3D Printing Design Guide

3D Printing is a type of additive manufacturing and is a process whereby physical objects are created by depositing material in layers determined by a digital model, usually created on CAD software. 3D printing requires specific software, hardware and materials that make up the 3D model.

3D printing technology is used to create prototypes, simple parts, as well as complex parts. Some examples of parts made by 3D printing technology include medical implants, airplane and rocket parts.

Types of printing technology looked at in this guide include Selective Laser Sintering (SLS), Stereolithography (SLA), MultiJet Fusion (MJF), Direct Metal laser Sintering (DMLS).

Benefits of 3D Printing

Speed of prototyping parts compared to traditional methods.
Low cost – cost depends only on the amount of material used.
No tooling or moulds required to form parts (as in moulding or metal casting).
Large range of materials available – materials can be composites, metal, ceramics, wood or carbon filled.
Easy fabrication of complex shapes.
Customization of each and every part.

Limits of 3D Printing

Lower strength and anisotropic material properties – Parts are built up in layers
Cleaning up and support removal – printed parts often require supports to be removed and parts to be cleaned up (sanded, smoothing etc) to obtain a quality finish.
Expensive for high volumes
Limited accuracy and tolerances (desktop machine 0.5mm, Material Jet and
Stereolithoraphic (SLA) 0,1 mm accuracy , bare in mind finishing when designing)

3D Printing Service Process

1. Upload CAD files (.STL)

2. Specify your requirements (Material, process, leayer, dimensions, time)

3 . Get a quote!

Why use an online service

Use online process to print using multiple processes, allows for rapid prototyping and bulk processing, saves time and money.

Types of Online 3D Printing Services

SLS – Thermoplastic Polymers – Nylon PA220, Nylon PA11, PA12.
SLA – Thermoset Polymer (resin)
MJF (HP) – Thermoplastic Polymers – 40% Glass Bead Nylon PA12
DMLS –Metals – Stainless steel, mild steel, Aluminium, Titanium

CAD Design for 3D Printing CAD

If you can design in 3D CAD then you can easily create a 3D model that can be 3D printed. You can use 3D CAD and save your model in STL format which is a format that can be sent to the 3D printer.

STL Format for 3D Printing

STL is the industry standard used by 3D printers, the format you need to send 3D CAD files to the printer in. In STL’s triangles are used to represent inner and outer surfaces of a solid. STLs contain all the information needed to print a model.

A quick look at other technologies

Material Extrusion (FDM): Material is selectively dispensed through a nozzle or orifice

Binder Jetting (BJ): Liquid bonding agent selectively binds regions of a powder bed.

Direct Energy Deposition (LENS, LBMD): A high-energy source fuses material as it is deposited.

Common 3D Printing Applications

MATERIALS FOR 3D PRINTING

Materials used in the 3D printing process depend largely on the 3D Printing method, as well as the properties required by the designer and application. Plastics – thermoplastics and thermosets are most commonly used in 3D printing. Some composites may be printed. Metals are also more commonly being used in 3D printing.

PA220 Material Properties
Mechanical properties
Tensile strength (MPa)	48
Tensile Modulus (MPa)	1700
Elongation at break (%)	24
Thermal Properties
Melting point (degrees C)	172-180

Nylon PA220

Nylon PA2200 is widely regarded as the industry standard for high end 3D printing, yet still remains one of the most affordable materials. The material is both strong and smooth and can be polished even smoother.

The official melting point is just above 170°C. The Nylon can be both flexible when thin and rigid when thick.

Nylon PA11

Nylon PA11 has properties quite similar to Nylon PA12. However, PA11 has a lower environmental impact, consumes less non-renewable resources to be produced, and has superior thermal resistance. Indeed, PA11 is stable to light, UV, and weather. It is also characterized by good elasticity, high elongation at break and high impact resistance, unlike some of the other materials offered. Moreover, black polyamide has an excellent resistance to chemicals, especially hydrocarbons, aldehydes, ketones, alcohols, fuels, detergents, oils, fats, mineral bases, and salts.

Nylon PA11 is typically used for mechanically loaded functional prototypes and series parts with long-term moving elements such as hinges. In the automotive industry, it is mainly used for interior components for crash relevant parts. PA11 is also well suited for abrasively stressed and manually manipulated visible parts and is especially well suited for small to medium sized parts, thin walls, and lattice structures.

Nylon PA11 Material Properties
Mechanical properties
Tensile strength (MPa)	44
Tensile Modulus (MPa)	1500
Elongation at break (%)	150
Thermal Properties
Melting point (degrees C)	185

Nylon PA12

Nylon PA12 is exceptionally strong even at low temperatures. It has high strength, stiffness, strong resistance to cracking under stress, and an excellent long-term constant behavior. Nylon PA12 absorbs very little moisture as it has less nitrogen containing compounds than polyester, it has an excellent resistance to chemicals including hydraulic fluids, oil, fuels, grease, salt water, and solvents, dampens noise and vibration, and is highly processable.

Nylon PA12’s applications go above those of PA11, as fully functional quality plastic parts of can be produced using this material. Their excellent mechanical properties are used to substitute typical injection molding plastics. Furthermore, the biocompatibility allows materials for medical parts such as prostheses to be manufactured. The high abrasion resistance allows the realization of movable part connections like gears or hinges. Both PA12 materials are not affected by light. Parts are adaptable to every weather.

Many finishing options are available for Nylon PA12 parts. As the objects printed come out white, colors can be applied whether it is through paint or dyes. Nylon PA12 objects can go through a number of post-treatment operations: they can be either polished, varnished, or go through a chemical smoothing process. The process brings smoother to every section of the object and works by sealing the porous surface of the plastic parts.

The main material used in both processes is PA 12 (Nylon). When printing in this material, MJF parts have superior strength and flexibility and more homogeneous mechanical properties compared to SLS parts, which are weaker along the print direction.

Nylon PA12 (HP) Material Properties
Mechanical properties
Tensile strength (MPa)	48
Tensile Modulus (MPa)	1700
Elongation at break (%)	20
Thermal Properties
Melting point (degrees C)	175

40% Glass tube bead filled PA12 Nylon

PA 12 Glass Beads is a Multi Jet Fusion nylon plastic infused with glass beads that improve product stiffness and structural integrity. This material is 40% glass-filled which reduces warping during the printing process and over the product’s life. PA12 Glass Beads is great for flat and large parts that are prone to warping in Versatile Plastic and MJF PA12 Plastic and for functional parts that require high strength and dimensional accuracy.

3D Printing Materials Comparison

Materials: Mechanical Properties	Density of Laser Sintered Part (g/cm3)	Tensile Modulus (N/mm2)	Tensile Strength (N/mm2)	Elongation at Break point (%)	Melting point (degrees C)
	0,40	1700	48	24	172 - 180
Nylon PA 11	0,99	1585±25	48	36,5±8,5	201
Nylon PA 12	0,9 min -0,95 max	1700±150	45±3	20±5	172 min/180 max
MJF PA12 (40% Glass-filled beads)	1,01	1700	48	20	187

DESIGN TIPS FOR 3D PRINTING (DO's AND DONT's)

Adapt existing designs to use 3D printing guidelines.

Create lightweight structures – try to use as little material as possible.

Designs need to be specific to the technology, material and project, a part designed for CNC manufacture isn’t necessarily set up for 3D printing.

Eliminate support structures – support structures add additional cost and time to production, this is true for metal 3D printing which has much higher costs.

Overhangs should be kept to less than 45 degrees.

Consider the print orientation, top-heavy parts may be printed best upside down.

Adhere to material guidelines – materials can be brittle or strong.

Understand printing technology.

Keep to the guidelines on wall thickness.

If this is not adhered to prints may not be printable, this is based on the material selected and printing method.

Apply fillets to reduce stress and increase strength on small pillars.

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