Fictiv has submitted this post.
Rapid injection molding is fast because it uses tools that take less time to produce. With traditional injection molding, a complex tool can take eight weeks or longer to cut, while rapid injection molds can be machined in two weeks or less. But toolmaking speed isn’t the only difference. Compared to traditional tooling, rapid injection molds differ in five important ways:
- Mold materials
- Mold design
- Mold machining
- Complexity
- Engineering changes
The following sections explain what engineers need to know to get the best rapid injection molds.
1. Mold Material
Production-quality injection molds are made of hardened steel because they need to last for millions of cycles. Rapid injection molds are made of softer and less expensive materials because they’re used for prototyping or low-volume production instead. Common choices include machined aluminum, soft steels, and 3D-printed tooling from durable and heat-resistant resins such as Accura Xtreme. All can be produced in just a few days or less, but even machined aluminum molds won’t last longer than 10,000 cycles – and much fewer with complex part designs or glass-filled resins.
An alternative approach is to produce tools from soft steels like P20. Because this steel is significantly harder than aluminum, P20’s tooling life is 5 to 10 times longer. Depending on the part design and the plastic resin used, a P20 rapid injection mold can produce as many as 100,000 parts. P20 steel molds can also achieve tighter tolerances than aluminum molds, which scratch easily, don’t polish well and can’t handle high clamping pressures.
2. Mold Design
Some rapid injection molders allow an engineer to purchase a core and a cavity that fits inside a frame that the injection molder owns. This is called a “master unit die” (MUD), and there are two advantages to this stand-alone tooling approach:
- Less steel and fewer components lower the initial cost of your molds.
- Inserts can be changed out quickly, which reduces setup times and lowers fees.
Many injection molders don’t support MUD molds, however. In fact, they might not even quote a project that could benefit from this approach. To take advantage of this approach, you’ll need to have the right options in your supplier network.
3. Mold Machining
Production-grade injection molds require CNC machining, and in some cases EDM (electrical discharge machining), for material removal. Yet many rapid injection molders only offer CNC machining, which limits the possible mold and part features to those their equipment can support. In turn, this limits your part design and can necessitate the removal of small but important features. With the right network of manufacturing partners, however, both CNC and EDM machining are readily available for rapid injection molds.
4. Design Complexity
Injected molded parts can be highly complex, and the same is true for parts made with rapid injection molding. Consequently, part designers may require intricate rapid injection molds with lifters for internal undercuts or sliders for external undercuts. Depending on the molder, however, you may not be able to get a tool that supports these and other features. With the right partner, you can get complex parts quickly, and rapid injection molds that can support more than just simple parts.
5. Engineering Changes
Finally, because the focus of many rapid injection molders is to produce tools quickly, engineers may not be able to update a part design after a mold is cut. If you request an engineering change, the molder may require you to buy a new tool for the updated design instead. Some injection molders allow changes, but the kinds of modifications they support are limited. With P20 steel, however, molds can be easily welded for greater flexibility with engineering change orders.
Now that you know how to get the best injection molds, are you ready to try rapid injection molding for your next plastics project? Check out Fictiv’s Rapid Injection Molding: The Ultimate Guide for more information.