Arburg Plastic Freeforming is predestined for the additive manufacturing of medtech components. The associated Freeformer-type additive manufacturing systems process the same plastic pellets that are used in injection molding. That makes the open systems very economical to use.

Medical Product Manufacturers Are Processing Original Materials Using the Freeformer

Anlagen Additive Fertigung / 3D-Druck, andere

Anlagen für die Additive Fertigung

Biokunststoffe

Kunststoff Werkstoffe

Additive Fertigung

Medizintechnik

Medizinprodukte

Werkstoffe für additive Verfahren

Andere Werkstoffe

Arburg Kunststoff Freiformen

Verfahren für die additive Fertigung

Freiraumverfahren

New Possibilities for Use  in the Human Body

With K 2016 in Düsseldorf, Germany, and formnext in Frankfurt/Main, Germany, professionals with an interest in additive manufacturing had two opportunities last year to gain a sense of the spirit of innovation in the industry. One issue was particularly prominent: the increase in production efficiency. This improves the economy of using the different 3D printing processes. 

A Diversity of Suppliers and Physical Cross-Linking Make Possible New Business Models and Application Scenarios for Additive Manufacturing  

Steuern, Regeln

Rapid Prototyping

Rapid Manufacturing

Selektives Laserschmelzen von Kunststoff, Metall, Keramik

Selektives Lasersintern von Kunststoff, Metall, Keramik

Faserverarbeitung

Spritzgießwerkzeuge

Industrieroboter

Qualitätssicherung

All Elements at a Glance 

Is there a quantum leap on the horizon for 3D printing? The prototype of a newly developed 3D printer is able to process commercial pellets – also those of high-performance plastics such as PEEK, PPS, PSU, PA and PC, with or without fibers. The machine applies the usual strand-deposition process, though with a simply designed print head that includes a radial screw. 

A Novel Type of Print Head Gives Fresh Impetus to the FDM Branch 

Polysulfone / Polysulfide

Kohlenstofffasern / -matten

Faser- und Filamentextrusion

3D-Print with Affordable Pellets 

Much as when injection molding materials were being developed 30 years ago, the current trend in additive production is toward higher melting materials and materials with improved mechanical properties. The latter can be achieved, for example, by fiber embedding. In machine technology, the developments are increasingly aimed at adapting processing times, sensor systems, and quality monitoring to the demands of high-tech companies.  

Materials Manufacturers and Process Developers Face Growing Demands in 3D Printing  

Rapid Tooling

Pulver-Spritzgießen

Schleifen, Polieren

Additive Adolescence 

What AM technology is considered capable of today and how it can be applied in many areas of application is shown (representative) by this expert’s view of medical technology.

Status and Perspectives for Human Medicine

Anlagen Additive Fertigung / 3D-Druck, Kunststoff

Anlagen Additive Fertigung / 3D-Druck, Metall

Medical Applications of Additive Manufacturing

In order to minimize the development time for new products, Geberit International AG manufactures many prototypes using 3D printing. Since 2016, the Swiss company uses a Sintratec S1 for design optimization and material testing in its prototyping laboratory. A visit to Switzerland.

Geberit: „Selective Laser Sintering Really Sparks our Imagination“

Anlagen Selektives Lasersintern, Kunststoff

Sanitary Prototypes with  High Requirements

3D printing is a fast-growing market, opening up completely new product and manufacturing options for customers and industry. The newly developed SEAM process significantly extends the options for the efficient manufacture of printed components. An impression of this is conveyed by the example of a fiber-reinforced clamping fixture.

Additive Manufacturing of Plastic Components in a High-Speed Process Using Standard Pellet Stock

3D-Drucker (für FDM, FFF, etc.)

Faserverbundwerkstoffe

Ultrafast 3D Printing

Ineos Styrolution announced first results of the PolySLS project, which is focused on developing a new energy saving styrenics based material for additive manufacturing, otherwise known as „3D printing“.

Technik Trend

kunststoffe-international.com

Polystyrol

Thermoplaste

Kunststoff-Erzeugung

Energy Savings with Styrenics Polymer Tailored for 3D Printing

In no other field the possibilities and advantages of 3D printing are more pronounced than for medical devices. With the right high-performance materials, complex patient-customized implants can be produced that medical doctors are using to push the boundaries of the possible – for the benefit of patients.

New Ways for Production of Plastic Implants by 3D Printing

Custom Implants from the 3D Printer

Besides compounds modified for special applications and lightweight components, sustainable materials are also becoming an increasingly important focus. In the additives sector, too, recyclates, the circular economy, and reprocessing are now playing a key role.

Not only Polymers but also Additives and Masterbatches Must Be Sustainable

Zubehör / Hilfsmittel Wärmebehandlung

Wärmebehandlung

Compound

PVC-Additive

Masterbatches

Additive

Vernetzungsmittel

Farbstoffe und Pigmente

Compoundeure

Dienstleistungen

Handel

PVC-weich (Compounds)

Farbkonzentrate (Batches)

Farbstoffe

Verarbeitungshilfsmittel, allgemein

Flammhemmende Mittel, allgemein

Betriebsausrüstung / Betriebsmittel

Verarbeitungshilfmittel

Filamente für additive Verfahren

Flammschutzmittel

Gleitmittel für Kunststoff

Attention to Detail

New developments by the raw material producers are responding to current application trends. Requirements are changing due to the advent of networked and semi-automated electric vehicles and the different mobility infrastructure. Products for digitalization and energy and resource efficiency are also moving center stage.

New Mobility Forms and Digitalization Are Shaping the Development of Engineering and High-Performance Plastics

Polyetherketon

Polyacrylate

Oberflächenbeschichtung

Holz

Hybridwerkstoffe

Polyacetale

Verbundwerkstoffe / Werkstoffverbunde

Polyamide

Oberflächentechnik

Oberflächenveredelung

Lohnfertigung

Polycarbonat

Technology Made Easy

A new series of extremely soft TPEs have a soft surface similar to human skin.

Kraiburg TPE Presents Its Next Generation Supersoft TPEs

Thermoplastische Elastomere

For Extremely Soft Applications

Semifinished products made of metal and plastic can be joined after suitable surface modification of the metal component by thermal joining processes to form an integral part. In doing so there are no constraints with regard to the possible shape from the injection molding process. 

Verbindungstechnik, hybride

Thermal Joining Processes: Hybrid Joints 

Selected plastic-metal joints can be produced with high strength using thermal joining methods. The fundamental principles for an improved process compared with the joining methods to date have been developed with the framework of a Cluster of Excellence at RWTH Aachen University. This method opens up new design possibilities, in particular for lightweight construction. 

Laserschweißen

Lightweight Construction: A Strong Connection of Unequal Partners 

The basic principle of hybrid technology, which is already well known from injection molding, has now been applied to thermoforming. The objective of this is to provide a cost-effective means of manufacturing small numbers of polymer/metal composite components, especially those with large areas and thin walls. 

Warmformen / Thermoformen

Hybrid Technology: Integrating Functions 

3D Printing with Pellet Extruded Plastics on Metal

Plastic-Metal Hybrid Cuts Costs and Time in Additive Manufacturing

Additive manufacturing processes count as future-oriented manufacturing techniques. Numerous studies and award-winning demonstrators underline the interest of the industry. Nevertheless, up to now there are only a few plastic-based applications with significant quantities. Today, screw-based additive manufacturing is a solution for the economic and technical challenges and has the potential for series production.

Additive manufacturing processes count as future-oriented manufacturing techniques. Numerous studies and award-winning demonstrators underline the interest of the industry.

The debate surrounding the conditions for cost-effective and scalable additive manufacturing processes is currently dominated by a certain amount of wishful thinking. In many cases, the feasibility of a specific realization can be called into question as from the very beginning of the project due to the lack of an economic basis and the high requirements on the mechanical properties of the components. Certainly, additive manufacturing offers advantages in terms of tool maintenance, flexibility, freedom of design and functional integration. However, the simple fact remains that the transfer to mass production is never carried out if the resulting production costs per part exceed the current possibilities of a mold-based process. We also need to break free from the mindset of manufacturing current injection molding designs with a 3D printer. Like any production process, additive manufacturing processes require specific designs to reach their full potential.

In this situation, a team of scientists at the Institute for Plastics Processing (IKV) at RWTH Aachen University, Germany, developed a screw- and robot-based additive manufacturing process and introduced it for the first time during the Plastics Technology Colloquium 2016 in Aachen <a href="http://[1]">[1]</a>. This concept was applied by Yizumi Germany GmbH, Alsdorf, Germany, involving the same research team, and was industrialized into a scalable production system.

The technical key element is a lightweight extruder weighing only 7.5 kg. It can still be used to process all common materials from PMMA and PC to PP and PA – with and without fiber reinforcement. At the same time, the lightweight construction approach also allows for small robot sizes to be used. Their range is usually more than sufficient.

Using Strand Shapes to Systematically Influence Anisotropy

Considering the required mechanical properties, the use of fiber-reinforced plastics is particularly beneficial for structural 3D-printed components. The use of pellets enables a higher content of reinforcing materials compared to other additive manufacturing processes. All manufacturing processes influence the fiber orientation and therefore the mechanics of a plastic part. Due to the excellent mechanical and rheological properties as well as the high thermal conductivity, which contributes to the dissipation of heat during layer composition, carbon fiber-reinforced materials are highly suitable for a fast additive manufacturing process. A carbon fiber-reinforced polyamide 6 (grade: Akromid B3 ICF 30 9 AM black (7451); manufacturer: Akro-Plastic GmbH, Niederzissen, Germany) is used in the following investigations.

By adapting the processing, the anisotropy of the mechanical properties can be significantly influenced. An anisotropic behavior is influenced by the parameters of the selected nozzle diameter as well as the ratio of feed rate and mass flow relative to the nozzle diameter.

Three different types of strand shaping can be defined. This means that we are dealing with either a preceding melt, a drawn melt or an intermediate state. Based on these boundary conditions, the fiber and molecule orientation of a drawn melt is stronger than that of an preceding melt.

Examining the flexural modulus and flexural strength, a significant increase in the mechanical properties can be seen with increased nozzle diameter at identical strand width (Fig. 1). Due to the increased anisotropy, the 3D-printed test specimens reach the property range of injection molded parts.

Why Does 3D Printing Plastics  Need Metal?

The integration of metal components in 3D-printing is advantageous for several reasons. Firstly, hybrid structures offer the opportunity to use materials according to requirements. Secondly, flat structures, which can only be printed inadequately by hatching operations, can be easily integrated. The flat, aerial pattern is simply added to the process as a semi-finished product.

This also replaces the necessary building platform management. The “building platform” remains in the part as a functional component. Thirdly, both aspects save time and money. Apart from additive manufacturing on metal sheets, the hybrid process also opens up the option of direct manufacturing on three-dimensional structures (metallic or polymer).

In a first step the required metal sheets are coated with a storage-stable plasma-polymerized adhesion modifying layer using the PST process (Plasma-SealTight) developed by Plasmatreat GmbH, Steinhagen, Germany, and Akro-Plastic GmbH. The process is successfully used in injection molding to produce high-strength plastic-metal bonds [2, 3]. The metal sheet can then be printed on directly after the coating.

At this point, it is important to ensure a sufficient contact temperature between the sheet metal and the melt. A variothermal fixture is required for this. In contrast to variothermal injection molding, it can be very compact and feature heating elements close to the surface, since the forces on the mold are much lower than in injection molding.

The processes can be combined with different metals <a href="http://[2]">[2]</a>. In an initial process evaluation, an aluminum alloy and stainless steel were used to produce beam structures and the test specimens used in the following investigations <a href="http://[4]">[4]</a>. However, to evaluate the mechanical potential of the plastic-metal hybrid bond, it is necessary to investigate the influencing parameters.

Approach to Analyze the  Mechanical Properties

In order to investigate the influences of the combination of processes and materials on the mechanical properties of 3D-printed plastic-metal hybrids, test specimens for three-point bending tests were developed in accordance to DIN EN ISO 178. The plastic component of the test specimens consists of a closed contour of four parallel strands over the entire test area. The height of the test specimen is set at 10 mm.  To reduce the influence of shear stress on the layered test specimens, the length to height ratio was defined to 25 <a href="http://[5]">[5]</a>. Plastic test specimens and hybrid test specimens fitted with 1mm thick stainless steel inserts were used in testing (Fig. 2).

To assess the process influences of 3D-printing, the nozzle diameter is varied at constant strand width during the production of the plastic specimen. As part of the experimental design, the peak temperature of the variothermal fixture is also varied. The surface temperature of the metallic insert was set to 175 °C, 190 °C and 220 °C. During the production of the plastic test specimens, the variothermal heating with a peak temperature of 175 °C is maintained on the surface of the fixture.

The plastic and hybrid test specimens are tested in a three-point bending with a span of 200 mm and scaled test speed. The force is applied both on the substrate side and on the side facing away from the substrate, so that the metal inserts are loaded in tension or compression.

Mechanical Properties at  an Optimal Level

The temperature influences of the metal insert on the mechanical properties of plastic-metal hybrids are shown in the results (Fig. 3) and exemplary force/displacement curves (Fig. 4). The data shows a high consistency with minimal scattering of the maximum force. Due to the negligibly small standard deviation the processing is regarded to be robust.

The achieved maximum force, which is almost twice that of a plastic part, illustrates the mechanical potential of 3D-printed plastic-metal hybrids. Moreover, this is also reflected in the increased stiffness of plastic-metal-hybrids (Fig. 4). On the other hand, it can be seen that the flexural strength does not increase significantly above an insert temperature of 175 °C, irrespective of the type of load on the metal component. Thus, excellent bonding behavior is achieved over a wide temperature range.

However, the fracture behavior varies considerably throughout the temperature range, as the various temperature and load-dependent strain at break illustrates. At the same temperature (175 °C), when load is applied to the metal component, the plastic component fails in the extreme outer fiber under tensile load resulting in a migrating crack through the plastic at the slightest deflection. The bond between metal and plastic remains intact.

When load is applied to the plastic component at the same temperature, the applied force leads to plastic deformation of the metal component. The failure in turn occurs in the plastic under tension and thus in the interface between metal and plastic. This results in a complete separation of the plastic component (Fig. 5).

The fracture patterns indicate a well-developed bond between plastic and metal. The residues on the metallic surface after test show that the failure occurs in the plastic component.

With an increased insert temperature of 220 °C, the failure mode changes. It is remarkable here that the deflection nearly triples until the total failure of the test specimen (Fig. 6).

With regard to stiffness and the progression before reaching the force maximum, the test characteristics of specimens at higher temperatures largely match the lower temperature levels (Fig. 4).

The fracture mechanics are also impressive at the macroscopic level. Here, too, plastic deformation of the metal component occurs. The fracture also starts at the interface between plastic and metal. However, the bond remains intact. This means that initial failure does not occur between the layers of the 3D-printed plastic, but perpendicular to the direction of the buildup up to the neutral fiber. Further and complete failure is caused by compressive stresses.

As shown, the process for producing a plastic-metal hybrid component can be easily automated (Fig. 7).

According to the investigations, the bonding strength between metal and plastic via the plasma-polymerized adhesion layer is very high and the resulting parts exhibit improved mechanical properties compared to solely plastic parts.

In addition, the hybrid approach to additive manufacturing also offers economic advantages in comparison to conventional approaches in injection molding. A reduction in component costs of 10 % for the demonstrator (Title figure) shown clearly demonstrates the economic potential of additively manufactured plastic-metal hybrids.

Akro-Plastic GmbH  

https://www.akro-plastic.de

Ausgabenartikel

The bicycle frame (600 g, produced in 80 min) is printed directly onto a metal sheet. This combination unites the advantages of two worlds

Fig. 1. Increasing nozzle diameters have a positive effect on the anisotropy of mechanical properties in the part

Fig. 2. Test set-up: variothermal fixture in production area of a SpaceA manufacturing unit, temperature load cycle and test specimen geometry

Fig. 3. Maximum load at different insert temperatures. This demonstrates the strong bond between plastic and metal over a wide temperature range

Fig. 4. Force-deformation chart of the tested specimens. The hybrid structure increases the stiffness and strength compared to plastic-only test specimens

Fig. 5. Testing of the hybrid part: initial position (force applied to the metal component on the left, force applied to the plastic component on the right), maximum deflection of the test specimen and failure with fracture mode (insert temperature 175 °C)

Fig. 6. Test in starting position (force application to the plastic component), maximum deflection of the test specimen and failure with fracture mode (insert temperature 220 °C) 

Fig. 7. A modular plant strategy allows scaling (here the largest model SpaceA 2000–500-S) and integration of all known automation concepts

Name - Hauptartikel

Dipl.-Ing. Thilo Stier is Global Sales Director & Innovation Manager at Akro-Plastic GmbH, Niederzissen, Germany

Michael Rieck, <a href="http://M.Sc">M.Sc</a>. RWTH, is Business Development Manager at Akro-Plastic; <a href="mailto:Michael.Rieck@akro-plastic.com">Michael.Rieck@akro-plastic.com</a>

Dr.-Ing. Nicolai Lammert is Head of Business Unit Additive Manufacturing at Yizumi Germany GmbH, Alsdorf, Germany; <a href="mailto:N.Lammert@yizumi-germany.de">N.Lammert@yizumi-germany.de</a>

1 Hopmann, C.: Additive Fertigung in der Kunststoffverarbeitung. In: Hopmann, C. (Hrsg.), Integrative Kunststofftechnik 2016. Umdruck zum 28. Internationalen Kolloquium Kunststofftechnik. Aachen, Februar 2016, 978–3–8440–4033–3

2 N. N.: PST Der besonders haftungsstarke Hybridverbund. Firmenschrift der Akro-Plastic GmbH, URL:https://akro-plastic.com/de/prozess-und-technologie/plasma-sealtight/

3 Melamis, A.: Ultra-Strong and Media-Tight. Kunststoffe international 106 (2016) 6–7, pp. 8–13

4 Heinz, C.; Lammert, N.; Stier, T.; Unger, N.: Additive manufacturing based on screw extrusion – Applications, machines and materials in the automotive industry. PIAE, Mannheim 2020

5 Grellmann, W.; Seidler, S.: Kunststoffprüfung. 3. Aufl. Hanser, München 2015

Read the German version of the  article in our magazine Kunststoffe or at  <a href="http://www.kunststoffe.de">www.kunststoffe.de</a>