Here at JCAD-Inc., we can provide cost-effective casting of polyurethane and urethane products and rapid prototyping of parts using short run, low-volume manufacturing processes.

What Is Vacuum Casting?

Industrial parts manufacturing can be a tricky business due to the complexity of parts and a high cost of production for standard manufacturing processes. The invention of vacuum casting was a successful attempt at solving these problems.

Vacuum casting — also sometimes called urethane or polyurethane casting — refers to a manufacturing process where a cast of an object is made using a silicone mold and casting equipment. Injection molding, a similar process, differs by having the liquid materials for casting pushed into the mold via a screw, rather than being pulled in via suction or negative pressure. Vacuum casting works differently from injection molding, mainly in the mold material used – silicone molds for vacuum casting and metal molds for injection molding. Vacuum casting is excellent for making short-runs of high quality prototypes.

A primary benefit of using a vacuum chamber is its removal of air bubbles that can alter the fine details of the finished product in other manufacturing processes. The vacuum casting process, therefore, is a good technique for rapid prototyping and manufacturing of products with fine details.

The process starts with the creation of a master pattern of the object that will be used to form the silicone mold using a casting box and liquid silicone. After the mold is formed, it is used to create casts of the master pattern inside a vacuum casting machine with the desired polyurethane or urethane resin.

Vacuum casting machine

A vacuum casting machine. Image by Lukadent, CC BY-SA 3.0


Vacuum-Assisted Metal Casting

Just like polyurethane casting, this process can be applied in the production of high-quality parts used in aerospace and other industries that rely heavily on metallic parts with intricate details.

The process is essentially similar to casting in poly. In this method, metal is heated to a liquid state and then pulled through negative pressure into the mold in a controlled fashion.

A similar casting process, gravity pouring, has its advantages but within some geometries, it can result in an unpredictable metal flow that can lead to air pockets forming within the cast. The objective of vacuum casting is to control the metal flow to allow the mold to be filled smoothly. When done well, this process will deliver a great result when there is a need to create parts requiring great surface texture and integrity.

Learn more about the vacuum casting process here.

Our Vacuum Casting Services

Creation and Casting of Your Master Patterns and Molds

At JCAD-Inc., our highly-skilled team of CAD designers and engineers can help you design the master model for the master pattern used in making the silicone mold. For this we use CAD software and additive manufacturing technologies or CNC machining. Our care and high attention to detail ensure that we meet your design specifications and that your master model is perfect in every way, as any flaws in the master pattern will be transferred to the copies made from the mold created.

Post-production Finishing

We offer several finishing options for the copies of the master patterns. These options range from the assembly of poly cast parts with off-the-shelf components to cleaning and painting as well as sanding & pad printing services and removal of excess parts. EMI/Blackout/RFI can also be used for internal surface finish and the parts can be metallized.

Vacuum casting materials

Vacuum casting requires a casting box, liquid silicone, a casting machine, and casting resins.

Unlike cast parts made from a polyurethane or urethane liquid material, the master model used in the vacuum casting service can be made from a variety of materials and methods including CNC machining. These materials may or may not need post processing.

Several vacuum casting resins are commercially available to fit the surface texture and hardness your product requires and include rubber-like polyurethanes, ABS-like polyurethanes, PE/PP-like polyurethanes, etc.

The structural qualities of your desired product will dictate the type of polyurethane we use in creating your products.

Our Vacuum Casting Capabilities

With our casting process and machines, we achieve A-grade quality due to finely tuned pressure control systems and automated silicone degassing capabilities. These capabilities allow us to produce products with a precision of ±0.3% (with a lower limit of 0.3 mm on dimensions smaller than 100mm).

Depending on the volumes and specifications of the master pattern, we have a lead time of up to 15 days (not including shipping) to make up to 20 parts. Depending on the mold’s complexity and the casting material used, we can often re-use the silicone mould to create more copies of the prototype. Typical quantities achieved are between 20 to 25 copies of the prototype from each of the silicone molds created, when the molds have a minimum wall thickness of at least 0.75mm. For this reason vacuum casting is ideal for short run production, but not for mass production.

Applications For Our Vacuum Casting Service

There are many applications vacuum casting. At J-CAD Inc. we have clients from many different industries including. Some examples of prototyping applications for these industries are below. This is, however, just a small selection, the possibilities for short-run production are almost endless;

  • Aerospace: Brackets, handles, turbine parts
  • Architecture: Sculptures, artistic elements
  • Automotive: Handles, grills, reproducing out of stock parts
  • Medical: Surgical models, equipment parts
  • Consumer products: Prototypes of household goods, tools, etc.
  • Oil and Gas: silicone rubber parts, fluoropolymer parts, etc.

What Are the Advantages of Vacuum Casting?

  • Low cost for molds
  • Reduced lead times, which mean you can get your products to market faster
  • Many types of polyurethane resins are available for casting, including over-molding with two or more materials.
  • Coloring pigments can be added to the polyurethane resins. We can even make completely transparent or partially transparent parts depending on the casting material used.
  • Cast copies are highly accurate with an excellent surface finish superior to injection molding.
  • Molds are durable for 20 or more copies
  • Perfect for engineering models, samples, rapid prototypes, bridging processes to mass production
  • Eco-friendliness

Vacuum Casting FAQ

Why Would You Choose Vacuum Casting Instead of Injection Molding?

Like injection molding, silicone molding produces has the ability to produce very high quality parts through a cost-effective process. Vacuum casting is therefore highly suited to making parts to diagnose any problems with the design, for function testing or marketing purposes. The vacuum casting procedure allows for a varied surface finish that will match the ideal final appearance of your intended product.

Why is a Vacuum Used?

The negative pressure created by the empty cavity ensures the silicone mould is filled properly to avoid air entrapment that may alter the fine details of the product. When filled properly a wall thickness that is completely or almost completely even (±0.3% precision) can be created.

What is the Difference Between Vacuum Casting and Centrifugal Casting?

Urethane casting uses suction to fill the mold, centrifugal casting uses the weight of the metal and centrifugal force.

What are the advantages of plastic parts over metal?

Plastics are cheap and easy to handle in vacuum casting work. They are also corrosion resistant, have insulating properties, and are reusable.

Should I Choose Vacuum Casting or 3D Printing?

Why should you use polyurethane casting for your parts instead of 3D printing them? 3D printing is good for one-off, smaller parts or protoypes. Vacuum casting is the manufacturing process of choice however, when the product requires rapid replication on a short-run basis, which is both affordable (for short runs) and precise. 3D printing can be a good option for making master patterns.

Additive manufacturing is limited by the size of the printer bed. With casting, the maximum volume and maximum part dimensions are limited only by the size of the vacuum casting chamber.

Are There Any Cons or Drawbacks of vacuum casting?

Although a very efficient process, vacuum casting has a few disadvantages which might make you choose a different manufacturing technique;

  • Vacuum casting uses silicone molds, which are prone to wear and tear and have a relatively short production lifespan.
  • The mold life is limited to about 40 to 50 molds, so its application is limited to low-volume production
  • The molds require regular cleaning
  • Silicone molds undergo shrinkage (at a rate of about 1% to 4%) due to thermal expansion. This calls for the usage of high-quality silicone with lower shrinkage rates when making the molds

How much does a vacuum casting service cost?

Vacuum casting is a cost-effective manufacturing method. Compared to injection molding, it is relatively cheap. However, the cost of vacuum-casted parts will vary depending on what stage of the process you are at (eg. do you also need CAD design or a master pattern created?), the complexity of the design, and the volume of production.

Why choose us?

At JCAD-Inc., our work is produced at very high standards by adhering to strict quality control measures including verification and testing of the casting material and strict temperature and humidity control.

Our vacuum casting services provide excellent parts in appearance, finish and functionally. With years of expertise, we are equipped to handle all steps of your product fabrication process. With your specifications, our knowledge and the right material you will be very happy and impressed with the outcome!

If you need help making some high quality prototypes or short-run products give us a call on 1-888-202-2052 or fill out our quote request form. If you already have CAD designs, you can send the CAD files to us (we’ll sign an NDA so you’re protected), or just send us your project specs and we’ll get a free quote to you in 5-10 minutes!

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