13 Cosmetic Defects and How to Avoid Them

As with any manufacturing process, injection molding comes with its own set of design guidelines, and design engineers who understand these best practices will increase their chances of developing structurally sound and cosmetically appealing parts and products.

Learn about different cosmetic issues that commonly occur on injection-molded parts, and how to eliminate them to improve overall part appearance and performance. This month’s tip discusses sink, warp, flash, knit lines, drag, vestiges, jetting, splay and other cosmetic issues.

Read the full design tip here.

DESIGN TIP: Thermoplastic-like vs. Thermoplastic

Many factors come into play when comparing the material properties of thermoplastics found in injection molding versus “thermoplastic-like” materials used in a 3D printing technology like stereolithlography (SL). At Proto Labs, a thorough selection of thermoplastic-like materials are offered through SL, but what may surprise you is the versatility and range of potential applications for SL parts.

This month’s tip discusses:

  • heat deflection, tensile strength and other important properties of thermoplastic-like materials
  • how SL materials compare to similar injection-molded thermoplastics
  • the benefits and range of suitable applications for each SL material
  • the impact of light and moisture exposure on 3D-printed parts

READ THE FULL DESIGN TIP HERE.

5 Ways to Improve Part Moldability with Draft

When designing parts for plastic injection molding, applying draft (or a taper) to the faces of the part is critical to improving the moldability of your part. Without it, parts run the risk of poor cosmetic finishes, and may bend, break or warp due to molding stresses caused by the plastic cooling.

Equally important, an absence of draft may prevent parts from ejecting from the mold, damaging not only the parts, but possibly the mold itself — a costly and time-consuming detour.

Chevron arrows indicate surfaces that require draft in Proto Labs’ design for manufacturability (DFM) analysis.

In this month’s design tip, learn how to improve the moldability of your plastic parts by:

  • drafting early and often
  • sticking to the rules of draft
  • factoring in surface finish
  • implementing the core-cavity approach
  • leveraging design for manufacturability analysis

READ FULL DESIGN TIP

‭Design Essentials for Injection Molding

A good rule of thumb is to apply 1 degree of draft per 1 inch of cavity depth.

‭There are multiple paths to injection molding. Some parts are first prototyped through 3D
‭printing where moldability considerations are of limited concern. Others take a more
‭traditional machining route that allows for iterative testing in engineering-grade materials
‭similar to that of molding. And many simply jump right to injection molding.

‭Before production begins, there are important design considerations that will improve the
‭moldability of the parts, and ultimately, reduce the chance of production hiccups,
‭cosmetic defects and other issues.

In this month’s design tip, we walk through these key design elements:

  • ‭Draft and radii
  • ‭Wall thickness
  • ‭Coring out and ribbing
  • Ramps and gussets
  • ‭Undercuts
  • Gating and ejection

Read the full design tip here.

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.