Additive Manufacturing Process Chain PDF

Chapter 3 Generalized Additive Manufacturing Process Chain  Generalized AM Process Chain Objectives: – Discuss on: Key steps in the process sequence – Conceptualization and CAD; Conversion to STL; Transfer and manipulation of STL file on AM machine; Mac...

Chapter 3 Generalized Additive Manufacturing Process Chain  Generalized AM Process Chain Objectives: – Discuss on: Key steps in the process sequence – Conceptualization and CAD; Conversion to STL; Transfer and manipulation of STL file on AM machine; Machine setup; Build; Part removal and cleanup; Post- processing of part; and Application Variation from one AM machine to another – Photopolymer based systems; Powder-based systems; Molten material systems; and Solid sheets Metal systems – The use of substrates; energy density; Weight; Accuracy; and Speed Maintenance of equipment Materials handling issues Design for AM – Part orientation; Removal of supports; Hollowing out parts; Inclusion of undercuts and other manufacturing constraining features; Interlocking features; Reduction of part count in an assembly; and Identification markings/numbers Generalized AM Process Chain Application areas that don’t involve conventional CAD modeling – Medical modeling; Reverse engineering data; and Architectural modeling Future discussion Assignment: – Read Chapter 3, Pages 43 - 61 Homework: – Exercises: 1-5 YouTube Videos: – Additive manufacturing – The process explained » https://www.youtube.com/watch?v=4Jyj1fQbXCw – How Metal 3D Printing Works » https://www.youtube.com/watch?v=da5IsmZZ-tw – Additive Manufacturing and Machining: » https://www.youtube.com/watch?v=gu408bB9TEc  Eight steps in AM Conceptualization and CAD: – Some ideas as to how the product will look and function. – Can take many forms from textual and narrative descriptions to sketches and representative models including 3D CAD models. Conversion to STL: – STL derived from STereoLithography. – STL is a simply way of describing a CAD model in terms of its geometry alone. – It approximates the surface of the model with a series f triangular facets. – The process of converting to STL is automatic within most CAD systems. Transfer to AM Machine and STL File Manipulation: – Once the STL file has been created, it can be sent directly to the target AM machine. There may be a number of actions required prior to building the part: Verify the part is correct Use the visualization tool that allows to view and manipulate the part Reposition the part or change the orientation to allow it to be built at a specific location within the machine It is quite common to build more than one part at a time – may be multiples of the same part – or completely different STL files Some parts may require shrinkage or coating allowances Unusual cases may even require segmentation of STL files Numerous STL file manipulation software tools are available for purchase or for free download  Eight Steps in AM (Cont.) Machine Setup: – All AM machines will have at least some setup parameters that are specific to that machine or process. – Some machines are designed to run perhaps one or two different materials and with no variation in layer thickness or other build parameters – a very few setups. – Other machines are designed to run a variety of materials and may also have some parameters that requires optimization – with numerous setup options. – An incorrect setup procedure will still result in a part being built – final quality, however, be unacceptable. Build: – First few stages are semi-automated – considerable manual control, interaction, and decision making. – Once these steps are completed, the process switches to computer controlled building phase – layer based manufacturing takes place. – All AM machines will have a similar sequence of layer control, using a height adjustable platform, material deposition, and layer cross-section formation – some machines will combine the material deposition and layer formation simultaneously – others will separate them. – All machines will repeat the process until either the built is complete or there is no source material remaining – in either case the machine will alert the user to take action.  Eight Steps in AM (Cont.) Removal and Cleanup: – Ideally, the out from the AM machine should be ready for use. – More often the parts will still require significant amount of manual finishing before they are ready for use. – In all cases, that part should be separated from a build platform on which the part was produced or removed from the excess build material surrounding the part. – Some AM machines need support structures to help keep the part from collapsing or warping during the building process. – Some processes have been developed to produce easy-to-remove supports – there is still often significant amount of manual work required at this stage – a degree of manual skill also required since mishandling of parts and poor technique in support removal can result in a low quality output. – The cleanup stage may also be considered as the initial part of the post-processing stage. Post-process: – Usually manual stages of finishing the parts for application purposes – may involve abrasive finishing, like polishing and sandpapering, or application of coatings – this stage in the process is very application specific. – Some applications may require a minimum of post-processing – other application may require very careful handling of parts to maintain good precision and finish. – Some of the tasks can benefit from the use of power tools and additional equipment, like polishing tubs or drying and baking ovens.  Eight Steps in AM (Cont.) Application: – Following post-processing, parts are ready to use – parts may not behave according to standard material specifications like in molding and casting. – AM machines create parts with small voids or bubbles trapped inside them – could be the source for part failure under mechanical stress. – Some processes may cause the material to degrade during build not to bond, link, or crystallize in an optimum way – in almost every case, the properties are anisotropic (different properties in different direction) – this may result in parts that behave differently than if they were made using a more conventional manufacturing approach. – AM materials and processes are improving all time, and many applications do not require high performance from many of their components. – The number of applications for the output from AM processes is therefore constantly increasing. Steps in AM Process  Variations from One AM Machine to Another Variations: – The nominal layer thickness for most machines is around 0.1 mm – however, the layer thickness for most FDM Dimension machines is 0.254 mm – contrast that with standard layer thicknesses between 0.05 – 0.1 mm for SL technology. – Many technologies have the capacity to vary the layer thickness – the reasoning is that thicker the layer parts are quicker to build but are less precise. – Fine details in a design may cause problems with some AM technologies, such as wall thickness – particularly if there is no choice but to build the part vertically – even though positioning within the machine may be very precise, there is a fine dimension to the droplet size, laser diameter, or extrusion head that essentially defines the finest details or thinnest wall that can be fabricated. – Use of different materials even within the same process may affect the time, resources, and skill required to carry out a stage. – Post-processing that involves heat must include awareness of heat resistance or melting temperature of the material involved – abrasive or machining-based processing must also require knowledge of the material properties of the materials involved. – General understanding on variations can be had by considering whether the build material is processed as a powder, molten material, solid sheet, vat of liquid photopolymer, or in-jet deposited photopolymer.  Variations from One AM Machine to Another Photopolymer-Based Systems: – Easy to setup the system; - all liquid vat systems must use support from that same material as that used for the part. – With droplet deposition – possible to modify the support material as it comes out of the print head – supports will come away easily. – Advantage of photopolymer system –accuracy is generally good with thin layers; have poor mechanical properties compared to other AM materials. Newer resins offer improved temperature resistance, strength, and ductility – but degradation can occur quite rapidly if UV protected coating s are not applied. Powder-Based Systems: – No need to use supports – deposits a bed of powder layer-by-layer – easiest to setup for a simple build. Zcorp. parts created using binder printing into a powder bed are somewhat unique in AM in that parts can be colored by using colored binder material. Molten Material Systems: – Systems which melt and deposit materials in a molten state require support structure – For droplet-based systems like with the Thermojet process these supports are automatically generated; but with the extrusion process like FDM supports can either be generated automatically or the user can use come flexibility. Solid Sheets: – With lamination methods where the sheets are first placed and then cut, there is no need for supports – instead, there is a need to process the waste material in such a way that it can be removed from the part. – Cleaning up the parts can be most laborious process and there is general need to know exactly what the final part is supposed to look like. – The paper based systems experienced problems with handling and the Solido process based upon bonding of polymer sheets – does not seem to be problematic.  Metal Systems Metal Systems: – Similar to polymer systems. However, the following points are worth considering: The use of subtracts Energy density Weight Accuracy Speed Maintenance of Equipment: – Some machines use fragile laser or printer technology – carefully monitored – not to be used in dirty or noisy (both electrical noise and mechanical vibration environment Material Handling Issues: – Exposure to moisture and to excess light should be avoided. Loading material done offline using software systems. Recycle some or all the material from a build that did not form the part. Design for AM: – Part orientation – Removal of supports – Hollowing out parts – Inclusion of undercuts and other manufacturing constraining features – Interlocking features – Reduction of part count in an assembly – Identification marking/numbering Interlocking Features  Application Areas Application areas that do not involve conventional CAD modeling: – Medical modeling: Computerized Tomography (CT), Magnetic Resonance Imaging (MRI), 3D ultrasound etc. – Reverse engineering data: Laser scanning technology – Architectural modeling Designs are modified to show textures, colors, and shapes that may not be exact productions of the final design Further Discussions: – Some AM technologies may move to thicker layers or to processing regions rather than layers, both of which have been successfully demonstrated. – There are also processes that do not work well with the STL file format. – Color and other forms of multiple material systems will become more common in the future. – Other formats will be necessary so that part information can be described in a hierarchical fashion or volumetrically as well. – We can expect processes to become more complex within a single machine – we already see numerous additive processes combined with subtractive elements – as technology develops further, commercialization of hybrid technologies that include additive, subtractive, and even robot handling phases in a complex coordinated and controlled fashion. – Software is increasingly being optimized for AM processing – there is also a special software designed to convert the designs of World of Warcraft models into “Figureprints” as well as specially designed post-processing techniques. – As direct digital manufacturing becomes more common, we will see the need to develop standardized software processes based around AM. Figureprints Model, Post-processed Exercises: