David Paloušek

Pilot study of the wrist orthosis design process

Purpose – The purpose of this paper is to describe a manufacturing methodology for a wrist orthosis. The case study aims to offer new approaches in the area of human orthoses. Design/methodology/approach – The article describes the utilization of rapid prototyping (RP), passive stereo photogrammetry and software tools for the orthosis design process. This study shows the key points of the design and manufacturing methodology. The approach uses specific technologies, such as 3D digitizing, reverse engineering and polygonal-surface software, FDM RP and 3D printing. Findings – The results show that the used technologies reflect the patients requirements and also they could be an alternative solution to the standard method of orthosis design. Research limitations/implications – The methodology provides a good position for further development issues. Practical implications – The methodology could be usable for clinical practice and allows the manufacturing of the perfect orthosis of the upper limb. The usage ...

Finite element analysis for the evaluation of the structural behaviour, of a prosthesis for trans-tibial amputees

The finite element analysis (FEA) has been identified as a useful tool for the stress and strain behaviour determination in lower limb prosthetics. The residual limb and prosthetic socket interface was the main subject of interest in previous studies. This paper focuses on the finite element analysis for the evaluation of structural behaviour of the Sure-flex™ prosthetic foot and other load-bearing components. A prosthetic socket was not included in the FEA. An approach for the finite element modelling including foot analysis, reverse engineering and material property testing was used. The foot analysis incorporated ground reaction forces measurement, motion analysis and strain gauge analysis. For the material model determination, non-destructive laboratory testing and its FE simulation was used. A new, realistic way of load application is presented along with a detailed investigation of stress distribution in the load-bearing components of the prosthesis. A novel approach for numerical and experimental agreement determination was introduced. This showed differences in the strain on the pylon between the experimental and the numerical model within 30% for the anteroposterior bending and up to 25% for the compression. The highest von Mises stresses were found on the foot-pylon connecting component at toe off. Peak stress of 216MPa occurred on the posterior adjusting screw and maximum stress of 156MPa was found at the neck of the male pyramid.

Use of digital technologies for nasal prosthesis manufacturing

Background and aim: Digital technology is becoming more accessible for common use in medical applications; however, their expansion in prosthetic and orthotic laboratories is not large because of the persistent image of difficult applicability to real patients. This article aims to offer real example in the area of human facial prostheses. Technique: This article describes the utilization of optical digitization, computational modelling, rapid prototyping, mould fabrication and manufacturing of a nasal silicone prosthesis. This technical note defines the key points of the methodology and aspires to contribute to the introduction of a certified manufacturing procedure. Discussion: The results show that the used technologies reduce the manufacturing time, reflect patient’s requirements and allow the manufacture of high-quality prostheses for missing facial asymmetric parts. The methodology provides a good position for further development issues and is usable for clinical practice. Clinical relevance Utilization of digital technologies in facial prosthesis manufacturing process can be a good contribution for higher patient comfort and higher production efficiency but with higher initial investment and demands for experience with software tools.

Use of micro computed-tomography and 3D printing for reverse engineering of mouse embryo nasal capsule

Imaging of increasingly complex cartilage in vertebrate embryos is one of the key tasks of developmental biology. This is especially important to study shape-organizing processes during initial skeletal formation and growth. Advanced imaging techniques that are reflecting biological needs give a powerful impulse to push the boundaries of biological visualization. Recently, techniques for contrasting tissues and organs have improved considerably, extending traditional 2D imaging approaches to 3D . X-ray micro computed tomography (μCT), which allows 3D imaging of biological objects including their internal structures with a resolution in the micrometer range, in combination with contrasting techniques seems to be the most suitable approach for non-destructive imaging of embryonic developing cartilage. Despite there are many software-based ways for visualization of 3D data sets, having a real solid model of the studied object might give novel opportunities to fully understand the shape-organizing processes in the developing body. In this feasibility study we demonstrated the full procedure of creating a real 3D object of mouse embryo nasal capsule, i.e. the staining, the μCT scanning combined by the advanced data processing and the 3D printing.

Wear Analysis of Extracted Polyethylene Acetabular Cups Using a 3D Optical Scanner

ABSTRACT Wear analysis of total hip replacements (THRs) is considered one of the most relevant research areas helping to improve the longevity and overall design of THRs. The coordinate machine method (CMM) and Fourier profilometry are the most common methods for measuring THR wear. This article presents optical scanner digitalization as a new method for measuring the wear of polyethylene (PE) acetabular cups. The aim of this article is to explore the potential of this method for the PE wear measurements. Optical scans for the purposes of this study were produced using an ATOS Triple Scan 3D optical scanner. The optical scanner is efficient and it can measure a large number of points for polygonization and for further development of the preworn models. In this study, the scanner first generated point clouds on a sample of 13 retrieved ultra-high-molecular-weight polyethylene (UHMWPE) acetabular cups. Next, volumetric models of the cups were created by polygonizing the point clouds. Reverse engineering was used to develop models of the original acetabular cups using the geometry of the unworn parts of the retrieved cups. A comparison of the two models then showed the total volume of the PE debris. The optical scanning method was validated against the gravimetric method using three new acetabular cups that were worn out on a hip pendulum simulator. Validation shows that the optical scanning method is a valid method for wear analysis of the retrieved UHMWPE acetabular cups.

Geometrical Accuracy of the Metal Parts Produced by Selective Laser Melting: Initial Tests

The paper deals with the inspection of the geometric accuracy of the parts produced by additive manufacturing. Tested parts were produced on commercial machine SLM280HL based on selective laser melting technology. Tests were focused on determination of the geometric precision of building process and dimensional variations within the machine’s platform. The results shows change in surface quality at different wall angles and large variation of part outer dimensions. The tests of different settings of laser power and scanning speed are also presented.

Determination of the cause of selected canine urolith formation by advanced analytical methods

OBJECTIVE The goal of this study was to determine the cause of selected canine urolith formation using less conventional but more advanced analytical methods. METHODS A routine laboratory specialising in urinary calculi analysis noticed a special type of core zone in some canine uroliths, which was typically made up of cylindrical holes. Of 4028 canine samples analysed, non-absorbable suture material was detected in 9 (0·22%) cases. A hollow cylindrical central area was found in a further 13 (0·32%) samples. X-ray microtomography (μCT) was utilised in order to reveal the channel structure inside this urolith sample. Matrix-assisted laser desorption-ionisation - time of flight mass spectrometry was used in order to assess the cause of this urinary stone formation. RESULTS The diameter of the channel structure corresponded with the diameter of the previously utilised suture material and indicated that this urolith was formed around residual suture material. Further confirmation was provided by the comparative matrix-assisted laser desorption-ionisation - time of flight mass spectrometry chemical analysis. This channel structure is formed by a surgical thread that serves as a base for the urolith growth. CLINICAL SIGNIFICANCE Results of this study confirm the causative role of absorbable suture material in the pathogenesis of hollow channel structures in some canine compound uroliths.

Influence of Scanning Strategies on Processing of Aluminum Alloy EN AW 2618 Using Selective Laser Melting

This paper deals with various selective laser melting (SLM) processing strategies for aluminum 2618 powder in order to get material densities and properties close to conventionally-produced, high-strength 2618 alloy. To evaluate the influence of laser scanning strategies on the resulting porosity and mechanical properties a row of experiments was done. Three types of samples were used: single-track welds, bulk samples and samples for tensile testing. Single-track welds were used to find the appropriate processing parameters for achieving continuous and well-shaped welds. The bulk samples were built with different scanning strategies with the aim of reaching a low relative porosity of the material. The combination of the chessboard strategy with a 2 × 2 mm field size fabricated with an out-in spiral order was found to eliminate a major lack of fusion defects. However, small cracks in the material structure were found over the complete range of tested parameters. The decisive criteria was the elimination of small cracks that drastically reduced mechanical properties. Reduction of the thermal gradient using support structures or fabrication under elevated temperatures shows a promising approach to eliminating the cracks. Mechanical properties of samples produced by SLM were compared with the properties of extruded material. The results showed that the SLM-processed 2618 alloy could only reach one half of the yield strength and tensile strength of extruded material. This is mainly due to the occurrence of small cracks in the structure of the built material.

PROCESSING OF NEARLY PURE IRON USING 400W SELECTIVE LASER MELTING – INITIAL STUDY

e-mail: palousek@fme.vutbr.cz The proposed article deals with development and initial tests of nearly pure iron powder ATOMET Fe AM (Rio Tinto, QMP) using 400W selective laser melting technology. Magnetic properties in conjunction with 3D printing possibilities of metals could be used in many applications. Metal powder was analyzed for verification of distribution and shape of particles. The main laser parameters such as laser power, laser scanning speed and hatch distance were tested to achieve low porosity and sufficient, high building speed. Laser scanning speed was tested in the range from 200 mm/s up to 1400 mm/s and laser power from 100 W to 400 W. The hatch distance was set to the values of 90, 120 and 150 μm. Porosity was evaluated via microscopy image analysis and micro CT. To obtain mechanical properties the tensile testing was performed.

IMPACT RESISTANCE OF DIFFERENT TYPES OF LATTICE STRUCTURES MANUFACTURED BY SLM

The presented paper describes the impact resistance of lattice structure samples made by Selective Laser Melting with the use of AlSi10Mg powder material. The samples with five types of different unit cells of lattice structure were used in this study. The topology of the unit cells structure was changed to describe various impact resistance behavior while the relative density of lattice structure was kept constant. The samples were tested by drop-weight impact testing device with spherical shape of indenter. During the test the maximum reaction force, deceleration and position of load element (indenter) were measured. The results showed, that samples with the same relative density, but with a different shape of unit cell had a different impact resistance. It is because the mechanical properties are significantly influenced by the cell topology which determined the type of failure under loading – bending or buckling. The FBCCZ had the highest impact resistance, but the energy was absorbed with very high reaction force during absorption.