Rapid Overmolding – THE SHORT LIST: 4 Ways to Leverage Ovemolding

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.

WEBINAR: Rapid Manufacturing Methods for Plastic Parts

Tony Holtz, Tech Specialist.

You’re invited to join Proto Labs’ live webinar presentation on rapid manufacturing. The free webinar will be hosted by our technical specialist Tony Holtz and last around 45 minutes with a Q+A to follow.

You’ll hear about the different industrial 3D printing, CNC machining and injection molding processes at Proto Labs, and learn which one is best suited for your next project, based on the project’s material requirements, quantities and lead times.

TITLE: Choosing the Right Rapid Manufacturing Method for Plastic Parts

DATE: Thursday, April 21 at 1 p.m. CDT

REGISTER:
http://event.on24.com/wcc/r/1158589/3BE5D1B5A337F26F67DEE106F834E163

Unable to attend? Register anyway and we’ll email you the recording afterward!

TIPS WITH TONY: Mixing It Up with Plastic Colorants

Proto Labs’ material selection and available color options for thermoplastics can be found online at protolabs.com.

You may require colored resin or transparent coloring for your injection-molded parts, but exactly how much colorant is added and what consistency can you achieve?

Salt-and-Pepper Mix
Proto Labs offers colorant at no charge to most natural, white or clear materials. In most cases, we do this by adding a 3 percent salt-and-pepper mixture of colorant based on weight to the base resin, but on occasion, less colorant is added to transparent resins like polycarbonate.

A 3 percent salt-and-pepper colorant mix is typically used.

 

Since we hand mix the colorant and base resin, you may have a higher or lower concentrate of colorant throughout the order. The injection molding press does a good job of mixing the colorant and base resin when it melts and grinds the resin in the barrel before molding, but it isn’t 100 percent.

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TIPS WITH TONY: Watch Out for Warp, Sink and Voids!

In my years of working closely with product designers, I’ve seen some really great designs, but on occasion, I’ve encountered part designs by both novice and experienced designers and engineers that have needed some work to improve moldability and reduce cosmetic defects. Let’s look at some common design mistakes that could result in parts with sink, warp and voids.

Wall Thickness
Why is uniform wall thickness important? Thermoplastics simply don’t like transitioning from thin to thick sections due to the ununiformed cooling. All thermoplastics shrink as they cool but when thin areas cool before thick areas, stress is created. The results may vary depending on material selection and part design, but if you’re not following the proper material guidelines for wall thickness and mold design, you may end up with unsightly voids, sink and possibly even warp within your parts.

How can you reduce the risk of these molding concerns? Provide proper wall thickness through appropriate coring, rib and boss design, which in turn, helps you avoid excessive thick or thin wall sections.

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Finding the Right Surface Finish

Molded parts are everywhere — from highly cosmetic housings hiding in plain sight to internal components where a fine polish is unnecessary. Most people pay no attention to the surface finish on those parts, but for product designers and engineers, it’s an important design consideration.

Identifying the right surface finish is dependent on a few important elements, namely the development or production stage that your parts are in, the materials they’re being manufactured in and their end-use applications.

On custom finishes, use color coding to provide a clearly marked image of your CAD model with its required finishes.

This month’s tip discusses:

  • available surface finishes for injection molded parts at Proto Labs
  • how to create a custom surface finish involving two or more finishes
  • navigating finishes within ProtoQuote
  • why gating and ejection play a limited role in liquid silicone rubber parts
  • secondary options applied to magnesium components

Read the full design tip here.