Vacuum casting is excellent way to make 10 to 50 of prototypes from wide range of polyurethanes, which can simulate ABS，PMMA，Rubber，PP，Nylon, etc.
RpProto provides a complete vacuum casting and urethane casting service. We have tens of vacuum casting machines, which can cast prototypes with the max dimension up to 2200mm*1200mm *1000mm.
We can accurately reproduce the prototypes with original color, over-mold, texture and geometries from the master model and components.
RpProto produces tens of thousands of high-quality prototypes by vacuum casting for customers all over the world every year. RpProto is the most competitive vacuum casting factory in China.
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What is Vacuum Casting
Urethane casting or vacuum Casting uses the original product to make a silicone mold in a vacuum, and then pours it with PU material to create a replica of the original.
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Application of Vacuum Casting
Vacuum casting has a wide range of applications in various industrial fields, such as medical equipment, aviation, automotive industry, electronic products, etc. When you need a small quantity of production-quality plastic parts (from 10 to 50 sets), you should choose vacuum casting to avoid the long lead time and high cost of creating plastic injection mould tools.
These parts are used in prototypes and display models to verify the fit and function of a new design. In some instances, vacuum casting can also be used for end-use parts. Because the casting polyurethane can simulate the properties of ABS, Nylon, PP, PMMA, and soft TPE rubber.
Advantages Of Vacuum Casting
Lower Cost
Since silicone molds are cheaper than the tooling for injection molding
Color options
Coloring pigments can be added to the resin for a variety of color options.
Fast Turnaround
Molds can be made in a few days, depending on specification and volume.
Repeatability
Silicone molds are durable for 30 or more copies before they need replacing.
Superior surface
Cast copies are highly accurate with excellent surface texture
Tolerances for Vacuum Casting
| Dimension | Tolerances |
|---|---|
| 0.5 – 6.00 mm | ± 0.10 mm |
| 6.00 – 30.00 mm | ± 0.20 mm |
| 30.00 – 120.00 mm | ± 0.30 mm |
| 120.00 – 400.00 mm | ± 0.50 mm |
| 400.00 – 1000.00 mm | ± 0.80 mm |
| Angular: ±0.5° | |
A shrinkage rate of 0.15 % is to be expected in general.
Example of application of tolerances:
Vacuum Casting Polyurethane
Materials used in Vacuum Casting include thermoplastics, rubbers and resins, all of which can emulate specific properties and characteristics including :Surface texture,Transparency,Rigidity,Strength,Hardness,Temperature resistance,Colour.
The materials used in Vacuum Casting can simulate the following production materials and properties:
- Rubber : high flexibility
- ABS : high rigidity and strength
- Polycarbonate and PMMA : shock resistance, translucence, high temperature resistance
- Polypropylene and HDPR : high elasticity
- Polyamide and glass filled nylon : high rigidity
- Filled ABS : fire resistance and retardance
| References | Description | Hardness (shore) | Strength （MPa） | Elongation (%) | Tg (°c) | Colour | |
|---|---|---|---|---|---|---|---|
| TRANSPARENT SYSTEM | |||||||
| Axson PX 522 HT | The same properties as PMMA, cristal PS, MABS. High transparency, Easy polishing, Good UV resistance. | 87D | 75MPa | 9% | 110°c | transparent | |
| Axson PX 521 HT | For crystal glass like parts. High transparency (water clear) , Easy polishing ,High reproduction accuracy . | 87D | 75MPa | 9% | 110°c | transparent | |
| AXSON UPX 5210 | For crystal glass like parts. High transparency, Easy polishing, High reproduction accuracy , Low shrinkage | 83D | 65 – 70 MPa | 15 – 20% | 80°c | transparent | |
| Axson PX 225 | Low viscosity for easy casting. Good impact and flexural resistance. Very easy coloring with all kind of pigments. | 80D | 70MPa | 15% | 80°c | transparent | |
| FLEXIBLE | |||||||
| Axson UPX 8400 | Rubber-Like, Easy to process and pigment, outstanding strength, low aggressiveness to silicone moulds | 20A-85A | 6-22MPa | 450-660% | 80°c | off white | |
| Hei-Cast T0387 | Cured material is transparent. Hardness in a range from Shore A 30 to 80. | 30A-80A | 1.5-40MPa | 260-300% | 60°c | Clear | |
| SPECIFIC, TECHNICAL PLASTICS | |||||||
| Hei-CAST PU8263 | Well-balanced physical properties, difficult-inflammability and excellent dimensional stability | 83D | 68MPa | 15% | 80°c | white | |
| Axson PX 330 | Conforms to FAR 25 (fire resistance) standard. Easy to use. Compliance ROHS. | 87D | 70MPa | 3% | 100°c | white | |
| HDPE – PP type | |||||||
| Axson UP5690 | High elongation, High impact resistance, no breakable, Easy processing, Good flexibility | 75-83D | 25-35MPa | 50-90% | 70°c | White/Black | |
| ABS – HIPS – FILLED PP TYPE | |||||||
| Hei-CAST PU8150 | Well-balanced physical properties, excellent cure properties and superior dimensional stability , high practical strength | 84D | 73MPa | 16% | 85°c | Amber,white and black | |
| Axson UP4280 | Easy processing, High mechanical properties, Good heat resistance up to 100°C | 81D | 84MPa | 13% | 93°c | Dark Amber | |
| Axson PX 100 | Low viscosity. Manual application possible. Long pot life. | 74D | 40MPa | 20% | 75°c | White/Black | |
| Axson PX 527 | Like ABS type or PC. Good impact and flexural resistance. Clear aspect. Can be easily coloured with CP pigments. | 80D | 73MPa | 13% | 80°c | White/Black | |
| Axson PX 223 HT | Low viscosity. Good impact resistance. High temperature resistance. Temperature stability up to 110°C. | 80D | 60MPa | 11% | >120°c | black | |
| Axson PX 245 / PX245L* | Filled.Very short demoulding time. Very rigid. Good abrasion resistance. | 85D | 85MPa | 3% | 95°c | off white | |
How does vacuum casting work?
1.Master Patterns
2. Positioning of the model in a box and casting of silicon
3. Mold cutting and RP model removal
4. Polyurethane or other material casting
5. Printed model with inlet to be removed
Before making the silicone mold, you need to make an master patterns, which can be made by cnc processing or 3D printing. Start making the silicone mold, and mix the silicone and curing agent evenly. The appearance of the silicone mold is a flowing liquid, and the component A is silicone. The B component is the curing agent.
Vacuum and bubble removal treatment:
After the silica gel and the curing agent are evenly stirred, perform the vacuuming to remove the bubbles. The vacuuming time should not be too long. Under normal circumstances, it should not exceed ten minutes. If the vacuuming time is too long, the silica gel will solidify immediately, resulting in a cross-linking reaction. The silica gel becomes piece by piece and cannot be painted or poured.
Painting or operation process:
The silica gel that has been evacuated and evacuated can be brushed or poured. Pour it on top of the product (Note: The product or model to be copied before pouring the silica gel must be coated with a release agent or release agent). Then apply the silica gel on the product. The application must be even. After 30 minutes, paste a layer of gauze and weft cloth to increase the strength and tensile force of the silica gel.
Production of outer mold:
The generally used method and material is to surround the mold with rubber sheets or wooden boards, and fill the mold cabinet with plaster. The other method is to use resin brushing. After applying a layer of resin, a layer of glass is pasted. Fiber cloth, brush and paste, repeat two or three layers to complete the outer mold of the mold.
The operation method of filling mold or pouring mold:
Pouring molds or perfusion molds are used for relatively smooth or simple products. There is no mold line to save labor and time, that is, to copy the product or model you want to copy, pour the vacuumed silica gel directly onto the product, and wait for the silica gel to dry and form After that, take out the product. (Note: The perfusion mold is usually made of soft silicone, so that it is easier to demold and will not damage the product in the silicone mold).
Vacuum Casting FAQs
Vacuum casting is also known as urethane casting or polyurethane casting. It is a process of producing plastic and rubber prototypes using silicone moulds.
The cost varies depending on the materials, complexity, and quantity. It consists of three parts. The cost of making master parten, the cost of making silicon mold, the cost of casting polyurethane.
Vacuum casting works in the same way that traditional injection moulding does. It needs the use of a mould tool with a part-shaped cavity, but soft silicone moulds are used.
Low cost for molds, Short lead time, A wide range of polyurethane resins available
When you need a small quantity of production-quality plastic parts (between 10 and 50 pieces), without the long lead time and hefty expense of building a plastic injection mould . Vacuum casting is suitable for making appearance prototypes, like non-mechanical end-use parts like cases and covers.
The materials used in Vacuum Casting can simulate the following production materials: Rubber, ABS, PMMA, glass filled Nylon