THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

Given the attention around additive manufacturing (AM), organizations want to know if their products should be fabricated using AM. To facilitate product development decisions, a reference system is shown describing the key attributes of a product from a manufacturability stand-point: complexity, customization, and production volume. Complexity and customization scales enable the grouping of products into regions of the map with common levels of the three attributes. A geometric complexity factor developed for cast parts is modified for a more general application. Parts with varying geometric complexity are then analyzed and mapped into regions of the complexity, customization, and production volume model. A discrete set of customization levels are also introduced. Implications for product development and manufacturing business approaches are discussed.

Making sense of 3-D printing: Creating a map of additive manufacturing products and services

For the first time, graphene nanoplatelets (xGnP) were incorporated at 4 wt% in acrylonitrile–butadiene–styrene (ABS) filaments obtained by a solvent-free process consisting of melt compounding and extrusion. Nanocomposite filaments were then used to feed a fused deposition modelling (FDM) machine to obtain specimens with various build orientations. The elastic modulus and dynamic storage moduli of 3D printed parts along three different build orientations were increased by the presence of xGnP in the ABS matrix. At the same time, a decrease in both stress and strain at break was observed when xGnP is added to ABS. Moreover, a higher thermal stability was induced on 3D printed parts by xGnP, as indicated by a reduction in both coefficient of linear thermal expansion and creep compliance. A comparison between 3D printed and compression moulded parts highlighted the importance of the orientation effects induced by the fused deposition modelling process.

Fused deposition modelling with ABS–graphene nanocomposites

There has been a trend in recent years to develop polyetheretherketone (PEEK)-based medical devices due to the excellent cell biocompatibility and desirable mechanical properties of PEEK, which has elastic modulus comparable to cortical bone. Different manufacturing techniques such as injection moulding, particulate leaching, compression moulding, and selective laser sintering (SLS) have been used to produce porous PEEK for biomedical applications. Despite a large number of publications on extrusion-based additive manufacturing (AM) of porous structures using various materials, there have been very few general reports on extrusion AM of low quality small PEEK parts without defects such as warpage and delamination and no further assessment of mechanical properties. Successful low-cost 3D printing of PEEK structures using filament-based extrusion AM process is reported in this paper for the first time. Hot extrusion head design, extrusion temperature, and ambient temperature were identified as impor...

Extrusion-based additive manufacturing of PEEK for biomedical applications

Three dimensional printing has gained considerable interest lately due to the proliferation of inexpensive devices as well as open source software that drive those devices. Public interest is often followed by media coverage that tends to sensationalize technology. Based on popular articles, the public may create the impression that 3D printing is the Holy Grail; we are going to print everything as one piece, traditional manufacturing is at the brink of collapse, and exotic applications, such as cloning a human body by 3D bio-printing, are just around the corner. The purpose of this paper is to paint a more realistic picture by identifying ten challenges that clearly illustrate the limitations of this technology, which makes it just as vulnerable as anything else that had been touted before as the next game changer.

Ten challenges in 3D printing

Purpose – The purpose of this paper is to establish a general method for achievable speed and accuracy evaluation of additive manufacturing (AM) machines and an objective comparison among them.Design/methodology/approach – First, a general schematic is defined that enables description of all currently available AM machines. This schematic is used to define two influential factors describing certain parts' properties regarding the machines' yield during manufacturing. A test part is defined, that will enable testing the influence of these factors on the speed and accuracy of manufacturing. A method for implementing and adapting test parts is established for individual machine's testing. This method was used to test four different machines that are predominantly used in Slovenia at the moment.Findings – Research has proven that the machine's yield had a predominant influence on the achievable manufacturing speeds of all the tested machines. In addition, the results have shown different ranges of achievable ...

Speed and accuracy evaluation of additive manufacturing machines

PEEK, poly(ether etherketone), is one of the high-quality industrial polymers. It is widely used in extremely demanding areas like automotive, aircraft and space industries. Because of the fact that it is bio-compatible, PEEK is also used for medical implants that are usually made by milling a block of the material. The article presents the results of an investigation of processing PEEK on a 3D printer for thermoplastic modelling. The used procedure is one of the additive manufacturing procedures and, as such, it builds a product by adding material layer by layer to get the finished product. Commercially available machines are unable to achieve the required melting and environment temperatures, so a new machine was developed. The machine was designed and built at the company Ortotip d.o.o. and it is able to produce the parts of up to 130 mm Ž 130 mm Ž 150 mm. After the initial testing, test specimens, according to standards EN ISO 527-2: 2012 and EN ISO 178: 2011, were produced and tested at the facilities of the PEEK manufacturer Invibio (from the UK). The article presents the steps taken when developing the PEEK modelling machine, the test methods to verify the mechanical properties of manufactured products and the results of the material testing. The machine was developed to produce medical implants (specific maxillofacial prosthesis), but with additional testing (that will help to improve the mechanical properties of produced parts) practically all bone-replacement implants can be made.

Processing poly(ether etherketone) an a 3D printer for thermoplastic modelling

Non-contact optical three-dimensional measuring, scanning and digitising are increasingly present in quality assurance systems. Simple scanning procedures, high density of data acquired in a single scan, and the possibility of integrated reverse engineering and inspection, are all advantages of optical scanning compared to conventional measuring methods. Due to the three-dimensional acquisition of measuring data, an optical scanner is often considered to be an alternative possibility for coordinate measuring machines. However, the accuracy of the measured data acquired by optical scanning (even with a high-end system) is still far below the level achieved by high-level coordinate measuring machines. This paper examines the possibilities of using a three-dimensional scanner for workpiece inspection. The first part presents a special field of workpiece inspection in which, even with currently achievable accuracy, optical scanning is a viable solution for the inspection of manufactured parts. In addition, the achievable dimensional accuracy of an optical scanner is tested by scanning several gauge blocks. In conclusion, a head to head comparison with a coordinate measuring machine is made by scanning and verifying a sphere.

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Possibilities of Using Three-Dimensional Optical Scanning in Complex Geometrical Inspection

In the last decades, the technical field of additive layered manufacturing (ALM) has offered aid in medical reconstruction procedures in order to help surgeons reconstruct physical faults and anomalies of their patients. Using a combination of Computer Assisted Design (CAD), high medical skills and latest ALM technologies, it is now possible to help patients with birth defects or those suffering from craniofacial injuries of variable severities, retain aesthetic and functional properties of their bodies. Combined with traditional CT scanning techniques rapid technologies (prototyping and tooling) can be used as instruments for better (three-dimensional) visualization, simulation of procedures and treatment of patients. They also improve the overall performances of medical and nursing staff thus influencing the quality of medical service. Using a combination of Computer Assisted Design (CAD), high medical skills and latest rapid prototyping and manufacturing technologies, it is now possible to help patients with craniofacial deformities as birth defects, orthognathic deformities, deformities after malignancy treatment or the consequences of craniofacial injuries of variable severities, resulting in both aesthetic and functional alterations. This paper presents some clinical cases, carried out in cooperation of Faculty of Mechanical Engineering in Maribor and both University Clinical Centres in Slovenia, where virtual models have been used for surgical preparations and RP models for manufacturing of implants.

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Applications of Rapid Prototyping in Cranio- Maxilofacial Surgery Procedures

Purpose of this paper is to present basic solutions on shape complexity, based on basic information of the STL data. Design/methodology/approach: Paper presents a few methods of mathematically evaluating the complexity of the shape. Methods vary from very simple based on the number of triangles in STL file, STL file size and the parts volume, to the more complex mathematical evaluation based on the basic relations of the STL data. Findings: We discovered that evaluation of shape complexity based only on basic data of STL data gives us some basic results on part complexity and can be used for further researches. Research limitations/implications: For parts with large block volume/part volume ratio and thinner parts with free form surfaces only the first method is suitable and gives suitable results. Practical implications: In a rapidly developing field of manufacturing technologies choosing the optimal manufacturing procedure is a difficult and crucial decision. Usually the decision is based on experience evaluation that is fast and can be optimal. Usually, this method produces goods results, but in some cases this method can lead to cost increases and reduced economic efficiency without us even knowing that. Therefore, it is crucial, that a fast and simple solution is developed, by which the optimal way of manufacturing can be determined. Originality/value: Choosing maximum efficient manufacturing processes on base of part complexity is a new perspective in manufacturing, which, properly evolved and complied can cause revolution in manufacturing optimization, especially in hybrid manufacturing processes.

Bogdan Valentan

Papers

Speed and accuracy evaluation of additive manufacturing machines

Processing poly(ether etherketone) an a 3D printer for thermoplastic modelling

Possibilities of Using Three-Dimensional Optical Scanning in Complex Geometrical Inspection

Applications of Rapid Prototyping in Cranio- Maxilofacial Surgery Procedures

Basic solutions on shape complexity evaluation of STL data