When considering using an injection molding service, here are some basic principles of the technology and design tips to assist you in quickly determining the action needed to cut costs and save time.
Most manufacturers utilize injection molding in creating the part of their choice. The injection molding process starts with melting the plastic and injecting it into a mold’s cavity. As the material cools and solidifies, it captures the form of the mold. Then, the part is ejected and the process repeats.
The molds are typically CNC machined from various materials depending on the size of production. Aluminum is the material of choice for units of 1,000 to 5,000 counts. On the other hand, tool steel is the preferred option for projects with greater than 100,000 units. Furthermore, for low-production runs of less than 100 units, the molds can be 3D printed to speed up the process and saves on lead time.
Three steps to consider when deciding on injection molding manufacturing:
Step 1: Prototyping with Low-run Injection molding:
Prototyping is typically a low-run molding. A prototype mold is capable of producing the same parts as a production mold; however, it is only suitable for 10,000 units due to the utilized tooling process. Consequently, the cost of a prototype mold is lower than a production mold. Since it is less expensive, the warranty covers only 10,000 parts, versus the lifetime warranty of a production mold.
Prototyping has many benefits, of which is the product is realistic with actual material properties. It simulates the real process of mold design. On the other hand, the prototyping solution comes with a bit of a higher cost, and it is less available than CNC machining or 3D printing.
Step 2: Define a “pilot run” (optimal for 500 – 10,000 parts)
Once the engineers finalize their design, they get started with a pilot run to test the injection molding design.
Typically, the minimum units for an injection molding order are 500 pieces. Like we mentioned above, for these numbers, the molds are CNC machined from aluminum. In fact, aluminum molds are easier to manufacture and are low in cost. They cost from $3,000 to $5,000, yet endure up to 5,000 – 10,000 injection cycles.
At this step, the typical cost per part is between one dollar and five dollars, depending on the material and geometry of the unit. The standard lead time for these orders is between six to eight weeks.
The parts made from pilot aluminum molds have identical physical properties and accuracy as the parts made with “full-scale production” tool steel molds.
The “pilot run” is not meant for the production of a few thousand pieces. If the project is a few thousand units, then the project is in the final production step.
Step 3: Scale-up production (Suitable for 100,000+ parts)
If the company is looking to mass-produce 10,000 to 100,000 or more units of identical parts, then they need a special Injection molding tooling. Or they can use sheet metal fabrication services.
For these massive volumes, it is the standard practice to CNC machine the molds from tool steel. Tool steel withstands multi-millions injection molding cycles.
Typically, at this stage, the unit cost is from a few cents to one dollar, and the standard lead time is four to six months. The lead time is based on the complexity of the design and make of the mold.
Learning the steps needed to start injection molding manufacturing is essential to succeed. The article above is meant to shed some light on the process.
This article was published in collaboration with 3D Hubs.