Rapid Overmolding: Consider These 3 Elements

Injection molding is a common, cost-effective method for manufacturing parts, but, sometimes, those parts need a little help. Low impact or vibration resistance, slippery surfaces, poor ergonomics, and cosmetic concerns are only a few of the reasons why a second molded part is often added as a grip, handle, cover, or sleeve.

Proto Labs now offers rapid overmolding for parts, including the three samples pictured here.

The process of rapid overmolding will get the job done. This method, which Proto Labs now offers, and is the focus of our October design tip, uses a mechanical or chemical bond (or both) to permanently marry two parts together.

This month’s tip discusses:

  • Bonding: A strong bond between the two materials is critical to overmolding.
  • Materials: This is a key consideration in overmolding.
  • Principles: Overmolding uses the same playbook as injection molding, but with a few quirks.


DESIGN TIP: Choosing Industrial 3D Printing for Production Parts

Using 3D printing for fully functional end-use metal and plastic parts is becoming increasingly common in rapid manufacturing with industrial-grade processes like direct metal laser sintering (DMLS) and selective laser sintering (SLS).

Industrial-grade 3D printing is well suited to produce organic shapes, like this nylon turbine (left) and end-use production parts such as this titanium drill component (right).

With an expanding material selection and improving material properties, designers and engineers have another good option for small quantities of production parts.

Accordingly, our monthly design tip covers this emerging trend.

This month’s tip discusses:

  • Choosing the best 3D printing process for your application
  • Selecting the right thermoplastic and metal materials
  • Designing part geometry for 3D printing
  • Using SL, SLS, and DMLS for end-use production parts


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.


DESIGN TIP: Metal 3D Printing Redefines Part Design

Metal 3D printing is helping to redefine part design, with capabilities to build ever-increasingly complex parts in less time and with little human intervention. Welcome to the industrial-grade 3D printing process of direct metal laser sintering (DMLS), which is the focus of our monthly design tip.

Med device developers are turning to industrial-grade metal 3D printing to produce a variety of prototype and end-use parts, including these components used for surgical instruments.

Through additive manufacturing technology, DMLS produces fully function metal prototypes and end-use parts, simplifies assembly by reducing component counts, offers virtually unlimited complexity with no additional cost, and works for a variety of industries, including the med device space (see part photo).

This month’s tip discusses:

  • A short overview of DMLS
  • Ways to avoid warping and curling with certain part features
  • Part orientation
  • Wall thickness considerations


DESIGN TIP: Improving Part Design with Uniform Wall Thickness

Designing parts with consistent wall thickness is a fundamental rule of plastic injection molding, and ignoring it can lead to sink, warp and inaccurate or non-functional parts. Yet the functional requirements of consumer, medical, aerospace and industrial products often leave designers little consideration for the material flow and fill properties of plastic, both of which are at least partially determined by wall thickness.

Pay close attention to rib-to-wall thickness ratios. To prevent sink, the thickness of the rib should be about half of the thickness of the wall.

This month’s tip discusses:

  • Guidelines to avoid cosmetic defects associated with thin and thick features
  • Material alternatives to improve wall thickness consistency
  • Important questions to ask about material properties
  • The benefits of design for manufacturability analysis