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What is Vacuum casting?
Vacuum casting, sometimes referred to as Urethane Casting or Polyurethane Casting,using silicone moulds to make plastic and rubber components under vacuum. It is an extremely adaptable manufacturing process capable of mimicking the injection moulding to produce complex parts in polyurethane resins and cast nylon.
Due to the process being under vacuum, it produces high-quality bubble-free casting with smooth surface texture similar to painting effect.Vacuum casting can be extremely useful and worth considering when selecting rapid prototyping processes for plastic or rubber parts.
Advantages of Vacuum Casting
Low cost for silicone molds
Cast urethane parts are made of cheap molds, eliminating the need to invest in expensive and time-consuming metal tooling. It is a cost effective method for making high quality prototypes and low volumes of parts.
Fast delivery
Up to 50 functional cast urethane parts can be produced in 10 to 15 days when you choose vacuum casting.
A wide selection of materials
Casting resins materials range from soft and flexible to rigid and impact-resistant, as well as colored and clear.
High precision and fine details
Vacuum casting provides end-use parts of high precision and fine details with production-level quality.
Excellent surface finish
Urethane casting can provide better surface textures compared with CNC prototyping or 3D printing.
Vacuum Casting Process
There are three steps to making polyurethane vacuum cast parts: making the master pattern, making molds and casting the parts.
01 Master Patterns
Patterns are 3D solids of your CAD designs. They are usually made by CNC machining or with 3D plastic printing such as SLA/SLS. You can supply your own patterns or we can make them for you. Patterns need to be able to withstand heating to 40°C.
A master pattern can be any physical solid of your design. They are often made either by CNC machining or some form of 3D printing such as SLA. Note, however, that a pattern made from 3D printing will not be quite the same as the CNC counterpart, since the later process uses round cutting tools that cannot make very tight radius corners.
02 Making the Molds
Casting molds are made from liquid silicone. This silicone is poured around the master pattern inside of a casting box, and then allowed to cure in an oven for 16 hours. Once dried, the mold is cut open and the master removed, leaving behind an empty cavity in the exact negative shape of the original.
First the pattern must be carefully prepared, and that means sanding and sealing the surface with primer. Once it’s ready, it’s placed into a casting box and liquid silicone is poured around it. Depending on the size of the part, it can take 12~24 hours to fully cure inside of an oven. Once dried, the mold is cut open and the master removed, leaving behind an empty cavity in the exact negative shape of the original.
03 Vacuum Casting Tolerances
The finished dimensions of vacuum cast parts are dependent on the accuracy of the master pattern, the part’s geometry and the type of casting material used.
Generally a shrinkage rate of 0.15% is to be expected.
Typical technical specification
Time frame Within 24 hr – 5 working days for up to 30-50 parts
Material choice Wide variety of materials available
Accuracy ±0.3% (with a lower limit of ± 0.3 mm on dimensions smaller than 100 mm)
Minimum wall thickness To ensure that the mould is filled properly, a wall thickness of at least 0.75 mm is necessary. But best results are achieved with a recommended wall thickness of 1.5 mm
Maximum part dimensions The size of the mould is limited by the dimensions of the vacuum chamber
Typical quantities Up to 50 parts per mould
Surface structure Gloss to Matt surface finish can be obtained
Materials of vacuum casting
Vacuum casting polyurethanes resins (Transparent PU, Soft plastic PU, ABS PU, PP/PE PU, Polycarbonate PU) | ||||||||
Material | Supplier (Country) | Material Simulation | Strength Shore | Flexion(MPA) | TC Max | Product color description | Advantage/Disadvantage | Shrinkage |
ABS TYPE | ||||||||
---|---|---|---|---|---|---|---|---|
PU8150 | Hei-CAST (Japan) | ABS | 83 shD | 1790 | 85 | Amber,white and black | Good resistance | 1 |
UP4280 | Axson (France) | ABS | 81 shD | 2200 | 93 | Dark Amber | Good resistance | 1 |
POLYPRO TYPE | ||||||||
UP5690 | Axson (France) | PP | 75-83 shD | 600--1300 | 70 | White/Black | Good resistance | 1 |
COLORABLE ELASTOMERS | ||||||||
PU8400 | Hei-CAST (Japan) | Elastomer | 20-90shA | / | / | Milky white/Black | Good Bend | 1 |
T0387 | Hei-CAST (Japan) | Elastomer | 30-90shA | / | / | Clear | Good Bend | 1 |
HIGH TEMPERATURE | ||||||||
PX 527 | Hei-CAST (Japan) | PC | 85 shD | 2254 | 105 | White/Black | High T℃ 105° | 1 |
PX223HT | Hei-CAST (Japan) | PS/ABS | 80 shD | 2300 | 120 | Black | IdealTG 120° | 1 |
UL-VO | ||||||||
PU8263 | Hei-CAST (Japan) | ABS | 83 shD | 1800 | 85 | White | 94V0 flame retarding | 1 |
PX330 | Axson (France) | Loaded ABS | 87 shD | 3300 | 100 | Off White | V 0 far 25 | 1 |
CLEAR | ||||||||
PX522HT | Axson (France) | PMMA | 87 shD | 2100 | 100 | Clear | Coloration TG100° | 0.996 |
PX521HT | Axson (France) | PMMA | 87 shD | 2200 | 100 | Clear | Coloration TG100° | 0.996 |
FAQ
1.Why Use Vacuum Casting Services
Vacuum Casting is a vital element of professional rapid prototyping services and low volume production. It is a very cost-effective and efficient manufacturing process, small batches high quality similar injection molding parts are made within several days.
2.What Are Vacuum Casting Applications
Doing test of the products before starting new products development.
Attending Exhibition & Market research.
Rapid prototyping.
Low Volume Production.
Conduct propaganda new products to user.
3.What Materials Are Used In Vacuum Casting?
Vacuum Casting resins are available in various hardness and colors, depending on customer's product's requirement. In vacuum casting services, Polyurethanes(PU) is probably the most widely used type of casting resins
4.The Advantages Of Our Vacuum Casting Services
Our vacuum casting prototyping manufacturing cost is low and production time is short.
Cost effective for Low volume production. After making a master pattern and the silicone mold, it can be duplicated according to the master pattern.
Flexible de-mould operation. After the mold is dry and solidified, the mold is soft and flexible, conductive to cutting and de-mould.
Diverse material and colors for your choosing.
High quality. The defect rate is small. As long as there is no defect on the master pattern, the vacuum casting parts will not be wrong. Most of the time we have avoided it.
Good repeatability, ensure same quality and consistency.
We attach great importance to customers' needs for product quality and rapid production.
We always insist that meeting customers' needs is to realize our value!