How to Design 4 Common Metal 3D Printing Features

Click to watch an on-demand webinar on how to design for direct metal laser sintering (DMLS).

Direct metal laser sintering (DMLS) is not intended to replace traditional metal manufacturing like casting, metal injection molding, or machining. Rather, it’s a product development tool that opens up new design possibilities. Product designers and engineers commonly rely on metal 3D printing to manufacture complex geometries, reduce the number of components in an assembly, or even lightweight objects.

Here’s a look at how to design 4 common features found in metal 3D-printed parts.

1. Self-Supporting Angles
A self-supporting angle describes the feature’s angle relative to the build plate. The lower the angle, the less the likely it is to support itself.

Support angles built with direct metal laser sintering

Designing support angles no less than 45 degrees will ensure a quality surface finish and detail.

Each material will perform slightly different, but the general rule of thumb is to avoid designing a self-supporting feature that is less than 45 degrees. This tip will serve you well across all available materials. As you can see in the picture above, as the angle decreases, the part’s surface finish becomes rougher and eventually the part will fail if the angle is reduced too far.

Metal 3D printing overhangs

Overhangs are sudden changes in a part’s geometry.

2. Overhangs
Overhangs differ from self-supporting angles in that they are abrupt changes in a part’s geometry—not a smooth slope. DMLS is fairly limited in its support of overhangs when compared to other 3D printing technologies like stereolithography and selective laser sintering. Any overhang greater than 0.020 in. (0.5mm) should have additional support to prevent damage to the part. When designing overhangs it is wise to not push the limits as large overhands can lead to reduction in a parts detail and worse, lead to the whole build crashing.

3. Channels and Holes
Internal channels and holes are one of the primary benefits of DMLS since they are impossible with other manufacturing methods. Conformal channels provide even cooling throughout a part and aid in reducing a components weight.

Designing internal channels in metal 3D-printed parts.

Internal channels can help reduce a part’s weight or be used for cooling.

It’s recommended that channels do not exceed a diameter of 0.30 in. (8mm). Similar to unsupported structures, as you exceed 0.30 in., the downward facing structures will become distorted. A tip to work around this constraint is to avoid designing circular channels. Instead, design channels with a tear drop shape or diamond. Channels that follow these shapes will make for a more uniform surface finish within the channel and allow you to maximize the channel’s diameter.

4. Bridges
A bridge is any flat down-facing surface that is supported by 2 or more features. The minimum allowable unsupported distance we recommend is 0.080 in. In relation to other 3D printing technologies, this distance is relatively short due to the stresses of the rapid heating and cooling. In the picture below you will see how the bridge pulls in the supporting structures as the unsupported distance increases. Parts that exceed this recommended limit will have poor quality on the downward facing surfaces and not be structurally sound.

Bridges that are too long will have rough downward facing surfaces.

Learn More About Metal 3D Printing Design
If you would like to learn more about how to design for DMLS and metal 3D printing in general, check out our webinar “Designing for DMLS.” You’ll find more details and tips on how to optimize your part design for metal 3D printing, select the right material, and reduce multi-part assemblies. Click here to view the on-demand webinar.

The Short List is a regular compilation of quick tips, trends and timely topics of interest.

WEBINAR: Designing for Direct Metal Laser Sintering

In our next webinar, we’re focusing on direct metal laser sintering—our industrial 3D printing process for metal parts. Join David Bentley, our DMLS expert, to learn why product designers are turning to DMLS for prototyping and end-use parts. The presentation will include:

  • An overview of DMLS including materials and design guidelines
  • A case study on an innovative bike design
  • An open Q&A session 

TITLE: Designing for 3D Printing: Direct Metal Laser Sintering
DATE: Thursday, August 25 at 1 p.m. CDT
REGISTER: Click here to sign up

Busy that day and can’t make it? Not a problem. You can still register and we’ll send a recording that can be watched on-demand. Also, feel free to forward this invite to your colleagues.


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 Rules Revolution: DMLS Requires New Thought Process

By Heather Thompson, Senior Editor, Medical Design and Outsourcing

As product development speeds up, the design rules are changing. Nowhere is this more apparent when looking at the industrial 3D printing process of direct metal laser sintering (DMLS). Direct metal laser sintering is an additive manufacturing technology with significant potential in the medical device space. But it requires a new way of thinking even at the early design phases. In many ways it represents the transition designers must face when looking at new technologies to make medical device design and manufacturing faster and more innovative. 

Internal channels that are impossible to machine are achievable with DMLS.

There are several benefits of DMLS explains Tommy Lynch, metals project manager at Proto Labs Inc., primarily that designers can prototype designs in unusual shapes at both time and cost savings. “DMLS is different from other 3D printing because you are using real metal. Many of these materials have been used for industrial applications for decades.”

Lynch says designers like the process because they can experiment with organic shapes that can’t be readily machined. For example, one intriguing opportunity is the ability to build implantable body parts that are custom fit to the recipient. “These implants would normally need to be delicately built on a 5-axis machine at a high expense,” he says. “Technology exists to scan a person’s actual bone structure, and print a direct DMLS replacement.”

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TIPS WITH TONY: Prototyping with Hard Metals

Last week we discussed prototyping with soft metals like aluminum, copper and brass, so this week we turn our attention to hard metals and processes (3D printing, CNC machining and injection molding) used for rapid prototyping in low volumes.


SS 316

SS 17-4

SS 304

Nickel Steel

Steel Alloy



Cobalt Chrome




























Hard metals that are offered in three different manufacturing processes at Proto Labs: direct metal laser sintering (DMLS), CNC machining (CNC) and metal injection molding (MIM).

Stainless Steel
Stainless steel (SS) is one of the most widely used metals in our material library and is available in three different grades and all three services: 3D printing, machining and molding.

  • 304L is only available for machined parts and offers a higher tensile strength and good corrosion resistance while offering a slightly lower price than other stainless steel materials.
  • 316L is available in machining, industrial 3D printing through direct metal laser sintering (DMLS) and metal injection molding (MIM). 316 offers an improved corrosion and chemical resistance over 304 while offering a high temperature tolerance.
  • 17-4PH is also available in all three manufacturing methods and offers a higher yield and tensile strength with good resistances to corrosion. 17-4 also offers a higher magnetism of all our SS offerings.