Near Net Shape Manufacturing Processes

The main objective of this chapter is to increase the existing knowledge in Incremental Sheet Forming (ISF), as a near net shape medical manufacturing process specifically for obtaining polymer of prostheses-parts, evaluating and defining the process parameters involved to improve the technology based on the analysis of quantitative outputs. This should help to provide process guidelines useful for manufacturing complex and customized parts, to be applied for example in the biomedical field. The chapter is divided into two main blocks: (i) the study of the influence of the process parameters on basic polymeric geometries manufactured by SPIF, and (ii) an analysis of some case studies of cranial implants manufactured by ISF using non-biocompatible and biocompatible polymers.

Friction Stir Processing (FSP) is a material processing technique which is gaining a lot of popularity in recent times as it is a solid state technique. Recently, FSP gained a lot of attention due to its various application such as grain refinement, superplasticity as near net shape forming, surface composite manufacturing, and friction stir casting to alter the cast properties. In the present chapter, FSP as near net shape forming technique has been described in different sections. Superplastic forming (more than 200% uniform elongation at elevated temperature) is considered as near net shape forming, which demands the fine-grained microstructure (<15 µm grain size) prior to forming. This microstructural requirement can be achieved in work material by FSP. Friction stir processed materials alike Al and Mg alloys have exhibited superplastic properties in order to produce near net shape material. FSP variables for superplastic forming includes tool rotation, travel speed, tool geometry, and multiple passes. Whereas superplastic forming variables include strain rate and forming temperature. The chapter focusses on application of FSP for the superplastic forming by reviewing the grain sizes achieved and elongation obtained and shall provide a comprehensive inputs to researchers/manufacturers active in field.

Among the various development in product development techniques near net shape manufacturing has assisted the manufacturers to develop complex structures with precision as per requirement. This chapter reports about three different types of additive manufacturing that has evolved out of near net shaped manufacturing. The three types of additive manufacturing are laser additive manufacturing, wire arc additive manufacturing and cold spray deposition technique. The effect of the various process parameters of the respective process are discussed in detail. The discussion is primarily focused on the development of shape memory alloy structures using the techniques mentioned and an analyses on the nature of the developed alloys. The surface morphology of the developed structures were evaluated using Scanning Electron Microscopy (SEM). The micro-hardness test reveals the mechanical properties of the samples. All the characterized results showed that SMA could be manufactured successfully using the mentioned techniques, though each system have their own pros and cons. Hence this chapter will give the researchers in beginning stage a clear idea about the evolution of near net shape manufacturing systems, that can be used by their research works in developing novel research ideas.

Dental implantation was introduced as a restorative procedure to reinstate the teeth functions and put the patient in normal contour, comfort, speech and health. Dental implants have been used over the centuries and the production techniques have been developed over the years. One of the advanced technologies is additive manufacturing (AM) which enables high degree of freedom ability to produce complex shaped and customized parts similar to human teeth. AM facilitates the production of complex geometric structure without the need of preparing expensive tools, hence it is more cost effective and time saving process. The current chapter provides an overview of AM as a promising technology for near net shape production of dental in preparing customised dental implants. The chapter also explore the anatomy and mechanical properties of human teeth together with the requirements for the design of teeth implants. The chapter survey the current AM technologies used for dental implant, clinical implications and highlights the future trend of AM in the development of near net shaped dental implants.

Laser-based additive manufacturing is a group of manufacturing processes widely used to produce three-dimensional near net shape components. Lasers can provide localized and controllable amounts of energy with the aim to cure a liquid photopolymer, to sinter or melt powders of different nature or even to cut laminates in order to obtain a physical model in the macro- or microscale. This work provides an overview on some major near net-shape manufacturing processes based on laser. Influence of the processing parameters, materials suitable for each one, and main advantages and current limitations of these techniques are reviewed for readers to understand and undertake research to establish the field further.

This chapter specifically reports a part of the detailed investigation conducted on near net shape manufacturing of miniature spur brass gears by abrasive water jet machining (AWJM). The machined miniature gears are external spur type and have 8.4 mm pitch diameter, 12 teeth, and 5 mm thickness. A total of 9 experiments (with two replications each) have been conducted based on Taguchi’s robust technique with L9 orthogonal array. A detailed analysis of the effects of three important AWJM parameters i.e. water jet pressure, abrasive mass flow rate and stand-off distance on surface quality i.e. micro-geometry (profile error) and surface roughness (mean roughness depth) of miniature gear has been done. Water jet pressure is found to be the most significant parameter affecting surface quality of miniature gears. This chapter reports the effect of AWJM parameters on micro-geometry of miniature gears and optimization of AWJM process to produce the best surface quality of miniature gears using Desirability technique. Miniature gear machined at optimum AWJM parameters possesses high surface quality with profile error 14.15 μm and mean roughness depth 4.6 μm. Based on the profile error value, this gear is assigned manufacturing quality of German standard DIN-8 which is better than that produced by conventional processes. Investigation reveals the capability of AWJM to manufacture near net shape miniature gears and identifies this technology as a sustainable alternate to the conventional processes of gear manufacturing.

The continuous innovations in sheet metallic materials lead to the need of the development of new and innovative forming methodologies. The emergence of the near net shape technologies, with the aim to create a product as close as possible to the final component, is an answer to these recent progresses. The knowledge of the formability limits of a material, that define the capacity of a material to deform permanently without failure (by necking or fracture) allows a better design of a near net shape manufacturing process. This chapter describes the methodology to determine experimentally the fracture limits by tension (fracture forming limit line—FFL) and in-plane shear (shear fracture forming limit line—SFFL). For this, commonly utilized laboratory test specimens for mechanical, fracture and formability characterization are used to determine gauge length strains at the post-testing cracked regions of the specimen and involves the determination of the gauge length strains at the cracked regions of the specimens.

Injection moulding (IM) is a well-established manufacturing process for cost-effective replication of polymer-based components. Advanced IM processes have been developed; modifying the final polymer part produced to create microcellular structures. Through the creation of microcellular materials, not only can the final weight be reduced but also, the near net shape can be improved. Microcellular Injection Moulding (MIM) shows high potential to improve near net shape of polymer parts and, the green aspect of polymer manufacturing platforms. This chapter aims to present the significant developments that have been achieved to enhance the MIM technology. Aspects covered include co-injection moulding, core back processing, gas counter pressure, vario-thermal moulding and mould coating. The resulting characteristics of each enhancing technique is presented.