The journey of parts through injection molding begins early, when customers must choose between aluminum and steel tooling. The choice of path is mainly based on quantity requirements. If you are producing more than 1 million parts, you will need steel tooling and a capital investment of more than $50,000.
If your part quantity does not reach millions, then aluminum tooling at a fraction of the cost may be your choice. By bypassing the mass production paradigm (large investment, long waiting times, and especially inflexibility), aluminum tooling allows product developers to be flexible.
The above benefits of aluminum are partly due to the material’s machinability. Compared with steel, aluminum is softer, which means it can be CNC machined into shape faster than steel. Less machine time equals lower costs. As a rule of thumb, aluminum can mold production quantities of about 10,000 parts, but the quantity is usually much higher. Mold life depends on the material type and geometry. Nevertheless, it may need to be replaced before the steel mold.
In general, aluminum tooling is ideal if the number of parts does not exceed millions, if you need to produce parts on demand within days, and if you want to avoid risky tooling investments before the part design is truly validated.
Key Advantages of Aluminum Molds
Aluminum tooling has several advantages. Molds start at around $1,500 and can be delivered in 7 days or less. In contrast, steel tooling has a longer lead time.
Aluminum molds can produce at least 10,000 parts, but usually much more. At Protolabs, customers can choose prototyping or on-demand production quantities and corresponding price points according to their needs (more on that later).
Aluminum molds are also capable of achieving many of the functions that customers expect from production tooling, including:
- Single-cavity and multi-cavity molds: Depending on part size and complexity, 1-cavity, 2-cavity, 4-cavity, and 8-cavity molds are available.
- Extensive material library: The same thermoplastic and thermoset materials as those used in mass production are available. More than 100 different materials can be used, including ABS, polycarbonate (PC), polypropylene (PP), liquid crystal polymer (LCP), and polyoxymethylene (POM).
- Beneficial material properties: The thermal conductivity of aluminum can improve heat dissipation, reducing the need for messy cooling lines.
- Aluminum molds also save additional costs and eliminate the need for maintenance of feed, which will cover mold damage during its service life.
Design Considerations for Aluminum Molds
Part Surface Finish
Choosing the right surface finish for your part application will prevent unnecessary costs. If part appearance is critical, a smooth SPI-A2 surface finish requires hand polishing of the mold cavity surface with diamond polishing to 1-2 Ra. This drives up mold manufacturing costs and increases lead times. If aesthetics are not an issue, PM-F0 is a machined surface that may show some tool marks but is the lowest price. You will find the full range of surface finishes offered by Protolabs below:
| Surface Finish Specification | Description |
|---|---|
| PM-F0 | Non-decorative, surface finish at Protolabs’ discretion |
| PM-F2 | Non-cosmetic, EDM allowed |
| PM-F1 Series | Low decorative, most tool marks removed |
| SPI-C1 | 600 grit stone |
| SPI-B1 | 600 grit paper |
| SPI-A2 | Grade #2 diamond buff |
| PM-T1 | Light bead blast |
| PM-T2 | Medium bead blast |
Part Ejection Draft
Whether it is aluminum or steel tooling, draft must be added to the mold to improve part moldability. Without it, the part surface finish may be poor, and the part may bend, break, or warp due to molding stress caused by plastic cooling. By adding a taper to the part’s surface, draft prevents the part from scratching when ejected from the mold.
Wall Thickness
Each thermoplastic family has a recommended minimum wall thickness. Following these guidelines will help prevent warping and sinking during cooling. The general rule for wall thickness is between 0.040 inches and 0.140 inches (1 to 3.5 mm), applied consistently throughout the part.
Adding Radii to Corners
Aluminum molds are CNC machined at Protolabs, which is fast and efficient; however, the end mills used make it difficult to machine sharp internal corners. In addition, sharp corners on any mold create stress and weaken structural integrity. Therefore, it is recommended to use radii (rounded edges or vertices) extensively in part design.
Aluminum Tooling at Debaolong Seiko
Debaolong Seiko is able to meet the unique needs in the product development process. Welcome to upload your design to Debaolong Seiko for a quote.
