This powerful and versatile manufacturing technique leverages the advantages of silicone moulds and vacuum technology. These components are leveraged to produce high-quality intricate parts, but at a price lower than traditional methods.
Also known as urethane casting, vacuum casting is a cost efficient solution with design flexibility and the ability to replicate complex geometries with high precision.
How vacuum casting works
To start the vacuum casting process, a master model is created, which usually happens via CNC machining or 3D printing. This model is then leveraged to fabricate a silicone mould, serving as the negative for casting the final parts. The three primary steps of vacuum casting are explained below:
1. Master model creation: The first step involves creating an accurate master model by using either 3D printing or CNC machining. This model serves as a template for the silicone mould. It is essential to achieve a smooth and flawless surface finish, as the final product will replicate all the details from the master model.
2. Silicone mould creation: After the master model has been finalized, the model is suspended in a casting box. Hereafter, liquid silicone is poured around it. The silicone is then cured inside a vacuum chamber, with the purpose of ensuring air bubbles are eliminated, so that the mould perfectly matches the original design. After the curing process, the mould is cut open. Hereafter, the master model is removed, which leaves cavity ready for casting.
3. Casting process: Once the hollow silicone mould is ready, it is filled with polyurethane resin, or a similar material. This also happens under vacuum conditions. The reason for the vacuum is to ensure an even distribution of resin, to avoid air bubbles, and to ensure the part replicates the master model and all the details of it. Following this, the part is cured at around 70 C and then removed. One silicone mould can be used to produce between 10 and 20 parts, but then it will lose dimensional accuracy.
Advantages of vacuum casting
The most significant advantage of vacuum casting is the ability to produce high-quality parts, but with minimal upfront costs. Instead of injecting moulding, which is a technique that requires costly steel or aluminium moulds, vacuum casting uses silicone moulds. These types of moulds are cheaper and faster to produce. Vacuum casting moulds are inexpensive compared to other tools and methods. Furthermore, the process of creating a silicone mould takes a few hours, and the entire cycle from design to finished part can be materialized within 15 days, which is an ideal solution for projects running on tight deadlines.
Vacuum casting also leaves great material flexibility. Engineers can select from various materials, such as polyurethane, ABS-like, PP-like, and PC-like resins. The choice should just depend on the desired mechanical properties. This flexibility means that vacuum casting can produce parts with varying levels of rigidity, transparency, impact resistance, and heat tolerance. Another advantage is the soft silicone moulds used for vacuum casting, as these offer great design flexibility. It is easy to incorporate features like undercuts, ribs, and embossed logos. Yet another advantage is that vacuum-cast parts can achieve excellent surface finished, enhanced by post-processing techniques including sanding, painting, and silk-screening.
Cases of applications of vacuum casting
There are many industries which are leveraging vacuum casting due to its versatility. As vacuum casting can both be leveraged for prototype development and the production of end-use parts, it is becoming a sought-out technology for various industries.
Automotive industry
In the automotive sector, vacuum casting is used to create prototype parts. This often includes dashboards, door handles, and light covers. What engineers can use these prototypes for is to help validate designs before moving into the full-scale production of the parts.
Consumer electronics
Vacuum casting has also been widely used for producing enclosures and functional prototypes for electronic devices. This goes across various devices, including smartphones, laptops, and wearable technology. For engineers, this makes it possible to test the form, fit, and function of devices, leaving out the cost and time with mass production tooling.
Medical devices
In the medical and healthcare sectors, vacuum casting is used to create prototypes of devices, which includes enclosures for diagnostic equipment, orthopaedic devices, and custom implants. Since vacuum casting enables quick testing of designs, it ensures safety and efficacy in an affordable manner.
Aerospace industry
In the aerospace sector, vacuum casting is used to produce non-structural components. This includes items such as interior panels, air ducts, and cabin fittings. As all these parts must meet stringent specifications, vacuum casting allows engineers to experiment with various designs and materials at a cheaper price.
When to use vacuum casting
There are specific situations where vacuum casting is particularly advantageous, which is especially the situation when small production runs are required. For prototyping, vacuum casting allows engineers to iterate rapidly and make changes to designs in the early-stage product development, since this process involves testing various designs.
For low-volume production, where projects require between 1 and 50 parts, vacuum casting is an efficient solution, as it bridges the gap between prototype development and mass production. This results in high-quality parts without spending many finances on expensive tooling. Lastly, vacuum casting is great for functional testing, as the parts produced through vacuum casting resemble injection-moulded parts in terms of mechanical properties. This makes it useful for the process of functional testing.
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