While CNC machining and casting are traditional manufacturing methods for metal parts, metal 3D printing offers an alternative way by extruding high content metal filament or solidifying metal powder on a build plate.
As an additive process, 3D printing requires no part-specific tools or moulds other than supports printed during production.
3D printing is a cost-effective manufacturing solution for producing metal parts that are difficult to machine making it a complementary technology.
But what exactly is metal 3D printing, and how does it work? This introductory guide covers everything you need to know about metal FFF printing.
Let’s jump in!
What is metal 3D printing?
Metal 3D printing describes a range of additive manufacturing processes where metal powder or metal filament is printed in layers.
The most common industrial technology is Laser Powder Bed Fusion (LPBF), known as selective laser melting (SLM), which uses multiple lasers to melt layers of metal powder, fusing particles on the print bed. However these machines come at a high cost.
The more affordable to route into industrial metal 3D printing is metal FFF printing with the Metal X. Which is a three part system including the printer, wash and sinter.
Metal Binder Jetting is also relatively popular, distributing a layer of metal powder and using a jetting head to deposit a binding polymer to create the part.
How does metal 3D printing work?
The two most common 3D printing processes are metal FFF and Powder Bed Fusion. We review the critical workings of these below.
In metal FFF 3D printers like the Metal X, printers extrude a metal filament to print the part (green state). The part is then washed in a solvent to remove the binding wax and polymers (brown state). This part is then put into a sinter to form the final metal part.
The Metal X prints the following metals:
- 17-4PH Stainless Steel
- H13 Tool Steel
- Inconel 625
- A2 and D2 Tool Steel
You can find out more about the metals here.
The process sees plastic-bound metal powder filament printed alongside ceramic release material. The ceramic material creates a layer between the part and supports, letting you remove parts from supports with the light tap of a hammer.
Parts printed with the Metal X are between 95 and 99 per cent dense, depending on the sintering stage.
The Metal FFF workflow
Here’s what the metal FFF workflow involves:
- Design: Every 3D print starts within a CAD/3D modelling environment, with designs exported as 3D printing files (e.g., STL).
- Slicing: Slicing turns 3D printing files into G-codes, which contain instructions for the 3D printer, including build paths. Slicing software automatically generates G-code, with Eiger being Markforged’s offering.
- Printing: Metal bound in plastic (metal filament) is printed layer by layer into the shape of your part on the print bed. The Metal X compensates for shrinking for successive processes like sintering.
- Debinding: After printing, so-called “green” parts are placed into a solvent wash with debinding fluid (solvent) to dissolve and soften the plastic binder.
- Sintering: After debinding, parts are placed inside a furnace and heated to a material-specific temperature to melt and burn off the remaining plastic. The metal powder solidifies, transforming the parts into solid metal.
The Markforged system is completed with the Wash 1 is an automated washing station that uses Opteon SF-79, a high-performance fluid designed to offer superior cleaning power.
The Sinter 1 turns washed brown parts into solid metal parts with a high-performance furnace optimised for plastic-bound metal filament.
The Sinter 2 is more advanced than the Sinter-1, with a larger working volume, more precise temperature control, and a mechanical door interlock.
Comparing Powder Bed Fusion
Powder Bed Fusion fuses metal powder in layers by tracing a laser on a gantry across specified paths. The powder bed is a loose material that solidifies in the areas the laser hits, producing solid metal parts.
A powder distribution system pushes layers of loose powder over the forming part, and the laser traces over it repeatedly until the part is complete.
After printing, parts are de-powdered to remove loose material, but they do not require washing or sintering because they are solid metal.
Here’s what the process looks like:
- Design: The process begins with the creation of a 3D CAD model. Slicing software then produces instructions for the printer from the STL file.
- Printing: A layer of metal powder spreads over a build plate, and a laser traces a path over it, solidifying the powder. A powder distribution system then pushes a new layer of loose powder over the forming part, and the process repeats until the part is complete.
- Post-processing: Parts are solid metal off the print bed but typically require sanding and de-powdering to turn them into usable parts.
Powder Bed Fusion is a mature technology that can print fully dense parts rapidly.
The downside is the cost – Powder Bed Fusion has an entry-point north of £300k to buy and install, making it an industrial operation.
While Powder Bed Fusion is the market leader in the metal 3D printing industry, it occupies a different space than FFF metal printing in terms of price point.
However, no matter their technologies, metal 3D printers are valuable production tools, perfect alongside CNC machines for rapidly producing parts that require complex geometries and infills with minimal waste.
Find out more
To find out more about metal 3D printing, please get in touch with the team at 01765 694 007, email email@example.com, or you can