Technologies for rapid prototyping (RP) - basic concepts, quality issues and modern trends

The paper describes the basics of the 3D printing technologies for rapid prototyping (RP). It shows the benefits of their utilization in product design and manufacturing of conventional parts and items with medical and other application. The most mature RP principles are presented and compared.Some trends in developing new 3D printers and corresponding materials for micro/nano and biological applications are described.  Some modern budget platforms are suggested for technology users.The paper also provides a summary of the main quality issues in the layering technologies as well as methodologies for studying the process capabilities, accuracy and maturity

Grid method studies of the geometrical uncertainties in free form and micro processes

This research is devoted to the engineering of a generic, reliable and cost-effective method for the investigation of accuracy in layer based fabrication technologies. It begins with a review of the causes of deviations and uncertainties in component parts, analyses of the existing approaches for accuracy investigation and their limitations and disadvantages. The main focus of the research is the development of an original and convenient methodology capable of defining the dimensional uncertainties and accuracy of the technologies and the distribution of dimensional errors within the entire build area. The Grid Methodology is based on the discretisation of the object to allow the measurement, calculation, visualisation and analysis of part distortion in terms of linear and shear deviations from nominal. A single test piece and routine measurement procedure are utilised to estimate the distribution of the above entities; calculated in a similar way to the geometrical characteristics of strains in solid mechanics. The methodology was applied to research the causes of inaccuracy in the vertical direction of SLS Polystyrene. The presence of a critical dimension in height from where the distortion changes from shrinkage to extension was revealed and explained. The methodology was also utilised to estimate the necessary scaling factors to improve part accuracy, based on the calculated distortions. Implementation of the Grid Method to Micro Projection Stereolithography resulted in the ability to describe and estimate curling distortion in terms of angular deviations from nominal and separate it from linear distortions. - ii - Furthermore the application of the GM to the emerging micro-nano manufacturing sector has been shown to support the assessment of process capability. This provides a means of calculating process tolerances using results obtained from the single test piece. Investigation of the accuracy capabilities of three micro-processes was performed and their compatibility for designing process chains presented.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Grid method studies of the geometrical uncertainties in free form and micro processes

This research is devoted to the engineering of a generic, reliable and cost-effective method for the investigation of accuracy in layer based fabrication technologies. It begins with a review of the causes of deviations and uncertainties in component parts, analyses of the existing approaches for accuracy investigation and their limitations and disadvantages. The main focus of the research is the development of an original and convenient methodology capable of defining the dimensional uncertainties and accuracy of the technologies and the distribution of dimensional errors within the entire build area. The Grid Methodology is based on the discretisation of the object to allow the measurement, calculation, visualisation and analysis of part distortion in terms of linear and shear deviations from nominal. A single test piece and routine measurement procedure are utilised to estimate the distribution of the above entities; calculated in a similar way to the geometrical characteristics of strains in solid mechanics. The methodology was applied to research the causes of inaccuracy in the vertical direction of SLS Polystyrene. The presence of a critical dimension in height from where the distortion changes from shrinkage to extension was revealed and explained. The methodology was also utilised to estimate the necessary scaling factors to improve part accuracy, based on the calculated distortions. Implementation of the Grid Method to Micro Projection Stereolithography resulted in the ability to describe and estimate curling distortion in terms of angular deviations from nominal and separate it from linear distortions. - ii - Furthermore the application of the GM to the emerging micro-nano manufacturing sector has been shown to support the assessment of process capability. This provides a means of calculating process tolerances using results obtained from the single test piece. Investigation of the accuracy capabilities of three micro-processes was performed and their compatibility for designing process chains presented

Bulk Metallic Glass based Tool-Making Process Chain for Micro- and Nano- Replication

Existing and emerging micro-engineered products tend to integrate a multitude of functionalities into single enclosures/packages. Such functions generally require different length scale features. In practice, devices having complex topographies, which incorporate different length scale features cannot be produced by employing a single fabrication technology but by innovatively, integrating several different complementary manufacturing techniques in the form of a process chain. In order to design novel process chains that enable such function and length scale integration into miniaturised devices, it is required to utilise materials that are compatible with the various component manufacturing processes in such chains. At the same time, these materials should be able to satisfy the functional requirements of the produced devices. One family of materials, which can potentially fulfil these criteria, is bulk metallic glasses (BMGs). In particular, the absence of grain boundaries in BMGs makes them mechanically and chemically homogeneous for processing at all length scales down to a few nanometres. In this context, this research presents an experimental study to validate a novel process chain. It utilizes three complementary technologies for producing a Zr-based BMG replication master for a microfluidic device that incorporates micro and nano scale features. Then, to validate the viability of the fabricated BMG masters, they are utilized for serial replication of the microfluidic device by employing micro-injection moulding

Grid Method for Accuracy Study of Micro Parts Manufacturing

The paper introduces a methodology for accuracy estimation of micro stereo lithography and micro milling processes. The experimental procedure is a combination of producing simple test parts, routine measurement by optical metrology equipment, and computerised calculations and visualisation by purpose made software. The accuracy and precision of the process are revealed after calculating the linear and shear strains following an approach initially developed for sheet metal forming analysis. The strains in this study are defined on the basis of offset between measured and nominal coordinates of the grid points on the test part. The specific strains of meso-micro parts due to different factors during and after manufacturing are illustrated and explained. Directions for further research are also presented

Grid method for accuracy study of micro parts manufacturing

The paper introduces a methodology for accuracy estimation of micro stereo lithography and micro milling processes. The experimental procedure is a combination of producing simple test parts, routine measurement by optical metrology equipment, and computerised calculations and visualisation by purpose made software. The accuracy and precision of the process are revealed after calculating the linear and shear strains following an approach initially developed for sheet metal forming analysis. The strains in this study are defined on the basis of offset between measured and nominal coordinates of the grid points on the test part. The specific strains of meso-micro parts due to different factors during and after manufacturing are illustrated and explained. Directions for further research are also presented

Function and length scale integration in innovative products - technical solutions and new organisational models

This paper presents the issues typically occurring when integrating, into a single product, functions that can only be realised by employing different length scale features (macro, meso, micro and down to nano). The discussion is supported by the responses of a survey performed on 88 European research and development projects conducted by members of the multi-material micro manufacture (4M) community in Europe. Two main issues are highlighted as critical for a successful multi-scale integration. The first one relates to the concurrent design of materials properties and manufacturing processes. The second focuses on the need for new production approaches and organisational models applied by companies

Utilizing a Grid method for Accuracy Study of Micro SLA parts

The paper introduces a methodology for strain estimation in studying the accuracy of the micro SLA process. The calculation of strains is carried out following the approach utilized in sheet metal forming analysis. The method consists of building a set of test plates with square grids. The simple geometry of the reference points on the grids allows easy measurement with optical metrology equipment controlled by purpose made software. The obtained set of grid point coordinates is used to calculate the offset between measured and nominal grid coordinates. A specially developed program calculates strains in each grid cell. Plots of strain distributions alongside x, y, z axis are generated and interpolated. The specific strains of meso-micro parts due to different factors during and after building is illustrated and explained. Directions for further research are also presented