Digital production of functional models in metal can yield improvements for a variety of medical and dental applications. LayerWise, a company specialising in the technology, focuses on selective laser melting (SLM), a technique that shapes a desired metal part geometry by melting metal powder layer by layer. Using this digital approach, the shape of complex parts can be produced in a single manufacturing step. The company applies SLM to manufacture patient-specific orthopaedic and cranial and maxillofacial (CMF) implants, implant-supported dental prostheses and medical instrumentation. According to the company, SLM makes tooling and time-consuming CAM preparation obsolete, enables medium-size series production economically to be viable and allows the production of high-grade parts in a specified metal alloy without scrap.
Building up parts in layers
“At LayerWise, we reverse the entire process,” says Jonas Van Vaerenbergh, director of the industrial division of the company, which is based in Leuven, Belgium. “Our core business is selective laser melting, a technology developed to build up material in layers instead of removing it in different steps. In the meantime, we have optimised the process for a variety of metals and alloys, including titanium (ASTM grades 1, 2, 5 and 23), stainless steel (316L and 17-4 alloys) and cobalt-chromium.”
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| Usually, the products leaving the LayerWise facility cannot be produced any other way. Demonstration piece produced in stainless steel 316L showing internal shapes for weight reduction, transportation and cooling. |
In the machine, a high-precision laser is directed to metal powder particles to selectively build up a 20- to 40-µm horizontal metal layer. Since all articles are built up by successively adding such thin metal powder layers that are molten completely by a focused laser beam, any desired 3-D geometry can be realised. The powerful fibre laser with high energy intensity operating in the inert area inside the machine guarantees that metal parts being built up exhibit a dense and homogenous material structure. CAD directly drives the machine without requiring any programming, clamping or tooling.
Focus on technology
LayerWise reportedly operates the first production centre in Belgium that exclusively focuses on this additive production process for metal parts. The company was founded by Jonas Van Vaerenbergh and Peter Mercelis, both of whom were involved in the development of selective laser melting at the Katholic University of Leuven. The firm collaborates with the university and invests 30% of its resources in research and development.
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Personalised orthopaedic protheses are generally produced in titanium, equipped with a fine surface geometry that actively encourages surface retention. Photos courtesy Mobelife. |
“By bringing together technological expertise, production capacity and customer support, LayerWise occupies a unique position on a European level,” indicates Van Vaerenbergh. “Our engineers control SLM to such an extent that they are capable of perfecting the technology and realise challenging specifications. Also the implementation of process control tools in and around the melting zone is important to guarantee high part quality.”
Dimensional accuracy down to 50 µm can be achieved,” says Peter Mercelis, director of the medical division. Parts measuring up to 250 × 250 × 250 mm can be produced. High-resolution systems are capable of producing very thin walls with thicknesses down to 300 µm. Selective laser melting products have a surface finish of around 5 µm Ra. Accuracy and surface quality may be further improved by combining our additive manufacturing processes with CNC machining. Moreover, a variety of surface treatments is offered to obtain polished surfaces.
By precisely controlling the production process, LayerWise can achieve a homogeneous micro structure with a relative density of up to 99.98% for an increasing number of metals and alloys. Research shows that the mechanical properties are virtually the same as those of conventional metals. To prove this, the company systematically carries out mechanical tests on the level of density, hardness, elongation and fatigue. In advance, the chemical composition of the bulk metal powders are examined in a chemical laboratory.
Dental suprastructure
The manufacturer is also is involved in the dental industry, for which the company manufactures products such as implant-supported suprastructures. Using patient-specific geometry data, acquired through medical imaging or 3-D scanning, the personalised structure is designed in software and printed in titanium. As a concluding step, the dental technician finishes off the structure and completes the final prothesis.
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| Through patented DentWise technology, geometry and surface retention related limitations set by traditionally moulded or milled suprastructures no longer apply. |
“Through digital SLM technology, geometry and surface retention related limitations set by traditionally moulded or milled suprastructures no longer apply,” Mercelis says. “In addition, the implant connections are completed with high precision. Implant bars and bridges achieve a fit accuracy better than 20 µm at the implant interface. They also can integrate complex surface textures and sealing edges.” DentWise suprastructures are manufactured using ultra-strong titanium alloy (Ti6Al4V, grade V), which outperforms the commonly used titanium grade II in terms of mechanical properties.
Orthopaedic, cranial and maxillofacial implants
LayerWise is also specialised in producing orthopaedic, CMF implants though additive manufacturing technology. Examples include acetabular cups, trauma fixation plates, spinal components and CMF plates. In addition to prototyping and serial production of standard components, custom prostheses can be manufactured through the seamless integration between the digital design and digital production stages.
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| On an implant LayerWise manufactured for a major maximillan reconstruction, it integrated a titanium layer structure that stimulates surface retention and strengthens the implant to withstand surgical manipulation. |