The permanent mold casting process is reuse of the molds to make parts whereas expendable mold casting uses disposable molds. Though the molten aluminum is the initial material of the two methods, differences in the shape and reshaping of the material, the strength of the product in the end and the cost implication are drastic. 

Among several industries using aluminium as one of the most versatile materials, it should be noted that this is because of its strength-to-weight ratio, non-corrosiveness and conductivity. In case of making the aluminium take the form of parts and components, there are two major processes which are used, namely Permanent Mould Casting, and Expendable Mould Casting. The procedure involved in both of these processes is not the same, and the end product has its own mechanical characteristics, use, and production needs.

This guide shall entail the request of differences in process, mechanical property, cost, applications and environmental impacts in order to make an informed decision on the next project you may be undertaking.

Comparison and contrast between Permanent Mould Casting and Expendable Mould Casting

What are Permanent Mould Castings?

Permanent mould casting refers to the process of pouring molten aluminium into a metal mould, which can be used to create many parts. It is well suitable in the manufacture of parts that need high strength and dimensional accuracy. The mould material is generally cast iron or steel in order that the substance can be subjected to the heat of the molten aluminium over a large number of cycles. The process is ideal for the mass production of medium to high volume components.

Characteristic of the Permanent mould casting is:

• There are reusable moulds: Metal moulds are reusable, and thus, it is economical to use them for mass production.
• Exact dimensions: The moulds offer high-quality dimensions.
• Güçlü: The parts are stronger as compared to those created through other casting procedures.
• Surface finish: It leads to high-quality surface finishes, and the post processes are reduced to a minimum.

Common Applications:

• Auto parts like blocks, housings and brackets.
• Structural parts of aerospaces.
• High or medium strength industrial parts.

Harcanabilir Kalıp Döküm Nedir?

Expendable mould casting entails the production of a mould which gets destroyed following only one application. Popular ones are sand casting, investment casting and shell moulding. The process can frequently be put into use in the development of complex or tailor-made parts, which do not need large quantities. There is a great deal of design freedom along with material variability in expendable moulds.

Some Major attributes of Expendable Mould Casting:

• Single-use moulds: The moulds are scrapped once the casting is done, and this increases the per-unit price.
• Complex geometry: These are suitable when it comes to manufacturing pieces with a complex geometry or internally.
• Reduced material expenses: The moulds could be prepared in the form of various types of materials, i.e. sand or ceramics.
• Yüzey bitirme: Surface finishing might need further post-processing.

Common Applications:

• OEM and custom parts and prototypes.
• Components made for aerospace and defence.
• Sculpture, art, and decoration items.

Üretim Süreçleri

Perma cast process:

• The Aluminium Melting: The aluminium is melted in a furnace to a liquid state.
• Pouring into Moulds: The liquid aluminium is poured into the permanent metal mould.
• Soğutma ve Katılaşma: The aluminium cools down and solidifies within the cavity.
• Mold Removal: The mold is removed and the cast which has been shaped to the durability of the part during the casting process and by no means the weakest point is removed.
• Casting Post-Processing: The casting can be burned, machined or refined as required.

Key Characteristics:

• Ideal for meeting complex designs.
• High rate of production.
• Money-saving for large quantities.

Mould Casting Process comes with Expendable:

• Mould Preparation: The disposable mould is made with some materials such as sand, ceramic or shell.
• Melting induction and pouring: molten aluminium is poured into the mould.
• Soğutma ve Katılaşma: The piece is enabled to cool and to solidify.
• Mould Destruction: To eject the finished part, the mould is destroyed.
• Post-processing: There can be an additional machining/finishing.

Key Characteristics:

• Better suited to make custom or low-volume parts.
• Being able to give intricate designs and features.
• Increasing the cost per unit.

Microstructure and Mechanical properties

The microstructure, as well as the mechanical properties of the aluminium, depend largely on the manufacturing process.

Grain Structure

• Permanent Mould casting: The grains in the permanent mould casts are very fine and regular, and this is attributed to the controlled cooling nature of the metal moulds. This improves the strength and the mechanical properties.
• Expendable Mould Casting: In an expendable mould casting, the grain tendency is less uniform, the grain is larger, therefore there is less strength and ductility.

Porosity and defects

• Permanent Mould Casting: Metal moulds are used to decrease the internal pores and internal defects in the casting, making it strong and reliable.
• Expendable Mould Casting: They have an expendable mould that is porous and, as such, may allow internal defects such as gas porosity or shrinkage cavity into the part, making it perform poorly under stress.

Mechanical Performance

Table 1: Mechanical Performance

The Permanent Mould Casting Robots Materials

Metal Molds

The moulds of permanent mould casting are normally based on steel, cast iron or alloy steels. They are selected in combination with such high-temperature and cycle-resistant materials. Steel moulds are specifically preferred due to their durability and strength, whereas cast iron moulds give good thermal conduction.

Metals – the casting

The most commonly used metals to produce casting in the permanent mouldings are:

• Aluminium: It is soft, lightweight, and has corrosion-resistant properties, which are perfect in applications of high strength.
• Magnezyum: Classified as a lightweight but strong metal, popular in the aerospace and even the automotive industry.
• Çinko: It has good strength/ductility, and it is often applied in high-volume die-casting.
• These metals, combined with durable moulds, lead to strong, precise and consistent castings.

Raw materials in casting with expendable mould

Mold Materials

In expendable mould casting, the moulds are sacrificed every time the mould is used. They may consist of many types of moulds, so the casting technique varies:

• Sand: The most predominant use of sand is during sand casting, where a mixture of silica sand and binders is used to make the mould.
• Ceramic: Applied in the application of investment casting, and fine powders of ceramics are fabricated into shells to cast metal with high precision.
• Plaster and Shells: They are applied to the lost-wax casting process and shell moulding procedure in producing parts with fine details and tight tolerance.

Metals – the casting

The expendable mould casting has a broad spectrum of metals capable of usage of choice, which include:

• Aluminium: Aluminium, well known for its lightweight, versatility, is commonly used in industrial materials in parts of the auto industry and consumer items.
• Steel and Iron: They are widely employed in the sand and investment casting process in terms of industrial machines, tools, and structural pieces.
• Brass and Bronze: Ideal in casting complex parts like decorative items, valves and fittings.
• Titanium: Titanium is more costly, but it finds applications in special purposes such as aerospace and implantable medical devices, as it is both strong and corrosion resistant.
• Requirements: The expendable moulds should be made of a material suitable for the complexity of the part and the metal being cast, and the requirements of the production.

Permanent Mold Casting forms Types

1. Gravity Permanent Mould Casting

In gravity permanent mold casting the molten metal is poured into a re-usable mold cavity referencing gravity. It is being employed to make high quality, simple parts having good surface finish. It is appropriate to the metals such as aluminium and magnesium and it is commonly applicable where moderate strength and detailed work is to be done.

2. low-pressure permanent mould (LOPRVM)

Low pressure. The molten metal in low-pressure permanent mould casting is injected into a mould at a low pressure, which causes easier cavity filling of complex shapes with a smooth surface finish. The process is commonly applied to aluminium alloys and magnesium alloys and is suited where parts have a high level of mechanical properties and close tolerances.

3. High-pressure permanent mould casting (HPDC)

This approach entails pressure injecting molten metallic into a mold forming a quick fill up and a highly efficient process. It finds wide application in large scale manufacture of parts such as auto parts and parts where there is need of precision, strength, and smooth finished surface.

4. Die Casting

Die casting is a permanent mould casting; after the mould is filled with the molten metal, this metal is forced out, or squeezed, of the mould. It is mainly used in high volume manufacture of complexly shaped parts, e.g. automotive parts, and commonly die-cast metals include aluminium, zinc and magnesium.

Expendable Mould casting types

1. Kum Döküm

One of the most widely cast and universal expendable mould casting processes is sand casting. It entails the formation of a mould that is made of a mixture of sand, clay and water. Molten metal is then poured into a mould after the mould is prepared. Casting of large parts by using sand casting is perfect and is widely applied in metals like aluminium, iron, and steel. It is applicable in low/medium volume production.

2. Investment casting (Lost-Wax casting)

An investment casting is applied, which is made in the form of a ceramic shell pattern separated from a wax pattern. Once the pattern has been removed after melting, molten metal is poured into the mould. This method is best applied when the parts are very detailed and applies well in industries that produce aeronautical products, medical equipment and jewellery. Investment casting is able to process high precision and complex geometry.

3. Shell Mould Casting

Shell mould casting refers to the process of applying an extremely thin-walled mould to a casing shaped by coating a process called a pattern, which is a thin layer of sand and adhesive. After the mould is cast, the pattern is taken off and the cavity filled with molten metal. It is commonly applied to smaller, detailed parts and has superior product finishes relative to kum döküm. It is mostly applied in aluminium, brass and steel alloys.

4. Lost Foam Casting

Where a foam pattern is the mold, it is called lost foam casting. The foam pattern is ceramic shelled and when molten metal is poured into the mould, the foam melts off and evaporates. This is mostly done where castings of complex shapes are involved and most common industries with this type of casting offered is automotive and aerospace industries.

5. Centrifugal Casting

Centrifugal casting The centrifugal casting process consists of pouring the molten metal into a rotating mold. The centrifugal force flings the metal to the outer side of the mold, and this creates a compac,t strong casting. This technique applies to the manufacture of cylindrical items such as pipes, tubes, and bushings, especially in cast iron, steel and bronze.

Uygulamalar

Uses of Permanent Mould casting:

The parts made with permanent mold casting are appropriate to use where high strength, precision and durability are required. It is suited to medium and high-volume manufacturing operations in, e.g. automotive, aerospace and industrial machine manufacturing.

Common Applications:

• Automotive Engine Blocks:  The design of the vehicle block of an engine with a complicated internal geometry.
• Aerospace Components: Structural parts that are lightweight and have strong strengths.
• Industrial Equipment: Great performance components such as pumps and pump housings, as well as brackets.

Uses of Expendable Mould casting:

Expendable mold casting has been an ideal choice where low volume, custom or prototype projects are being designed and flexibility of design is vital. It has become common in industries including aerospace and defense and manufacture of custom products.

Common Applications:

• Aerospace Components: Speciality parts which include the turbine blades and engine parts.
• Defence: Unique-shaped custom and military grade parts.
• Art and Sculpture: Designing and personalisation or application of art products.

Price and efficiency, Cost and Production Efficiency, Cost and Production Efficiency

Permanent Mould Casting:

• Start-up Costs: Very costly tooling of metal moulds.
• Per-Unit Cost: lower per-part cost at large-volume manufacturing.
• Speed of production: It is quicker in the case of large production runs.
• Long-lasting: The moulds made of metal can last long, resulting in cost reduction in the long run.

Cast-Metal-Tooling-Expendable-Mold

• Start-up Cost: Low cost of tooling used on expendable moulds.
• Cost Per Unit: It is more expensive with a high cost per part for the manufacturer because of one-time moulds.
• Production speed: The slowing down occurs since production involves the creation of moulds and longer cooling processes.
• Dayanıklılık: Moulds only produce a single unit, hence increased cost per piece produced.

Çevresel Hususlar

Energy Use

• Permanent Mould Casting: As a rule, it requires less energy than is effective with metal moulds.
• Expendable Mould Casting: The input of energy per particular unit is greater, particularly for the intricate moulds.

Malzeme Kullanımı

• Permanent Mould Casting: Material flow is great with little waste.
• Expendable Mould Casting: The use of moulds exposes them to more material waste as they are used once.

Geri Dönüştürülebilirlik

• Permanent Mould Casting: Aluminium is easy to recycle, and money is made after usage.
• Expendable mould casting: The moulds would not be recyclable in most cases, even though aluminium can be recycled. 

When to Prefer Permanent Mold Casting to Expendable Mold Casting

• High-Volume Production: A permanent mould casting is more economical in high volume production since its moulds can be used repeatedly, and it also offers rapid production rates.
• Elements of High Strength: In cases where the final product needs a high strength grade, tight tolerances and low internal defects, then a permanent mould casting is the preferred option.
• Components application: Permanent mould casting is preferable to complex geometries where no complexity has to be achieved internally on the components application, such as in automotive parts and the industries.
• Long run production cycles: Long run production projects that consider the use of the mould and reuse of the moulds in the long term should also use permanent mould casting as it is long-term efficient.

The Situation to Select Expendable Mold Casting Instead of Permanent Mold Casting

• Low-Volume or Made to Order: Low-volume or made to order at a low initial tool cost, which was the weakness of expendable mould casting.
• Geometries and Intricate Designs: In case the piece has complicated interior systems or very detailed designs and shapes that can be hard to accomplish by using permanent moulds, expendable mould casting would be suited.
• High-Temperature Alloys: Expandable mould casting may be included when a metal or alloy which melts at an extremely high temperature,e like steel or titanium, is to be cast, since it is usually only those metals with low melting points, like aluminium or zinc, which can be cast in permanent moulding.
• Prototyping and One-Off Products: In the case where a particular company is testing out a new design in its product or where a one-off custom component is required, then expendable moulds will prove better since the cost of making the moulds is lower.

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Sonuç

Permanent Mold Casting and Expendable Mold Casting have each distinct benefits according to the purpose and creation requirements. It can be noticed that permanent mold casting should be used in medium to high volume production that requires the emphasis on precision and a great level of detail whereas expendable mold casting should be used when more flexibility is required to create complex designs, custom parts, and low quantity production.

In choosing between the two processes, considerations should be made on the nature of the material property needed, volume of the required production, price and complexity of the design. Knowing both the strengths and the shortcomings of all the methods means that the manufacturers have the option of selecting the best casting method to be used in that project, thus guaranteeing an effective production with the final product exhibiting its best performance.

SSS

1. Which one is cheaper for casting large-scale productions?

The permanent mould casting becomes cheaper in producing high volumes since the moulds can be used over and over again, hence the shorter production process.

2. Is it possible to use complex designing in expendable mould casting?

Yes, expendable mould casting is the best to manufacture complex and complicated designs, such as parts having internal geometries.

3. Which casting process suits better when it comes to strength reasons?

Permanent-mould casting will normally result in better parts, and expendable mould casting may be utilised in high-strength applications, particularly aerospace and defence.

4. Are there material wastes in the two kinds of casting?

In expendable mould casting, the waste material is more because moulds are used just once, as compared to the use of moulds that are permanent and have less wastage.