What you will find in this article

In this article, you will learn about investment casting and sand casting, two of the most important processes in steel casting; Gamarra offers both processes. We will specifically analyze the advantages and disadvantages of investment casting, comparing and contrasting it with sand casting. Before getting into details, if you don’t need the complete information or you are short of time, Gamarra has prepared a list of the main advantages of investment casting:

Main advantages of investment casting

• Maintains design integrity
• Save time and money on alteration costs
• Enables a broad choice of materials
• Capable of producing a broad range of component sizes
• Production to tight tolerances and high accuracy
• Uncompromised integrity of parts
• Fine surface finish
• Cheaper tooling costs compared with other casting processes
• Tooling is easy to alter
• Regular inspections take place during production 

What is Investment Casting?

 Investment casting, also known as lost wax casting, is a method that can produce steel casting parts with good surface quality and exceptional accuracy in dimensions. It is mainly used to produce large numbers of high quality castings. Investment casting uses a wax copy of the component, dipped (invested) in a ceramic slurry to produce a ceramic mold. The wax is then removed to leave the ceramic shell, into which molten metal is poured. This metal working process can easily cast complex and intricate shapes and obtain superior surface finishes. As a curiosity, it has existed for over 5,000 years, which makes it one of the oldest metal processes in the world.

It requires the use of a metal die (usually aluminium), wax, ceramic slurry, furnace, molten metal, and also any machines needed for sandblasting, vibratory tumbling, cutting, and grinding.

What about sand casting?

 Sand casting is another casting method which produces castings in a sand mold, which can obtain steel, iron and non-ferrous alloy castings. It is a great method to obtain larger components, but it does not stand out for achieving complex accuracy or to give smooth surface finishes, as the finish is rougher and it is more difficult to cast components with predetermined weight and size specifications. In addition, the molding materials are cheaper and easier to find and manufacture than the ones used in investment castings. It is one of the basic processes in foundry production.

Now that we know both methods, what are the differential points that make investment casting stand out from sand casting?

The advantages of investment casting

• This process can be used in a wide variety of industries, as it can produce a vast range of castings and it can cast ferrous and non-ferrous materials. Moreover, lost wax castings provide the maximum design flexibility in order to manufacture complex, multi part products.
• Design and accuracy. When choosing investment casting, you are choosing reliability as components turn out exactly as you intended with great quality and integrity. Due to its accuracy, design engineers can easily create products with precise dimensions and add features such as product ID’s and numbers, logos or letters into their components when using investment casting. So the design can take almost any shape. On the other hand, sand casting (although is best for creating large pieces) it is a challenge to make parts with internal voids or cavities with this method. So sand casting is more limited in this area due to its technology.
• As we already have pointed out, the surface we get from investment casting is very polished and of great quality. On the other hand, the surface of sand casting can be affected by sand inclusion, sand wash, clip sand, air hole and other casting defects.
• Gamarra’s casting holds to tolerance of ± 0.08 mm which is not totally possible with other casting solutions.
• As an investment casting is produced from wax, it can be reused again in most cases. Moreover, the wax pattern is the best method to see the final part before it is cast. This way, we avoid further revisions, which can be expensive, and we reduce metal scrap.
• Due to its raw materials (polyethylene of paraffin wax, sodium, silicon sol and sodium silicate) the cost of investment casting can be higher than sand casting. Sand casting’s materials are either chemical self-hardening sand or clay sand, which are cheaper in comparison. To sum it up, investment casting can be more expensive than sand casting, but as results are better as you save time and money on alteration costs.

The disadvantages of investment casting

• Cost and lead time. The materials used in investment casting are more expensive than the ones used in sand casting. However, as it is a reliable method, you can save money as you don’t need to worry about revisions during the process, which can happen with sand casting. In the end, it is up to you to choose the process that best fits your needs. Also, lead time (the time that passes from the start of a process until its conclusion) is longer in the investment casting process – although Gamarra has a proven reputation for delivery on time and efficient production.

Technical specifications of investment casting and sand casting