chapter  4
46 Pages

Additive Manufacturing of Metals Using Powder-Based Technology

WithMichael Jan Galba, Teresa Reischle

ABSTRACT Additive manufacturing (AM) in metal objects can be used in various applications such as aerospace, medical, tooling, automotive, general industry, consumer goods lifestyle, prototyping, and many more. The applications are rapidly growing with the increasing acceptance of the AM capabilities. As a general statement, it is possible to say

CONTENTS

4.1 From Rapid Prototyping to Rapid Manufacturing ......................................................... 98 4.2 Functional Description of Powder Bed-Based Additive Manufacturing Systems .......101 4.3 Generic Process .................................................................................................................. 107

4.3.1 CAD File .................................................................................................................. 107 4.3.2 STL Conversion into Slice File ............................................................................. 107 4.3.3 File Transfer to the Machine ................................................................................ 110 4.3.4 Building Process .................................................................................................... 111 4.3.5 Post-Processing ...................................................................................................... 111

4.4 Parameters of the Laser ..................................................................................................... 111 4.5 Specic Requirements for Implants or Biomedical Devices ........................................ 117 4.6 TiAl6V4 ................................................................................................................................. 119 4.7 Standards for Porous Structures ...................................................................................... 121 4.8 Design of Porous Structures ............................................................................................. 122 4.9 Design of Lattice Structures ............................................................................................. 123

4.9.1 Design of Lattice Structures Using Netfabb ...................................................... 123 4.9.1.1 Unit Cells ................................................................................................ 124

4.9.2 Design of Lattice Structure Using within Enhance .......................................... 125 4.10 Inuencing Factors of the Process ................................................................................... 130

4.10.1 Exposure Strategies ............................................................................................... 132 4.10.1.1 Exposure ................................................................................................. 132 4.10.1.2 Curing Zone ........................................................................................... 132 4.10.1.3 Beam Offset ............................................................................................ 133 4.10.1.4 Basic Exposure Type ChessRotLx ....................................................... 134 4.10.1.5 Basic Exposure Type Contours ........................................................... 135 4.10.1.6 Basic Exposure Type SkinCore............................................................ 135 4.10.1.7 Basic Exposure Type SLI_HatchLx ..................................................... 135 4.10.1.8 Basic Exposure Type UpDownStripesAdaptiveLx ........................... 136 4.10.1.9 Basic Exposure Type UpDownStripesAdaptiveRotLx..................... 138

4.11 Summary ............................................................................................................................. 139 References ..................................................................................................................................... 139

that AM will not replace conventional machining in the near future. It is a complementary technology to conventional machining like milling, drilling, welding, turning, and EDM processes that can add value to the product manufactured. This is possible as an example for parts where a near-net shape component is additively manufactured and only nal functional features like threads, ttings, and high tolerance areas need to be post machined by conventional machining methods. It can as well aid in the reduction of manufacturing or assembling effort by using functional integration. Very often objects manufactured by AM are more expensive than conventional machining methods but cost benets could be gained through the lifetime of the component. As an example you could use in aviation components on an aircraft that would save weight. The initial manufacturing and validation costs can be signicantly higher than conventional machined components but save the customer in the end a lot of money through reduced fuel consumption over the lifetime of an aircraft. Another example is the medical device sector in which lattice structures on implants can save the manufacturer labor intensive post-processing like plasma spray coatings and bead sintering among others. Lattice structures can also extend the lifetime of implants in two ways. One way is the reduction in stress-shielding caused by stiff implants, which leads to bone resorption. The other is the effect of cell ingrowth that improves the strength of the boneimplant interface for possible better primary xation and cementless implantation. Selective laser sintering/melting makes it possible to produce complex structures and to create individualized implants with the biocompatible titanium alloy Ti6Al4V. This chapter shall give the reader a brief overview about the selective laser melting/sintering process using a laser as source of energy.