VACUUM CASTING

Vacuum casting is a rapid prototyping process quite different from the other techniques present at Axis.

Indeed, we still need a 3D file to launch in production but it is also possible to reproduce parts if you have a master model.

Vacuum casting usually works in 3 main steps:

First, you have to print the master in stereolithography. Then we create a footprint of this master model with a silicone mold. Finally, this mold makes it possible to pour a number of polyurethane parts under vacuum. Once the polyurethane parts (PU) solidified, they are removed from the mold. It is then, for a more realistic rendering, that our prototypists debur the casts.

Vacuum casting : Our strong points

At Axis we have a wide range of technical materials that allow us to make bi-material parts both flexible and rigid, or even to make overmoldings. Thanks to our technicians we can install metal inserts according to your plans.

The parts are tinted in the mass, that is to say directly in the material, but we can also apply other finishes on your prototypes to have a realistic rendering (grained, frosted, gloss, satin, EMC paint …) It is also possible to make transparent pieces. Finally, in the case of production of complete prototypes we can ensure the functionality and assembly of your prototypes.

Vacuum casting: Applications

La coulée sous vide est souvent conseillée lorsqu’il est nécessaire de produire des préséries de prototypes en quantités plus important qu’avec le frittage ou la stéréolithographie. Effectivement, les possibilités sont telles qu’il est plus facile de produire des prototypes réalistes et esthétiques. Chez Axis, il s’agit de la seule technique d’impression permettant de produire des pièces souples allant du 35 au 90 shores A.

De plus, la réalisation de préséries via le procédé de coulée sous vide est généralement un excellent moyen de faire des tests fonctionnels et ainsi de tester l’assemblage, l’esthétisme ou la mécanique des pièces, car les prototypes finis sont souvent proches des pièces d’injection.

Offered Material

Accura 25: White colour resin. An accurate and flexible plastic which is ideal for assemblies with instant adaptation, master models for vacuum molding and functional and durable prototypes, with the appearance of polypropylene (PP).

Clearvue: Translucent or transparent resin depending on the finish. It’s a very clear kind of plastic with excellent resistance to humidity, suitable for several kinds of applications in which transparency is essential, such as headlights, complex assemblies or fluid flows. This plastic has an appearance of a transparent polycarbonate (PC).

Evolve: White colour resin. This resin is adapted for applications where mechanical resistance is necessary. It is almost impossible to distinguish it from traditional finished thermoplastics, which makes it perfect for the manufacture of pieces and prototypes for functional test applications.

GP plus: White colour resin. This material mirrors production plastics like ABS (Acrylonitrile Butadiene Styrene) and PBT (Butylene Polyterephtalate), which makes it an ideal choice for practically any kind of application.

Next: White colour resin. This plastic has the look, feel and performance of a thermoplastic, but with a hardness, durability and accuracy which are not traditional characteristics in stereolithography resins.

HPC (Nanotool): Broken white resin. It is adapted for tests requiring a high temperature. It allows for the production of composite pieces which are robust, rigid and resistant to elevated temperatures and which are ideal for tooling and wind tunnel testing.

Taurus: A stereolithography which is extremely durable and resistant to high temperatures. Its robustness, combined with its anthracite gray appearance, makes it ideal for functional prototypes and accurate pieces which have an excellent surface quality and isotropic mechanical properties.

Xtreme: Grey colour resin with properties identical to those of Accura 25 resin.

Our equipments

2  MCP 5/01 : 400 x 400 x 400 mm

1  MCP 4/01 : 400 x 400 x 400 mm

1  MCP 003: 560 x 600 x 600 mm

1  MCP 4/04 : 900 x 750 x 600 mm

1  MCP 4/05 : 1 300 x 750 x 800 mm

Vacuum casting: How does it work?

Vacuum casting necessarily requires a master model. It is therefore necessary to have a 3D file (formats: IGES, .STEP, .STL, .CatPart) to launch in production a stereolithography piece that will serve as a master, or to send us an existing part that can fulfill this role. . In this case, be aware that it will be necessary to take into account the withdrawal of the cast material and thus to discuss it with our salesmen to use the most suitable material or to provide slightly larger or smaller than the desired rendering.

This additive manufacturing technique is often favored when parts are to be produced in reasonable quantities. In addition, this process makes it possible to produce a wide range of parts with varying hardnesses and properties.

Once your 3D file is received, we launch the realization of the master in Stereolithography. If you wish to have more information on this 3D printing process, please consult our page dedicated to stereolithography. Your 3D file is treated by our technicians who apply a more or less important withdrawal to the file according to the material chosen for the castings. The master model in stereolithography produces, we clean, sand and sand the room. Our prototypists apply a finish to the master model according to the specifications to be applied for the castings because the polyurethane part will be related to the appearance of its master (graining, transparency, shine, …).

Our moldmakers prepare the master to produce its imprint in a silicone mold consisting of a core of feed, vents and marking of the joint plane. Once the master model is installed in its box, the silicone is poured. When silicone is hardened, our molders open the mold. The master is gently removed to avoid damaging the silicone mold.

The casting operator in charge of the project tightly closes the mold hermetically to avoid letting the polyurethane material escape, injected into the mold. He installs it in his vacuum machine, prepares the two components of the material to mix separately and places them inside with the mold. This is closed and evacuated while mixing component A (isocyanate) and component B (polyol). The two materials are incorporated into each other under vacuum and then poured into the silicone mold by gravity.When the material leaves by all the vents created, the air is put back into the machine, and the filled mold is placed in a hot oven for several minutes until the material hardens. Once the material hardened, the casting operator goes to mold release and out the molded part.

The pilot project then goes to the deburring step of the molding. He puts the inserts or transfers (if ordered), and brings any element corresponding to your specifications.

 

Vacuum casting on video at Axis

ADVANTAGES OF VACUUM CASTING
Vacuum casting is a 3D printing process that creates a wide variety of prototypes. Indeed, according to your criteria we can produce small and medium series of flexible prototypes, rigid, transparent tinted in the mass. The materials used are similar to the materials used in series, which allows, after finishing, to obtain prototypes with a close finish of injected parts. Vacuum casting has the advantage of making it possible to produce parts with multiple characteristics of polyurethane resin (PU).

DISADVANTAGES OF VACUUM CASTING
Importantly, the parts to be produced must be demoldable.

The life of the silicone mold is limited. When drawing up your estimate and according to the quantity of moldings desired, we define the life of the mold, that is to say the number of moldings it is able to produce.

Finally, it is necessary to take into account the time of realization of the duplicates in this process of 3D printing: the realization of the master model and the mold will take several days and to this is added the time of casting of the models.

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