Prototyping guide to Vacuum Casting 

What is Vacuum Casting? 

Vacuum casting is used to bridge the gap between 3D printed models and the production method, which is typically injection moulding. The moulds used to produce the parts are made from silicone rubber, the moulds have a limited life and are normally capable of producing 20-25 parts, though this is dependent on the polyurethane (PU) material being used. 

Did you know? 

Used in conjunction with other prototyping technologies, Vacuum Casting removes the requirement for expensive purpose made production tooling.

How does Vacuum Casting work? 

A master model (normally an SLA) is produced, then encapsulated in silicone rubber to create the mould (tool).  

Once the mould (tool) is completed and ready for use it is heated then placed in the chamber. The PU (A+B) resin is placed inside the upper chamber ready to be degassed and mixed. Once fully mixed, and the chamber has been evacuated, the PU resin is slowly released into the mould (tool). 

When enough resin is flowing into the tool, the vacuum is released, forcing the mixed resin to flow through the tool. Once the tool is filled with resin it is placed in an oven to cure for up to an hour. 

Once cured, the tool is removed from the oven and opened so the solid part can be removed. Finally, the part is finished by hand removing any flash and vent points. 

Did you know? 

The PU resin does not reach full material properties until seven days after it has been cured.

When should Vacuum Casting be used? 

Vacuum Casting is used for producing small numbers of polyurethane prototype parts with characteristics and quality comparable to the final product. 

The process can replicate patterns, dimensions, profiles and textures, and as such is widely used to produce parts for: 

• functional testing such as thermal and air flow testing 
• assembly line trials 
• marketing purposes e.g. presentations and trade shows.
  

What are the benefits of Vacuum Casting? 

Vacuum Casting can deliver parts with varying degrees of flexibility or rigidity, in a wide range of materials and colours, including clear parts. It has several benefits: 

• Low volume runs 
• High quality 
• Fine detail and accuracy 
• Range of properties can be achieved to mimic the final product 
• No requirement for expensive hard tooling. 

Technical information 

 Vacuum Casting Technical Details 

• Maximum casting weight: 1400 g 
• Maximum mould size: 450 x 470 x 400 mm
  

Vacuum Casting Part Properties 

• Heat resistance 
• Colours and tints 
• Fire retardance 
• Flexibility and rigidity 
• UV stability
• Range of surface finishes 
• Insert options 
• Water clear 
• Flexible polyurethane casting resin grades range 
• Inserts can be moulded in 
• Range of finishes from grades of spark texture, smooth matt and satin to a high gloss finish. 

Plastic material simulation 

 Vacuum Cast parts produce material simulations of: 

• ABS 
• POM 
• Elastomers (Range: 25 – 95 Shore A) 
• Nylon including glass filled 
• Polypropylene 

Vacuum Casting options 

Various finishing options are available for vacuum cast parts. These can be tailored, depending on the requirements of each project. 

The timescale for the production of multiple sets of vacuum cast parts will vary from project to project. Please speak to us about your next prototype project. 

Ready to start your next prototype project? 

Prototype Projects is a UK-based prototyping bureau delivering high quality prototype parts in fast turnaround times. 

As well as vacuum casting, we also deliver a range of 3D printing solutions with 4 dispatch options, including next day dispatch. We also offer a dyeing service for SLS prototype parts, as well as a texturing service for SLS and SLA parts. 

Contact us on 01763 249760 to discuss your next prototype project.