -Centrifuge

Continuous casting mold

Precession or investment -Lost wax method -Ceramic shell process -Co2 mold hardening process

Short Introduction to Casting 12

-Cameras.

-Mobile covers.

-Door handles.

(a) (b)

Examples for Casting

Examples for Casting

-Pulleys .

-Taps.

-Children toys.

-Automobile parts (Engine block, door handles, pistons) .

Short Introduction to Casting 14

Sand Casting

• Sand Casting High Temperature Alloy, Complex Geometry, Rough Surface Finish

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Drag

Pattern

Sand Mold Product

Mold cavity

Drag

cope

Sprue pin riser pin

Show video

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Example:

-It is required to draw the mold prepared for casting process.

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Example:

-It is required to draw the mold prepared for casting process.

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Riser

Sprue

Cope

Drag

Sand Mold

vents

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Sand

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Sand: Silica sand (SiO2) is well suited for molding purposes

Withstand high Temperatures

(melting point 1600 -1725 C) Low in cost

Available for wide range of grain sizes and shapes

(Sand grains from 0.0625 mm to 2mm dia.)

Silica sand can be classified according to its size or its shape.

Material Aluminum Copper Cast iron Magnesium Steel Zinc

Melting temp. (C)

660 1084 1200 650 1500 419

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1- Grain size: - The size of sand grains may be fine, medium or course. -For small castings a fine sand is desirable, so that all the details of the mold are brought out sharply. - As the casting size increases, the sand particles should be coarser to permit the gases that are generated in the mold to escape.

Sand:

Iso 14688 grades sands as fine, medium and coarse with ranges 0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm. In the United States, sand is commonly divided into five sub-categories based on size: very fine sand (⅟16 – ⅛ mm diameter), fine sand (⅛ mm – ¼ mm), medium sand (¼ mm – ½ mm), coarse sand (½ mm – 1 mm), and very coarse sand (1 mm – 2 mm).

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2- Grain shape: - Sharp, irregular-shaped grains are usually preferred because they interlock and add strength to the mold.

Sand:

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Properties of molding sand:

1. Porosity or Permeability:

- Molten metal always contains a certain amount of dissolved gases which are evolved when the metal freezes.

- Molten metal also coming in contact with the moist sand, generates water vapors.

- Sands which are coarse or have rounded grains exhibit more permeability.

- Sub-angular and angular grains exhibit low permeability.

- To avoid open blows and porosity.

Open blows Porosity

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2. Strength : - Sub-angular grains give better strength than rounded sand grains.

- Angular sand grains give higher mold strength.

- To avoid drop of sand.

3. Fineness: - Finer sand mold (grain size small) resist metal penetration and

produces smooth casting surface.

Properties of molding sand:

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4. Flow ability (plasticity):

- Flow ability assists molding sand to flow and pack all around the pattern and take up the required shape.

- Round sand grains exhibit greater flow ability.

- Flow ability increases as clay and water content increases. - The sand must retain its shape when the pressure is removed.

5. Refractoriness: - It is the ability of the molding sand to withstand high

temperature of the molten metal without fusion, cracking.

- The higher the roughness of grain shape and size, the higher the refractoriness of the sand.

- To avoid fusion of sand.

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Properties of molding sand:

6. Collapsibility: - It is that property of the sand due to which the sand mold

breaks (collapse) automatically (or with very less forces) after the solidification of the casting occurs.

7. Durability: - The molding sand should withstand repeated cycles of heating and

cooling. 8. Molding sand should be cheap and easily available.

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Testing of molding sand

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Grain size or Fineness test:

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Mold and core hardness test:

indentation hardness tester

Refractoriness test:

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Test for Moisture content:

Moisture content should vary from 2 to 8%

Strength test:

The green strength of sands is generally in the range of 30 to 160 KPa.

Compressive test:

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How can the following tests affect the quality of castings? 1) Grain size test:

Selecting suitable grain size: -Avoid material penetration problems. - Avoid bad surface finish.

2) Moisture content test:

- Avoid porosities inside the casting, and open blows on the casting’s surface.

3) Hardness & strength tests:

-Avoid metal penetration. - Avoid drop of sand.

4) Refractoriness tests:

-Avoid sand distortion. - Avoid melting and adhesion of sand.

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Types of molds (according to the types of molding sand)

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Types of molds:

Molds are classified as to the materials used:

Green sand molds Skin dried molds

Dry sand molds

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Green sand molds:

Silica sand (silicon dioxide) 80-82% 8-30% clay 6-8 % water -Green sand molds contain moisture, therefore certain defects like

blow holes may occur in casting. The surface finish is also not good.

Skin dried molds: - These molds are dried only up-to a depth varying from 8 mm to 25 mm.

- If a skin dried mold is not poured immediately after drying, moisture from green backing sand penetrate the dried skin and make dried sand ineffective.

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Dry sand molds:

-A dry sand mold holds its shape when poured and is free from gas troubles due to moisture. -Dry sand molds posses higher strengths as compared to green sand molds.

- They are more expensive and consume more time in making as compared to green sand mold.

- Casting produced are having better surface finish.

Dry sand molding is the green sand practice modified by baking the mold at 204-316 C.