Joining Techniques - Laser Welding of Plastics

 

Hello and welcome to this blog post. Today we discuss laser welding of plastics as an efficient and effective way of joining plastic parts together.

Overview joining of plastics

There are three established ways on how to join plastic parts together: mechanical joining using screws and bosses, adhesive joining using different types of glues, and welding. Within the welding techniques we can further distinguish between vibration, ultrasonic, high frequency, extrusion, hot air, hot plate, and laser using infrared light as energy source.

Let us now focus on the laser welding technique.

Laser welding – 4 key working principles

Important for the understanding of how laser welding works are the four key working principles:

1.    Transmissive upper polymer layer: most thermoplastics transmit near-IR beam and the upper polymer layer needs to be transparent for wavelengths between 808 nm – 1064 nm. Laser welding radiation is outside the visible light spectrum of the human eye and therefore, polymer parts are laser transparent although they are not optically transparent through our human eye view. For example, you can have a black upper layer which is transmissive to a 980 nm laser. A minimum transmission rate of 5% is required, however optimal would be 30% and greater. 

2.    Absorbing lower polymer layer: the lower polymer layer is responsible for turning the remaining laser energy into heat at the surface of the absorbing layer. Additives, colorants and fillers all play a role for absorption. The most effective and most economical additive for the absorbing layer is carbon black soot. The amount is usually between 0.2 and 0.4% by volume and provides excellent absorbing properties to any thermoplastic.

3.    Contact between upper and lower layer: excellent contact during the welding process to ensure proper heat conduction. Contact is accomplished with various methods of clamping devices or special component designs.

4.    Material compatibility: two polymers which are to be joined can, but are not required to, be the same type of thermoplastic. The most critical material factors are melt-temperature, and the surface energy of the plastics. The most common thermoplastics such as PA 6, PA 66, POM, PBT, PC, ABS, PP, TPE and PE are easily weldable.

Advantages and disadvantages

In the table 1, advantages and disadvantages of plastic laser welding is shown:

 

Advatages and disadvantages of plastic laser welding

4 process types of laser plastic welding

Next we discuss the four most commonly used process types in plastic welding: contour welding, simultaneous welding, quasi-simultaneous welding, and mask welding.

In contour welding, the laser beam is focused into a point which moves relative to the component contour. It is suited for large parts and three dimensional parts.

In simultaneous welding, the entire weld seam is heated at the same time. This is achieved by using specially designed fiber-optics. The laser energy is formed into the pattern of the weld seam and is projected onto the entire seam simultaneously. This process is suitable for high volume runs that require ultra-low cycle times and little flexibility or variation.

Quasi-simultaneous welding is a combination of contour and simultaneous welding. In this process, a single, focused laser beam is guided by galvo-scanning mirrors, which traces the weld path multiple times at very high speeds. The entire joint line is effectively heated simultaneously.

Mask welding is an inflexible process since for each contour, a new mask is needed. Allover, it consumes much more laser power than needed and results in an inefficient process.

Overview joint types and clamping units

There are several possibilities of joints such as the lap joint (overlap of the two polymer parts), butt joint (end-on-end of plastic parts; more difficult to realize), radial joints (in case you weld pipes or cylindrical cases), and T-joints (also called collapsing rib joint since the inner rib will be heated and melted which results in a collapse of the rib).

Training video with application examples

I invite you to check out my training video on plastic laser welding which provides an introduction and includes also several welding examples:

 

Thank you for reading and #findoutaboutplastics

Greetings,

Herwig

Interested to talk with me about your plastic part design needs - here you can contact me 

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Literature:

[1] https://www.lpkf.com/de/branchen-technologien/laser-kunststoffschweissen/technologie-schweissverfahren

[2] https://www.lpkfusa.com/articles/lq/LPW_GL_Hybrid_Laser_Wedling_Design_Guidelines.pdf

Design Properties for Engineers: Key Properties vs. Density of Filled High Performance Polymers

In this blog post, we compare selected design performance properties vs. densities of glass fiber filled high performance polymers.

Glass fiber is the most commonly used filler in high performance polymers. The influence on the properties of polymers by adding glass fibers varies: in PTFE, glass fibers improve mainly the compression and wear properties.

In comparison to unfilled semi-crystalline polymers, glass fiber reinforced materials exhibit increased mechanical strength and higher rigidity. Furthermore, improved creep strength and dimensional stability are achieved by adding glass fibers. In amorphous polymers, glass fibers improve the thermal and mechanical performance, compared to unfilled amorphous polymers, in a limited range.

In the following, the different property figures are shown.

HDT,  Tensile Modulus, Tensile Strength, Tensile Elongation, Notched Izod Impact, vs Density of Filled High Performance Polymers

The key properties vs. density of unfilled high performance polymers can be found here.

Thanks for reading and #findoutaboutplastics

Herwig

Herwig

Interested to talk with me about your plastic part design needs - here you can contact me 

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Design Properties for Engineers: 7 Key Properties vs. Density of Unfilled High Performance Polymers

 In this blog post, we compare selected performance properties vs. densities of unfilled high performance polymers. Density plays an important role in material selection, since the selected polymer compound needs to fill a certain part volume. Higher polymer compound density results in a higher material demand and costs.

In the following, the different property figures are shown:

 

HDT, Thermal Rating, CLTE, Tg, Tensile Modulus, Notched Izod impact, water absorption vs Density of Unfilled High Performance Polymers

More design data can be found here.

Thanks for reading and #findoutaboutplastics

Herwig

nterested to talk with me about your digitalization needs - here you can contact me 

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The Future of Plastics Manufacturing: From Material Supplier to Service Ecosystem and Platform (Part 2)

 

Hello and welcome back to the second part of my “the future of plastics industry” series.

In this second part we keep the focus on polymer manufacturing only and how the future can evolve in this segment of the plastics industry. I still do not have a crystal ball, however orienting on the megatrends, we can try to anticipate a scenario for the future. Other areas such as plastics converting I have touched already in this post. 

Here you can jump to part 1

Key factors for success in polymer manufacturing

Before we jump into a future scenario, let us examine how business is done currently at a polymer manufacturer. Apart of operating state-of-the-art polymerization technology, the following three key product factors are keeping a polymer manufacturer in business for a long time:

-High performance

-Consistent properties

-Competitive costs

Using the optimal technology, a polymer manufacturer is able to produce high-performance products with consistent properties at competitive costs. Product and process development are critical, since new products are an enabler for growth and process optimization can make any product more profitable.

Altogether, there are four major strategies a polymer manufacturer can follow:

-Be the first with your polymer and compound solutions

-Be better with your polymer and compound solutions than the first one

-Be different with your polymer and compound solutions

-Be faster approaching certain applications with your polymer and compound solutions

In past decades, world economies were growing with an average of 6% yearly and polymer manufacturers could participate on this growth. However, in the past ten years digitalization is exponentially changing the way we do business and also the way we consume. New technologies allow the rise of businesses with complete new business models attacking all incumbent old industries.

Revenue growth rates for digital players are in the double digit range year over year. Digital players have the advantage of scaling their businesses in a fast way and keeping the margins very high too. For polymer manufacturers to grow, more material needs to be made and sold as well as and new high end niches need to be found where high prices can be achieved with polymer solutions.

Also, business volatility is increasing and it can be best summarized with the Law of Requisite Variety or for short Ashby’s Law. It is the ability to react to a situation and to have a portfolio of alternatives to pick from (scenario thinking). It also states that when the business world seems to fall apart, it is not helping to build walls and pretending not to see the change. This is the wrong way. One need to meet complexity with complexity itself. Therefore, all industries need to use the new technologies to re-shape and re-invent their businesses. This we discussed in my post where I show 5 ideas on how you canget the digital revolution started in your plastics business [2, 3].

New economy and new business models – when data is the new plastic product

“The goal is to turn data into information, and information into insight.” – Carly Fiorina, former executive, president, and chair of Hewlett-Packard Co.

Several years ago, Eric Schmidt already said that all those companies that define themselves through their product or their technology will struggle in the coming years and those companies that define themselves through their ecosystems and platforms will survive and strive [4,5].

The idea is simple, however it has a tremendous impact: from product manufacturer to platform and ecosystem provider.

We see already established plastic industry players such as Lanxess with their material platform Chemondis, as well as plastics machine manufacturer company KraussMaffei set up with Polymore their own market platform for compounds, recyclates and post-industrial waste, which can serve plastic converters as well as compounders. It is a good example of thinking outside the box and leaving the industry standard of selling plastics machinery since over such a platform it is possible to link polymer manufacturers and plastics convertors together.

Aim is for polymer manufacturers not only to create and participate in B-2-B marketplaces, but also establish ecosystems with their own services and products.

Circular economy as a service platform for polymer producers

Circular economy allows the shift away from linear business models (“take-make-dispose”) to a model of recycling, re-use, and designing for recyclability (DfR). The polyolefins industry is already setting foot into this major change since polyolefins are used in large quantities in packaging where the potential and need of circular recycling is given. A recent example is the EverMinds™ platform where polyolefin producer Borealis is a major driver behind. This platform connects stakeholders with the aim to innovate together and create a product portfolio based on circularity [10].

Ecosystem – polymer manufacturer as service provider

Also for polymer manufacturers, digital services become more and more important. It is not enough anymore to just sell plastics pellets. Successful polymer manufacturers will establish themselves as service providers in the next ten years or even earlier. There are several services which can be horizontal or vertically integrated along the current value chain. From polymer materialselection, part design, virtual engineering (filling simulation and FEA) to manufacturing key components including material, regulatory and logistics support. Key is to cleverly add the service business onto the product business and combine it with platforms to establish ecosystems.

An industry example is Diversey Inc. which started out as a chemical company providing cleaning products to hospitals and other facilities. Now, it is a solution provider, not a product provider anymore. For example, they combine cleaning care plans for hotels and hospitals which include their chemicals, application tools, smart machines, as well as training and support [7].

Collecting data over sensors on production facilities as well as online in the web via marketing tools is key part for this change too. The more structured the information is, the better new strategies can be established and decided upon on by the business executive teams.

New service based revenue streams will stabilize current business streams and may outgrow the established business in the next 10 years. Amazon Web Services (AWS) is such a case, where it was a small offering of external online storage space in 2014 and now it is with 60% the largest operating profit contributor of the Amazon ecosystem [11].

Conclusions

In plastics manufacturing, there are well established industry standards which the majority of the companies follow. They follow the norm and achieve normal results. Extraordinary results are achieved by breaking out of the industry standards. Developing to a service platform provider with an ecosystem represents such a breakout. Only 3% of organizations or people are able to create such changes which lead to high performance results [8]. And those will get the biggest share of the cake, since in the new economy the “winner takes it all” principle rules.

I want to close this post with a quote to keep in mind when driving your business forward:

“That which we need the most will be found where we least want to look.” ~ Carl Jung.

Thank you for reading and #findoutaboutplastics

Herwig Juster

Here you can jump to part 1

Interested to talk with me about your digitalization needs - here you can contact me 

Interested in my monthly blog posts – then subscribe here and receive my high performance polymers knowledge matrix.

New to my Find Out About Plastics Blog – check out the start here section

My YouTube channel

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Enroll here for watching the free parts of the course

Literature:

[1] W. R. Ashby: An introduction to Cybernetics. Wiley, New York 1956

[2] https://www.findoutaboutplastics.com/2016/12/plastics-industry-level-up-your-digital.html

[3] https://www.findoutaboutplastics.com/2017/02/a-mind-sharpener-guide-for-plastics.html

[4] https://repository.fteval.at/191/1/2016_RadikaleInnovationen_Endbericht.pdf

[5] https://wien.orf.at/v2/radio/stories/2801064/

[6] https://www.berndtsoninterim.de/aktuelles/im-service-liegt-die-zukunft

[7] https://diversey.com/en/solutions/floor-care

[8] https://www.youtube.com/watch?v=VNGFep6rncY

[9] https://www.findoutaboutplastics.com/2019/07/second-wave-of-digitalization-from.html

[10] https://www.borealisgroup.com/polyolefins/circular-economy-solutions/overview

[11] https://www.geekwire.com/2021/amazon-web-services-posts-record-13-5b-profits-2020-andy-jassys-aws-swan-song/

Polymeric Materials in Automotive: The Increasing Importance of Plastics for EVs and Autonomous Driving

 

In this blog post I cover six areas which deal with the increasing importance of plastics for Electric Vehicles (EVs) and autonomous driving starting from 2020.

Table 1: overview of key focus areas for plastics in EVs and autonomous driving

Let us walk through all the six areas:

Light-weighting – range extension and efficiency for electric cars

Light-weighting plays in several areas of the EV an importance and aims to provide smaller and lighter components. In a standard internal combustion engine car, plastics represent over 50% of the volume, however only 10% of the car weight.  The battery pack is the heaviest part of the whole electric car and plastics light-weighting solutions have the potential to lower the overall weight situation. Current battery housings are made using an aluminum cast solution [1]. Furthermore, battery housings need to fulfill several requirements such as crash protection, battery cooling and ease of maintenance. Thermoset based composites, as well as step by step thermoplastic composites show potential to replace aluminum castings and fulfill the afore mentioned requirements.

Amorphous materials for sensors and LEDs

LED-based lighting technology is already state of the art in cars and it offers many possibilities for the design and functionality of classic front and rear lamp applications. There are already diffractive seamless lens structures which integrate a holographic film into a polycarbonate rear-end structure. Ongoing is the integration of electronics and driving sensors such as LiDAR and radars into one operating unit. The integration of LiDAR systems into invisible components is achieved by using black-panel-based polycarbonate color technology. This solution guarantees the highest IR transmission based on the required IR laser wavelength. Polycarbonate will play a key role for so-called people mover which have large transparent structures. Realizing these structures can be done via the polycarbonate glazing technology (360° glazing concepts).

Electroactive Polymers

In a previous post I highlighted already the importance of electroactive polymers. Polyvinylidene fluoride (PVDF) has piezoelectric as well as ferroelectric properties which can be used to make car speaker systems. The integration of vibrating surfaces all over the car (dashboard; turning headrests into resonating chambers) evolves the car into an entertainment center. Piezoelectric polylactic acid is another potential material solution for such new applications.

System integration

Injection moulding allows the production of complex geometries. Furthermore, system function integration with engineering polymers (e.g. integration of damping elements for noise and vibration reduction) will further reduce costs and weight in electric cars. Metal replacement of transmission housings of electric cars are an example for integration of different materials and technologies: local reinforcement is achieved by thermoplastic composite tapes (unidirectional tapes based on PPA or PPS with carbon fiber) and overmoulded with short fiber reinforced PPA or PPS. Since transmission and power electronic housings need to have EMI shielding, placing the tapes in a 0° and 90° orientation will lead to a filtering effect and as a consequence EMI shielding can be achieved. Another integration field is the two component moulding using a hard component (PA, ASA, POM) and combining it with a soft component (thermoplastic elastomer). In particular for sealing of power electronic parts and housings in electric cars, two component solutions where a flame retardant TPE is moulded on a flame retardant PP are already existing.

Interpolymer substitution and recycling

In several areas of the internal combustion engine (ICE) car, replacement of established plastics takes place. This trend will continue in electric cars as well. Polypropylene blended with polystyrene is replacing ABS in interior decorative parts. Another example is polyketone. It is an engineering polymer which shows higher heat performance compared to polyamide 6 and 6.6. Polyketone has excellent wear resistance and impact strength, outperforming POM. Furthermore, they have a low moisture absorption (similar to PBT) and have an excellent chemical resistance, in particular toward automotive fluids, hydrocarbon solvents and salts. Commercially it is attractive to replace aliphatic polyamides, POM and PBT in the automotive market, as well as other markets. Future aim of the automotive industry is to minimize the amount of different grades and simplify the polymer chemistries in electric cars. This will accelerate recycling efforts and re-usability. Key focus area is the recycling of the battery chemistry and polymers used for making cathode and anode binders.

Battery materials

Here, different polymers play a role for developing improved lithium-ion battery systems by optimizing the binder materials for anode and cathode (PVDF basis) and to develop robust solid-state batteries. Solid-state batteries will allow the customer to recharge the battery in a short period of time and offer more mileage range too. Furthermore, metal replacement of battery housings and module parts will continue, as already highlighted in section one. Engineering polymers are more and more used as battery module separators and end plates.

How electrification influences plastics manufacturing

The next five years will show an increase of plastics demand from the automotive industry. Demand increase will be seen in certain polymer types, combined with application focus. Polyolefins such as polypropylene will grow due to expanding exterior and interior applications. Also, thermal conditions are much lower in electric cars (60-80°C) allowing polypropylene to replace engineering polymers, as well as engineering polymers replacing high heat polymers in certain areas.

Higher growth rates are expected in the Asia-Pacific regions compared to established automotive markets. Focus on innovation will allow manufacturers to meet the upcoming application requirements. Also focus will be on the establishment of a circular economy and structured recycling. 

Thank you for reading and #findoutaboutplastics

Greetings,

Herwig Juster

Interested in my monthly blog posts – then subscribe here and receive my high performance polymers knowledge matrix.

New to my Find Out About Plastics Blog – check out the start here section

My YouTube channel

Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Enroll here for watching the free parts of the course

Literature

[1] https://www.spotlightmetal.com/solutions-for-ev-battery-housing-at-euroguss-2020-a-900422/

[2] https://www.composites.media/the-future-of-thermoplastics/

[3] G. Pilz, et al. : Dynamic Mechanical Profile of Polyketone Compared to Conventional Technical Plastics, AIP Conference Proceedings 1779, 070008 (2016); https://doi.org/10.1063/1.4965540

[4] http://www.poketone.com/en/applications/automotive_index.do

[5] https://www.kraiburg-tpe.com/en/flame-retardant-tpe-electrical-sector

[6] https://www.solvay.com/en/article/future-of-mobility-is-light?utm_medium=social&utm_source=linkedin&utm_campaign=Stories+or+Medium&utm_content=100001741732062&linkId=100000034561877

[7] https://doi.org/10.3144/expresspolymlett.2021.25

Rule of Thumb in Polymer Processing: Crystallinity of Thermoplastics

 

Hello and welcome to a new rule of thumb blog post. Today we discuss how processing conditions are impacting crystallinity and as a consequence the performance of plastics parts.

Crystallinity only plays a role with semi-crystalline polymers such as polyamides and polyolefins. High-density polyethylene can achieve crystallinity levels of 85% and ranges among the polymers with the highest crystallinity. Allover, for most semi-crystalline polymers crystallinity ranges below 50%.

Mechanism of crystallinity

Main drivers for crystallinity are time and temperature. Formation of crystallinity starts below the melting point and stops below the glass transition area. As long the material is above the glass transition point, molecule mobility is given to form regions of crystallinity within the amorphous regions. Therefore, the most effective temperature window is below the melting point and above the glass transition point. Crystal formation and growth varies for each semi-crystalline polymer and there is an optimum temperature for growth. Slowest growth is achieved just below the melting point.

What to take care during processing (injection moulding)

In general, the faster the crystals form and with them the material modulus, the faster the part demoulding can take place. For optimizing the cycle time, moulders tend to lower the mould temperature, which in fact is counterproductive. Selecting the optimal mould temperature will result in high yield quality parts. Table 1 shows the crystallinity of selected polymers with their tool temperatures.

Table 1: Overview crystallinity and mould temperatures of selected semi-crystalline polymers

Advantages of high crystallinity

The high crystallinity results in high strength, stiffness, higher chemical resistance and a higher resistance towards environmental stress cracking (ESC). Furthermore, the modulus retention of unfilled semi-crystalline polymers above the glass transition temperature is higher compared to amorphous polymers. Unreinforced PBT has a modulus of 2340 MPa at room temperature and at 100°C the modulus still achieves levels of 330 MPa. Another example are polyamides: the water uptake occurs mainly in the amorphous regions. The higher the crystallinity, the lower are the amorphous regions with water uptake possibilities. As a result part dimensions will be kept more accurate.

Conclusions

Polymers such as PE with a glass transition below room temperature can handle colder mould temperatures better than engineering polymers which have glass transitions above room temperature. In the latter case, colder mould temperate will result in lower crystallinity and problems with part performance. 

Based on the feedback of injection moulders, level of crystallinity of POM and PA66 are lower than the presented values. With a proper processing, one can reach with POM-C around 70%, around 5% more with POM-H and for PA66 33% in crystallinity.

Thank you for reading and #findoutaboutplastics

Best regards,

Herwig Juster

Interested in my monthly blog posts – then subscribe here and receive my high performance polymers knowledge matrix.

New to my Find Out About Plastics Blog – check out the start here section

My YouTube channel

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Enroll here for watching the free parts of the course

Literature

[1] https://www.hanser-elibrary.com/doi/book/10.3139/9783446443532

[2] https://www.ptonline.com/articles/materials-a-processors-most-important-job-part-2

Design Properties for Engineers – Tribological Properties of High Performance Polymers

 In this blog post, we discuss the tribological properties of high performance polymers and what to consider when selecting materials for sliding applications.

In tribology, the friction coefficient µ plays an important role. It is the resistance of two different surfaces to each other. Also, wearing of the surfaces is of interest. It is measured in µm/km. Tribological properties of plastics are described with the friction coefficient (µ) and wear (µm/km).

Friction properties of high performance polymers

In Figure 1, the friction properties of selected high performance polymers are shown. PTFE has a very low dynamic coefficient of friction compared to other high performance polymers. If you consider the wear too (Figure 2), it can be seen that PTFE has a high wear factor due to its low mechanical strength.

Figure 1: Coefficient of friction of different high performance polymers

Figure 2: Wear of different high performance polymers

Polyimides (PI, PAI, PBI) have low wear properties, combined with a low coefficient of friction of 0.4. It is beneficial to select materials in sliding applications which have a low wear rate together with a low coefficient of friction.

Optimization of tribological properties is done by using additives such as graphite, carbon fibers, molybdenum sulfide, and carbon nanotubes. However, certain additives can reduce the mechanical strength of the base resin (up to 50% reduction).

Conclusion

Friction and wear properties should be evaluated as good as possible on the life part. Among the high performance polymers, polyimides (PI, PAI, PBI) have overall good tribological properties due to their high resistance molecular structure. Using additives can help to reduce the wear of the material and improvement of friction coefficient is limited. 

Thank you for reading and #findoutaboutplastics

Best regards,

Herwig Juster

Interested in my monthly blog posts – then subscribe here and receive my high performance polymers knowledge matrix.

New to my Find Out About Plastics Blog – check out the start here section

My YouTube channel

Polymer Material Selection (PoMS) for Electric Vehicles (xEVs) - check out my new online course

Enroll here for watching the free parts of the course

Literature

[1] Saechtling Kunststoff Taschenbuch