For a cutlery series made of a new biopolymer, three full hot runner molds with digital process monitoring were developed in close cooperation with mold maker Uniform and hot runner specialist Ewikon.

The 16-drop family mold on the machine. The removal and packaging of the parts are fully automated

16:9

Complete Digital Hot Runner Solution for Automated Biopolymer Processing

Spritzgießen

Kunststoffverarbeitung: Verfahren

Condition Monitoring / Prozessüberwachung

Instandhaltung

Spritzgießwerkzeuge

Kunststoffverarbeitung: Maschinen und Komponenten

Werkzeuge für die Kunststoffverarbeitung

Biokunststoffe

Kunststoff Werkstoffe

Virtual Reality für die Qualitätssicherung

Industrie 4.0

Industrie 4.0 für die Qualitätssicherung

Heißkanalsysteme

Komponenten für die Kunststoffverarbeitung

Process Reliability Is Crucial

Family molds belong to the state-of-the-art in injection molding – at least when wall thicknesses and volumes of individual components vary considerably. Using a trial mold soon ready for series production, Synventive demonstrates that – though demanding – optimal process control can be achieved using the right technology. The filling of each mold cavity is controlled individually and in real time. The Kunststoffe editorial team were among the first guests at the new Tech Center.

View into the mold space of the Engel Duo 2700 at the Tech Center. In the background, a 6-axis robot with 180 kg load-bearing capacity which removes the components.

Single-Shot Injection Molding of Heterogeneous Components

Schröder, Susanne

Leading-Edge Process Control

The new “Heat-Inject” product from Incoe International Europe stands out in that it uses the hot runner system as a carrier platform, but instead of melt, it brings heat into the cavity.

The heat pulse from heat-inject ensures good surface quality where a weld line may otherwise be visible due to the part geometry and gating.

Targeted Heat Pulses in the Cavity

Nowhere are the demands imposed on materials higher than in the area of medical technology. That is understandable because, after all, what is ultimately at stake here is the patient’s health. But any materials manufacturers seeking to use hot runner technology to process polymers in compliance with strict directives and differentiated legal regulations also need the expertise possessed by the hot runner manufacturer’s application engineers.

Günther has recently installed two new injection-molding machines for customer trials in its technical center.

Testing the Processing Limits of Modified POM Copolymer

Polyoxymethylen

Thermoplaste

Normalien und Heißkanaltechnik

Medizintechnik

Looking over the Application  Engineer’s Shoulder

With immediate effect, a new generation of compact linear servo motors is available for Ewikon‘s electric needle valve systems.

Ewikon has now fitted the electric needle valve system with a new generation of compact linear servo motors.

Messe K-Kunststoffmesse

kunststoffe-international.com

kunststoffe.de

Servo Motors for Needle Valve Technology

Production systems for large molded parts can be flexibly and economically reconfigured or expanded using hot runner adapter plates.

Melt transfer from two on the side injection units of an Engel v-duo 2300 RTM into the middle of the hot runner intermediate plate mounted on the sliding table. 

Economical Solution for the Production of Thermoplastic Large-Structure Components

Co-Injektion (Barriere-/Sandwich-Spritzgießen)

Kunststoff-Rezyklat

Flexible Injection Solutions  with Adapter Plates

We look behind the cavity walls and along the data cable at what hot runner technology now offers in terms of mechanical, electronic and digital expertise.

The smart Control monitoring unit permits integrated monitoring of the injection molding production cell, including the mold, hot runner system and all ancillary components. The “Luer connector” application case was on show at K 2022.

State-of-the-Art Injection Molding Solutions at K 2022: Hot Runner Technology

Doriat, Clemens, Dr.

Mikrospritzgießen

Digitale Transformation

Wirtschaft

Innovationen und neue Technologie

Mess-, Steuer- und Regelgeräte

Qualitätssicherung

Qualitätssicherung Kunststoff

Temperaturregler

Messtechnik

Sensoren / Messwertaufnehmer

Additive Fertigung

Everything under Control

Witosa is replacing titanium with 3D-printed steel elements in its hot runner systems. Its long-term goal is carbon neutrality.

Reducing the CCF through Titanium-Free Mold Constructions

Hot Runner, Carbon Neutral

Injection molding: Family molds can produce a wide variety of parts in a single shot. Where the challenges lie in process control.

Three at once: a six-axis robot removes the final injection-molded assembly, consisting of door trim, map pocket and sill.

One Tool, One Shot, Three Parts

Oerlikon HRSflow hot runner systems combine cost-efficient production of automotive parts with a precise process control.

Gate Insert for Difficult Process Conditions

Männer: The first steps towards automatically designing a flow-optimized flow-channel geometry by additive manufacturing of the hot runner manifold block.

Six-cavity mold with naturally balanced three-in-a-row layout instead of the conventional double-Y layout.

Three-Dimensional Melt Flow System in the Hot Runner Manifold Block

A low-build-height mini-valve-gate system allows the advantages of micro injection molding to be combined with those of valve gate technology.

Thanks to its low overall height, the new valve-gate system can also be accommodated in the confined space of a micro injection molding machine.

Medizinprodukte

The Great Art of Small Parts

A solution, which is unique in Europe, significantly increases productivity and comprises the production from a 12+12 stack mold with fully automated in-mold labeling and removal with visual 100 % inspection of the parts.

Before relocation to the production site, extensive functional tests and the final trial were carried out at the roth technical center

Fully Automated Production Line with Stack Mold and In-Mold Labeling

Award-Winning Packaging Solution Increases Productivity

Starting with the systematic design of manufacturing processes and the precise simulation of part manufacture, through smart tooling technology and sophisticated melt guidance, to efficient mold temperature control, numerous exhibitors have many innovations in the field of tooling technology on offer at K 2019.The current debates concerning marine pollution as well as anthropogenic climate change and its consequences seem to be having an effect at this world-leading trade show for plastics processing in Düsseldorf, Germany. A number of companies are noting the growing customer interest in sustainable, carbon-neutral and resource-efficient modes of production, and offering products and services intended to satisfy this interest.

Resource-Efficient and Environmentally Friendly Products Are the Trend in  Tooling Technology

Werkzeuginnendrucksensoren

Temperiergeräte

Gießanlagen

Temperiertechnik

Normalien für die Kunststofffertigung

Normalien

Spritzgießsimulation

Software

Simulation

Kaltkanalsysteme

Exhibitors See Green

The new Reverse Cube developed by Foboha manufactures various components or multi-component parts from varying materials in one step and assembles individual parts into finished products independently from the cycle time using an integrated handling robot. The automated process improves quality, accelerates cycle times by up to 40 % compared to separate injection molding and assembly processes, and thus enables substantial productivity gains at lower costs.

Two thermally separated cube molds rotate in opposite directions at a 90° angle. Bottom: injection and cooling of component 1 (roller made of PP) and component 2 (female connection made of POM), staggered by 180°

Manufacturing and Installing Multi-Component Parts on a Two-Part Cube Mold

Montage

Montagetechnik

Steuern, Regeln

Mehrkomponenten-Spritzgießen

Werkzeugtemperatursensoren

Industrieroboter

Spritzgießmaschinen

Reverse Rotation

While Processing Trials Proved Highly Successful, an Intuitive Feeling Is Required

Bio-Fed and Günther Heisskanaltechnik have performed various trials, which show that even supposedly sensitive bioplastics can be reliably processed in hot runner molds.

The Cologne-based compounder Bio-Fed and Günther Heisskanaltechnik GmbH of Frankenberg in Hessen, Germany, have performed various trials, which show that even supposedly sensitive bioplastics can be reliably processed in hot runner molds.

Biodegradable polymers that are manufactured from biomass are gaining in importance for formulating plastic compounds. Not least, they permit sustainable material designs to be realized. Nevertheless, their shear sensitivity poses a challenge for processing, in particular where thin-walled parts and slender hot runners are concerned.

One example of this is polyhydroxyalkanoates (PHAs), which are obtained through the microbial fermentation of carbohydrates and fats [1]. Under special conditions, they can be readily degraded by microorganisms at room temperature. The generic term PHA [2], covers a whole group of polymers with different structures (Fig. 1) and a wide bandwidth of mechanical properties. Annual production of these biopolyesters is predicted to increase from the current 50,000 t to 250,000 t by 2025 [3]. The low CO2 footprint and outstanding biodegradability of PHAs qualify them as ideal components for bioplastics, which perform their function as replacements for fossil raw materials in various applications [4].

To generate empirical values in the processing of such materials, Günther Heisskanaltechnik has performed trials on the grades M·Vera GP1012 (with natural fibers) and GP 1045 supplied by Bio-Fed. Both are home-compostable, PHA-based compounds consisting entirely of renewable raw materials that are high-temperature resistant (HDT>100 °C). They are also suitable for food contact.

The M·Vera compounds can be processed on conventional injection molding machines with a universal screw configuration. They have already been successfully used for various commercial applications, such as packaging or cutlery. However, special conditions must be observed: PHA compounds require moderate processing temperatures, and the melt temperature must not exceed 165 °C.

The low processing temperatures increase the melt viscosity and thereby the flow resistance, and higher injection pressures may therefore be necessary compared to standard thermoplastics. In addition, it is important to avoid high shear forces and long residence times that can lead to excess heat development and possible polymer degradation, in particular for thin-walled applications with conventional cold runners. In the mold design, nozzles, runners and gates with small diameters should be avoided, since they hinder the melt flow and increase the shear heat [5].

A rheometer analysis (Fig. 2) shows the influence of different melt temperatures on the viscosity of M·Vera GP1012. A viscosity drop of the material can already be observed at between 140 and 150 °C, indicating a smaller processing window compared with conventional polymers. During the cooling phase, PHAs crystallize fastest at 40 °C mold temperature, so that temperature control is important for an efficient cycle. The mechanical properties are not dependent on the temperature of the mold (Table 1).

The main goal of the cooperation between Bio-Fed and Günther Heisskanaltechnik is to analyze the flow behavior and processing stability of newly developed PHA compounds in two state-of-the-art hot runner types. This is intended to broaden the application range of these bioplastics, in particular where precision parts with short cycle times are to be manufactured.

Special Hot Runner Nozzles Help  with Processing

Experience shows that, for processing the biomaterials, hot runner systems with an adequate temperature behavior should be used in order to avoid thermal damage. In order to ensure this temperature behavior, the hot runner system should be designed according to thermal and rheological principles.

The necessary temperature behavior in the hot runner is influenced, for example, by good thermal separation between the temperature-controlled mold and the heated hot runner nozzle, The hot runner nozzles from Günther Heisskanaltechnik achieve this thermal separation by means of a two-part shaft comprised of a titanium alloy with a thermal conductivity of about 7 W/(m·K) as well as of steel. An air gap between the nozzle shaft and heating produces an additional thermal separation. The use of BlueFlow heating (Info box p. 55) permits targeted distribution of the heating power. For example, over 50 % of the entire heating power is concentrated at the front region of the nozzle (tip). This ensures that an adequate amount of thermal energy is conducted into the tip. Since there is no heat dissipation in the central region of the nozzle, the heating power is significantly reduced in this region in order to avoid overheating (Fig. 3a).

Many of the hot runner nozzles available on the market are centered in the cavity insert either directly or via a titanium ring. This metal connection from steel to steel in the region of the gating point results in very good thermal conduction. Since heat obviously always flows from the hot to the cold body, a high heat loss in the hot runner nozzle can be expected (Fig. 3b). The result is that the actual temperature in the hot runner nozzle is in some cases significantly above that displayed. As a result, sensitive polymers – including additives – may be thermally damaged.

In the case of the nozzle with a two-part shaft, there is a significantly lower heat loss, and consequently a more homogeneous temperature profile without huge temperature excesses. As a result, thermally sensitive plastics such as PHA can be readily processed.

The processing trials performed in the pilot plant of Günther Heisskanaltechnik are intended to show to what extent the selected M·Vera grades can be processed with different hot runner systems (open vs. valve gate). The following items were assessed during the performance of the trials:

<ul><li>Determination of parameters for a stable process.</li><li>Opening behavior of the gate points/filling study.</li><li>Maximum holding pressure time of valve gate.</li><li>Start-up behavior after simulated process interruption.</li><li>Evidence of process stability over a defined period.</li></ul>

For the trials, a two-cavity trial mold from Günther Heisskanaltechnik (Fig. 4) was operated on an electrical injection molding machine (type: Allrounder 520A, 1500–400; manufacturer: Arburg). The mold is constructed so that exchangeable inserts with various designs of test specimens can be used at the moving mold half. The fixed mold half can optionally have open nozzles with a tip or valve gates.

The trials with an open hot runner were performed using two type 6SHF80 nozzles with BlueFlow heating (Fig. 3), in which the heat is conducted into the gating point via the tip, which is made of a highly conductive metal. This results in a largely uniform opening behavior at the gates in conjunction with a high-quality gating point. In this case, a disk-like sample body (Fig. 5) was measured using a 1.2 mm diameter gating point.

The PHA blends were processed with a process temperature of 150 °C (injection unit and hot runner) and a mold temperature of 40 °C. The process here was found to be stable without pressure fluctuations. The temperature of the hot runner nozzles was gradually reduced to 135 °C without process fluctuations occurring.

A filling study could be generated with the same nozzle temperatures. The restart after a simulated process interruption of 15 minutes was possible without restriction. The quality of the gating point is assessed as good for a nozzle with tip. In the type GP1012, the natural fibers act as nucleation agents: Compared to GP1045, the sample bodies are demolded with a cooling time that is 5 s shorter. With the optimized parameters, the PHA blends were processed in a stable process over a period of one hour.

The trials with the valve-gate system were performed using two type 8NHT2–80LA nozzles. For a valve-gate system, the opening behavior is even more precise and the quality of the gating point is best in terms of optical and tactile properties. In the needle guide type LA used here (Fig. 6), the gating point is integrated in the needle guide and thus shapes the contour. The needle guide consists of a powder-metallurgical steel, characterized by high wear resistance. The needle guide is positioned floating in the nozzle and if needed can be easily exchanged without reworking the mold insert.

Valve needles with a gating point of 2.0 mm are used, which are moved by means of a pneumatic individual valve with a maximum valve closing force of 800 N. The chosen rod-shaped test sample (Fig. 7) has a wall thickness of 2 mm and a flow path length of approx. 90 mm.

Both M·Vera grades GP1045 and GP1012 could be processed in a stable process at a hot runner temperature of 150 °C and a mold temperature of 40 °C. As is generally the case with valve systems, the holding pressure time for the two PHA grades is limited due to the solidification behavior of the melt during the holding pressure phase. With a holding pressure time that is too long, overloading of the article, or flash formation, may occur during closing of the valves.

After a simulated process interruption of 15 minutes, the process could be restarted without restrictions for both material types. The first parts showed a slight discoloration.

Both GP1045 and GP1012 could be readily demolded after a cooling time of 3 s. However, impressions or deformations due to the ejector pins can be seen up to a cooling time of 6 s. To be able to demold the article with a wall thickness of approx. 2 mm without deformation or impressions, the cooling time should be over 6 s. In addition, it is advisable to provide temperature control near the gate, which can be separately operated. The injection pressure profile does not show any anomalies and the documentation of the process capability with a running time of one hour shows that the process is stable.

The tests show that, both PHA grades can be equally well processed with the standard hot runner nozzles from Günter Heisskanaltechnik as open (tip) and valve gate alternatives. With the use of the above-described hot runner nozzles, stable and gentle processing of the M·Vera grades by Bio-Fed is possible within the specifications.

[1] Rinaldi, R.; Palkovits, R.; Schüth, F.: Depolymerization of Cellulose Using Solid Catalysts in Ionic Liquids. Angewandte Chemie International Edition 47 (2008) 42, pp. 8047–8050, <a href="https://doi.org/10.1002/anie.200802879" target="_blank">https://doi.org/10.1002/anie.200802879</a>

[2] Lindh, H.: Evaluation of the biopolymer Poly-hydroxi-alkanoates for use in Tetra Pak packages. Master Thesis, Lund Institute of Technology, 2005

[3] N.N.: Bioplastics Market Development Update 2020 European Bioplastics. Bioplastics Magazine 17 (2022) 3, S.7 / Nova Market Report: Mimicking Nature: The PHA Industry Landscape Latest trends and 28 producer profiles

[4] Deconinck, S.: Quantifying biodegradability in soil of slowly biodegradable materials. 16th European Bioplastics Conference, Berlin 30.11.2021

[5] Kerkstra, R.; Brammer, S.: Injection Molding Advanced Troubleshooting Guide. Carl Hanser Verlag, München 2018

Günther Heisskanaltechnik GmbH  

https://www.guenther-heisskanal.de

BIO-FED Zweigniederlassung der AKRO- PLASTIC GmbH

https://www.bio-fed.com

Ausgabenartikel

Fig. 2. Capillary rheometer analysis of M·Vera GP1012 shearing vs. viscosity sweep at various temperatures.

Fig. 3. Hot runner nozzle with tip and BlueFlow heating (left) and heat dissipation (right) by the metal connection of the nozzle to the mold insert. 

Table 1. Mechanical properties of M·Vera GP1012 at various mold temperatures.

Fig. 1. Chemical structure of poly-(R)-3-hydroxybutyrate (P3HB), a polyhydroxyalkanoate. 

Fig. 4. Interchangeable inserts for various test samples can be installed in the two-cavity trial mold.

Fig. 5. Shot-weight 3 g, diameter 60 mm, wall thickness 1 mm; the “disk” test sample. 

Fig. 6. Type LA needle guide, made of a wear-resistant steel.

Fig. 7. Shot-weight 4 g, flow-path length 90 mm, wall thickness 2 mm; the “rod” test sample. 

Name - Hauptartikel

Bio-Fed and Günther Heisskanaltechnik have performed trials, which show that even supposedly sensitive bioplastics can be reliably processed in hot runner molds.

Bioplastics: Processing in Hot Runners

The BlueFlow hot runner technology uses heating elements based on thick-film technology. The dielectric layers and the heating elements are applied by screen printing under cleanroom conditions. This offers the following advantages:

<ul><li>Precise and homogeneous power distribution across the entire nozzle length</li><li>Avoidance of temperature spikes in the melt-guiding material tube</li><li>High power concentration in the front nozzle area</li><li>Fast thermal reaction, resulting in lower energy consumption and shorter cycle times</li><li>Intricate structure with low exterior diameter, resulting in lower gauge diameters and greater degrees of freedom for the temperature profile and direct gating</li></ul>

Dipl.-Ing. Jörg Essinger is Head of Applications Technology & Service at Günther Heisskanaltechnik GmbH, Frankenberg, Germany;

<a href="mailto:essinger@guenther-heisskanal.de">essinger@guenther-heisskanal.de</a>

Dr.-Ing. Alejandro Puentes is Development Application Manager at Bio-Fed, a subsidiary of Akro-Plastic GmbH in Cologne, Germany; <a href="mailto:lejandro.puentes@bio-fed.com">lejandro.puentes@bio-fed.com</a>

Dr. Inno Gaul is R&D Director of Bio-Fed; <a href="mailto:inno.gaul@bio-fed.com">inno.gaul@bio-fed.com</a>

Read the German version of the article in our magazine Kunststoffe or at <a href="https://www.kunststoffe.de/a/fachartikel/biokunststoffe-im-heisskanal-verarbeiten-3086237" target="_blank">www.kunststoffe.de</a>