Passividade na interface prótese/pilar intermediário de infraestrutura implantossuportadas confeccionadas pela tecnologia CAD/CAM e método convencional

The objective of this research was to evaluate the passivity and strain induced in infrastructures screwed on abutments, made by CAD/CAM technology, and to compare these samples with parts manufactured by conventional casting. Using CAD/CAM technology, 4 samples were made from zirconia (Zircad) and 4 samples were manufactured from cobaltchrome (CoCrcad). The control groups were 4 specimens of cobalt-chrome, made by onepiece casting (CoCrci), for a total of 12 infrastructures. To evaluate the passivity, the infraestructures were installed on the abutments. One end was tightened and the vertical gap between the infrastructure and the prosthetic abutment was measured with scanning electron microscopy (250×). The mean strain in these infrastructures was analyzed via the photoelasticity test. A significant difference (p = 0.000) in passivity was observed between the control (CoCrci) and sample groups (CoCrcad and CoCrci). CoCrcad exhibited the best value of passivity (48.76 ± 13.45 μm) and CoCrci the worst (187.55 ± 103.63 μm), Zircad presented an intermediate value (103.81 ± 43.15 μm). When compared to the other groups, CoCrci showed the highest mean strain around the implants (17.19 ± 7.22 kPa). It was concluded that the zirconia infrastructure made by CAD / CAM showed a higher vertical marginal misfit than those made in cobalt-chromium alloy with the same methodology, however, the tension generated in the implants was similar. The CAD/CAM technology is more accurate for passivity and mean strain of infrastructure screwed on abutments than conventional manufacturing techniques

Otimização do fresamento de roscas internas com a técnica de interpolação helicoidal

In machining of internal threads, dedicated tools, known as taps, are needed for each profile type, diameter, and low cutting speed values are used when compared to main machining processes. This restriction in the cutting speed is associated with the difficulty of synchronizing the tool s rotation speed and feed velocity in the process. This fact restricts the flexibility and makes machining lead times longer when manufacturing of components with threads is required. An alternative to the constraints imposed by the tap is the thread milling with helical interpolation technique. The technique is the fusion of two movements: rotation and helical interpolation. The tools may have different configurations: a single edge or multiple edges (axial, radial or both). However, thread milling with helical interpolation technique is relatively new and there are limited studies on the subject, a fact which promotes challenges to its wide application in the manufacturing shop floor. The objective of this research is determine the performance of different types of tools in the thread milling with helical interpolation technique using hardened steel workpieces. In this sense, four tool configurations were used for threading milling in AISI 4340 quenched and tempered steel (40 HRC). The results showed that climb cut promoted a greater number of machined threads, regardless of tool configuration. The upcut milling causes chippings in cutting edge, while the climb cutting promotes abrasive wear. Another important point is that increase in hole diameter by tool diameter ratio increases tool lifetime

Influência da técnica de fabricação e dos materiais sobre o ajuste da interface pilar/implante em infraestruturas implantossuportadas

The aim of this study was to compare the misfit vertical, horizontal and passivity of zirconia and cobalt-chromium frameworks fabricated for CAD / CAM technology and conventional method of casting. Sixteen frameworks in one-piece, were obtained from a metallic matrix containing three Brånemark compatible implants with regular platform (Titamax Cortical Ti, Neodent). Eight frameworks were fabricated by CAD / CAM system (NeoShape, Neodent): four in zirconia (ZirCAD) and four cobalt-chromium (CoCrcad). Eight other frameworks were obtained by conventional casting method: four cobalt-chromium with UCLA abutment premachined Co-Cr (CoCrUCci) and four cobalt-chromium with UCLA abutment castable (CoCrUCc). The fit vertical, horizontal and passivity by one-screw test were measured using scanning electron microscopy with magnification of 250x. Initially evaluated the passivity by one-screw test and subsequently to assess the vertical and horizontal misfit, tightened all the screws with a torque of 20 Ncm. Mean, standard deviation, minimum and maximum values were calculated for each group. Measurements of horizontal misfit were transformed into cumulative frequency for categorization of the variable and the group later comparison groups. To evaluate the existence of quantitative differences between the groups tested for vertical misfit and passivity, we used the Kruskal-Wallis test. The Mann-Whitney test was used to compare group to group statistical differences (p <0.05). Were observed the respective mean and standard deviation for vertical misfit and passivity in micrometers: ZirCAD (5.9 ± 3.6, 107.2 ± 36), CoCrcad (1.2 ± 2.2, 107.5 ± 26 ), CoCrUCci (11.8 ± 9.8, 124.7 ± 74), CoCrUCc (12.9 ± 11.0, 108.8 ± 85). There were statistical differences in measures of vertical misfit (p = 0.000). The Mann-Whitney test revealed statistical differences (p <0.05) between all groups except between CoCrUCci and CoCrUCc (p = 0.619). No statistical difference was observed for the passivity. In relation to the horizontal misfit groups ZirCAD and CoCrcad did not show best values in relation to CoCrUCci and CoCrUCc. Based on the results it can be concluded that frameworks fabricated by CAD / CAM technology had better values of vertical fit than those manufactured by the casting method, nevertheless, the passivity was not influenced by manufacturing technique and material used. The horizontal fit obtained by frameworks manufactured by CAD / CAM was not superior to those manufactured by casting. A lower variability in vertical adjustment and passivity was observed when frameworks were fabricated by CAD / CAM technology

CAD e engenharia reversa como ferramentas de auxílio na fabricação de cartuchos para próteses ortopédicas

The manufacturing of above and below-knee prosthesis starts by taking surfac measurements of the patient s residual limb. This demands the making of a cartridg with appropriate fitting and customized to the profile of each patient. The traditiona process in public hospitals in Brazil begins with the completion of a record file (according to law nº388, of July 28, 1999 by the ministry of the health) for obtaining o the prosthesis, where it is identified the amputation level, equipment type, fitting type material, measures etc. Nowadays, that work is covered by the Brazilian Nationa Health Service (SUS) and is accomplished in a manual way being used commo measuring tapes characterizing a quite rudimentary, handmade work and without an accuracy.In this dissertation it is presented the development of a computer integrate tool that it include CAD theory, for visualization of both above and below-knee prosthesis in 3D (i.e. OrtoCAD), as well as, the design and the construction a low cos electro-mechanic 3D scanner (EMS). This apparatus is capable to automatically obtain geometric information of the stump or of the healthy leg while ensuring smalle uncertainty degree for all measurements. The methodology is based on reverse engineering concepts so that the EMS output is fed into the above mentioned academi CAD software in charge of the 3D computer graphics reconstruction of the residualimb s negative plaster cast or even the healthy leg s mirror image. The obtained results demonstrate that the proposed model is valid, because it allows the structura analysis to be performed based on the requested loads, boundary conditions, material chosen and wall thickness. Furthermore it allows the manufacturing of a prosthesis cartridge meeting high accuracy engineering patterns with consequent improvement in the quality of the overall production process

Adaptação eletrônica de um leitor mecânico de coto, investigação e desenvolvimento de interface CAD

Due to advances in the manufacturing process of orthopedic prostheses, the need for better quality shape reading techniques (i.e. with less uncertainty) of the residual limb of amputees became a challenge. To overcome these problems means to be able in obtaining accurate geometry information of the limb and, consequently, better manufacturing processes of both transfemural and transtibial prosthetic sockets. The key point for this task is to customize these readings trying to be as faithful as possible to the real profile of each patient. Within this context, firstly two prototype versions (α and β) of a 3D mechanical scanner for reading residual limbs shape based on reverse engineering techniques were designed. Prototype β is an improved version of prototype α, despite remaining working in analogical mode. Both prototypes are capable of producing a CAD representation of the limb via appropriated graphical sheets and were conceived to work purely by mechanical means. The first results were encouraging as they were able to achieve a great decrease concerning the degree of uncertainty of measurements when compared to traditional methods that are very inaccurate and outdated. For instance, it's not unusual to see these archaic methods in action by making use of ordinary home kind measure-tapes for exploring the limb's shape. Although prototype β improved the readings, it still required someone to input the plotted points (i.e. those marked in disk shape graphical sheets) to an academic CAD software called OrtoCAD. This task is performed by manual typing which is time consuming and carries very limited reliability. Furthermore, the number of coordinates obtained from the purely mechanical system is limited to sub-divisions of the graphical sheet (it records a point every 10 degrees with a resolution of one millimeter). These drawbacks were overcome by designing the second release of prototype β in which it was developed an electronic variation of the reading table components now capable of performing an automatic reading (i.e. no human intervention in digital mode). An interface software (i.e. drive) was built to facilitate data transfer. Much better results were obtained meaning less degree of uncertainty (it records a point every 2 degrees with a resolution of 1/10 mm). Additionally, it was proposed an algorithm to convert the CAD geometry, used by OrtoCAD, to an appropriate format and enabling the use of rapid prototyping equipment aiming future automation of the manufacturing process of prosthetic sockets.

Desenvolvimento de um núcleo versátil e integrado de ferramentas CAD/CAE para a modelagem e simulação de peças mecânicas

Currently there is still a high demand for quality control in manufacturing processes of mechanical parts. This keeps alive the need for the inspection activity of final products ranging from dimensional analysis to chemical composition of products. Usually this task may be done through various nondestructive and destructive methods that ensure the integrity of the parts. The result generated by these modern inspection tools ends up not being able to geometrically define the real damage and, therefore, cannot be properly displayed on a computing environment screen. Virtual 3D visualization may help identify damage that would hardly be detected by any other methods. One may find some commercial softwares that seek to address the stages of a design and simulation of mechanical parts in order to predict possible damages trying to diminish potential undesirable events. However, the challenge of developing softwares capable of integrating the various design activities, product inspection, results of non-destructive testing as well as the simulation of damage still needs the attention of researchers. This was the motivation to conduct a methodological study for implementation of a versatile CAD/CAE computer kernel capable of helping programmers in developing softwares applied to the activities of design and simulation of mechanics parts under stress. In this research it is presented interesting results obtained from the use of the developed kernel showing that it was successfully applied to case studies of design including parts presenting specific geometries, namely: mechanical prostheses, heat exchangers and piping of oil and gas. Finally, the conclusions regarding the experience of merging CAD and CAE theories to develop the kernel, so as to result in a tool adaptable to various applications of the metalworking industry are presented