Jenoptik is linking up two technologies that have already been successfully introduced into the automotive market to speed up the production of bumpers. This combination, which is unique in this form, offers higher flexibility compared to stamping or ultrasonic welding. 

3D Laser Cutting Combined with 3D Laser Welding  

Verbindungstechnik

Thermisches Fügeverfahren

Laserschweißen

Verbindungstechnik, hybride

Flexible Machine Concepts Support  the Variety of Models 

Hot gas welding has now become an established alternative to vibration and infrared welding. The reasons for this are the mechanically and visually excellent welds obtained and the low-emission, particle-free process. A further development of the welding tool avoids long process times and reduces material degradation. 

Tools Adaption Reduces Process Times and Improves Weld Quality 

Thermoplaste

Polyamide

Faster and Better Welding 

Customized solutions for joining plastics are gaining in importance. Modern developments in plant engineering, digitalization and design, through to entire process variants, give the visitors to the K 2019 halls new insights into contemporary and future solutions to the challenges in the field of joining technology.

Plastics Joining Technology Characterized by Flexibility, Individualization and Digitalization

Verbindungstechnik Verfahren

Mechanisches Fügeverfahren

Fügen / Verbinden

Fertigungsautomation

Anlagen / Systeme

Weld Your Way

According to the state of the art, there are numerous thermal welding processes for joining thermoplastic components. Every welding processes, be it heated tool, infrared or laser, offers process-specific advantages and disadvantages. Selecting a process requires expert knowledge of the different welding processes and the material used. Cemas Elettra S.r.l, Carmagnola, Italy, bundles this know how with a wide product portfolio. The company has developed a multi-fiber laser welding machine for the simultaneous welding option. Since the development work concentrated on a tail light, particular attention was paid to the optical requirements of the weld seam. In simultaneous welding, the weld seam can be simultaneously heated and joined, so that constant seam thicknesses can be achieved. This permits short machine cycle times and welds of high optical quality. 

Cemas 

Vibrationsschweißen

Thermal Welding 

With the increasing industrial use of plastics, joining processes, in particular welding processes, are gaining in importance. According to the physical principles, various thermal joining processes are available for welding plastics. Choosing a suitable welding process, and setting up and controlling the process correctly, are very important for the quality of the weld seams. Support for this is offered by KLN Ultraschall AG, Heppenheim, Germany, which originally only offered ultrasound welding machines for cleaning processes in the medical sector. The company has since extended its welding machine portfolio to six main areas: Ultrasound, vibration, heated tool, rotation, thermal and infrared welding. The welding machines are now used worldwide in the medical sector, and the automotive, white goods and electrical industries. Besides providing advice on welding processes, KLN Ultraschall supplies complete production lines on demand, including standard machines, special components, tools, tool exchange cells, robot systems and the adequate feed technologies. 

KLN Ultraschall 

Thermal Joining Processes 

With the help of CFD simulations, a nozzle system (top nozzle) for hot gas welding is developed, which encloses the weld seam during heating. The significantly more controlled flow behavior of the hot gas improves the processing window, increases the reproducibility and achieves a significantly more efficient heating time of the polymer weld seam. The CFD simulations used to develop the new nozzle system are validated by temperature measurements in the hot gas welding process with IR camera and thermocouples.

Hot gas welding station (left) and flow field of the investigated process (right)

Düsen, allgemein

Kunststoffverarbeitung: Maschinen und Komponenten

Kunststoff-Aufbereitung

Simulation Schweißen

Software

Simulation

Analysis of two different nozzle systems for hot gas welding using CFD simulations and measurement results

A nozzle system optimised by CFD simulation makes immersive nozzle systems for the hot gas welding process suitable for series production and allows a reduction in heating time of up to 50 %.

Gas-, Autogenschweißen (WIG, MIG, MAG)

Prozesssimulation

Kunststoff Werkstoffe

Contribution to efficient hot gas welding of thermoplastics

The joining and retaining forces on snap beams can be calculated substantially more realistically using an improved computing model that includes the beam deformation. 

Calculation of Snap Beam Forces 

Aging and creep in plastics hampers optimum connections to other materials. This can lead to oversizing on one side and product failure on the other. A bolted plastic-concrete connection in a washing machine serves as an example of how to arrive at the best-possible design. 

Schraubensicherung

Parts Design: A Coexistence of Unequals 

are continuing their advance as lightweight engineering materials. An important factor in the part design is the orientation of the fibers in the loading direction. However, the method of laying individual fiber rovings in the direction of force is almost never used. It is facilitated by a new process in which a robot tracks the lines of force and fixes the filaments with a cold adhesive system. 

Verbundwerkstoffe / Werkstoffverbunde

Kohlenstofffasern / -matten

Faserverarbeitung

Chemisches Fügeverfahren

Klebstoffe

Fiber Composites: Adhesive Fixing of Rovings Increases Load Bearing 

Ultrasonic sealing is a reliable and economical alternative to typical contact heat sealing. Narrow seams, tight seals in spite of product contamination and high efficiency in terms of energy usage characterize the latest technology that provides optimal protection for the fill goods. 

Kunststoff-Verpackungsmaschine

Verpackungsmaschinen

Sealing: Packaging with Ultrasonics 

As a result of the current climate protection debate, plasticmetal composite technology is more than ever in demand in automotive engineering. At the present time, automotive manufacturers are systematically examining their new model designs to identify possible applications for this lightweight construction method, which is also known as hybrid technology. New polyamide materials take account of this trend. 

Hybrid Technology: Lighter than Steel 

Though joining technology is one of the last steps in the manufacture of plastic parts, it takes first place in terms of its innovation potential. Driven by ever higher demands for efficiency, reliability and miniaturization, many improvements and trends have been initiated and implemented since the last K trade show. 

Schraubtechnik

Joining: Bonding Required 

Laser staking is a new method for positive connection of two components by plastic deformation of one of the two components. The sturdy and matured basic technology of laser transmission welding offers the necessary reliability here for use in automated production. 

Laser Technology: Riveting with Light 

A hybrid construction principle for joining fiber-reinforced plastic composites and metals can be used to develop weightoptimized structures with high stiffness and load-bearing capability. For such applications, a novel joining process which maintains the force flux and, in addition, is suitable for mass production has been developed for high-performance applications. 

Nieten, Toxen

Heavy-Duty Lightweight Structures: Force Flux-Maintaining Spot Connections 

Thermal Direct Joining Allows Plastic and Metal to Be Fused together

hyJoin, the Kist + Escherich joining technology is mainly used where space is too limited even for a seal, and where bolting or gluing is not desirable. The partner materials are joined together in a few seconds for a media-tight, long-lasting, stable and highly resilient connection.

How Kist+Escherich ensures media-tight, long-term stable and highly resilient joints with hyJoin joining technology.

Many devices and products are tightly packed with sensitive electronics and sensors. To protect the inside from moisture and dust, enclosures must be tightly sealed. But there is not always room for a seal and a screw flange at the circumference. hyJoin is a thermal direct joining technology for metal and plastic assemblies without additives to form a stable and media-tight connection. This is made possible with induction heating and intelligent process control, implemented with hyJoin technology by Kist + Escherich.

We encounter hybrid joints of metal and plastics everywhere and daily. To produce these joints, it can be advantageous to encase the metal with the plastics already during the injection molding process. However, this cannot be realized in a classic assembly process. In those cases, the parts are often bolted, glued or connected as snap-fit joints. If the interconnection has to be dust- and splash-proof, additional seals must be installed.

In contrast, the thermal direct joining process requires no added material. The parts are pressed together in the area to be joined. At the same time, electromagnetically induced eddy currents heat the metal. The plastic softens in the contact area and binds to the metal surface during cooling (Fig. 1). First, the metal is structured or coated to ensure that the connection produced in the process is media-tight, long lasting, stable, and highly resilient. Otherwise, plastics adhere rather poorly to untreated metal surfaces.

The joint strengths that can be achieved with this process are comparable to structural bonding, but the joining process takes only a few seconds and can be easily automated.

Customized Heating Tools thanks to FE Simulation

The design and layout of the joining tools are of great importance to ensure these short joining times. The geometry of the joint determines the inductor design for the process. Since the coupling efficiency of the electromagnetic field depends on several factors such as material, distance and vibration frequency, the process developers use FE simulation tools for thermal field modeling. The result is a part geometry-specific joining and heating tool. These are then used to produce initial samples and prototypes for validation tests in the hyJoin laboratories at Kist + Escherich’s Dresden location.

Structural Guidelines for Optimum Joint Design

When looking at bolted or glued connections, models for dimensioning the joint according to load requirements are already available. The situation is different with hyJoin. Because, in contrast to gluing, the parts hold together mostly through form and force fit in the interface, which is less than one millimeter thick. As a result, the failure pattern differs significantly from purely adhesive connections as used before.

The hyJoin team is motivated to deal fundamentally with the topic of joint design and failure mechanisms. For example, a bursting pressure testing specimen was developed as part of a student project. An extensive series of tests enabled them to determine the influence of material, type of metal surface and the width of the joining flange on tightness and bursting pressure. The water fountain was particularly impressive, with a burst pressure of 25 bar and a circumferential flange width of less than 5 mm (Fig. 2).

However, not only the transferable stresses in a specified load case must be considered when designing the joint. Component tolerances, which can be significant, especially for injection molded plastic parts, can be taken into account and compensated easily during the joining process.

Particle-Free Joining for  Clean Environment

Enclosures for modern electronics and sensors should not only protect against dust, moisture and impact risk. They also ensure good heat dissipation. Aluminum is the best heat sink. In order to maximize both weight and cost efficiency, enclosures made of one half aluminum and one half plastic have caught on. The hyJoin technique is very suitable for sealing these assemblies. At first the electronic or sensor assemblies will be fixed to the metallic heat sink. Any remaining particles must be removed immediately before sealing the enclosure to prevent a potential short circuit in the electronics. Kist + Escherich has been active in the field of cleaning with ionizers and pulsating compressed air for 50 years and can accommodate this step perfectly.

The enclosure halves are placed into the joining station. An upper and a lower joining die fix the assembly pieces to each other. During the heating process, a servo-electric drive applies moderate pressure to the parts so that the resulting plastic melt can completely wet the metal. Once the plastic has cooled down sufficiently, the joining tool opens and the assembly can be removed (Fig. 3).

It is important, especially for this application, that no particles are formed when closing the housing, which could contaminate the inside of the enclosure. Since only small joining forces have to be applied to deform the plastic melt and abrasion on the metallic joining partner is prevented, this challenge can also be met.

Many Different Uses thanks to Flexible Joining Equipment

The current development projects show the broad application potential of this joining technology. For example, fingernail-size assemblies can be joined, hybrid coolers the size of shoe boxes and even entire car seat structures are produced. It is not unusual to join two or more metal parts to a plastic component basically all at once to optimize processing times. This is why we expanded our plant engineering unit at the “Tech Center” in Dresden at the beginning of the year. A large C-bracket supports the coreJoin modular press – the heart of the hyJoin system. This experimental setup facilitates flexible demonstrations of creating joints on large complex structures (Fig. 4).

A number of other requirements clearly still had to be met to use joining technology in series production. Specifications that the team was able to meet were a 10 s cycle time, high process stability, and in the process an easy changeover to different product types.

The giroJoin production plant consists of a rotary indexing table with an integrated joining station. A Pick & Place robot removes the assembly from a workpiece carrier and places it on the rotary indexing table. Every 10 s, a part is fed into the joining station. Both the joining path and force as well as the heating rate are monitored during the joining process. Should significant deviations in the output occur, the parts are taken out at the removal station. A gripper then places all other parts in trays for further processing.

The wide range of application fields continues to place new requirements on plant engineering. The current product portfolio therefore includes semi-automatic machines for manual loading, fully automated systems as well as joining systems in various sizes and configurations that can be integrated into larger assembly lines.

Thanks to Kist + Escherich’s decades of experience as a manufacturer of special machines for industrial component cleaning, the company is very familiar with customer requirements for a special machine manufacturer of their new business unit.

KIST + ESCHERICH GmbH  

https://www.kist-escherich.com

Ausgabenartikel

giroJoin processing cell with rotary indexing table for automated joining of metal and plastic assemblies. Configuration with workpiece carrier transfer system and Pick & Place robot for component placement.

16:9

Fig. 1. Process steps for thermal direct joining of metal with plastic. 

Source: Kist + Escherich; graphic © Hanser

Fig. 2. Media-tight sealing of an aluminum electronic enclosure with a polycarbonate cover using the hyJoin joining technology.

Fig. 3. Burst pressure test on a test  piece of die-cast aluminum and PA6-GF30.

Fig. 4. Test carrier with coreJoin module press for the thermal direct joining of large and complex structures in the Dresden laboratory.

Hauptartikel Kist Escherich

Direct Joining: Fusing Plastic and Metal together

Annett Klotzbach is Key Account Manager Joining Technology at Kist + Escherich GmbH, Dresden, Germany.

The joining technology described in the article can be seen at Fakuma:

<a href="https://en.kunststoffe.de/fakuma">www.plasticsinsights.com/fakuma</a>

Read the German version of the article in our magazine Kunststoffe or at <a href="https://www.kunststoffe.de/a/fachartikel/thermisches-direktfuegen-laesst-kunststo-5161384" target="_blank">www.kunststoffe.de</a>

issue 05/2025

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