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Manufacuting of Engine Block

Manufacturing of engine block, selection of suitable manufacturing pro...
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manufacturing process

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Academic year: 2019/2020
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University of Engineering and Technology Lahore

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Manufacturing of Engine Block

1. Introduction

Cylinder block which is also called as engine block is the main structure of the engine which give the space for the cylinders, and it also give passages for the coolant, exhaust, and in take gases to pass over the engine and host for the crankcase and cam shafts. Engine block is the main housing of hundreds of parts found in modern engines. And it is the largest among the engine parts and it also constitute 20% to 25% of the total weight of the engine.

The first successful internal combustion engine which can be used in an automobile was built by Siegfried Marcus in about 1864. It was an upright single cylinder, two stroke petrol engines. Today's engines have come to their maximum development and still being developed for the next years too. These developments have caused to increase the power, durability, resistance to wear, and efficient of the engine. Material used to build the engine block has being given the engine a higher strength with low weight which is more important for the power of the engine.

For many years the engine block has being manufactured using cast iron alloys, it is due to its strength and low cost and its wear resistance. But as the engine become more complicated engineers found new materials to reduce its weight as well as to increase strength and wear resistance. A common alloy which is widely used is aluminum alloy, it is more popular due to its low weight but mostly within petrol engines.

Project. 1: Engine Block

2. Manufacturing Process Selection

There are several factors involved in choosing a suitable casting process for manufacturing cast engine blocks. Some of these factors include

➢ The type of material that can be used in the casting process ➢ The type of part that can be cast ➢ The finish of the product ➢ The amount of time it takes for the process ➢ The cost involved

There are several different types of manufacturing processes to choose from out there and many different alloys that are at one’s disposal to be used. Some processes include:

➢ Sand casting ➢ Die casting ➢ Lost-foam casting ➢ Shell Casting

In all four processes, hot molten metal is poured into a mold. The engine block can be cast in one piece from gray iron, or it can be alloyed with other metals such as nickel or chromium. The specific type of metals or metal used depends on many factors, including the intended use of the engine block, the type of environment it will be run in, and the cost.

In this report, sand and die casting will be discussed with the focus on sand casting. Also, choosing a suitable alloy will be discussed. Sand casting has the capability of using any alloy whereas; die casting is generally limited to non-ferrous alloys.

For many years the engine block has being manufactured using cast iron alloys, it is due to its strength and low cost and its wear resistance. But as the engine become more complicated engineers found new materials to reduce its weight as well as to increase strength and wear resistance. A common alloy which is widely used is aluminum alloy, it is more popular due to its low weight but mostly within petrol engines.

Aluminum is a very common alloy to use and it can be used for almost any process. Although, this alloy possesses some qualities that would be desired by most, gray cast iron was decided by us to possess even stronger qualities that led us to choose it for the material used in the design of a cast iron block. Sand casting is now and has been for some time one of the most commonly used manufacturing processes and the use of gray cast iron fits very well with this process. The reasons for choosing sand casting as the manufacturing process and gray cast iron as the alloy will be discussed further in the report.

3. Objectives

The main objectives of this report are:

➢ To discuss the various casting processes that can be used to manufacture an engine block ➢ To select a suitable alloy for the part ➢ To select a suitable casting process ➢ To justify the above selection ➢ To design the selected process to cast an engine block ➢ To discuss the defects in the casting and challenges to be faced while using the selected process and the methods to overcome these ➢ To discuss the cost consideration and environmental impact of using the selected process

4. Selection of Suitable Material

An engine block is the main part of an engine which holds all most all the parts of the engine. It should house the internal moving parts, fluids and also withstand the forces and pressure developed during combustion.

The material used for manufacturing the product should contain many properties. They are:

➢ It should have high strength ➢ Wear resistance ➢ Good machinability ➢ Good vibration absorption capacity ➢ Corrosion resistance ➢ Low thermal expansion

5. Tooling required for casting engine block

The main tool needed for sand casting is the mold, the mold is generated by a mixture of sand, clay, and water. The pattern is the main tool required to form the mold, it is normally machined by wood or aluminum which can be easily machined. The pattern is kept on the wood or metal frame and the sand mixture is poured in to it, then vibrations are applied for the mixture to get free from air bubbles. After the mold has being hardened it can be used for the casting process.

After the casting process is over the casted engine block is passed through few machines to get the surface finish and correct dimensions. Computerized milling machines and boring machines are used in this operation.

6. Manufacturing Process of Engine Block

Manufacturing of engine blocks are mainly done using sand casting, although die casting also used it is more cost effective as the die wear out easily due to the high temperature of the molten metal. The casted engine block is then machined to get the surface finish and coolant passages.

6. Mold Making

In the sand-casting processors, the widely used in engine block casting is green sand mold casting. The term green denotes the present of moisture in the sand mold. A combination of silica sand, clay, and water are poured in to the one half of the aluminum block pattern with wood or metal frame. The mold is then compacted by applying pressure or vibrating on the metal frame. This process is repeated for the other half of the mold. Then both halves of the mold are removed from the pattern.

Project. 2: Patterns

6. Core Making

Core making is the process which forms the interior part of the casting. The mold provides a space for the molten metal to go, while the core keeps the metal from filling the entire space. Cores can be used to extend mold projections to create extra mold sections, or to block out and create negative drafts.

The core shown below provides the space for water jackets around the cylinders. The core has been painted to seal the gas formed during the casting process within the core. And the pink colored ends are not painted to let the gas escape to the outside. Aluminum reinforcing rods are used to give more strength to the core. These rods get melted due to the molten metal poured during casting.

Project. 3: Core

6. Mold Arrangement

Then the water jackets and cylinder molds are arranged in the main mold as a one cube. The mold is then tightened using clamps to withstand the pressure of gravity when pouring molten metal.

Project. 4: Main Mold as One Cube

are fitted temporally to check the clearances at the bearings. Now the engine block is ready for the further fittings of crank, cam, cylinders, connecting rods, and valves.

8. Theory behind casting

Casting is a solidifying process which means solidification phenomena controls the most of the properties of casting. And most of the casting defects occur during solidification. Solidification occurs in two steps; they are nucleation and crystal growth. In nucleation stage solid particles are formed within the liquid and these solid particles have lower internal energy than the surrounded liquid. There for they go below the freezing temperature because of the extra energy required. Then again it gets heated up to form crystal structures.

9. Quality consideration during the production

The quality of the sand used widely affects the surface finish of the engine block. The sand should contain these features to get the required finish.

➢ Strength of the sand has to be high to maintain a rigid shape. ➢ Permeability is the size of the sand grains. Higher permeability can reduce the porosity of the mold, but a lower permeability would let to have a good surface finish. ➢ The thermal stability of the mold should be high to resist the damages such as cracking due to the molten metal. ➢ Ability of the sand to compress during solidification has to be high, unless the casting will not be able to shrink freely in the mold and it may result in cracking. ➢ The sand has to be reusable for next sand molds to be formed, because one sand mold can be only once used. ➢ The sand mixture must be well compressed around the pattern to get a higher strength, unless it will get cracked during the casting or when the molds are set on each other. ➢ The risers have to be well planned to make sure they do not get solidified until the whole block has being solidified. ➢ The contains in the molten alloy must be up to the standard to overcome the defects. ➢ The clearance in the cylinder bores, crank and came bearings has to be up to the correct standard measurements. ➢ The cooling rate has to be up to the standard. The cooling rate is mostly controlled by the molten metal and the surrounding temperature; therefore, the casting should be done in its certain thermal conditions.

Possible defects during the production

Any defect will reduce the strength of the engine block, as the engine block is running under higher temperatures small defect can be a reason for any failure of it.

If the permeability of the sand used for casting is high, the strength and the surface finish of the mold will be reduced.

➢ If the thermal stability of the sand is low, the mold may crack due to the molten metal. ➢ If the compression of the sand is low the casting would not be able to shrink and will end up with cracking. ➢ If the risers get solidified before the other parts of the casting, it would give an engine block with less strength. ➢ If the molten alloy is not up to standard it will failure in high running conditions. ➢ If the clearances in the cylinder bores, crank, and came bearings are not up to the standard measurements, under the running conditions it may arise with unwanted friction or loose.

10. Cost Consideration

The cost associated with sand casting can be divided into three broad categories: Material cost, Production cost and Tooling cost.

10. Material cost

As the name suggests, material cost includes the cost of all the materials used in the sand-casting process. These materials include the metal, the mold sand and the core sand. The cost of the metal will depend on a number of factors such as cost of the alloy, purity of the alloy and the castability of the alloy. For more pure alloys, the cost will be higher. For alloys with lower castability, additional metal will be required in order to fill the flow channels and the feed heads to assure a good casting, so in such cases, the cost will be higher. The cost of the mold sand and the core sand will depend on the shape and size of the mold and the core respectively. In this case, since our part is an engine block, due to its size and geometric complexity, the cost is bound to be high.

10. Production Cost

Again, as the name suggests, production cost will include the cost of all the operations that will take place during the process of sand casting. These will include core making, mold making, pouring, and cleaning. The addition of cores to the casting will increase its cost because it will slow the process down. An engine block, a very complicated part, will definitely have cores which will increase the overall production cost by slowing down the production. Pouring and cleaning costs are determined by the size and weight of the casting. So, these will be high for an engine block as it is a big and heavy co mponent, and the mold will take longer to fill and the cast block will take longer to be cleaned.

10. Tooling Cost

Tooling cost is the cost associated with the tools used during the sand-casting process. These include the patterns used to make the molds and the core-boxes to make the cores. Since an engine block is huge and geometrically complicated, tooling cost will be high. Also, since we are designing for mass production, the patterns as well as the core-boxes will have to be used more frequently. The constant use of the tool will result in the wearing down of the tool at a high rate, which in turn will increase the overall cost as the tool will have to be replaced. A solution to this problem will be to use patterns and core-boxes of a better-quality material, but again the cost will be high.

11. Environmental Impact of using Sand Casting

Foundries are generally regarded as being dirty and unfavorable to the environment. The primary issues being faced by the casting industry are the excessive volumes of by-products that are to be sent to landfills, and the Hazardous Air Pollutants (HAPs) which are released during the process.

Of all the by-products generated by volume, sand is the largest. Even in processes which involve a high level of sand recovery, some amount of new sand is always required to maintain the optimum quality of sand in the system. This in turn will result in loss of sand from the system. After its use, the sand is either sent to a landfill for disposal, resulting in soil pollution, or it is reclaimed off-site.

Not all foundry sands are considered hazardous, especially the ones from ferrous foundries, which pass the TCLP (Toxic Characteristic Leaching Procedure), which, after use can be sent to unlined landfills for disposal. Some non-ferrous sands on the other hand contain high levels of metal because they have to be sent to secured landfills and not the unlined ones. Chemical binders’ unwasted sand can become a crucial issue if resin-coated sands are wasted in large volumes before the pouring stage as most of the binder in the mold is burnt off during the pouring stage. Hence, the binder level should be carefully monitored so as to prevent it from reaching unacceptable levels over a period of many reclamation cycles.

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Manufacuting of Engine Block

Course: manufacturing process

65 Documents
Students shared 65 documents in this course

University: University of Engineering and Technology Lahore

Was this document helpful?
Manufacturing of Engine Block
1. Introduction
Cylinder block which is also called as engine block is the main structure of the engine which give the
space for the cylinders, and it also give passages for the coolant, exhaust, and in take gases to pass
over the engine and host for the crankcase and cam shafts. Engine block is the main housing of
hundreds of parts found in modern engines. And it is the largest among the engine parts and it also
constitute 20% to 25% of the total weight of the engine.
The first successful internal combustion engine which can be used in an automobile was built by
Siegfried Marcus in about 1864. It was an upright single cylinder, two stroke petrol engines. Today's
engines have come to their maximum development and still being developed for the next years too.
These developments have caused to increase the power, durability, resistance to wear, and efficient of
the engine. Material used to build the engine block has being given the engine a higher strength with
low weight which is more important for the power of the engine.
For many years the engine block has being manufactured using cast iron alloys, it is due to its strength
and low cost and its wear resistance. But as the engine become more complicated engineers found new
materials to reduce its weight as well as to increase strength and wear resistance. A common alloy
which is widely used is aluminum alloy, it is more popular due to its low weight but mostly within
petrol engines.
Project. 1: Engine Block
2. Manufacturing Process Selection
There are several factors involved in choosing a suitable casting process for manufacturing cast engine
blocks. Some of these factors include
➢ The type of material that can be used in the casting process
➢ The type of part that can be cast
➢ The finish of the product
➢ The amount of time it takes for the process
➢ The cost involved
There are several different types of manufacturing processes to choose from out there and many
different alloys that are at one’s disposal to be used. Some processes include:

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