Isotropic and ‘voidless’

Isotropic and ‘voidless’

Bond3D performs with its own PEEK printer

PEEK is a popular
high-performance thermoplastic polymer

Nowadays, almost any material can be printed and a high-performance thermoplastic polymer like PEEK cannot be left behind. However, due to the high viscosity in the molten state and the anisotropy of conventionally printed products, printing high-quality PEEK products is a challenge. Bond3D developed a pressure-controlled printing process that retains the favorable bulk properties of PEEK. The Enschede-based company now builds printers not for sale, but for production – supported by application engineering – in-house. For the future, print facilities in the United States and Asia are on the map.

PEEK (polyetheretherketone) is a high-performance thermoplastic polymer loved for its wide range of beneficial properties: light weight, high strength, chemical resistance, thermal stability (from -50 to +150°C) and biocompatibility. It therefore finds applications in diverse markets, such as semiconductors, medical, aerospace, energy and automotive. Designers are very keen to combine the favourable properties of PEEK with the freedom of form that 3D printing offers. For years, a great deal of effort has been put into 3D printing PEEK and the development and construction of PEEK printers. At the end of last year at Formnext in Frankfurt (D), a prominent trade fair for additive manufacturing, these printers were on display in all shapes and sizes.

Own business model

A striking debutant at Formnext was Bond3D from Enschede, which has also developed a 3D printer for PEEK. It is even a unique printer, they claim, that works according to a pressure-controlled printing process. This process retains PEEK’s high-performance properties in end products that are isotropic and void-free. Bond3D does not sell PEEK printers, however, but bases its business model on printing PEEK products and supporting customers in design and print preparation. In doing so, Bond3D is building on its partnership with one of the world’s largest PEEK producers, UK-based Victrex, which invested in Bond3D in 2019 to help the start-up make the move to the market. The relationship is a two-way street, explains Marc Kunst, manager Sales and Business development at Bond3D: “Victrex provides us with the material and leads; after all, they have been active in this market for 35+ years. Conversely, when we do business development with clients, we engage Victrex as a material expert.”

Spinal Cage

A spinal cage to replace a worn out intervertebral disc in the back is often made of titanium or PEEK. PEEK scores better in terms of biocompatibility – human bone can grow easily on the rough printed surface on the front end, human bone can easily grow into it – and mechanical properties, comparable to those of human bone. The British PEEK producer Victrex was already active in this field and saw opportunities to expand its position with 3D printing. to strengthen its position with 3D printing of these products (freedom of shape!); hence the investment in Victrex. hence the investment in Bond3D. The two parties are now going for FDA approval and hope to be able to use their product in the human body for the first time in 2023. into the human body for the first time.

Technology release

Exhibition visitors were really enthusiastic about Bond3D at the end of last year, says Kunst. “Since 2014 we have been in our own tech bubble, but now we have actively stepped into the market for the first time. With leads that already came to us through Victrex in the past two years, we have done development projects, printed prototypes and worked on releasing our technology; we are now at the stage of serial production. It definitely was a nice confirmation that that there are no other parties who have a printer with the same capabilities as ours.” Because of the favourable properties of PEEK that are retained in the process, Bond3D concentrates on critical functional parts. “We have three focus markets: semiconductor, medical and energy. In addition, we do some for automotive and industrial.”

Formula 1

In semicon, lightweight – when replacing metal with PEEK in a product – is important, explains Kunst. “Just like the fact that our products retain the properties of the bulk material, which engineers are already familiar with. As a specific application, we make a lot of manifolds (for the distribution of fluid flows, ed.), because of the leak-tightness of our voidless products and the chemical resistance of PEEK.” In the energy market, PEEK has long been used in the oil & gas industry, due to its chemical resistance.

Kunst shows a part for an energy-efficient oil pump made from the hard, difficult to machine super duplex stainless steel. “We can print it much faster in PEEK and now we are going to optimize the design as well.” Tim Veldhuis, application development engineer, adds: “Here you can clearly see the combination of printing and finishing. For functional surfaces, because they have to be closed off, we print a little bit of extra material, which we then mill to a smooth size. This gives us the best of both worlds and is only possible because our product is voidless. If it wasn’t, milling would put holes in it, so it wouldn’t seal.”

Kunst continued: “But for the energy transition – think of fuel cells and electrolyzers for hydrogen – PEEK is also the perfect choice because it is also heat-resistant.” In the medical world, the favourable mechanical properties of PEEK and the freedom of design offered by 3D printing, such as in a ‘spinal cage’, are also important. Veldhuis: “The best designs are those in which we can use our USP’s such as strong, leak-proof and heat-resistant.

Personally, I like Formula 1 customers the best. Several racing teams have already come to us via Victrex. We are working for them to validate our process and already print strong, weight-saving products that cannot be made in any other way. But unfortunately, we are not allowed to tell anything else about it.”

Pressure controlled printing

A common printing technique such as FDM (fused deposition modelling) is flow-controlled. With a constant flow, layers of heated material are extruded from the print head. The risk is that the tracks do not quite connect (underextrusion) or that too much material is printed (overextrusion). Voids can occur in the product and this effect is further enhanced by the fact that the webs in successive layers are often printed crosswise (in the x and y directions). In the z-direction (the direction in which the product is built up layer by layer), the layers often do not completely connect to each other. The printed product therefore has a lower tensile strength in that direction and is therefore anisotropic in its material properties.

Cross-section of a product that is flow-controlled (top) or pressure-controlled (bottom).

Cross-section of a product that is flow-controlled (top) or pressure-controlled (bottom).

Flow-controlled printing, with the risk of under-extrusion (left) or over-extrusion (right).

Flow-controlled printing, with the risk of under-extrusion (left) or over-extrusion (right).

Pressure-controlled printing with always exactly 100% filling, whether the space to be filled is narrow (left) or wide (right).

Pressure-controlled printing with always exactly 100% filling, whether the space to be filled is narrow (left) or wide (right).

Technological feat

The Bond3D printing process also works in layers, but is pressure-controlled. The printhead has a built-in mechanism for pressure measurement, to determine when the space under the nozzle is filled. After first printing the contours of the desired product in a layer flow-controlled, the space between the layers is then filled exactly 100 per cent under pressure. Thus, no cavities are created and the material properties are the same in all directions, comparable to bulk properties. The process, incorporated in a printer as a mechatronic/controlling tour de force, produces products that are isotropic and ‘voidless’ – hole-less, hole-less or cavity-less sounds a bit strange, hence the English term.

Adding more printers

Now that Bond3D is actively entering the market, it’s time to set up a mature printing facility in Enschede, the Netherlands. Next year, the number of printers will double, from eight to sixteen. The ambition is to establish hubs in the United States and Asia to be closer to customers there. At the same time, work is continuing on the further development of the printer, reports operational manager Arry Wegdam. “We want to improve the robustness even further and make machines suitable for certain markets. For example, a printer for the semiconductor industry that works extra clean and, for the medical market, a special printer that meets the requirements of the FDA (American certifying body for food and medical products, ed.). Or printers that work at higher speeds or higher temperatures, whatever the market demands; or for larger products (than the current construction volume of 400 by 400 by 400 mm allows, ed.).” In addition, Bond3D is working on a printer with multiple print heads, to be able to combine materials when printing a product. Initially, this will involve combining PEEK with carbon fibre or an electrically conductive PEEK variant, but in the future it may also involve other materials.

Static Mixer

This static mixer is used in the chemical industry. When liquids flow through this exotically shaped product, turbulence occurs and turbulence and this promotes mixing. Previously, individual metal metal parts were screwed together, but now Bond3D prints this mixer as a single, strong PEEK product and the design has been optimised for maximum mixing.

In-house knowledge

The company now has about seventy employees. Wegdam: “This year we will grow to almost 100 people and with that we just fit in the Demcon Technology Center where we are now located. On the production floor we can still expand to 45 printers.” All employees are now employed by Bond3D, after the start-up worked closely with technology developer and manufacturer Demcon in the first years. “In 2018 we started to employ all people in-house, because of the risks in development. We really want to have all the knowledge in-house.” That’s also where the distinctive character lies, according to Kunst. “If a customer comes to us with a very specific question, we are very flexible with our people and can quickly adjust the printing process for that specific question, for example.” That’s why Bond3D also has no fewer than six application engineers. “They do not only think along with the client about making parts, but we also hire them out for the entire process: design, FEM analysis, writing documentation. We conclude joint development agreements with customers for this; we also sell hours, but ultimately we are focused on product sales.” A major effort goes into ‘educating’ customers. “A few years ago, they mostly came with ‘square blocks’ that we had to print – not very efficient. Now we give training sessions at customers, provide webinars and teach designers to think differently. In larger companies we see engineers following our design guidelines and increasingly they are coming up with print-ready designs.”

Part of the toolkit

The market is open to Bond3D’s offerings, concludes Mark Kunst. “Companies that previously wanted to buy machines are now developing partnerships with us to be able to use the printing technology when they need it. If they want to buy a printer themselves and operate it, there’s more involved; they also have to train people and have sufficient fill on the machine. Now they see us as a tool in their toolkit of production techniques. There are a lot of great production techniques and they should keep using them. Sometimes they are better off machining or injection moulding, sometimes they come to us to have their designs printed. That’s where we want to remain the market leader/trendsetter, supplying parts made of high-quality plastic that cannot be made using conventional techniques.”

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