The process of Vacuum Casting has become extremely popular in recent years, with both big business and small making use of this quick and cost-effective method of prototype building. Having built a master model which is highly finished, vacuum casting creates multiple replicas at the same high standard of the one-off piece, but in a material with better mechanical properties.
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For more information about the vacuum casting process, view our Vacuum Casting Process page. But what are the benefits of using vacuum casting to create your prototype models?
In terms of functionality, there are a host of benefits of vacuum casting. The PU resins that are used in vacuum casting will imbue the part, be it for fire retardation or electrical and shock resistance. Vacuum casting is also the best way of creating unusual shapes with differing thickness. While other methods can be used to form difficult shapes, vacuum casting is the quickest and most reliable way of getting the job done.
From an aesthetic point of view, vacuum casting produces a high-level of production accuracy as well as offering a number of different finishing options. Vacuum casting allows the addition of colour during the manufacturing process, adding the colouring pigments along with the resin components to ensure the final piece comes out with the exact colour required. Mixing colours with the resin means a variety of different finishes can be used for the part, whether its gold or even marble rather than the more typical colours.
One of the real success stories of vacuum casting is just how many different sectors it has been used in. As well as being used to produce a host of plastic prototypes for consumer goods and product marketing, vacuum casting has been used in industries as wide apart as medical and aerospace.
The automotive industry is another to have utilised vacuum casting for their prototypes. One recent example of our vacuum casting work in this sector was to create this Lamborghini tail light.
But its not just big businesses that can benefit from vacuum casting, with the process increasingly being used by interior designers to create decretive objects in low volume such as wall plaques and smaller ornaments.
The main benefit of vacuum casting to businesses might be its accuracy and the exceptional finish of the piece, but the speed it takes to turnaround a product is also another selling point. As well as appealing to those companies needing to design and produce a prototype quickly, vacuum casting means designers arent afraid to take chances with products.
The difference in time is one thing that makes vacuum casting a popular process, the other is the cost. For one-off prototypes or short run batches, vacuum casting comes in at a fraction of the price of other methods such as plastic injection moulding, resulting in an exceptionally finished end product.
If youre interesting in using the Vacuum Casting process in your next project, contact Ogle to see how we can help.
Vacuum casting, also known as urethane casting, is a method used for low volume production. It produces parts with quality similar to injection moulding but with much shorter lead times. This process is great for making small batches of plastic or rubber parts using various thermoplastics, rubbers, and resins.
The silicone vacuum casting process involves three main stages:
Maximum Size Up to x mm Vacuum casting materials
Considerations regarding the vacuum casting production process are important to note as well:
To take full advantage of this technology, it is important that your 3D model closely follows a set of geometric recommendations.
At Xometry, standard tolerances are controlled to ISO Coarse (C) for vacuum casting. For features left unspecified, standard tolerances are used. Tighter tolerances can be achieved but these are only recommended for critical features.
Consistent wall thickness is essential for successful vacuum casting. Varying thickness can result in uneven cooling and curing rates, potentially causing deformities or weak spots in the part.
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Generally, we recommend a minimum wall thickness of 0.75 mm to 1.5 mm for small to medium-sized parts, with larger parts requiring greater thickness. However, the optimal thickness may depend on your specific project and selected material.
Bosses should maintain a minimum height and diameter of 1 mm, while their wall thickness should not exceed 60% of the nominal thickness to reduce sinking.
Ribs can bolster strength and diminish warping on expansive flat regions. To mitigate shrinkage and sinking effects, rib thickness should be less than the wall thickness. Experts advise keeping rib thickness below 60% of the nominal wall thickness, with rib height restricted to less than three times its thickness.
Example of ribs added to a flat surfaceUndercuts and overhangs pose challenges in molding and casting as they are hidden or extend over a cavity. However, vacuum casting excels in handling these features more effectively than other manufacturing techniques.
Designing parts with undercuts or overhangs for vacuum casting will affect mold complexity and may necessitate additional considerations or adjustments.
These features are measured from or to the surface of the tool and can hinder tool component extraction. Aim for undercuts no deeper than 15 mm to avoid this issue.
Recessed or embossed text and logos should have a minimum depth or height of 1 mm and a width of 1 mm to ensure visibility. To optimize visibility, maintain a 1 mm gap between letters.
Draft angles are crucial in vacuum casting. They entail a slight taper on vertical walls of part designs, enlarging the mold opening compared to its base. This is vital for easy part removal from the mold, minimizing the risk of damage.
Aim for draft angles of 1 to 2 degrees in your design, although the ideal angle can vary based on part geometry and material. Incorporating draft angles enhances mold longevity and improves cast part quality.
Example of draft angles on the mold, allowing the par to be easily removedWall Thickness At least 0.75-1.0 mm Bosses Minimum height of 1.0 mm; minimum diameter of 1.0 mm Wall Thickness For Bosses No more than 60% of wall thickness Rib Thickness No more than 60% of wall thickness Rib Height No more than 3x of rib thickness Engraved and Embossed Details Minimum depth of 1.0mm; minimum width of 1.0 mm Draft Angles At least 1 to 2 degrees
Material choice is critical in vacuum casting, impacting design outcomes significantly. Variations in flexibility, strength, and temperature resistance among materials necessitate careful consideration during part design.
For materials with high flexibility, assess if your design can handle potential flexing without functional compromise. Conversely, for rigid materials, avoid stress concentrations that may cause cracking or failure.
A successful design considers not only part geometry but also its interaction with the chosen materials properties.
Example applications for vacuum casting encompass soft-feel grips on products like hairbrushes or handheld controllers. Its also prevalent in developing medical devices, drug delivery systems, consumer goods, and automotive trim.
The process involves overmolding materials of varying grades of PU, with the secondary molding occurring before the primary molding fully cures. This results in a robust bond between the materials, yielding parts suitable for handling trials.
Optimal outcomes are achieved through overmolding PU castings. However, we can also overmold CNC machined plastic or metal parts, as well as modified production parts.
Insert molding is commonly employed to integrate purchased components like threaded inserts or electrical contacts, or parts machined in-house, particularly when tight tolerances are crucial. For cases requiring multiple inserts, we can CNC machine a fixture to ensure accurate positioning relative to each other and the mold cavity.
Vacuum cast partsMastering vacuum casting design is crucial for superior part quality, production efficiency, and project success. By following outlined considerations and best practices, engineers and designers can unleash the full potential of vacuum casting technology.