Lars-Erik Rännar

Efficient cooling with tool inserts manufactured by electron beam melting

Purpose: This paper presents a comparative study, regarding cooling time and dimensional accuracy, of conventional injection mold cooling channel layouts, using straight holes and a baffle, and free-form fabricated (FFF) layout, manufactured by the direct-metal rapid tooling (RT) method electron beam melting (EBM). Many other methods have been proven useful for rapid tooling, but the authors have not found any publications where EBM has been used to manufacture injection molding tools. Design/methodology/approach: A test part was designed in order to replicate a common and important issue: inadequate cooling in deep cores. The part and the different cooling layouts were analyzed in an injection molding simulation software and the numerical results were compared with corresponding experimental results. Findings: The analyses showed an improvement in both cooling time and dimensional accuracy in favor of conformal FFF cooling channels manufactured by EBM. The experimental results correlate well with the numerical tests, however with some discrepancies. Research limitations/implications: The results presented are based on the direct-metal RT method EBM, and they were obtained using a specific test part. Orginality/value: This paper can be a useful aid when designing mold tools and especially when considering the usage of FFF cooling channels versus conventional cooling design. It can also serve as a reference when comparing the efficiency in terms of cooling time and dimensional accuracy between different layouts.

Imaging, virtual planning, design, and production of patient-specific implants and clinical validation in craniomaxillofacial surgery.

The purpose of this article was to describe the workflow from imaging, via virtual design, to manufacturing of patient-specific titanium reconstruction plates, cutting guide and mesh, and its utility in connection with surgical treatment of acquired bone defects in the mandible using additive manufacturing by electron beam melting (EBM). Based on computed tomography scans, polygon skulls were created. Following that virtual treatment plans entailing free microvascular transfer of fibula flaps using patient-specific reconstruction plates, mesh, and cutting guides were designed. The design was based on the specification of a Compact UniLOCK 2.4 Large (Synthes®, Switzerland). The obtained polygon plates were bent virtually round the reconstructed mandibles. Next, the resections of the mandibles were planned virtually. A cutting guide was outlined to facilitate resection, as well as plates and titanium mesh for insertion of bone or bone substitutes. Polygon plates and meshes were converted to stereolithography format and used in the software Magics for preparation of input files for the successive step, additive manufacturing. EBM was used to manufacture the customized implants in a biocompatible titanium grade, Ti6Al4V ELI. The implants and the cutting guide were cleaned and sterilized, then transferred to the operating theater, and applied during surgery. Commercially available software programs are sufficient in order to virtually plan for production of patient-specific implants. Furthermore, EBM-produced implants are fully usable under clinical conditions in reconstruction of acquired defects in the mandible. A good compliance between the treatment plan and the fit was demonstrated during operation. Within the constraints of this article, the authors describe a workflow for production of patient-specific implants, using EBM manufacturing. Titanium cutting guides, reconstruction plates for fixation of microvascular transfer of osteomyocutaneous bone grafts, and mesh to replace resected bone that can function as a carrier for bone or bone substitutes were designed and tested during reconstructive maxillofacial surgery. A clinically fit, well within the requirements for what is needed and obtained using traditional free hand bending of commercially available devices, or even higher precision, was demonstrated in ablative surgery in four patients.

Production of Customized Hip Stem Prostheses : a Comparison Between Machining and Additive Manufacturing

Purpose - The purpose of this paper is to study the use of the additive manufacturing (AM) method, electron beam melting (EBM), for manufacturing of customized hip stems. The aim is to investigate ...

The Effect of EBM Process Parameters upon Surface Roughness

Purpose The surface roughness of products manufactured using the additive manufacturing (AM) technology of electron beam melting (EBM) has a special characteristic. Different product applications can demand rougher or finer surface structure, so the purpose of this study is to investigate the process parameters of EBM to find out how they affect surface roughness. Design/methodology/approach EBM uses metal powder to manufacture metal parts. A design of experiment plan was used to describe the effects of the process parameters on the average surface roughness of vertical surfaces. Findings The most important electron beam setting for surface roughness, according to this study, is a combination of “speed and current” in the contours. The second most important parameter is “contour offset”. The interaction between the “number of contours” and “contour offset” also appears to be important, as it shows a much higher probability of being active than any other interaction. The results show that the “line offset” is not important when using contours. Research limitations/implications This study examined “contour offset”, “number of contours”, “speed in combination with current” and “line offset”, which are process parameters controlling the electron beam. Practical implications The surface properties could have an impact on the product’s performance. A reduction in surface processing will not only save time and money but also reduce the environmental impact. Originality/value Surface properties are important for many products. New themes containing process parameters have to be developed when introducing new materials to EBM manufacturing. During this process, it is very important to understand how the electron beam affects the melt pool.

New Metallurgy of Additive Manufacturing in Metal : Experiences from the Material and Process Development with Electron Beam Melting Technology (EBM)

Additive manufacturing (AM) is becoming one of the most discussed modern technologies. Significant achievements of the AM in metals today are mainly connected to the unprecedented freedom of component shapes this technology allows. But full potential of these methods lies in the development of new materials designed to be used specifically with AM. Proper understanding of the AM process will open up new possibilities, where material and component properties can be specifically tailored by controlling the parameters throughout the whole manufacturing process. Present paper discusses the issues related to the beam melting technologies AM and electron beam welding (EBW). We are speaking of new direction in material science that can be termed “non-stationary metallurgy”, using the examples from material and process development for EBW, electron beam melting (EBM®) and other additive manufacturing methods.

Clinical, Morphological, and Molecular Evaluations of Bone Regeneration With an Additive Manufactured Osteosynthesis Plate.

AbstractThere is limited information on the biological status of bone regenerated with microvascular fibula flap combined with biomaterials. This paper describes the clinical, histological, ultrastructural, and molecular picture of bone regenerated with patient-customized plate, used for mandibular reconstruction in combination with microvascular osteomyocutaneous fibula flap. The plate was virtually planned and additively manufactured using electron beam melting. This plate was retrieved from the patient after 33 months. Microcomputed tomography, backscattered-scanning electron microscopy, histology, and quantitative-polymerase chain reaction were employed to evaluate the regenerated bone and the flap bone associated with the retrieved plate. At retrieval, the posterior two-thirds of the plate were in close adaptation with the underlying flap, whereas soft tissue was observed between the native mandible and the anterior one-third. The histological and structural analyses showed new bone regeneration, ingrowth, and osseointegration of the posterior two-thirds. The histological observations were supported by the gene expression analysis showing higher expression of bone formation and remodeling genes under the posterior two-thirds compared with the anterior one-third of the plate. The observation of osteocytes in the flap indicated its viability. The present data endorse the suitability of the customized, additively manufactured plate for the vascularized fibula mandibular reconstruction. Furthermore, the combination of the analytical techniques provides possibilities to deduce the structural and molecular characteristics of bone regenerated using this procedure.

Failure location prediction by finite element analysis for an additive manufactured mandible implant

In order to reconstruct a patient with a bone defect in the mandible, a porous scaffold attached to a plate, both in a titanium alloy, was designed and manufactured using additive manufacturing. Regrettably, the implant fractured in vivo several months after surgery. The aim of this study was to investigate the failure of the implant and show a way of predicting the mechanical properties of the implant before surgery. All computed tomography data of the patient were preprocessed to remove metallic artefacts with metal deletion technique before mandible geometry reconstruction. The three-dimensional geometry of the patients mandible was also reconstructed, and the implant was fixed to the bone model with screws in Mimics medical imaging software. A finite element model was established from the assembly of the mandible and the implant to study stresses developed during mastication. The stress distribution in the load-bearing plate was computed, and the location of main stress concentration in the plate was determined. Comparison between the fracture region and the location of the stress concentration shows that finite element analysis could serve as a tool for optimizing the design of mandible implants.

Patient-Specific Clavicle Reconstruction Using Digital Design and Additive Manufacturing

There is a trend toward operative treatment for certain types of clavicle fractures and these are usually treated with plate osteosynthesis. The subcutaneous location of the clavicle makes the plat ...

Additive Manufacturing for Medical and Biomedical Applications: Advances and Challenges

Additive Manufacturing (AM) has solidly established itself not only in rapid prototyping but also in industrial manufacturing. Its success is mainly determined by a possibility of manufacturing components with extremely complex shapes with minimal material waste. Rapid development of AM technologies includes processes using unique new materials, which in some cases is very hard or impossible to process any other way. Along with traditional industrial applications AM methods are becoming quite successful in biomedical applications, in particular in implant and special tools manufacturing. Here the capacity of AM technologies in producing components with complex geometric shapes is often brought to extreme. Certain issues today are preventing the AM methods taking its deserved place in medical and biomedical applications. Present work reports on the advances in further developing of AM technology, as well as in related post-processing, necessary to address the challenges presented by biomedical applications. Particular examples used are from Electron Beam Melting (EBM), one of the methods from the AM family.

Electron Beam Melting: Moving from Macro- to Micro- and Nanoscale

This paper presents some results achieved in the biomedical applications of the EBM® technology, and describes the resolved and unresolved challenges presented by modern medical implant manufacturing. In particular it outlines the issues related to the cellular structure design and metal surface modification. Moving to precision control of the metal surface at a micro-and sub-micrometer scale is a serious challenge to the EBM® processing, because it uses the powder with average grain size of about 0.04 to 0.1 mm. Though manufacturing of components with solid-mesh geometry and porous surfaces using EBM® is quite possible, post-processing (for example chemical or electrochemical) is needed to achieve desired control of the surface at smaller scales to realize full potential of the technology for biomedical applications.