Over past months, many in-house workflows and development processes have slowed down and also changed. Nevertheless, time has not stood still, also not in injection molding technology. The debate and development have been shaped by two themes: digitalization and the circular economy. Below are some examples of developments and projects that underpin this trend.

Two displays are seamlessly integrated into the continuously 3D-formed instrument panel

Innovative Injection Molding in Times of Pandemic

Spritzgießen

Kunststoffverarbeitung: Verfahren

Schaumspritzgießen

Künstliche Intelligenz für die Qualitätssicherung

Industrie 4.0

Industrie 4.0 für die Qualitätssicherung

Steuern, Regeln

Software

Mehrkomponenten-Spritzgießen

Folientechnik (IMD, IML, FIM, u.a.)

Digitale Transformation

Wirtschaft

Innovationen und neue Technologie

Spritzgießwerkzeuge

Kunststoffverarbeitung: Maschinen und Komponenten

Werkzeuge für die Kunststoffverarbeitung

Biokunststoffe

Kunststoff Werkstoffe

Spritzgieß-Sonderverfahren

Nachhaltigkeit

Umweltmanagement

Spritzgießsimulation

Simulation

Schnecken und Plastifiziersysteme

Spritzgießmaschinen

Industrie 4.0 für die Kunststoffverarbeitung

Machine Learning / Künstliche Intelligenz für die spanende Fertigung

Industrie 4.0 für die spanende Fertigung

Kunststoff-Recycling

Kunststoff-Aufbereitung

Lasermarkieren

Oberflächentechnik

Laserbearbeitungen

Inline- / Online-Messsysteme

Qualitätssicherung

Qualitätssicherung Kunststoff

Kreislaufwirtschaft

There Is More beyond the Horizon

To be able to cost efficiently design complex molds, e. g. for BMC components, it is essential to take into account the mold cooling. Thus, the mold costs increase in a linear relationship with the number of heating cartridges provided. It is therefore desirable to aim for as few cartridges as possible, but at the same time, this can have a disadvantageous effect on the homogeneity of the temperature distribution and the robustness of the process. Until now, these conflicting goals were largely resolved based on experience. But it can also be done systematically. 

Simple Answers to Complex Questions in Mold Design 

Verbundwerkstoffe / Werkstoffverbunde

Temperiertechnik

DOE-Software

Determining the Optimum Heating Concept for BMC 

The toolmaker Siebenwurst uses injection molding simulation to optimize part design and production processes in its routine workflows. Among other things, Simcon’s software ensures the quality and dimensional accuracy of the plastic frame for the first series-produced injection molded e-bike.

The frames give the e-bikes an extraordinary design, with robustness comparable to steel or aluminum

Controlling Complex Development and Manufacturing Processes, Using Simulation

Composite-Halbzeuge

Halbzeuge und Zwischenprodukte

Kunststoff-Halbzeuge

Dienstleistungen

Werkzeug-, Formen- und Modellbau

A Bike Frame from an Injection  Molding Machine

Anyone seeking to replace a metal component by a plastic one, to reduce the number of component parts from eight to three and simultaneously cut both the weight and manufacturing costs needs to take great care to ensure that all specifications are met – especially if the component is used in a hot gearbox and is subject to high mechanical stress.

The shifter fork creates a positive lock between the gear wheel and the shaft so that the engine power can be transmitted to the wheels

Production-Ready Plastic Shifter Fork Offers a Maximum of Functional Integration

Kohlenstofffasern / -matten

Verstärkungsstoffe

Produktentwicklung (F+E)

Innovationsentwicklung

Inserttechnik

Hybrid-Spritzgießen (Metall / Kunststoff)

Replacing Metal in the Gearbox

In addition to excellent mechanical characteristics and suitability for recycling, the key feature of hybrid lightweight structures made of fiber-reinforced thermoplastics is that automated, large series production is possible. New mold and process technologies were successfully developed within the scope of the ReLei research project, enabling the production of complex shaped sandwich elements in an efficient combined process.

In the ReLei project, several research and industry partners developed a rear shelf based on a fiber-reinforced polyamide as an example for manufacturing a complex sandwich structure

Thermoplastic Sandwich Structures for Large Series Applications

Fasern

Faserverarbeitung

Industrieroboter

Montagetechnik

Faserverbundwerkstoffe

Andere Werkstoffe

Making It Big with Small Bubbles

In the realm of virtual product development, the idea of the cycle has been around for many years. But where does the cycle begin? When we take a closer look at this concept, new aspects rightly start to emerge.

Fig. 1. Stress-strain diagram as a function of microstructure. Shown are three different porosities (5 to 15 %) relative to the compact material

When Traditional Approaches Meet their Micromechanical Counterparts

Werkstoffprüfung, mechanisch

Messtechnik

Werkstoffprüfung

Analysetools, FEM

Produktentwicklung(sprozess)

Qualitätsmanagement

Cracking Product Development

Overmolded thermoplastic composites can give affordable weight savings for automotive applications. However, robust predictability procedures for these new materials are not yet state of the art. For this reason, Sabic has developed a test component that can be produced in a representative production process, and is able to validate predictions for all of the many different composite failure modes. To improve the simulations even further, an integrated simulation approach – one which takes into account the effects of processing on the material performance – is used. 

A New Test Beam Design Is Capable of Testing Different Composite Failure Modes 

Biegeprüfmaschinen

Zug-und Druckfestigkeitsprüfgeräte

Confidence in Composite Simulations 

In the second part of the series, calculations were carried out on the throughput behaviour, pressure build-up capacity and the melting process on the basis of an exemplary geometry. These results are now to be examined in more detail and subsequently optimized.

Through empirical tests and simulation-supported test series, a screw can be designed in a tailor-made manner for the respective application 

Part 3 of the Series Deals with the Tests to Optimize the Screw Geometry

Spritzgießmaschinen, allgemein

All about Plasticizing Screws

Zahoransky Automation & Molds GmbH has entered into a partnership with the Swiss company Kebo AG. The result of this collaboration is a new mold concept for the production of pipette tips, which features a double quick-change system.

If a core breaks during production, it can be replaced quickly

Messe Fakuma

kunststoffe-international.com

Medizintechnik

Double Quick-Change System Speeds up Production

SPS – Industrial Automation Fair (SIAF) Guangzhou and Asiamold, the first China fairs to be hosted by Messe Frankfurt in 2021, concluded on 5 March after three days, with the visit number increasing an impressive 27% to 63,968.

Sensorik für Werkzeugmaschinen

Verfahren für die additive Fertigung

Kunststoffverarbeitung

Lohnfertigung

SIAF Guangzhou and Asiamold Conclude Successfully

The consumables required for In-vitro diagnostics are manufactured in a production process that is subject to high requirements in terms of precision and quality, but also the complex cleanroom manufacturing environment. This has implications for the entire plant technology – especially toolmaking.

64-cavity tool for pipette tips. The hot runner system is balanced across all cavities

Strategic Approach through Classification according to Product Groups

Werkzeug- und Formenbau

Medizinprodukte

Mold Platforms for IVD Consumables

The fifth broadcast by arburgXvision was all about the exciting question of how productivity can be optimized by bringing together technology, organization and digitalization in the ideal manner.

Christoph Kiefer, Team Manager Technical & Commercial Sales Support (left), and Dr Thomas Walther, Head of Application & Process Development (center), had a discussion with presenter Guido Marschall on how to increase production efficiency by taking advantage of “hidden benefits“

Automatisierungstechnik

5. arburgXvision: „Savings through Hidden Benefits!“

In the injection molding of engineering plastics, mold temperature control consumes more than one third of the total energy input. A novel technology offers the opportunity to reduce this continuous major cost factor – and eliminate hotspots.

Fig. 1. The temperature control units have the highest energy share in the injection molding process

Source: M. Schläger et al [2]; graphic: © Hanser

Reduced Energy Consumption and Shorter Cycle Times due to Structurally Integrated  Heat Pipe Mold Cores

Cooling with Heat Pipes

Aside from offering high mechanical strength, versatility and durability, polymer materials are ideal for applications in the electrical industry because of their ability to isolate electrical current.

For the conduction cooled MicroTCA systems, Harting processes LCP, a material that is flame-resistant, dimensionally stable at high temperatures, chemically resistant, and has only a low thermal expansion

Connectors for Industrial Lifelines: High-Tech Injection Molding at Harting

Hybridtechnik

Polymere, flüssigkristalline

Thermoplaste

Heißkanalsysteme

Komponenten für die Kunststoffverarbeitung

Stanzen

Verfahren für die spanlose Fertigung

Schneiden

Steckverbinder

Elektromechanik

Well-Balanced Hot Runner Technology for LCP Processing

iQ process observer, the new process monitoring platform from Engel monitors hundreds of parameters from the injection molding cell in the background.

The injection molder is truly not a friend of changes – if they occur in the running process. The iQ process observer helps him to keep an eye on the process and thus keep a handle on the quality

A Process Monitoring Platform Monitors Several Hundred Parameters Simultaneously

Steuerungen (Hardware und Software)

Prozessvisualisierung

Condition Monitoring / Prozessüberwachung

Instandhaltung

IoT-Plattformen für die Kunststoffverarbeitung

An Eye on the Process –  a Handle on Quality

Design Methodology for Parts Subject to Internal Pressure

Mold System with Rotating Core Improves Mechanical Properties

Internal pressure loads are typical for fiber-reinforced plastic components. To increase the burst strength of components, the fiber orientation can be modified in a targeted way during injection molding by means of a rotating mold core. A newly developed simulation method allows this modified fiber orientation to be taken into account at the design stage.

During injection molding of fiber-reinforced polymers, the prevailing flow conditions create a layered structure in which the fibers are oriented in the flow direction at the outer region and transverse to the flow direction in the core [1, 2]. The resulting anisotropic mechanical properties lead to a part stability that is dependent of the position of the gate point [3]. Elongated, rotationally symmetrical parts under internal pressure load are usually filled in the axial direction due to manufacturing restrictions, and most of the fibers are therefore oriented in this direction. However, the internal pressure load leads to stresses in the tangential direction – the fiber orientation and the main loading direction therefore differ and the material is not optimally utilized.

This is where the mold system with rotating core (Fig. 1) comes in [4–6]. Due to the relative movement in the mold, the rotation of the mold core leads to shearing of the melt in the tangential direction. This shearing is superimposed on the injection-induced shearing in the flow direction and allows the reinforcing fibers to be reoriented – depending on the ratio between that shearing induced by injection and that by rotation. This influences fiber orientation so as to have a positive effect on the mechanical properties and improve the burst strength [6, 7].

In order for the potential of this manufacturing process to be exploited, the fiber orientation must also be taken into the structural simulation. In the state of the art [8], the fiber orientation from the injection molding simulation is used as an input parameter in the design of short fiber-reinforced components for calculating the anisotropic properties. In the mold system with rotating core, this is not possible because it is not yet possible to simulate the influence of the relative motion on the fiber orientation. The plastics-CAE and fiber composites lab at the University of Osnabrück, Germany, in cooperation with RIA-Polymers GmbH, Zimmern o.R., Germany, and Helmut Sundermeier GmbH, Hüllhorst, Germany, have developed a design methodology that uses the measurement data for fiber orientation to allow an initial estimation of the part properties.

To quantify the effect of rotation on the fiber orientation, the cup-shaped demonstrator (Title figure) with a length of 100 mm, an outer diameter at the end of the flow path of 57 mm and a variable wall thickness between 1.5 and 3.5 mm was investigated at varying rotational speeds. Here, the mathematical description of the fiber orientation is performed via the fiber orientation tensor [9], which can be determined, e.g., by evaluating microscopic photographs [10, 11]. The fibers in these sections are visible in the polished surface as ellipses, whose form depends on the orientation of the fibers in space. The principal axes and the tilt angle of the ellipses can be determined with image analysis algorithms, and used for calculating the orientation tensor. This microsection method was used to analyze the fiber orientation in the flow path center, and to determine the average orientation components, as well as the orientation profile across the wall thickness.

In a short fiber-reinforced polypropylene (PP-GF50, grade: Rialene P100 SGF50; manufacturer: RIA Polymers), the tangential degree of orientation can be significantly increased with increasing rotational speed (Fig. 2 left). With a wall thickness of 2.5 mm, it is possible to increase the tangential degree of orientation from 0.32 to 0.73. In the profile through the relative wall thickness (Fig. 2 right) it can be seen how the local microstructure changes. For unrotated samples, the familiar layer structure, consisting of outer and center layers, can be clearly seen. For a rotation of 0.95 s-1, the center layer is significantly broadened. A further increase of the rotational speed has the result that the actual layer structure is no longer present and the microstructure is dominated by the tangential degree of orientation across the entire wall thickness.

This information is now available for all measurement points and allows the orientation profile to be interpolated for further rotational speeds and wall thicknesses, and to be transferred to the simulation after suitable discretization.

For the development of the simulation methodology, the software program Converse was used for material modeling and S-Life Plastics for strength calculation (Part Engineering), since they offer an open data structure. Together with the structural simulation software Abaqus (Dassault Systèmes), it is thus possible to take into account the measured fiber orientation and perform the first structural-mechanical simulations with anisotropic material charts from Converse.

The new simulation methodology (Fig. 3) differs significantly in the manual assignment of the fiber orientation from the technology currently used for simulation of short fiber-reinforced injection-molded parts [8]. For this, the part must first be split into n layers, which should have a constant proportion of the overall wall thickness. Based on the present measured values, the profile of the fiber orientation for a given rotational speed can now be interpolated across the wall thickness. On the assumption that the fiber orientation is constant over the entire part length, and the principal orientation direction lies only in the axial or tangential direction, the tensor components of the fiber orientation that are necessary for the micromechanical computation are assigned to each of the n layers.

The same material charts from Converse can subsequently be used, which are also used for designing normal injection molded parts. Finally, the actual structural simulation and the strength analysis with S-Life Plastics are performed using a stress-based Tsai-Hill criterion [8], which takes into account the local orientation state.

The methodology was validated with the aid of burst pressure tests on the PP-GF50 (Fig. 4), at the same measuring points as the fiber orientation measurements. The test results demonstrate the significant increase of strength produced by reorientation of the fibers. It increases with increasing rotational speed and can be raised by over 100 % for all wall thicknesses. For a wall thickness of, for example, 2.5 mm, the strength can be increased from 57.5 bar to 120.2 bar.

The use of the simulation methodology for simulating the bursting pressure tests demonstrates that the increases in strength can be readily modeled in this way. In addition, it is possible to calibrate material charts with these simple component tests, which are then used for designing further components subject to internal pressure.

Practical Realization of a  Pressure-Loaded Component

The first practical application of this design methodology was a pressure-loaded component from the mobility sector (Fig. 5). In the load case presented here, pressures at various levels act along the component, from inside and outside, at a temperature of 80 °C, with a maximum pressure of 23 bar. For this, a reference with the fiber orientation from the injection molding simulation (unrotated) as well as a component with an interpolated fiber orientation at 2.2 mm wall thickness and a rotational speed of 4.5 s-1 were simulated. The Tsai-Hill criterion were used to calculate the anisotropic utilization degree, which predicts failure at values greater than 1. Since, according to the requirements profile, the component is required to have a safety factor of 2, the unrotated part would not withstand the stresses with a utilization of 1.8. Due to the rotation of the mold core, the material utilization can be reduced by 50 % to 0.9.

A mold system with rotating core allows significant influencing of the fiber orientation in the component and a significant increase in the burst strength of components subject to internal pressure loads. In the case of the PP-GF50 investigated here, it was possible to show how, with increasing rotational speed, the axial orientation component decreases and the tangential increases. This change of fiber orientation leads to an increase in the burst strength of over 100 %, almost independent of the wall thickness.

To allow the modified fiber orientation to be taken into account in component design, a simulation methodology was developed and validated on burst strength tests on a demonstrator. When the methodology is transferred to a practical component, it is found that components can be developed that would not meet specifications if produced by conventional injection molding. This illustrates the great potential of this manufacturing process and the practical relevance of the design methodology.

[1] Schröder, T.: Rheologie der Kunststoffe. 1. Aufl. Hanser, München 2018

[2] Johannaber, F.; Michaeli, W.: Handbuch Spritzgiessen. 2. Aufl. Hanser, München 2004

[3] Beaumont, J.; Sambale, H.: Auslegung von Anguss und Angusskanal: Spritzgiesswerkzeuge erfolgreich einsetzen. 2. Aufl. Hanser, München 2020

[4] US Patent US5798072: Process for moulding thermoplastic material by injection onto a rotating core (1998) Dehenau, C. et al.

[5] DE Patent DE696 13 283 T2: Verfahren zum Spritzgiessen von thermoplastischem Kunststoff auf einem drehenden Kern (2002) Dehenau, C. et al.

[6] Warkoski, G.: Das Spritzgiessen von verstä¨rkten Polymeren mit rotierendem Kern. Gummi, Fasern, Kunststoffe 06 (2006), pp. 439–443

[7] Land, P.; Krumpholz, T.: Targeted Manipulation of Fibre Orientation Through Relative Movement in an Injection Mould. In: Hopmann, C.; Dahlmann, R.: Advances in Polymer Processing 2020. Springer Vieweg, Berlin 2020

[8] Stommel, M.; Stojek, M.; Korte, W.: FEM zur Berechnung von Kunststoff- und Elastomerbauteilen. 2. Aufl, Hanser, München 2018

[9] Advani, S.; Tucker, C.: The Use of Tensors to Describe and Predict Fiber Orientation in Short Fiber Composites. Journal of Rheology 31 (1987) 8, pp. 751–784

[10] Bay, R.; Tucker, C.: Stereological measurement and error estimates for three-dimensional fiber orientation. Polymer Engineering & Science 32 (1992) 4, pp. 240–253

[11] Vélez-García, G.; Gregorio, M. et al.: Unambiguous orientation in short fiber composites over small sampling area in a center-gated disk. Composites Part A: Applied Science and Manufacturing 43 (2012) 1, pp. 104–113

Fachhochschule Osnabrück  

https://www.fh-osnabrueck.de

Ausgabenartikel

Practical implementation of a mold system with rotating core.

16:9

Fig. 1. The superimposition of the injection-induced axial shearing by the tangential shearing due to the rotation selectively influences the fiber orientation in the tangential direction due to the rotation.

Fig. 2. The rotation core can produce an increase in the tangential orientation component almost independent of the wall thickness (left). At correspondingly high speeds, the tangential fibers dominate the microstructure across the entire thickness (right).

Fig. 3. The layer-by-layer assignment of the fiber orientations, with the aid of Converse and S-Life-Plastics, enables the anisotropic structural simulation of rotated components

Fig. 4. Application of the simulation methodology allows, for the first time, the increased  bursting strength due to rotation of the mold core also to be taken into account in the design  of new components.

Fig. 5. This application case shows a significant reduction of the utilization ratio due to manufacturing with a rotating core.

Name - Hauptartikel

 <b>Prof. Dr.-Ing. Thorsten Krumpholz</b> has been head of the plastics-CAE and fiber composites laboratory at the University of Osnabrück, Germany, since 2012;  <a href="mailto:t.krumpholz@hs-osnabrueck.de">t.krumpholz@hs-osnabrueck.de</a>

<b>Philipp Land, M. Sc.</b>, has been a research assistant in the laboratory of plastics CAE and fiber composites at the University of Osnabrück since 2016.

The project (FKZ: ZF4153410TA9) is sponsored by the Federal Ministry for Economic Affairs and Energy (BMWi) as part of the “Central Innovation Program for SMEs (ZIM)“. The joint project by the University of Osnabrück, RIA Polymers GmbH and Helmut Sundermeier GmbH is supported in an advisory capacity by Uwe Becker, CEO of MKS-Kunststoffspritzguss GmbH, Lüdenscheid. Thanks are also due to Arburg GmbH + Co. KG, Lossburg, Germany, for providing an injection-molding machine for the investigations and Part Engineering GmbH, Bergisch Gladbach, Germany, for support in implementing the simulation.