An Introduction to Vacuum Casting

Vacuum Casting Process - Chizel

While 3D Printing has transformed the manufacturing industry in a humongous manner, there certain processes that enable 3D printing to become even more enhanced. In this article, we are going to learn of one such process known as Vacuum Casting. The combination of all such processes like Stereolithography, Laser Sintering, Vacuum Casting, etc. with the base technology of 3D printing makes it possible to enhance the prototyping process into much better.

Getting Started: Definition

In this section of the article, we will understand what Vacuum Casting represents basically. So, let us start with defining Vacuum Casting.

Vacuum Casting basically refers to a casting process which deals with employing a sand mold containing no moisture or binders. The internal cavity of this mold always holds shape because of forces exerted by vacuum pressure. This process is also referred to as Vacuum Mold Casting or popularly known in the manufacturing industry as V Process.

Let us quickly dive deep into this topic by studying the entire process and how it actually works.

Diving Deep: The Process

  • To begin with, we need to mention that a special pattern is used to carry out the process of vacuum casting. This pattern can be either a match-plate pattern or a cope and drag pattern. These patterns contain tiny holes within them. These tiny holes enable a vacuum suction. Now, over this casting pattern, we place a thin plastic sheet and turn on the vacuum pressure. This causes the sheet to stick with the surface of that pattern.

Vacuum Casting Process - Chizel
Vacuum Casting Process
  • It is important to mention that we use a special type of flask in the manufacturing process. This flask comes with holes that ensure proper utilization of vacuum pressure. It is placed over the casting pattern and then subsequently filled with sand.

  • Next up, for the task of metal casting pouring, we will cut a pouring cup and sprue into the mold.

  • Now, we place another thin plastic sheet over the mold at the top. When the vacuum pressure through the flask is switched on, the plastic film will stick to the top of the mold.

  • Now we will move on to the next stage of this manufacturing process. The vacuum acting on the special casting pattern is turned off. The pattern is subsequently removed. It should be noted that vacuum pressure acting from the flask is still on. This leads to the plastic film that’s on top to stick to the top. Also, the plastic firm that was formerly on the pattern now sticks to the bottom. We will see that the film on the bottom will be holding the impression of casting in sand along with the force exerted by vacuum suction.

Vacuum Casting Process - Chizel
Vacuum Casting Process
  • After this, we manufacture and prepare the drag portion of the mold in a similar manner. Both the halves are then assembled for the subsequent pouring of casting. It should be noted that at this step, there are a total of 4 plastic films being used. Each half of internal casting cavity contains a plastic film while there is one each on the cope and drag’s outer surfaces.

  • It should also be noted that during the process of casting pouring, the plastic can easily be burnt away by molten metal.

Vacuum Casting Process - Chizel
Vacuum Casting Process

Source(for all images above): The Library of Manufacturing

  • At the end of this process, individual components are extracted from the mold. Post-processing and cleaning methods can be used to achieve the desired look and finish.

Advantages and Disadvantages

Advantages

  • Silicone Molding has an upper handing in producing high-quality parts when compared to Injection Molding. This actually ensures that vacuum casting is perfect for function testing as well as marketing purposes for the production of limited quantities.

  • Vacuum Casting allows you to choose from a large range of finishes.

  • As Vacuum Casting does away from the need of any specific molding sand or binders, there is no need for any sand reconditioning or sand restoration.

  • As no water content used in the sand molds, any defects in metal casting can be avoided.

  • Vacuum Casting is very useful as it can be used for various major tasks as we discussed in the first point. It is even more important that vacuum casting reduces the general lead time. For example, 10 working days comes out to be the lead time to generate 10 copies with an accuracy of ∓0.3%.

Disadvantages

  • Vacuum Casting is a relatively slow procedure.

  • Vacuum Casting is not very well suited for process automation.

  • The usual lifespan of a silicone mold is about 20-25 pcs/mold which can be arguably

considered as lower than satisfactory.

  • It is suitable for the thickness of 1mm to 5mm.

Conclusion

This article was written to give you a glimpse into the process of vacuum casting and its importance. Vacuum Casting is a very important and useful process as we can successfully establish after going through the contents of this article. We shall go into even further details about Vacuum Casting by discussing materials being used in this process and their properties in future articles. Next article is a continuation of this article and it explains about the materials used in vacuum casting.

To know more about vacuum casting & the materials chizel offers – click this link.

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