Injection Molding: Aluminum vs. Steel Tooling

Aluminum molds are milled in rapid CNC machines.

Conventional injection molding typically uses steel tooling capable of producing millions of parts, however, it often takes months to manufacture a mold and a capital investment of $50,000 or more. But what if production demands call for smaller quantities? That’s where aluminum tooling is ideal. Here’s a quick look at the differences between steel and aluminum tooling.

Low-Volume Production with Aluminum Tooling

  • Mold production AND parts within 15 days or less
  • Low manufacturing costs with molds beginning around $1,500
  • Production quantities of up to 10,000 parts or more; depending on material type and geometry, some molds are capable of producing hundreds of thousands of parts
  • Simplified mold designs decrease manufacturing time and cost
  • Single and multi-cavity tooling: 1-, 2-, 4- and 8-cavity molds are possible depending on part size and complexity
  • Thermoplastic and thermoset materials identical to that of high-volume production materials; more than 100 different materials can be used including ABS, PC, PP, LCP, POM, and liquid silicone rubber
  • No maintenance fees and lifetime replacement of mold if damaged
  • Improved heat dissipation and without the need for messy cooling lines
  • Inexpensive mold-safe tooling modifications

High-Volume Production with Steel Tooling

  • Lower part cost when quantities increase
  • Part production in the millions
  • Multi-cavity tooling greater than 8 cavities
  • Part complexity can be increased
  • More finishing options

If you part volumes don’t stretch into the millions, if you need on-demand production parts within days, and if you’re looking to avoid risky tooling investments before your part design is truly validated, low-volume injection molding with an aluminum tool might be good option.

Once an aluminum mold is ready, part production begins almost immediately. This allows manufacturing to finish every order in three weeks or less.

At Proto Labs, we include a free interactive design for manufacturability (DFM) review within a few hours in every injection molding quote. In the time it takes to get the initial quote from a high-volume production molder, you can have several design reviews and a mold already in production.

If you have any further questions about rapid manufacturing at Proto Labs, check out protolabs.com or contact one of our application engineers at 877.479.3680 or customerservice@protolabs.com.

TIPS WITH TONY: New Silicone Rubber Materials

We’ve expanded our selection of liquid silicone rubber (LSR) materials, which have some distinct elastic and optical advantages over certain thermoplastics. In addition to three durometers of general-use Elastosil LSR, and medical- and optical-grade Dow Corning materials, we now have two new durometers of Elastosil and a fuel-resistant flourosilicone material at Proto Labs.

Elastosil LSR
Elastosil LSR is a great general-use material that has good moldability characteristics, a good overall appearance and is transparent until colorant is added. Shore A durometers of 40 and 60 have been added our current offering of 30, 50, and 70 durometers.

Technical specs:

  • 40 durometer Elastosil has a tensile strength of 10.0 N/mm² with a tear strength of 33 N/mm and an elongation break of 610%.
  • 60 durometer Elastosil has a tensile strength of 9.40 N/mm² with a tear strength of 27 N/mm and an elongation break of 340%.

THE SHORT LIST: 4 Ways to Leverage Rapid Overmolding

Rapid Overmolding is the latest addition to our injection molding service. Now, you have a fast way to create injection-molded parts with two different materials. We use a pick ‘n place method.

rapid overmolding services sample

That means we follow a two-step process. First we mold the substrate part. Then we place the substrate part into the mold and a second material is injected to form the final, two-material part.

Here are a few benefits of rapid overmolding.

Vibration dampening: Dampen vibration by adding liquid silicone rubber to parts made of hard plastic, like ABS, or if it’s a handhold device (think toothbrush), it can even be used to improve grip.

rapid overmolding services sample orange partMulti-color aesthetics: Add a stylistic flair to your product with overmolding. Using two materials, means two colors for high-quality looking products and can enhance your product’s design.

Fast, flexible volumes: Often, manufacturers will not process low-volume overmolding orders, but now you have the ability to manufacture 25 to 10,000+ overmolded parts within just a few weeks.

Simplify multi-part assemblies: Reduce cost and save time spent assembling parts by combining two materials in one molded part.

For information on rapid overmolding like designing mechanical interlocks or understanding chemical bonding compatibility, visit our rapid overmolding service page to see overmolding design guidelines and get free DFM feedback.

DESIGN TIP: Cutting Corners on Injection-Molded Parts

Sharp corners definitely have their place in part design, but they often spell trouble when injection molding plastic parts. Accordingly, designers should be aware of the pitfalls associated with “being square” when developing parts. Indeed, part accuracy, strength, and aesthetics suffer without the right amount of corner rounding and filleting.

This month’s design tip explores ways to strengthen injection-molded parts while reducing costs with proper placement of corner radii and fillet. You’ll learn about:

  • Material selection. Some plastics are more forgiving of sharp-cornered parts. Choosing the right one for your application is a necessary step towards accurate, functional parts.
  • Wall thickness. Beefing up adjacent walls may absorb some of the stress associated with sharp internal corners, but can create other design challenges.
  • Part geometry. Some parts are simply more “moldable” than others. Achieving proper form, fit and function depends on sound part design, a large piece of which is appropriate corner radii.

READ FULL DESIGN TIP

WATCH: Talkin’ Cosmetic Defect Blues

The next short video in our Fundamentals of Molding series takes a trip down the Mississippi River to explore different cosmetic flaws like sink, warp and blush, which can find their way into injection-molded parts.

 

For a lengthier examination on avoiding cosmetic defects when designing for injection molding, read our free white paper.

Thirsty for more quick tips? Here’s our previous video on draft considerations: