Direct Metal Laser Sintering (DMLS) Design Guidelines

DMLS is a metal 3D printing method to achieve complex designs that machining or casting are unable to attain. Mechanical properties of aerospace standard materials as well as design freedoms are offered when using Direct Metal Laser Sintering. It’s able to breakthrough challenges and deliver outstanding designs that would not be possible without Metal 3D printing. DMLS begins using a 3D CAD file that uses a high-powered and precise laser to melt powdered metal layer upon layer. These layers can build one or more designs. A build chamber infused with argon gas is used for printed parts. A YB-fibre laser selectively melts the design’s cross section through a computer-determined scan path. The laser, powder, and additive process come together to create a forceful design freedom triad.

Materials – The following are metals and alloys that are useable in 3D metal printing:

 Titanium – pure
 Titanium alloys
 Nickel-based alloys
 Cobalt chrome alloys
 Copper-based alloys
 Steel
 Stainless Steel

These materials are further explained what they are and how they are used in DLMS.

Materials	Specification	Application
Stainless Steel (15-5 PH)	Precipitation-hardened (PH) stainless steel is used in many industries due to its endless benefits such as strength, fabricability, ease of heat treatment, corrosion resistance and toughness.	A number of different industries use this product for production parts
Stainless Steel (17-4PH)	17-4 PH stainless steel has ferrite, where 15-5 steel is ferrite-free. But like the 15-5, 17-4 has great strength, fabricability, ease of heat treatment, and is corrosion resistant!	A number of different industries use this product for production parts
Stainless Steel (316L)	High strength and wear resistance while using austenitic chromium-nickel alloy. Benefits include good elevated temperature strength, formability and weldability. Like 17-4 and 15-5 stainless steel, it has excellent corrosion resistance.	Used in aerospace and medical industry for production parts
Aluminum	Known for its strength and hardness and is often used for mechanical and thermal properties when a specific low weight is needed.	Aerospace and automotive production parts
Maraging Steel	Martensitic hardening steel with durability and toughness. Also has tensile strength and low warping properties. Another great feature is that its easily machined, hardened and welded.It can be used with different applications because of its malleability.	Series production and mechanical parts use injection molding tools
Titanium (Ti6A14V/Grade 23)	Outstanding mechanical properties, with corrosion resistance and low specific weight. Strength-to-weight ratio is exceptional, as well as the fabricability and biocompatibility. Medical implants rely on this Titanium because of its improved ductility and fatigue strength	Used for production parts in medical (implants)
Titanium (Ti6A14V/Grade 5)	Like the above titanium, this also has outstanding mechanical properties, with corrosion resistance and low specific weight. Most commonly used for strength-to-weight ratio, fabricability, and its power to heat treat	Aerospace and automotive production parts, specifically motorsports
Cobalt Chrome	This superalloy has excellent wear and is corrosion resistant. Conveys good mechanical properties at elevated temperatures. Benefits such as wear and corrosion resistance and biocompatibility make it	Aerospace and automotive production parts, specifically motorsports
Nickel Alloy (Inconel™ 718/ UNS N07718)	Another superalloy with great yield, tensile and creep-rupture strength at high temperatures. Also used for high strength applications in extreme environments and has good weldability compared to the other nickel-based superalloys	Used in the aerospace industry for production parts, specifically high-temperature turbine components
Nickel Alloy  (Inconel™ 625/ UNS N06625)	This superalloy has amazing strength, and toughness when used at high temperatures. It’s commonly used for high strength applications in harsh environments. Shows supplementary resistance to pitting, crevice corrosion and stress corrosion cracking in chloride environments.	Used in the aerospace industry for production parts, specifically high-temperature
Nickel Alloy (UNS N06002/Hastelloy X)	Our last superalloy that has out of this world combination of high temperature strength, fabricability, and oxidation resistance.Also useful in extreme environments. Holds resistance to stress-corrosion cracking in petrochemical environments. Also forms and welds very well.	Production parts used in severe heated conditions. Also high risk of oxidation (combustion chambers, supports and burners in industrial furnaces)

 

Although the most popular industry that uses DMLS is the aerospace industry, other industries use the same process for different applications.

 

Aerospace	Injectors  Combustor liners  Rocket engine manifolds  Research efforts  Functional prototypes
Medical	Dental devices  Surgical tools  Orthopedic implant devices/prototypes  Educational models  Training tools
Energy	Rotors  Stators  Mud Motors  Turbine prototyping and research  Bridge applications
Industrial	Prototype tooling  Manufacturing fixtures  Low volume production

 

 

Feature	Description
Wall thickness	Minimum thickness of 0.4 mm
Pin Diameter	Minimum is 1 mm  If smaller diameter is needed, reduce contour sharpness
Hole Size	For accurate prints with no support use hole diameters between 0.5 mm and 6 mm  Support free building with hole diameters between 6 mm and 10 mm is orientation dependent  Support structure is required when horizontal holes with diameter of 10 mm is used
Escape holes	Holes are needed on hollowed metal parts so unmelted powder gets properly removed  Bore hole diameter between 2 and 5 mm is suggested
Support/Overhangs	Support is necessary in all situations
Unsupported Walls	0.5 mm is the maximum length a cantilever-style overhanging surface can be
Aspect Ratio	Maximum ratio is 8:1 Between the vertical print height and part section. This is yo stabilize the printed part on the build plate
Tolerances	Part tolerance is ± 1mm -layer thickness in print direction  0.127 mm is attainable in the XY plane
Minimum Features	0.6 mm required
Embossed/Engraved Details	0.1 mm wide/high

As the cost is often higher with both machines and materials, using this technique is not often fit for producing high volume orders.  Design also is a limitation when using DMLS. This is because not all applications designed when using traditional manufacturing can be converted to a additive manufacturing solution. More restrictions when using DMLS is product size. Most machines, even large machines, have a small build size volume. The average build volume size is 250 mm x 250 mm x 300 mm. Furthermore, machines are very complex to use, coming in industrial sizes and strict operating, material handling, post processing and maintenance procedures.

 

      

The most frequently used post processing methods are the following;

1. Surface treatment
2. Support removal
3. Heat treatment
4. Machining