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Vacuum casting

Vacuum multi-molding (also known as polyurethane vacuum casting) is an economical alternative to small-batch injection molding of plastic parts and can be used to closely simulate the final molded part or finished product.

Usually, molds are made of silicone rubber and use CNC or SLA parts as master molds.

These molds can replicate every structural detail and surface texture of the product, and another product can be replicated by over-molding. A set of silicone molds can replicate 10-15 sets of products.

Advantage of Vacuum casting:

11   Low cost for silicone molds
12   Fast delivery
13   Wide selection of materials and applications
14   High precision and fine details
15   Excellent surface finish

How Does Vacuum Casting Work?

At Shenzhen Jucheng Precision, we have very strong capability and it is the most advantaged service.

  • According to your 3D drawings, we will make a master part by CNC machining and 3D Printing (SLS/SLA).

    we also will consider making the master by SLA for those parts with more complex shapes and structures.
  • Paste tape in a flat position around the master, so that it is easy to open the mould later, which will also become the parting surface of the final mould. The master model is suspended in a box and place plastic rods to set gates and vents.

    Silicone is poured around the master and a vacuum is used to remove all air. This then is cured in an oven, at a temperature of 40℃. 
    It generally takes 8-16 hours depending on the volume of the mould. Once the silicone rubber is cured, remove the master from the silicone to form a cavity, and the silicone mould is made.
  • Prepare the polyurethane resins to preheat them to about 40°C before use. Mix two-component resins in exact proportions, and then fully stir and degas for 50-60 seconds under vacuum.

    The resin is poured into the mold inside the vacuum chamber under computer control and cured again in the oven. Average cure time: 1-3 hours for small parts and 3-6 hours for big parts.
    Remove the casting part from the silicone mold after curing. Prepare to repeat this cycle.


Vaccuum casting 

The material about Vacuum casting

The Material baout 

Polyurethane resin is a polymer with a wide range of characteristics and uses. 

We provide a variety of polyurethane materials to meet your application, including Hei-Cast in Japan and Axson in France. 

It is a material with certain characteristics, similar to engineering production plastics, such as ABS, PMMA, PC, PP, PA, etc. Casting parts can range from transparent, translucent to colored, from soft rubber to hard plastic. Various materials include impact resistance, high temperature resistance (120°C) or fire resistance (UL94-V0), glass-filled resin and silica gel of different hardness.

      Master Pattern   Clear casting requires high transparency, masters have to make via clear acrylic material by CNC machining.
      Sanding smooth with 1500l# sanding paper, then use the polishing paste to remove the sanding mark.
      Silicone Rubber Mold   The silicone mould material must be compatible with clear casting resin. Also, choosing the right release agent and applying it
      effectively is important.
      Mould Life   For clear casting normally 12-15 copies, up to 20 copies per mould. (depending on the mould's complexity)
      Accuracy of Cast Parts   Provide a standard tolerance of +/-0.15mm/100mm, the highest precision can be +/-0.05 mm.
      Minimum Wall Thickness   To ensure that the mould is filled properly, a wall thickness of at least 0.75mm is necessary.
      For best results, we recommend a wall thickness of at least 1.5mm.
      Maximum Part Dimensions   The size of the mould is limited by the dimensions of the vacuum chamber (1200*600*600mm for clear
      casting )and by the volume of the product(maximum volume:4 litres)
      Finishing for Cast Parts   Polishing the finished piece is almost always necessary, and upon de-moulding, most parts have parting lines and sprues that
      require removal.

      This can add a considerable amount of time and energy depending on the size and complexity of the piece.
      Typical Lead Time   Up to 20 parts in 15 days or less, depending on the part specification and volumes.
    Urethane Resin Properties Colour Flexural
    (Shore D)
    Tg(℃) Application
    Axson PX-5210 High transparency(water clear) transparent 2400 85 48 95 Optically clear acrylic
    Good UV resistance
    High reproduction accuracy
    Easy polishing
    Axson PX-527 Good flexural impact resistance transparent 2600 82 >100 90 Clear parts Similar to PC
    Good mechanical properties
    Similar to thermoplastic PC
    Can be easily colored

Technical Parameters of Silicion Molding

Our engineering manager will provide solutions for you note and consult with you on everyday details of your projects.

Standard accuracy
Standard tolerance on 
with the highest precision able 
to reach ±0.05 mm.
Standard lead time
Up to 50 copies 
can be produced in 7 to 10 days, 
depends on the part 
specification and volumes.
Maximum part dimensions
The vacuum equipment can hold 
mold specifications.
Lifetime of the silicone mold
Up to 20 copies per mold
while if the part requires high quality 
such as clear or complex structures
one mold can only make 12 or even 10 
casting parts.
Minimum wall thickness
The minimum wall 
thickness is 0.5mm
the best is 
1.5mm to 2.5mm.
Surface finish and other functions
Colored, textured, painted
coated, clear polished
insert, and over-molding.

  • Q When should I choose Vacuum Casting Services?

    Vacuum casting is a method for making high quality prototypes or low volumes of parts formed from inexpensive silicone molds. Copies made in this way show great surface detail and fidelity to the original pattern.
  • Q Can I use my own master model for making duplicate copies for vacuum casting or CNC machining?

    Yes, master models are used to create silicone molds for vacuum casting and can be made from any rigid solid that can withstand heat up to 100° C. Models used for CNC machining will be 3D scanned to create a CAD/CAM program for production.And attention for the transportation of your masters.
  • Q What is the mold life for a silicon mold?

    The service time of the silicone mold is directly related to the complexity of the casting part. Generally, it outputs 12-15 pieces before degradation. If the structure of the part is simple, one mold might be able to cast 20 parts; while if the part requires high quality such as the clear complicated part, one mold can only make 12 or even 10 casting parts.
  • Q How Long Will Jucheng Precision Keep the Silicon Mold?

    Silicion molds tend to deform after being kept for a long time, so we will keep them 30 days and then we will dispose them.

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If you have any questions, please contact us, we will answer all kinds of questions for you in time.

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