The Laser Powder Bed Fusion (L-PBF) Design Guide

During the design process, support must be considered. The choice of powder material is critical in ensuring the stability and quality of the support structures during the LPBF process. With metal additive manufacturing technologies like L-PBF, support structures have vital functions:

• Supporting parts when there is an overhang

• Fixing and strengthening the part to the platform

• Diverting excess heat away from the part

• Preventing warping

• Preventing the melt pool from dropping into the loose metal powder

• Resisting the mechanical force of the powder-spreading mechanism of the part

• Preventing a complete build failure resulting from any of the above situations

Designing the proper supports is essential. Here are some other critical considerations with L-PBF.

The area melted at the laser point cools very quickly, creating stress that can curl the material upwards. Sometimes, this stress might be strong enough to detach the part from its support or split it completely. Supports can be an anchor on the build plate to avoid this.

A part’s solidification can’t start in the middle of the powder bed. It needs to be connected to the build plate directly or through support.

Every area of the part facing the build plate with an angle lower than 45° requires support.

Successfully designing a part for additive manufacturing won’t be possible unless you consider print orientation. The quality of every part (e.g., strength, material properties, surface quality, amount of support, etc.) depends on the print orientation.

Although support material is essential to guarantee the success of a design and the printing process, it should be limited to only what’s necessary. The placement and amount of support material impact part quality, production time, and post-processing cost.

It’s best to print holes vertically with their axis if their roundness is critical to the part. Printing holes vertically ensures that each thin layer is accurately formed, maintaining the roundness and integrity of the hole.

Holes printed horizontally will experience the staircase effect and end up slightly elliptical. Holes with a diameter of up to 8 mm can be built horizontally without additional supports. Larger holes will require supports, although this diameter varies on machine and material.

If you’d like to avoid the need for support structures in the holes, follow these guidelines:

• Elliptical holes for when the ellipse height is twice the width. It can be to approximately 25 mm high.

• Teardrop-shaped holes can be almost any diameter if the top angle isn’t less than the minimum support angle (45°).

• Diamond-shaped holes can be almost any size, but it’s best to fillet the corners to avoid stress concentrations.

Fillet all corners. It’s generally good practice to fillet – or round – all sharp edges when designing a part. There are two reasons for this.

Selecting the appropriate powder material is essential for achieving the desired mechanical properties and surface finish of the final part.

The first reason is safety. The object becomes easier to hold or use when external corners are rounded. Fewer sharp edges mean fewer dangers from handling sharp edges. The second reason is to ensure the strength of the object. Rounding internal corners reduces stress concentrations that might affect the overall strength of the object. A good rule of thumb is to make the fillet ¼ of the wall thickness of the feature (e.g., ribs or pins).

Print release holes for hollow structures. If your part has a hollow area, consider designing holes to release the powder from the inside. To remove the powder easily, there should be a minimum of two escape holes per hollow area.

Keep wall thickness constant. Designing a part that goes from thin structures to solid blocks generates additional stress, increasing the risk of warpage and bending.

Next Steps

Every good L-PBF design contains these three elements:

1. Using the lowest necessary amount of metal powders, reducing print time and costs

2. Considering print orientation

3. Designing proper supports

4. Utilizing computer aided design (CAD) to optimize the geometry and functionality of the part

With those four elements, your LPBF part can go from an idea to a complete, finished, and functional part