Why use a rapid prototyping service before building a plastic injection mold?

Anyone who has ever designed a complex assembly knows that a mistake can be devastating, especially if it involves modifying or rebuilding expensive tooling. While CAD software can catch many errors before an injection molding tool is built, there is no substitute for having a real part or assembly in hand for testing in the real world.

Rapid prototypes enable quick checks on form, fit, and function of the new design. In some cases, rapid prototypes can be made from the same material as the injection molded plastic part. Today, the product development process for molded plastic parts can be streamlined by turning around rapid prototypes in as little as two days.

Rapid prototyping processes

Several years ago, the only viable options for “rapid” prototyping were machining and expensive SLA (Stereolithography) prototypes. Since then SLA technology has improved, and SLS (Selective Laser Sintering) and 3-D Printing have evolved.

The SLA process should be used when the tightest tolerances or smooth surface are required on the rapid prototype. However, plastic injection molding materials are not available for SLAs. SLA rapid prototypes are produced by building plastic parts a layer at a time by tracing a laser beam on the surface of a vat of liquid photo-polymer. A thin layer of material cures immediately wherever the laser hits.

SLS fits most applications by providing very close tolerances, while offering a variety of materials. SLS rapid prototypes can be dyed to add color. SLS parts are also formed by a laser, one layer at a time, but from fusing particles in a bed of plastic powder.

3-D printing has similar performance to SLS, with different material options and pre-colored material. The 3-D printer actually has a print head that places drops of plastic and a supporting material one drop and one layer at a time.

Plastic injection molding materials can be used in rapid prototyping

SLS rapid prototypes can be made from glass-filled or unfilled nylon (polyamide) or an elastomeric material. Unfilled nylon is a good material for general functional testing, especially for thin-walled parts or living hinges. Filled nylon is more appropriate when the prototype will be tested under more severe stress. The elastomeric material is useful for flexible parts (gaskets, strain reliefs, etc.)

3-D printers use strands of ABS. This robust material can be used for a variety of applications.

As these technologies evolve, more material options will become available. If a plastic injection molding material is not available for rapid prototyping, it could always be created by a machining operation.

Requirements for building a rapid protoype

Rebling Plastics can take anything from a napkin sketch to the latest 3-D CAD file and quickly turn around a rapid prototype. Our talented staff of engineers will review the part design before a prototype is created. This extra step saves time and money by ensuring manufacturability and finding ways to cut molding and tooling costs.

From the smallest, thin-walled part (.5mm minimum) to the largest possible injection molded part, a rapid prototype or set of parts can be made at a surprisingly low cost and short time. We work closely with local suppliers to keep the product development cycle moving.