Laser Sintering with Plastics E-Book

Manfred Schmid

• Herausgeber: Carl Hanser Verlag GmbH & Co. KG
• Kategorie: Fachliteratur
• Sprache: Englisch
• Veröffentlichungsjahr: 2024

Seitenzahl: 421

Beschreibung

Powder bed-based additive manufacturing with polymers (PBF-P) has a special position in the world of 3D printing. On the one hand, the components are manufactured without support structures, and on the other hand, the property profile of the components is similar to that of series components, as is also known from injection molding, but with clear advantages in terms of component complexity.


In laser sintering (LS), individual component layers are fused with the aid of suitable laser radiation. In recent years, LS components have gained widespread use in industrial applications, so that today one can already speak of an established technology. Nevertheless, there are still many hurdles for LS to overcome in the future in order to free itself from the status of a niche technology. Material diversity and industry-compliant, quality-assurance measures are among the challenges to be mentioned here.


To this end, the second edition of this book sheds light on the current state of the art in terms of machine technology and process flow, and specifically on the requirements for the materials used. In addition, the following topics are presented:

- Implementation of LS in industrial process chains

- Status of international standardization

- Innovations in the field of LS materials

- Properties of LS components
- Selected application examples
The second edition has been updated throughout; in particular, the material and machine specifications have been extensively revised.

Leseprobe

Manfred Schmid

Laser Sintering with Plastics

Technology, Processes, and Materials

2nd Edition

Print-ISBN:        978-1-56.990-921-8E-Book-ISBN:   978-1-56.990-929-4E-Pub-ISBN:     978-1-56990-337-7

All information, procedures, and illustrations contained in this work have been compiled to the best of our knowledge and is believed to be true and accurate at the time of going to press. Nevertheless, errors and omissions are possible. Neither the authors, editors, nor publisher assume any responsibility for possible consequences of such errors or omissions. The information contained in this work is not associated with any obligation or guarantee of any kind. The authors, editors, and publisher accept no responsibility and do not assume any liability, consequential or otherwise, arising in any way from the use of this information – or any part thereof. Neither do the authors, editors, and publisher guarantee that the described processes, etc., are free of third party intellectual property rights. The reproduction of common names, trade names, product names, etc., in this work, even without special identification, does not justify the assumption that such names are to be considered free in the sense of trademark and brand protection legislation and may therefore be used by anyone.

The final determination of the suitability of any information for the use contemplated for a given application remains the sole responsibility of the user.

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© 2024 Carl Hanser Verlag GmbH & Co. KG, Munichwww.hanserpublications.comwww.hanser-fachbuch.deEditor: Dr. Mark SmithProduction Management: Cornelia SpeckmaierCover concept: Marc Müller-Bremer, www.rebranding.de, MunichCover design: Tom WestCover picture: © courtesy of Rob Kleijnen, courtesy of irpd AGTypesetting: le-tex publishing services GmbH, LeipzigPrinted and bound by: CPI Books GmbH, Leck

The Author

Dr. Manfred Schmid began his professional career as an apprentice laboratory assistant at Metzeler Kautschuk AG in Munich. After graduation, his education continued through his studies in chemistry at the University of Bayreuth, resulting in a Ph.D. in Macromolecular Chemistry, during which he worked with liquid-crystalline polyurethanes under the guidance of Prof. Dr. C. D. Eisenbach.

After graduation, he moved to Switzerland, where he continued for 17 years through different positions in industry in the areas of polymer research and production, as well as material testing and polymer analysis. Polyamides and biopolymers were the focus of a variety of different activities carried out during that time.

Since then, for more than 15 years, he has led the research in laser sintering (LS) at Inspire AG, the Swiss Competence Center for Manufacturing Techniques. This acts as a transfer institute between universities and the Swiss machine-, electro-, and metal (MEM) industries.

The focus of his current activities is on new polymer systems for the LS process, the analytical evaluation of LS powders with regard to their specific property profiles, and LS process development. He supervises several collaborators and has led a wide variety of research projects in this environment. A number of frequently cited original publications have resulted.

As a guest lecturer, Dr. Schmid has given alternating lectures on the Material Science of Plastics, the Processing of Polymers, and 3D-Printing at two Swiss institutions – the Interstate University of Applied Sciences Buchs and the University of Applied Sciences St. Gallen.

The idea for this book arose from several training courses held at Inspire AG on behalf of large industrial companies on the subject of “Additive Manufacturing”.

Acknowledgement: The author would like to express his sincere thanks to Ms. Gabriele Fruhmann for preparing individual sections of the book, especially on the main topics of industrial integration of LS technology (Section 3.2) and polyamide 11 (PA 11) (Section 6.1.2), as well as for her many valuable comments on the revision of the entire text. Without her support and highly valued contributions, this second edition of the book on laser sintering of plastics in its present form would not have been achieved.

Gabriele Fruhmann

Gabriele Fruhmann studied mechatronics at the Technical University of Graz after a technical baccalaureate in Computer Science. After graduating, she joined the industry at Magna Steyr Fahrzeugtechnik in Graz in the area of multi-body dynamics simulation. She then moved to ZF Friedrichshafen AG to work in pre-development with a focus on fiber-reinforced polymer materials.

In 2013, she moved to the materials department at BMW AG, where she was responsible for pre-development projects. As part of her work, she began to focus more on additive manufacturing in 2014, and in 2017 she started to work in greater depth on material specifications for the feedstock materials used in laser sintering (LS), and the properties of the part following processing.

After an internal move in 2022 to the area of simulation, her current focus is on material model selection, material characterization, and material card generation for polymer materials in structural simulation, as well as on mapping the results from different process simulations to structural simulation in terms of material properties in the part.

The collaboration on the book came about because of Ms. Fruhmann’s collaboration with Dr. Schmid on a joint project, and because of her appreciation to him for the first edition of this book, which helped her to gain an understanding of laser sintering in a short time-frame.

Foreword

Foreword to the first edition

The history of additive manufacturing seems to be very short on a first view, but in reality the technology is more than a hundred years old. The first patent application was in 1882 by J. E. Blanther, who registered a method for producing topographical contour maps by cutting wax sheets, which were then stacked.

This is an amazing fact: layer-by-layer work processes are currently experiencing a huge amount of hype, which was not triggered by the development of new basic technologies. The background is rather that essential patents have expired, making it possible to recreate for example a melt deposition method using the simplest means, which can be used for the generation of three-dimensional bodies. This hype was created in a very short time, and it developed due to considerable inherent dynamics. The decentralization of users and the new degrees of freedom offered by the technologies coincide with the present boom of DIY (do it yourself) culture, so it is not surprising that “Fabber” and “3D printing selfies” are highly demanded.

Conversely, various new technologies were developed over the entire process chain as well. During my studies in the early 2000s, when I dealt with the topic for the first time, the importance of layer manufacturing was high only in the area of prototyping. The technologies have not changed radically since then, but nowadays the market for custom products and small production runs in many industries has increased massively. Consequently, both established machine manufacturers and many innovative startups have grown in this field. The additive manufacturing process has found immeasurable use today, from the production of individual toys to high-power components for powertrains. In the future, different scenarios for production are possible, and decentralized production “on demand” is tangible. This generates a field of high technological expectations with risks and potentials. A realistic estimation should be independent of the enthusiasm that is noticeable after seeing the first additive manufacturing process and having the generated part in one’s hand. Independent research on the topic is therefore essential.

BMW AG ordered the first SLA system in 1989. Thus, BMW AG was the first customer of a today world recognized and leading company for laser sintering systems. Over the years, Research and Innovation Center (FIZ) formed a model for a Competency Center in which various practical and basic research is carried out today. In addition to high quality prototypes for testing and validation of transportation vehicles, materials and processes are being developed, making it possible to realize the potential of layer-by-layer construction. For example, employees working in the automotive production are individually equipped with personalized assembly aids to increase ergonomics and performance in assembly lines.

In this case, the focus of the discussion will be less on the 3D printing processes mentioned in the media, but rather on the highly complex manufacturing machines on which the production is to take place in the future. One such technology is selective laser sintering (SLS), a laser-based unpressurized manufacturing process. However, the coincidence with a “real” sintering process, is solely that the generated part cross-section will be held near its melting temperature for a long residence time. This is the core process of laser sintering, which is already examined in diverse ways and is still subject of intensive further research.

When I dealt with my own Ph.D. thesis about the time and temperature dependence of the two-phase region, in which melt and solid are present synchronous, I had the chance to enter into one of the many interdisciplinary fields of research on additive manufacturing, and I am still excited about this topic. Anyone who intends to work with laser sintering will not be able to find a lot about such specialized topics in most of the general books for 3D printing and additive manufacturing. Because powder bed based technologies are established as one of the major additive manufacturing processes, it is essential also to present the results of basic research and transfer it to practical use in order to create, for example, as a service provider, viable high quality parts. The purpose of this book by Manfred Schmid, one of the recognized specialists in laser sintering, is precisely to give this depth of field without losing the benefits to the user.

May 2015

Dr.-Ing. Dominik Rietzel

Foreword to the second edition

In the last decade, laser sintering has gained a leading role among processes for additive manufacturing or (as it is often more figuratively expressed) 3D printing. This applies to both metals and plastics, which are the focus of this book.

On the one hand, laser sintering produces components whose properties are closest to those of “classic” thermoplastic processing. On the other hand, as a process without any kind of support structures, it offers the ideal conditions for almost limitless free component design, and thus supports the turn from tool-bound design to function-driven design of a component. This freedom of design is increasingly finding its way into industrial production for specialized components with a high degree of functional integration or a high degree of customization, right down to the individual piece.

One example of function integration is the production of gripper systems, where up to 100 individual parts such as valves, springs, hoses, and the gripper tools can be integrated into a single laser-sintered component. As well as eliminating assembly, the tool manufactured in this way weighs only a fraction of the conventional tool, and thus enables a significant reduction in costs in the life cycle of the component, because the gripper can move faster and simultaneously use less energy. The high degree of customization that is possible is also put to use, in particular for applications involving people, be it the production of customized orthoses and prostheses, or drilling templates for operations. But it doesn’t always have to be high-tech medicine; the production of laser-sintered insoles is already a reality today.

The first edition of the book Laser Sintering with Plastics: Technology, Processes, and Materials has become the standard volume for system and material manufacturers, users, and researchers. This is because even a newcomer to the field of additive manufacturing will find it easy to get started, and because of the depth of detail and technical precision with which Manfred Schmid manages to explain the highly complex interplay of materials and processes, which take place on completely different timescales than any other process used in the plastics industry. These long timescales also result in particular strains on the materials, and this challenge is one of the reasons why the choice of different plastics is still limited, even after 30 years of laser sintering. To overcome this problem, the chemical industry is working hard on adapted plastics, and system manufacturers are accelerating processes, for example by using many laser sources simultaneously.

May this second edition be as helpful, educational, and exciting a read as the first edition to a new generation of technicians working in the field of laser sintering of plastics, and give new impetus to veterans of this technology such as myself.

August 2022

Dipl.-Phys. Peter Keller

Contents

Title

Copyright

Contents

The Author

Foreword

1 Introduction

1.1 Manufacturing Technology

1.2 Additive Manufacturing

1.2.1. Application Areas and Technology Drivers

1.2.2. Main Groups of Additive Manufacturing

1.3 Additive Manufacturing with Plastics

1.3.1. Vat Photopolymerization (VPP)

1.3.2. Material Extrusion (MEX)

1.3.3. Material Jetting Technology (MJT)

1.3.4. Powder Bed Fusion (PBF)

1.3.5. Comparison of AM Processes for Plastics

1.4 Laser Sintering (LS) with Plastics

2 Laser Sintering Technology

2.1 Machine Technology

2.1.1. Machine Configuration

2.1.2. Temperature Control

2.1.2.1. Heat Sources

2.1.2.2. Surface Temperature at the Build Area

2.1.2.3. Laser Energy Input, Andrew Number (AN)

2.1.3. Powder Supply and Powder Application

2.1.3.1. Internal and External Powder Supply

2.1.3.2. Powder State (Conditioning)

2.1.4. Powder Application

2.1.4.1. Blade and Powder Cartridge

2.1.4.2. Roll Coater

2.1.4.3. Combined Coating Systems

2.1.5. Optical Components

2.1.5.1. Laser Beam Positioning

2.1.5.2. Focus Correction

2.2 Machine Market

2.2.1. Industrial Laser Sintering Equipment

2.2.1.1. Company: Electro Optical Systems, EOS (Germany)

2.2.1.2. Company: 3D Systems (USA)

2.2.1.3. Company: Farsoon Technologies (China)

2.2.1.4. Other Manufacturers of LS Equipment

2.2.2. Pilot Plant and Research & Development Facilities

2.2.2.1. R&D Plants with CO2 Lasers

2.2.2.2. R&D Systems with Laser Diodes

3 The Laser Sintering Process

3.1 Process Chain

3.1.1. Powder Supply

3.1.2. Data Preparation and Build Job

3.1.3. Build Process

3.1.3.1. Heating Up

3.1.3.2. Process Flow

3.1.3.3. Parts and Building Chamber Parameters

3.1.3.4. Exposure Strategy

3.1.3.5. Cooling and Unpacking

3.1.4. Process Error

3.1.4.1. Deformation of the Parts

3.1.4.2. Surface Defects: Orange Peel

3.1.4.3. Other Process Errors

3.2 Qualification for Industrial Series Production

3.2.1. Product-Related Processes

3.2.1.1. Pre-Process

3.2.1.2. In-Process

3.2.1.3. Post-Process

3.2.1.4. Process Validation

3.2.2. Functional Processes

3.2.2.1. Feedstock Management

3.2.2.2. Qualification of the Laser Sintering Machine

3.2.2.3. Qualification of the Laser Sintering Process

3.2.3. Status of Standardization

4 Laser Sintering Materials: Polymer Properties

4.1 Polymers

4.1.1. Polymerization

4.1.2. Chemical Structure (Morphology)

4.1.3. Thermal Behavior

4.1.4. Polymer Processing

4.1.5. Viscosity and Molecular Weight

4.2 Key Properties of LS Polymers

4.2.1. Thermal Properties

4.2.1.1. Crystallization and Melting (Sintering Window)

4.2.1.2. Heat Capacity (cp) and Enthalpy (ΔHc, ΔHm)

4.2.1.3. Thermal Conductivity and Thermal Radiation

4.2.1.4. Modeling of the Processes in the Sintering Window

4.2.2. Rheology of the Polymer Melt

4.2.2.1. Melt Viscosity

4.2.2.2. Surface Tension

4.2.3. Optical Properties

4.2.3.1. Absorption

4.2.3.2. Transmission and (Diffuse) Reflection

5 Laser Sintering Materials: Polymer Powder

5.1 Powder Production for Laser Sintering

5.1.1. Emulsion, Suspension, and Solution Polymerization

5.1.2. Precipitation from Solutions

5.1.3. Grinding and Mechanical Comminution

5.1.4. Melt Emulsification

5.1.5. Laser Sintering Powder Production at a Glance

5.1.6. Other Powder Manufacturing Processes

5.2 Powder Properties for Laser Sintering

5.2.1. Powder Density

5.2.1.1. Particle Shape and Surface

5.2.1.2. Particle Size Distribution (Number and Volume Distribution)

5.2.2. Powder Rheology

5.2.3. Measurement of Powder Flowability

5.2.3.1. Hausner Ratio (HR)

5.2.3.2. Rotating Powder Analysis

5.2.3.3. Flow Agents

6 Laser Sintering Materials: Commercial Materials

6.1 Polyamide (Nylon)

6.1.1. Polyamide 12 (PA 12)

6.1.1.1. Particle Size Distribution and Particle Form

6.1.1.2. Thermal Properties

6.1.1.3. Crystal Structure

6.1.1.4. Molecular Weight and Post-Condensation

6.1.1.5. Powder Aging

6.1.1.6. Property Combination of PA 12

6.1.2. Polyamide 11 (PA 11)

6.1.3. Comparison of PA 12 and PA 11

6.1.4. Compound Materials of PA 12 and PA 11

6.1.5. Flame-Retardant Materials Based on PA 12 and PA 11

6.1.6. Other Polyamides (PA 6, PA 613, PA 1212)

6.2 Other Laser Sintering Polymers

6.2.1. Thermoplastic Elastomers (TPU, TPA, TPC)

6.2.2. High-Performance Polymers (PAEK, PPS)

6.2.3. Polyolefins (PP, PE)

6.2.4. Polyesters (PBT, PET)

6.2.5. Thermosets

7 Laser-Sintered Parts

7.1 Component Properties

7.1.1. Mechanical Properties

7.1.1.1. Short-Term Loading: Tensile Test

7.1.1.2. Laser Sintering Parameters

7.1.1.3. Component Density

7.1.1.4. Partial Melting (DoPM)

7.1.1.5. Anisotropy of Component Properties

7.1.1.6. Long-Term Resistance

7.1.2. Component Surfaces

7.1.2.1. Influencing Parameters

7.1.2.2. Roughness Determination

7.1.2.3. Surface Processing

7.1.2.4. Finishing

7.2 Applications and Examples

7.2.1. Prototype Construction and Small Series

7.2.2. Function Integration

7.2.3. Part List Reduction

7.2.4. Individualization and Personalization

7.2.5. Business Models and Outlook

1Introduction