There are a variety of prototyping processes from industrial CNC machining to FDM 3D printing. However, for small quantities of plastic parts, companies often get into trouble between rapid injection molding (a common process of injecting molten material into metal molds) and vacuum casting (which uses more affordable silicone molds to make small amounts of plastic components.)
Injection molding and vacuum casting process in rapid prototyping are both very useful. Both are widely utilized, and each provides a different set of benefits. But as the procedures share certain similarities (both are perfect for plastic parts; equally use a mold with a pit to fabricate components, etc.) it can occasionally be tricky to choose between them both.
It's often better to consult with an expert for customized information on which production procedure is the most acceptable for any particular job, there are particular elements that you may contemplate when coming to your determination. Getting to understand these variables is the best way to know whether injection molding or vacuum molding would be the ideal procedure for the job.
What is rapid injection molding?
Rapid injection molding is a widely used manufacturing process in which molten material is injected into a mold. It is used to create a large number of parts for use in industries such as healthcare and consumer products. You may be sitting within easy reach of the injection molded parts.
The injection molding process involves heating and mixing materials (sometimes multiple materials) in the barrel. The material is melted and then forced into the mold where it cools and forms the interior of the mold. By repeating this process over and over again, the mold can be used to make many of the same parts.
Whilst rapid injection molding is usually considered as a manufacturing process, it's also possible for prototypes. This is largely due to quick tooling, a way of cheaply and fast generating model molds for the injection molding procedure.
What is vacuum casting process in rapid prototyping?
Although less popular than injection molding, vacuum casting is an intriguing alternative that may be used to create modest amounts of a part at a minimal price.
The vacuum casting process in rapid prototyping begins with a master model, which in some companies is created using CNC machinery. (3D printing can also be utilized.) The master model is then immersed in liquid silicone which is then cured, cut and separated from the master model.
The treated silicone can subsequently be utilized as a mold. Casting resin is then poured to this silicone mold, whereas the vacuum eliminates air pockets and bubbles to ensure a smooth surface. The resin component is treated and removed from the silicone mold, which is reused around 20 times.
When is vacuum casting more suitable than rapid injection molding?
Since injection molding is much more popular than vacuum casting, so many companies might not even think about the vacuum casting process in rapid prototyping. But there are particular scenarios where the silicone-based process reflects greater value for money and possibly higher quality.
Quantity
For quite large amounts of components, it's tough to check beyond injection molding. Even though the installation costs for injection molding are large (even by means of rapid tooling), the device prices are extremely low. This means that when companies need copies of hundreds or thousands of parts, they can easily make up for the initial cost of the installation by saving each unit.
On the other side, not every company needs thousands or hundreds of copies of a component. When smaller quantities of components are required -- everywhere between a few and a hundred -- vacuum casting might be the better choice because the setup costs are a lot lower.
Detail
Considering its tooling is usually made from high-quality alloys, rapid injection molding allows for the production of much more detailed parts than is possible with vacuum casting. Injection molding may hence be the better choice for highly complex pieces.
For easier components, especially those that just have to be made in tiny quantities, vacuum casting may be safer. It is not merely a cheap alternative though: vacuum molding can provide a very smooth surface finish, meaning easy parts may seem better when made with vacuum casting.
Speed & Iteration
The very low setup costs connected with vacuum projecting have favorable knock-on consequences. If a design has to be amended at any point during fabrication, it's far simpler and more economical to change vacuum casting molds than it would be to synthesize or synthesize tooling for injection molding.
Generally speaking, this implies that vacuum casting is often the better option during the previous phases of development. In reality, companies often make early prototypes utilizing vacuum casting, prior to making their end-use components or later-stage prototypes utilizing injection molding.
Significantly, producing molds for vacuum casting is a much quicker process than generating tooling for injection molding, so time-sensitive prototyping tasks for very tiny volumes can frequently be much better suited to vacuum casting. (Injection molding will probably be quicker for bigger volumes.)
Material Considerations
Even though all of the indications point to vacuum casting process in rapid prototyping, one ought to keep in mind that a few prototypes -- especially the ones that will be subject to physical testing -- need to be as close as possible to the end-use parts or products. Then it will be beneficial to produce the prototype utilizing the injection molding, even when outlay is higher.