Barton International

Permanent Mold Casting vs Expendable Mold Casting

Introduction

Permanent and expendable mold casting are two historic metal fabrication techniques, but which best serves your business needs? Read on to discover the differences between casting methods.

Mold casting is an ancient metal fabrication method with some techniques going back thousands of years. And with a global market valuation of $145.97 billion in 2020, casting metal remains relevant worldwide due to its reliability, versatility and quality assurance.

But depending on the materials and production purposes, manufacturers may opt for either permanent or expendable mold casting.

In this piece, we’ll discuss the differences between both casting methods to distinguish what technique best serves your operation and production intentions.

Permanent and expendable mold casting are historic methods for metal fabrication, but which mold casting technique best serves your business needs?

What are Molding and Casting?

Molding and casting share the same basic process of pouring liquid material into a mold. Whenever a distinction is required, it’s normally determined by the types of material used during the process. Casting typically involves metal, while molding uses plastics.

In metal fabrication, for example, the industry is much more concerned with casting capabilities over molding due to the material, despite “mold” being in the title of both permanent and expendable “mold” casting.

What Is Permanent Mold Casting?

Permanent mold casting is a metal fabrication manufacturing process that uses reusable molds to produce various metal components for high-volume production purposes.

Typically, molten metal is poured into a steel die and flows with the force of gravity to take shape. After the liquid metal is poured into the mold, the metal then solidifies inside to encompass the intended shape and structure.

Deviations can exist with the permanent mold casting process, such as runners being installed to cut into the die and direct the molten metal in specific directions. Another example can be the molten metal being left in a basin beside the die and tilted to achieve a more controlled mold filling.

Regardless of the technicalities, the flow of metal into the die cavity and heat flow from the metal to the die during solidification are the two essential criteria for permanent mold casting.  

Examples of Permanent Mold Casting

Permanent mold-casting components can be seen across numerous manufacturing industries where high volumes of items are necessary, such as the automotive and aerospace industries.

Some examples of permanent mold casting include:

  • Gears
  • Pistons
  • Wheels
  • Telecommunication equipment
  • Medical devices

 Permanent mold casting allows models to be used repeatedly and is particularly prevalent in die casting.

What Is Expendable Mold Casting?

Expendable mold casting is a process of metal casting that uses a mold that is broken when finished and unable to be used again. Common expendable mold casting processes include the following methods:

Sand Casting
Sand casting has been used for centuries and remains one of the most common and simplest expendable mold-casting processes. As an ancient casting technique, sand casting is ideal for manufacturers with smaller budgets and versatile component production demands.

Shell Casting
Like sand casting, shell casting uses sand, but within a finer state and formed within a hardened shell rather than a filled flask. Due to the use of resin, shell casting produces a polished finish and precise creation capabilities suitable for intricate small and medium-sized items. 

Investment Casting
Investment casting, also known as “lost-wax casting”, is a reliable expendable mold casting technique for producing accurate, consistent, and versatile components. Investment casting can be a more expensive process but has the power to produce intricate contours.

Plaster Casting
Plaster casting is a cost-effective metal molding solution due to the low expense of the plaster and its ability to produce near-net shape results. However, plaster casting is limited to low melting points and non-ferrous materials.  

Lost-Foam Casting
Lost-foam casting is characterised as an evaporative-pattern process that uses foam. By using a foam material, this form of expendable molding is cheaper and easier to remove the cast after solidification.  

Despite expendable mold casting being characterised by non-reusable mold processes, not all expendable molds are discarded after use. Depending on the casting process and material, sometimes molds can be reformed and reused.

What are the Advantages of Permanent Mold Casting?

Permanent mold casting has multiple benefits, such as:

  • The mold is reusable
  • It offers excellent dimensional accuracy and a lovely overall finish
  • It can produce high volumes of production
  • It provides superior directional solidification
  • It offers a high cooling rate due to metal mold conduction

All in all, permanent mold casting is ideal for higher volume production when a superior surface finish and dimensional accuracy are required. Permanent mold casting is used by metal manufacturers who require mass production demands and a high-quality finish.

During the solidification stage, permanent mold casting can create microstructures to form superior properties compared with expendable casting methods.

What are the Disadvantages of Permanent Mold Casting?

The disadvantages of permanent mold casting can involve some of the following issues:

  • Expensive tooling and equipment costs.
  • Only low melting point metal is possible.
  • Not a viable economical option for low-volume production.
  • Can offer a short mold duration for iron and steel castings.
  • Can cause erosion when casting lower melting point metals.

What are the Advantages of Expendable Mold Casting?

Expendable mold casting offers multiple benefits as an ideal metal casting solution. For example:

  • It’s significantly cost-effective with low tooling costs
  • It provides a wide variety of materials
  • It can cast a variety of sized parts, including large

Expendable mold casting is ideal for smaller budgets and a low production volume, with multiple methods, materials, and versatile component options available.

What are the Disadvantages of Expendable Mold Casting?

The disadvantages of expendable mold casting include:

  • Less accuracy in comparison to permanent mold casting
  • The process normally exceeds the intended weight
  • Less sustainable due to molds being non-reusable

Find Your Local Mold Casting Specialists

At Barton International, we provide permanent and expendable mold-casting solutions to suit all metal manufacturing needs and requirements. For over a century, we’ve designed, produced, and delivered quality-assured, affordable, and reliable components across multiple industries and supply chains.

Whether you require intricate, small to medium-sized items on mass or large structural components, we have metal casting solutions to serve your needs.

Get in touch to find out more about our mold casting services and other metal fabrication methods.