Vacuum Casting

Vacuum casting

What is Vacuum Casting used for?

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

At Prototype Projects we can produce parts to extremely fine levels of detail and keep concessions to the absolute minimum.

Our aim is to satisfy any toolmaker’s production tooling requirement.

The small numbers of parts are made from a single master mould, which is made using an SLA master model usually using silicone rubber.

Prototype Projects in-house Vacuum Casting facilities

Prototype Projects has a suite of MK Technology Vacuum Casting chambers and ovens which afford great flexibility in turning around tools quickly.

These systems feature electronic differential pressure systems and automatic silicone de-gassing. Our specialist process curing ovens ensure excellent surface quality with a minimal scrap rate.

Get the PDF:

Vacuum Casting PDF

Vacuum Casting Technical Details

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

What is the Vacuum Casting Process?

The Vacuum Casting process is typically used to produce small numbers (usually up to 20) of highly accurate polyurethane prototype parts.

Vacuum-casting-flexi It is a slightly slower process than SLA alone because of the additional steps involved in the process, some of which are manually intensive. The time to manufacture depends on the desired characteristics of the part, with size being a key factor as this affects the curing time of the material.

Parts are made from a single master mould, which is itself made using an SLA master model. The mould is made from silicone rubber, and the casting made by pouring resin into the mould in a vacuum chamber.

The result is high quality bubble free casting with blemish free surface texture.

When to use Vacuum Casting

Vacuum Casting is ideal when highly accurate, functional plastic prototype parts in very fine detail are required.

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

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

Vacuum Casting Benefits

As well as being a highly effective method for producing small numbers of good quality accurate polyurethane prototype parts, Vacuum Casting can also deliver parts with varying degrees of flexibility or rigidity, in a wide range of colours and materials – as well clear parts. Used in conjunction with other prototyping technologies, Vacuum Casting obviates the requirement for expensive purpose made production tooling.

In summary:

Ideal for functional testing and/or marketing
Cost effective
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.

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.

Silicone Tooling

Silicone tools have a limited production life. The number of parts that can be produced from a single silicone tool depends on one or two factors (and often both):

The polyurethane (PU) material used, and
The geometry of the part being produced

A silicone tool running a general PU material simulating ABS will on average yield 20-25 parts; a flexible material in the lower Shore A range will yield 25-30 parts; and a material with a filled content will yield around 10 parts, but could be a low as 5.

The geometry aspect is down to the part detail, normally within the “B” surface where clip features exist, which can cause the tool to degrade.

Some inserts may be required to hold certain features and will affect price and lead time.