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

Spritzgießen

Kunststoffverarbeitung: Verfahren

Spritzgießmaschinen, allgemein

Kunststoffverarbeitung: Maschinen und Komponenten

Spritzgießmaschinen

Spritzgießsimulation

Software

Simulation

Schnecken und Plastifiziersysteme

All about Plasticizing Screws

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

Schaumspritzgießen

Künstliche Intelligenz für die Qualitätssicherung

Industrie 4.0

Industrie 4.0 für die Qualitätssicherung

Steuern, Regeln

Mehrkomponenten-Spritzgießen

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

Digitale Transformation

Wirtschaft

Innovationen und neue Technologie

Spritzgießwerkzeuge

Werkzeuge für die Kunststoffverarbeitung

Biokunststoffe

Kunststoff Werkstoffe

Spritzgieß-Sonderverfahren

Nachhaltigkeit

Umweltmanagement

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

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!“

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

The ninth broadcast by arburgXvision was about strategies for significantly increasing the utilization rate of injection molding machines.

Moderator Guido Marschall and Arburg experts Christian Homp and Christoph Blöchle (from right) discussed how the right mold strategy pays off for injection molding companies

“Mold Strategy 2.0 – New Ideas for Reducing Costs”

Guido Frohnhaus has been Managing Director Technology & Engineering at Arburg for a good two years now. The pandemic restrictions meant that he has made very few appearances outside the company so far, but, as he says himself, he spent the time getting to know the in-house processes at all levels and in great detail. In this interview with Kunststoffe, the 52-year-old talks about the course he plans to set and how crucial the high level of in-house manufacturing and programming expertise is for the company’s independence.

16:9

Doriat, Clemens, Dr.

“Gestica Will Be the Fixed Star in the Customer’s Universe”

Thin wall packaging manufacturers think in terms of efficiency gains in tenths of a second. Every cycle time reduction leads to increased productivity. Another factor influencing part costs is the energy efficiency of the production equipment. In these two key dimensions, Netstal was able to optimize the smallest model in the Elios series with 4500 kN clamping force.

The optimized Elios 4500 with electrically operated toggle levers enables users to achieve cycle time reductions and savings in power consumption (the photo shows the previous variant).

Higher Output and Reduced Energy Consumption

Energieeffizienz

Elektrische Antriebe für Spritzgießmaschinen

Antriebe

Elektrische Antriebe

Clamping Unit of the Elios 4500 with Fully Electric Drive Concept

In cars, LEDs are taking over ever more applications and are increasingly used as differentiating design elements. In order to ensure a high luminous efficiency even with complex geometries and elongated structures, Engel has developed a new plasticizing process for manufacturing light guides.

The transformation of the automobile also strongly affects the vehicle interior. Light is gaining in importance as a design element

The Principle of Starve Feeding: Injection Molding Ultrahigh Purity Light Guides

Farbmessgeräte

Messtechnik

Optische Mess- und Prüftechnik

LED / OLED-Systeme und Faseroptik

Lichttechnik

Less Granules  Stock Means More Quality

ARBURG is one of the world‘s leading manufacturers of plastic processing machines. The product portfolio encompasses ALLROUNDER injection moulding machines with clamping forces of between 125 and 6,500 kN, the freeformer for industrial additive manufacturing, plus robotic systems, customer and industry-specific turnkey solutions, and further peripheral equipment.

ARBURG GmbH + Co KG  

https://www.arburg.com

Abkantmaschinen, -pressen, -bänke

Blechbearbeitungsmaschinen

Maschinen für die spanlose Fertigung

Additive Fertigung

Anlagen für die Additive Fertigung

Antriebselemente

Lineartechnik

Maschinenelemente

Ceramic-Injection-Moulding, CIM

Condition Monitoring für die Qualitätssicherung

Handling, Handhabungstechnik

Kennzahlen

Qualitätsmanagement

Kennzahlen, Q-Leitstand, Q-Monitor

Kühlelemente, aktive

Kühlkörper

Elektromechanik

Management-Informationssysteme

Medizintechnik

Mehrfarben-Spritzgießmaschinen

Mikrobauteile

Montage

Montagetechnik

Mikrospritzgießen

Mischer

NE-Metalle

Metall Werkstoffe

PUR-Schäummaschinen

Schäumen / Reaktive Verarbeitung

Partikelschäumen

Produktionssystem

Rapid Manufacturing

Rapid Prototyping

Reinraumsysteme / -technik

Reinraumtechnik

Betriebsausrüstung / Betriebsmittel

Reporting-Tools

Rückverfolgbarkeit, Traceability

Schnecken und Zylinder

Spanneinrichtungen

Systemperipherie

Spritzgieß-Zubehör und Einzelteile

Stetigförderer

Fördertechnik

Logistik

Trockner

Vorbeugende Instandhaltung für die spanende Fertigung

Haitian International, the Chinese manufacturer of injection molding machines, is consolidating its growth of the last ten years while its European business flourishes. New locations and additional investments will support its foreign activities. On the program for the K 2019 is the introduction of what is now their third generation technology.

Fu Nanhong, CTO of Haitian International, announces the third generation of all their important series for the K 

Haitian’s Success Story Continues with Big Plans

Plans for Further Expansion

Once again, the K 2019 in Düsseldorf, Germany, lived up to its claim to be the leading trade show for plastics technology. At least in the field of injection molding, there were exciting global innovations to see – if you looked closely.

Fig. 1. Smart Operation – the machine is operated with only four buttons (© KraussMaffei)

Injection Molding Trends at K 2019

Smart Factory

Fließpressen

Handling, Handhabungstechnik für die spanende Fertigung

Elastomer-Spritzgießen

Linearroboter für die Kunststoffverarbeitung

Industrieroboter

Montage-Spritzgießen

Knickarmroboter

Co-Injektion (Barriere-/Sandwich-Spritzgießen)

Hybrid-Spritzgießen (Metall / Kunststoff)

Ressourcenmanagement

Produktion

Technical Excellence thanks  to Digital Assistance

The required screw diameter can be ascertained on the basis of the shot volume. The formula for the average residence time can be used to estimate the degree of utilization and the thermal load on the material.

Various shapes of plasticizing screws. The correct design is approached in several steps

Part 1 of the Series Discusses the Basic Design of a Plasticizing Unit and the Correct Choice of Injection Unit

Investment strengthens Arburg´s expertise and electric drives portfolio. AMK has been Arburg‘s development partner in electric drives for decades.

By acquiring AMK Arnold Müller GmbH & Co. KG, Arburg Partners Juliane Hehl, Michael Hehl and Renate Keinath (from left) are investing in the future of electric injection moulding machines.

Kunststoffverarbeitung

Dienstleistungen

Lohnfertigung

Unternehmen

kunststoffe.de

Arburg Acquires AMK‘s Drives & Automation Division

To be able to carry out the practical test in a resource-saving manner, the designers use simulation tools to assess the screw geometry. What is important here is explained using a 3-zone screw as an example.

The screw geometry is finely optimized in several calculation steps until the desired result is achieved. Subsequently, test screws are manufactured in original size and tested in practical tests with various material types

20:7

Part 2 of the Series Deals with Basic Methods for Evaluating a Screw Geometry

The central control unit of the injection-molding machine is used by the machine operator for control, regulation and optimization of the entire production process. In order to directly integrate external systems as well as proprietary solutions that do not have a standardized interface, Engel uses a technology that is already widespread in day-to-day routine. Via a browser, the new Webviewer can be reliably integrated into the CC300 control panel of the injection-molding machines.

The Webviewer in the machine control system integrates not only ancillary equipment  with web interfaces, but also data from internal and external systems that are accessible via browsers. 

New Webviewer Merges Web and Control Applications

Bedienterminals

Computer Hardware

Central Control Unit Makes Use  of Web Technology

How Feed Rate, Injection Volume and Filling Time Correlate with Injection Unit Performance

Which injection molding machine is the right one for which application? Below we will demonstrate why performance is not always performance, but physics is always physics.

Which injection molding machine is the right one for which application? Is fast also powerful – and at what price? Anyone trying to answer these questions by comparing brochure data will be disappointed. This is because different manufacturers sometimes measure under different conditions and specify parameters so different from each other it is like comparing apples and oranges. In addition to injection volume and speed, filling time and component weight are also crucial factors when selecting a machine. Below we will demonstrate why performance is not always performance, but physics is always physics.

What this means can be illustrated using the example of a car driver: suppose someone wants to drive over the Alps on holiday. A powerful SUV, a sporty convertible and a tandem trailer are available. Both vehicles have roughly the same power output of 250 kW, i. e. around 350 hp. Which of the two vehicles will drive in a relaxed manner over the Alps to the destination, and which one would it be more fun to cruise through the various passes in? Should the driver load the SUV onto the trailer and drive the sports car to the destination – or would the other way around be better, so as to enjoy the bends of the landscape in the convertible? This is a decision that everyone will probably make intuitively in the same way.

If we transfer this analogy to the forming process world of injection molding, the answers are not particularly clear at present. One reason is the change in drive technology and in suppliers, who are increasingly coming from the machine tool sector. As a result, the injection speed for the injection axis is specified in some cases linearly in mm/s, and in others volumetrically in cm3/s. Other conventional brochure data relates to screw diameter, shot volume and injection pressure. Recognized substantiated values are those which are actually achieved under full load at 2000 bar counter pressure and 1 D screw stroke. Most (European) molds and screws are also adapted to this mechanical load.

Brochure Data for a Comparison  of Machines

Footnotes in the technical data sheets that quote “theoretical” idle speeds without the pressure factor or with limited holding pressure times are less significant. Whether such theoretical values in the brochure or on the control system screen are actually sufficient to realize the desired injection times with the machine in the actual process cannot be deduced from this. For example, a “theoretical” idling speed of 1000 mm/s simply means: according to the data sheet, the motor can rotate fast enough that the specified speed is theoretically achieved over the entire screw stroke – but without taking into account the counter pressure in the mold, into which the plastic does not “voluntarily” flow. The faster the injection, the higher the counter pressure and consequently the pressure required for injection. In addition, it is of course not possible to drive into the holding pressure at full speed because the mold would inevitably become completely overloaded if there was no slowing down. This value is therefore never reached in the actual process.

Hydraulic versus  Electric Injection Units

Modern hydraulic injection units require relatively little superimposed system pressure in order to be able to use the full injection pressure (2000 bar) at maximum programmed speed. At least that is how current data sheets for hydraulic injection units are designed. For fast and precise injection, hydraulically driven injection units are usually equipped with a servo valve and barely differ in terms of dynamics. While stored energy and high peak performance can be used here, the performance required for electric drives is always supplied directly from the mains to the injection axis and screw tip. In addition, with commercially available hydraulic injection units, the inertial mass of the construction plays virtually no role, in contrast to electromechanical solutions.

Intrinsic inertia is another crucial factor in electro-mechanical systems. This needs to be overcome in order to accelerate the drive components spindle or gearbox and servomotor to the required final speed. As a rule, at least 50 % of the installed drive power and the available torque must be used for this purpose. The dynamics of servo-electric direct drives depend heavily on the mechanical design. Arburg develops and manufactures its own planetary roller screw drives for its Alldrive and Hidrive series machines, which are particularly load-resistant and durable (Title figure).

Without getting lost in technical details, the mechanical design and the construction principle and consequently the target design play a key role in electric injection units. The dynamics and peak performance that can be achieved with these machines have a significant influence on the machine price and the technical possibilities in the injection molding process. Or to stay with the analogy mentioned at the beginning: an 800-kg sports car that needs to get a trailer with a 2.5 t SUV moving can no longer accelerate from 0 to 100 km/h in 3 s. That is, if it can even still pull it on a 15 % incline without the wheels spinning.

All Good Things Come in Threes – Different Performance Classes

Based on the filling time, the applications and injection molding machines suitable for them can currently be roughly divided into three classes (Table 1). The majority of all applications are technical injection molded parts with a filling time of 0.3 s and well above. Directly driven hydraulic standard machines are generally designed and ideally suited for this area.

Applications with extremely short filling times of less than 0.1 s are more of a niche for specially adapted injection molding machines, which by no means every manufacturer offers. These include, for example, thin-walled high-temperature components made of PEEK for the classic consumer goods and electronics industries. One example is charging plugs for smartphones.

Classic applications with filling times of approx. 0.1 to 0.3 s here are the processing of polyolefins into thin-walled packaging parts such as cups (Fig. 1.), buckets or screw caps with flow path to wall thickness ratios of 100 to 300:1. Such thin-wall applications require high dynamics. Therefore, hydraulic machines with hydraulic accumulator technology have been used to a large extent in this segment up to now. However, the trend here is also towards directly driven electric or hybrid high-performance machines. This is where the wheat is separated from the chaff, because the term “high performance” is elastic and relative.

The achievable injection speed in mm/s is one of the characteristic indicators for the technical performance of an injection molding machine. The use of mm/s actually comes from the machine tool industry, which describes the linear feed rate of an axis. In the dimension of km/h, this approach is a suitable SI unit for the maximum achievable movement speed of a motor vehicle, but not for injection. The situation here is fundamentally different. This is because the machine’s injection unit does not fill in millimeters, but injects a volume in the form of a fluid plastic melt into the mold cavities. This is where the screw size comes into play (Fig. 2).

Three-Dimensional Thinking:  Screw Size as an Influencing Factor

The same injection molding machine can be equipped with different screws. At the same feed rate, this results in different flow volumes per unit of time until the required volume has been injected. In addition, in Europe diameters are usually graduated in 5 mm steps, i. e. 25, 30, 35 mm, etc. Other manufacturers prefer a standard series with diameters of, for example, 28, 32 and 46 mm, so a direct comparison, in terms of process capability, based on feed rate alone is not meaningful.

What is ultimately relevant for the respective practical application is the volume of plastic melt that can be injected per unit of time, i. e. the time during which the “cake is baked” before the material solidifies. This filling process is characterized by the filling time, on which filling simulations are also based. The relevant variable is therefore the injection volume per unit of time, known as the injection flow volume (Q). Ever since the development of the first control systems at the end of the 1970s, Arburg has been specifying the associated injection molding physical unit as the injection flow volume in cm3/s and has been using this as a data sheet parameter for decades. A milestone in more recent times was the introduction of the Gestica control system in 2016 (Fig. 3.). The data for a filling simulation can also be transferred to this. A filling simulation can be done directly on the screen with the help of the “aXw Control FillAssist” function (Fig. 4).

Most machines can operate with a maximum screw stroke of 3.5 to 4.5 D, but this is only relevant for thick-walled components and for filling times in the seconds range. Particularly in the thin-wall sector, around 1 D of screw stroke can usually be used as injection volume with common three-zone screws and a usable throughput design. The filling time, which is achieved in the injection molding process with 1 D screw stroke, is therefore a great classification feature, irrespective of the abundance of materials and the width of the part spectrum. During this time, more than 95  % of the liquid plastic melt must have been injected into the mold by the injection unit.

For the filling process, the crucial factor for the given injection unit and machine is how much melt volume arrives in the mold during the available filling time. This constitutes another reason to state the injection flow volume in cm3/s instead of the feed rate in mm/s in data sheets relating to plastics. This value is therefore standardized with the corresponding screw diameter and can be easily calculated in your head for a desired plastic part: assuming a density of 1 g/cm3, a part volume of 50 cm3 and a required filling time of 0.1 s. This initially results in an injection flow volume of at least 500 cm3/s. With electric drives, which have to be accelerated and actively braked with not inconsiderable inertial masses, this value must be multiplied by a factor of 2 (triangular operation). So in this case the value in the data sheet suitable for this application – without a footnote – should be around 1000 cm3/s.

If it has been a while since GCSE physics for you: for a given feed rate and screw diameter (converted into cm), the injection volume flow (Fig. 5) can be calculated as follows: