Bahram Asiabanpour

An experimental study of surface quality and dimensional accuracy for selective inhibition of sintering

Selective inhibition of sintering (SIS) is a new rapid prototyping method that builds parts in a layer‐by‐layer fabrication basis. SIS works by joining powder particles through sintering in the parts body, and by sintering inhibition of some selected powder areas. In this research, statistical tools were applied to improve some important properties of the parts fabricated by the SIS process. An investigation of surface quality and dimensional accuracy was conducted using response surface methodology and through analysis of the experimental results, the impact of the factors on them was modeled. After developing a desirability function model, process operating conditions for maximum desirability are identified. Finally, the desirability model is validated.

SIS – a new SFF method based on powder sintering

Selective inhibition of sintering (SIS) is a layered fabrication process which is capable of rapidly producing accurate functional parts out of polymers and metals using a relatively inexpensive machine. This article presents a brief overview of the research and development aimed at establishing the feasibility and the potential of the process.

A new adaptive slicing approach for the fully dense freeform fabrication (FDFF) process

Fully dense freeform fabrication (FDFF) is a process based on thin line cutting processes, variable thickness layering, slicing in different orientations, and bulk layer attachment. The combination of these capabilities enables the production of good quality complex parts from practically any material at a very fast pace. As for rapid prototypes fabricated by the FDFF process, it is certainly possible to employ adaptive slicing technique due to the possibility of cutting different metal/non-metal sheet at various thicknesses. This paper proposes a new adaptive slicing method whereby the capability of cutting a 3D solid model at the predefined sheets’ thicknesses is achieved and the geometry of all internal and external features of a part is also investigated to ensure the reduction of part geometry deviation through the seamless curvature detection. Despite most previous works which start slicing a tessellated or direct CAD model at the maximum available thickness, this system commences the process with available minimum thickness by applying a new adaptive method to all pairs of contours at the top and bottom slices of the layer. Autodesk Inventor solid modeler, as a design-by-feature solid modeler, is used for 3D solid modeling. The proposed system is implemented by Visual Basic codes inside Inventor using API functions to access both geometry and topology information of the design-by-feature solid model. This system has been successfully tested on a variety of complex parts containing sophisticated internal and external features.

Optimising the automated plasma cutting process by design of experiments

Automated plasma cutting is an effective process for building complex, two-dimensional metallic parts in a short period of time. Because the plasma cutting machine has several factors or input variables to control (e.g., current, cutting speed, torch height, etc.) and the process requires compliance with a variety of part quality characteristics or response variables (e.g., flatness, clean cut, bevel angle, etc.), it is difficult to find a machine setting that improves the overall quality of the manufactured parts. This research was conducted to discover the relevant factors that affect the parts surface quality characteristics and the optimum machine settings by implementing a design of experiments and following a response surface methodology approach. Desirability functions were used to optimise the automated plasma cutting process. Final results identified an optimal machine configuration that facilitates the fabrication of parts with close-to-perfect quality for all the 18 quality responses considered.

Development of a Rapid Prototyping System using Response Surface Methodology

This case study presents an investigation of the relationships between eight process operating variables (factors) and five part performance measures (responses) in a rapid prototyping system. The use of fractional factorial, single-factor foldover, and central composite designs is demonstrated. Polynomial regression models are constructed for each response, followed by a desirability function model. Canonical and ridge analyses are used to identify a group of factor settings that simultaneously produce improved performance for all responses. Copyright

A novel engineering outreach to high school education

The demand for Science, Technology, Engineering, and Mathematics (STEM) students consistently outpaces supply. One of the recognized means for improving the readiness of high school students for STEM-related careers is outreach to high school programs. The newly created Ingram School of Engineering at Texas State University - San Marcos has partnered with the E3 Alliance and Project Lead The Way (PLTW) to create an opportunity for high school students to receive college credit in engineering disciplines for a set of advanced high school STEM courses.

Advancements in the selective inhibition sintering process development

Selective inhibition sintering (SIS) is a new layer-based rapid prototyping process that fabricates parts by joining polymer powder particles in the parts body to form a coherent solid and by preventing particles from joining at the parts boundary to form edges. This paper presents the fundamentals of the SIS process, its dedicated path generator, material selection research and the application of response surface methodology which has led to optimum performance, given various factors affecting part strength, surface quality and dimensional accuracy.

AN OVERVIEW ON FIVE APPROACHES FOR TRANSLATING CAD DATA INTO MANUFACTURING INFORMATION

All Rapid Prototyping and CNC material removal processes use information which is extracted from a CAD system. There are several ways to convert CAD data into usable manufacturing information. In this paper, five methods of translating CAD data into a usable manufacturing format are explained. These five methods are data translation from CAD files in STL, DXF, STEP-NC, and IGES formats as well as a platform-dependent area method of manufacturing information in a desirable format. For each method, algorithms and details about the CAD data translation into usable manufacturing and prototyping processes formats are presented. Finally, applications of each approach and its pros and cons are summarized in a table.

Close to CAD model curved-form adaptive slicing

Purpose – The main aim of this study is to generate curved-form cut on the edge of an adaptive layer. The resulting surface would have much less geometry deviation error and closely fit its computer aided design (CAD) model boundary. Design/methodology/approach – This method is inspired by the manual peeling of an apple in which a knifes orientation and movement are continuously changed and adjusted to cut each slice with minimum waste. In this method, topology and geometry information are extracted from the previously generated adaptive layers. Then, the thickness of an adaptive layer and the bottom and top contours of the adjacent layers are fed into the proposed algorithm in the form of the contour and normal vector to create curved-form sloping surfaces. Following curved-form adaptive slicing, a customized machine path compatible with a five-axis abrasive waterjet (AWJ) machine will be generated for any user-defined sheet thicknesses. Findings – The implemented system yields curved-form adaptive slic...

Micro scale silicon dioxide gear fabrication by bulk micromachining process

The purpose of this research was to find a cost effective and repeatable method for releasing high-quality micro-parts from a silicon substrate by bulk micromachining technology. Crystallographic shape removal technology on the finally released silicon oxide parts was put into scrutiny. Several methods were approached as possible solutions. These methods include ethylenediamine — pyrocatechol — water (EPW) etchant, the addition of a boron dopant to the silicon dioxide layer, pre-thinning of wafers, and the use of polyimide coatings to thin the silicon substrate subsequent to part release. The combined method of boron doping and polyimide coating produced the best results.