SIN≡SET

An Additive Engineers Mindset

Introduction to Metal Printing

I started writing another blog post (about build direction and the importance of defining the direction from the outset) and it occurred to me, my journey into Additive Manufacturing (AM) at this time, is roughly 7 years...and from that there is a lot of knowledge I take for granted. If I was to dive into technical talk straight away, it could be a little harder for readers to digest.

So here goes….SOME of the basics.

Printing Metal

There are many different methods in how to”print” metal. I will be talking about Powder Bed Fusion (PBF) - specifically Direct Metal Laser Melting (DMLM). PBF is the most common method of metal printing, so it provides a good introduction. This process involves the controlled laser welding...of you guessed it, fine metal powder! The process is layer based and you essentially stack weld, over weld, over weld to build up the thickness of your part.

Fig 1. DMLS Machine example- Mlab 200R - Image from GE.com

See the video below of an example of the process:

Fig 2. FDM Printer (Prusa Mk3s Pictured)

The Part or Model

Parts are drawn/designed/generated in Computer Aided Design (CAD) programs, such as Solidworks, Inventor, Fusion360 etc. or can be ready downloaded from sites in the Standard Tessellation Language (STL). file format (free website such as thingiverse.com). This file is then imported into a build processor program - this is the same for Filament Deposition Modeling (FDM) printers. Whereby the parts are split into layers to generate Geometric Code (G-Code) which informs the “Printer” and the various controlled elements, stepper motors, mirrors etc, how to behave. This is commonly referred to as a “sliced” file. Stacking these sliced layers together will build up your part - in the case of the video above 30um (0.03mm)

The Process

Simplifying it at this stage it is fundamentally:

Deposit a thin (and controlled) layer of metal powder across the build area - think of this as a raking or sweeping motion.
Read data from G-code about planned movements for this layer (Heat sources etc.)
Using a heat source, melt the powder in a controlled pattern, trace and “fill in” the cross section of the area you want to solidify - Common heat sources are laser(s) or an electron beam.
Lower the build plate by the thickness of the layer just deposited (0.03mm in our example)
Recoat with powder and repeat steps 2-4 until the model is finished.

As shown by the graphic below:

Fig 3. The Print Cycle

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