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:

 

NEW JOURNAL: How Technology is Transforming Injection Molding

The new issue of Proto Labs Journal is out and includes a cover story focusing on the digital transformation of injection molding. A related, second feature story explores the pros and cons of printed plastic molds.

The cover story reports on how automating the front-end of the manufacturing process has reinvented injection molding, and served as a game-changer for the entire industry.

The related feature, “3D-Printed Molds,” advises product designers, engineers and developers to take a careful look at part finish, size, design capabilities, mold longevity considerations and cost when comparing printed plastic molds to aluminum tooling.

Elsewhere in the Journal, look for our Eye on Innovation feature, which highlights cool new products and technology you should know about.

Read the entire Journal here.

We’re always on the hunt for though-provoking content, so send your cool project or article idea to our editor at angelo.gentile@protolabs.com.

Thanks and enjoy the issue!

On-Demand Webinar: Improving Manufacturability with ProtoQuote

Last week we hosted a quick webinar that explored how designers can use ProtoQuote to improve the manufacturability of their design. It’s available on-demand here.

Key Takeaways

  • How to get free design for manufacturability feedback for your part
  • Improving manufacturability by adding draft, adjusting wall thickness and incorporating radii
  • How to navigate ProtoQuote for each of our processes: 3D printing, CNC machining and injection molding

Top Questions Asked

Will Proto Labs help simplify my CAD file?
Yes, along with our automated DFM feedback, we have a full staff of engineers that will work with you on simplifying your design. Once you upload a 3D CAD file, they will look at it and explore ways of improving overall manufacturability and provide guidance based on your part’s requirements and intended application.

Are there any general design tips to avoid parts having side-pulls or side-actions?
Our free design cube shows the different side-actions that we use to produce parts. And, if you have snap features on your part that might require side-actions, you can cut away that geometry and use a pass-through core to alleviate the need for a side-pull or cam.

We also have resources that discuss implementing side-actions, as well as eliminating the need for them:

What are the material options for opaque materials for lighting applications?
We offer polycarbonate materials that provide transparent options for lighting and other applications requiring transparent materials. We provide multiple PC colors: amber, green, blue, transparent and even infrared.

Stay Tuned
Look for additional technical webinars throughout the year on various 3D printing, CNC machining or injection molding topics. The next webinar will be part one in a series of 3D printing webinars and we’ll discuss designing for stereolithography.

TIPS WITH TONY: Flame-Retardant Thermoplastics and UL Classifications

UL 94 is a plastics flammability standard released by the Underwriters Laboratories (USA). The standard classifies plastics according to how they burn in various orientations and part thicknesses from the lowest flame-retardant to most flame-retardant in six different classifications.

UL 94 Rating

Definition of Rating

HB

                                          Slow burning on a horizontal part.

V-2

                                          Burning stops within 30 seconds on a vertical                                             part allowing for drops of flammable plastic.

V-1

                                          Burning stops within 30 seconds on a vertical                                             part allowing for drops of plastic that are not                                               inflames.

V-0

                                          Burning stops within 10 seconds on a vertical                                             part allowing for drops of plastic that are not                                               inflames.

5VB

                                          Burning stops within 60 seconds on a vertical                                             part with no drops of plastic allowed but may                                               burn through the part.

5VA

                                          Burning stops within 60 seconds on a vertical                                             part with no drops of plastic allowed and                                                     cannot burn through the part.

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