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Process

Metal Powder-Bed Fusion—also known as Selective Laser Melting or Direct Metal Laser Sintering—is an Additive Manufacturing process using a laser to melt consecutive layers on a metal powder-bed. The powder fuses into the finished dimensional part, incorporating complex internal and external geometries.

The complete CAD-to-part process includes the following steps.
1. Pre-processing
  • Optimizing CAD build file for additive manufacturing
  • Support generation
  • Slicing
  • Selection of scanning strategy
2. Print Preparation
  • Loading build file
  • Preparing build volume and adding metal powder
3. Print
  • Precision controlled fusion of the metal powder into layers that form the desired shape and volume
4. Separation of Part from Build Plate
  • Removal of part from build plate with wire EDM, bandsaw, or flush cutting tool

5. Post-processing
  • Removal of supports 
  • Final surface finishing
  • Heat treating for mechanical properties
Within the Print stage, the part is fused layer-by-layer using the following steps.
POWDER FEED

Feed cylinder increments up placing powder in front of the recoater.

ADDING POWDER LAYER

Recoater moves across the feed cylinder delivering powder to the build cylinder.

FUSION

Laser fuses the cross section of the part.

BUILD CYLINDER

Build cylinder increments down one thickness layer.

COMPLETING THE BUILD

The process is repeated until the volume of the part is fully built.

BUILD PLATE AND PART REMOVAL

The build cylinder raises up and the build plate is removed.

Benefits

Additive Manufacturing systems print near-net-shape 3D components from Computer Aided Design (CAD) data. Compared to traditional machining and assembly processes, additive manufacturing significantly simplifies manufacturing and can produce components with highly complex features and all-in-one assemblies.

  • Prototypes can rapidly be printed, which minimize the time from engineering to full production. By eliminating the set-up and tooling costs, and the long lead times of traditional manufacturing processes, metal powder-bed fusion can produce finished prototypes typically in four to 48 hours and allow rapid design modifications.
  • Complex designs and difficult-to-machine parts, such as components with long or partial thru-holes, internal cavities, contours and tapered geometries, conformal cooling channels, and metal mesh or lattice structures can be efficiently printed with metal powder-bed fusion.
  • Multiple assemblies can be made into one part, eliminating the cost and time of machining, welding and assembling multiple components.
  • On-Demand Manufacturing minimizes manufacturing expense and time for one-off applications such as machine shop tooling for injection molding or die casting. Enables rapid printing of student-generated designs in college classes and graduate work.
  • Remote manufacturing allows on-site build of critical replacement components from digital CAD files.
  • Reduced physical inventory by replacing physical inventory cost and space with digital 3D CAD files. Components can then be rapidly and easily printed on-demand from the CAD files.

Technical Capabilities

Metal Powder-Bed Fusion enables manufacturing of complex geometries with many features not readily obtainable by conventional subtractive manufacturing processes such as machining and casting.

Design Guidelines

Design of components for Metal PBF manufacturing requires consideration of several key guidelines. 3D CAD programs such as AutoDesk Netfabb® and Materialise Magics have features to assist in your design including modules devoted to Additive Manufacturing.

Height:Width Ratio Graphic- Design for Additive
Height:Width Ratio

Tall, narrow features should have a maximum height:width (aspect) ratio of 8:1. Features with greater aspect ratios risk damage by the recoater during powder application. Adding a gusset to the component design will strengthen the feature and minimize damage.

Design for Metal 3D Printing: Overhanging Surfaces
Overhanging Surfaces
  • 0 to 30 degrees: Need supports
  • 30 to 45 degrees: Supports not needed but part may have poor surface on down-facing surfaces
  • Greater than 45 degrees: Supports not needed; good quality surface finish
Design for Additive: Flat Ceilings
Flat Ceilings

Flat ceilings larger than 1 mm (0.04 in.) will require a solid or mesh support. Fillets can also be added to prevent warpage out of the build plane.

Design for Metal Additive: Geometry Support Structures
Geometry Support Structures

Solid or mesh mechanical supports can be added to optimize anchoring, minimize wall distortion from thermal gradients, support overhanging geometry, and provide solid anchoring between the component and the build plate to eliminate component movement during printing. The supports are removed after separation of the component from the build plate. Extra care should be taken when removing supports from thin walled parts; the process of removing the supports could potentially warp the parts.

Design for Metal 3D Printing: Horizontal Holes and Shape
Horizontal Hole Size and Shape

Horizontal holes with diameters less than 5 mm (0.2 in.) can be printed reliably without internal support. Larger holes will require an internal mesh support or design change. Changing to a tear drop, oval, or square shape will eliminate the need for internal supports.

Design for Metal 3D Printing: Wall Thickness
Minimum Wall Thickness

Typical minimum wall thicknesses range from 100 to 200 microns
(0.004 to 0.008 in.).

Powder Escape

Holes are required to allow powder to escape from enclosed printed structures. A minimum hole diameter of 3.0 mm (0.12 in.) is recommended. Multiple or larger holes will increase the speed of powder removal.

Other Recommendations
  • Add fillets to decrease stresses at geometry changes
  • Minimize unnecessary blocks of printed material
  • Parts with large solid volumes (∼10 cm3/4 in3) could require a thicker build plate to minimize warpage
  • If practical, print internal holes parallel to the build direction (Z-axis)

Questions? Comments? Contact Us.

+1 (814) 205-1505  |  info@xactmetal.com  |