Introduction to 3D Printing V2.3



Introduction to 3D Printing3D Printing Technologies3D printing is employed in aerospace, automotive, manufacturing, construction and other industries for prototyping and low volume production of (typically) complex, intricate items.There are many different 3D printing technologies, known as ‘additive manufacturing’ technologies:Fused deposition modeling (FDM),Selective laser sintering (SLS),Stereolithography (SLA),Direct metal laser sintering (DMLS),and many more.The printers at Midland Public Library (MPL) use FDM technology where a solid filament of plastic is melted and then pushed through a nozzle and deposited on a moveable table to form the part on cooling. The spatial relationship between the nozzle and the table is computer controlled and the item is thus built up layer per layer. Printers for FDMThere are many different manufacturers of FDM printers covering a very large cost range. Large multi-nozzle industrial printers can cost many $10,000s. Personal FDM printers can be purchased from approx. $500 and up, and in combination with free software applications and open-source software, make the technology affordable for the enthusiast.Different printers will require different skill levels to operate and maintain.MPL has two, single nozzle FDM printers:Ultimaker 2+Anycubic i3 MegaCost CDN$ (approx)$6,000$600Build volume (mm)223 x 223 x 205 210 x 210 x 205 Supported materialsPLA, ABS, CPE, CPE+, PC, Nylon, TPU 95APLA, ABS, HIPS, WoodNozzle sizes (mm)0.25, 0.40, 0.60, 0.80 0.40 Filament diameter (mm)2.85 1.75 Layer resolution (microns)0.25 mm nozzle; 60 to 150-0.40 mm nozzle; 20 to 2000.40 mm nozzle; 50 to 3000.60 mm nozzle; 20 to 400-0.80 mm nozzle; 20 to 600-X, Y and Z accuracy (microns)12.5, 12.5, 512.5, 12.5, 2Input file type.gcode.gcodeOverview of 3D Printing ProcessStep 1. Design/Obtain the 3D Model (software)The software model is a complete and unambiguous representation of the three dimensional item(s) to be printed. The model file can be created by:designing from a ‘blank sheet of paper’ using suitable 3D modelling software,importing/copying from another source, i.e., website, friend, etc. and then modifying,using an appropriate scanner to scan the physical object. MPL employs a Matter and Form 3D scanner for objects with a max. height: 25 cm (9.8 in), diameter: 18 cm (7.0 in) and weight: 3.0kg (6.6 lbs).using photogrammetry software and many photographs of the physical object. Step 2. Check the 3D Model (software)Checks that the model is indeed complete and unambiguous, that is to say, the model is ‘watertight’. The software does not check that the model can be successfully printed – just solid.Step 3. Slice the Model (software)Determines all the coordinates, movements and actions for the 3D printer being used and creates the computer ‘program’/data file that is going to control the printer. Each ‘slice’ is a single layer of extruded plastic for the model.Step 4. Check the Slices (software)The software that slices the model can (typically) show the slices creating the model one layer at time, i.e., it can simulate and visually animate the nozzle and table movements and thus show exactly what the printer is going to print. Review this simulation.Step 5. Print the Model (hardware)Load the computer program from Step #3 into the 3D printer, press ‘Print’ and go have a break.Steps #2 and #4 are required so that printer time and extruded plastic are not wasted on incomplete or impossible to print models.The 3D printer will do whatever the program loaded into it tells it to do and will not correct any mistakes in the above process.As with all computers, the maxim ‘garbage in –garbage out’ applies.Remember - design and make is an iterative process!Data Flow for 3D Printing Process2105025299720Design/Obtain 3D Model0Design/Obtain 3D Model-8572534150300003491230Material Parameters00Material Parameters43522903500755Printer Parameters00Printer Parameters3752850366268000443801534150300014954253653155024384006329680Model0Model280987556438800019907254548505.gcode file00.gcode file280987543675300021050253948430Check Simulation00Check Simulation21050253538855Slice Model00Slice Model21050253119755Manipulate Model00Manipulate Model280987519767550021050255215255Print00Print21050252700655Slicer Software00Slicer Software21050251631315Check Model 00Check Model 16954502100580.stl or .obj file00.stl or .obj file16954501052830.stl or .obj file00.stl or .obj file28098759099550374332542418037433251640840374332519126204352290176530Save model in native file format00Save model in native file format43522901214755Sent to 3D Print Services00Sent to 3D Print Services43522901900555Save for Distribution/Web00Save for Distribution/WebDetailed Process for 3D PrintingStep 1. Design the 3D ModelThere are many free 3D design packages available, some with paid upgrades to professional level software. There is also a large user community for support and many members create publicly available additions to the functionality of the software. Many training videos, resources, etc. to assist users are also available including free video tutorials via the MPL website.In choosing a design package to use/learn, consideration should be given to:The intended environment for the final model – technical, engineering, architectural, artistic, toy/decoration, animation, etc.Do you have a use for design/drawing other than 3D printing? The age/skill set of the user. Many large packages have a steep learning curve but have powerful functionality once mastered. Some packages, while not so powerful, are suitable for younger users.The availability of existing models for download and modification.The size of and the support provided by the user community. The supported file types. MPL requires an .stl or .obj file to transmit to the Slicer. To swap models between two software design packages a common 3D file format is required – typically a .dae file.Some common 3D design packages include:Sketchup from Trimble. Standalone and web-based. Free and subscription versions. Targeted towards engineering, technical and architectural users. Many extensions are available to increase functionality. There is a large user community.Onshape Education. Web-based. Free for educational establishments. Powerful professional suite of software tools for design and make.123D Design from Autodesk. Download. Free. Powerful professional suite of software tools for design and make. There is a large user community.TinkerCAD from Autodesk. Web-based. Free. Software tool set for 3D design, electronics, and coding. It is used by teachers, kids, hobbyists and designers to imagine, design and make. There is a large user community.3D Builder from Microsoft. Standalone. Bundled free with Windows 10. Includes 3D model checking.3DSlash. Web-based. Free. It is an intuitive ‘block’ modeller for younger users with the look and feel of Minecraft. Blender. Download. Free. Blender is an open source 3D creation suite that supports the entirety of the 3D pipeline—modeling,?rigging, animation, simulation, rendering, compositing and motion tracking and even video editing and game creation.Sculptris from Pixologic. Download. Free. Digital sculpting that involves manipulating a ‘blob of clay’. The current version is no longer supported and may be ‘flaky’ to get running.MeshMolder. Download. Free. Digital sculpting that involves manipulating a ‘blob of clay’. A stable product.Nervous System. . Free. Web-based application for the design of custom bracelets with free .stl downloads.3D model libraries on the Web include:Thingiverse. A universe of things. Some models provide easy tools to change/scale the model.Pinshape. A great selection of free and pay for .stl files.Consider the following model characteristics when designing a model for 3D printing with FDM:Avoid unsupported horizontal surfaces. Add curved and angled surfaces to support horizontal features of the model if possible.Avoid unsupported faces greater than 45 degrees from vertical.Avoid ‘stalactites’ – pillars/features descending from a ‘ceiling’, not rising from the floor.Reorient the model to minimize the above features.Small details may be difficult to print, depending upon nozzle size and available increments of layer heights in the Slicer.The final printed model may not be exactly the same size as the drawing due to the thermal contraction of the plastic or the resolution of the printer. Curved surfaces may be made up of many facets due to the 3D design software and the layers of printing.It is advisable to do some test prints if high accuracy or model assembly is required.Consider how the Slicer is going to ‘layer’ the model for printing and how the newly extruded plastic is going to join to the previously printed ‘slowly growing’ model.Ensure the model is truly a solid entity – ‘watertight’. Joining of many and/or complex curved surfaces may cause gaps or single ‘stray’ surfaces to remain attached to the outer surfaces of the model.Consider splitting the model into two or more separate models for reassembly after printing. One 3D model file may contain many individual models/parts but they may all be printed at once (as a set). Step 2. Check the 3D Model Once the 3D model has been completed and exported as a .stl file, it needs to be checked to ensure that the geometry represents a solid ‘watertight’ body before being printed.The .stl file (STereo Lithography or ‘Standard Triangle Language’ or ‘Standard Tessellation Language)?describes only the surface geometry of the model as a series of interconnected triangles. This file is sometimes known as the ‘mesh’ or the ‘wireframe’ model.The following issues may be present in the .stl file or mesh:There are holes, cracks or missing features. Some of these faults may be very small and not easily visible when viewing the model using the original design software.There may be triangles in the mesh where the ‘inside’ and ‘outside’ of each triangle have been switched.Vertices and edges may be duplicated and unreferenced to any other part of the model.Other topological errors and geometric singularities.The following software automatically checks and repairs (if possible) .stl files:3D Builder from Microsoft. Bundled free with Windows 10. This 3D design software can correct meshes and may also be used to simplify complex fabb Online Services from Autodesk. Free. Web based. The original .stl file is uploaded and a corrected one is available for download seconds later. If the .stl file cannot be repaired then a message is displayed but no indication is provided on what the error(s) was. MeshLab is an open source suite of software tools for working with 3D triangular meshes. Free. Downloaded. This software has a steep learning curve and requires considerable manual effort to repair, edit, etc. .stl meshes.Step 3. Slice the 3D ModelOnce the .stl file has been verified as correct then it may be loaded into the ‘slicer’ software. This software creates the computer data file (.gcode) that is going to control all aspects of the 3D printer printing the model.In order to slice the model, the slicer software has to know the features and characteristics of the intended 3D printer. Typically, a 3D printer manufacturer will recommend which slicing software to use with their printers. Also, all the parameters required to control a specific 3D printer and/or print material may be available in a data file (profile) from the printer manufacturer or the author of the slicer software. These data files may be simply loaded and stored in the slicer software. The values used for the controlling parameters have a major impact on the quality of the final printed model.Slicing software:Cura from Ultimaker. Free. Downloaded. Used by MPL for both of its 3D printers. Uses .stl or .obj file types as input. Cura units are always millimeters so, if possible, convert your 3D model as you export it to create your .stl file. KisSlicer. Free. Downloaded. No pre-determined profiles for MPL’s 3D printers.Typical Slicer parameters include;Filament diameter (for machines that can use different size filaments)Filament material, i.e., PLA, ABS, etc.Nozzle size (for machines that can use different nozzle sizes)Nozzle temperatureLayer height, i.e., the thickness of each slice - thinner for detailed modelsPrint speed – slower for detailed modelsInfill density – how solid to make the core of the model – high density gives a stronger model but longer printing time and uses more plastic.Additional parameters may include;Create support(s) to stop overhangs in the model from collapsing during printing,Create raft to improve adhesion of model to the flat bed of the printer.Supports and rafts are manually removed after the print is complete.The slicer software may also allow the following simple manipulation of the full 3D model prior to slicing:Moving or rotating the model on the bed of the printer. This will enable features that may print poorly to be better positioned and also centralize large models across the bed.Scaling the model. Use this feature to convert .stl files using imperial units to millimeters. Placing multiple models on the bed either by copying the current model or by loading another model file. Some slicing software will indicate errors in .stl file geometry by the use of colors.Model geometry cannot be changed in the slicer.The slicer software typically takes seconds to create the .gcode file from the .stl file. Once slicing is complete then the software will typically indicate the duration of the print job, the weight of the object and the length of filament used.Step 4. Check the SlicesOnce the slicer has generated the .gcode file, and before it is transferred to the printer for printing, the simulation of the print process should be viewed using the viewing/animation features of the slicer software. This animation will show the path the print head is taking per slice in order to create the model.Review each layer of the print, starting at the bottom and working up one layer at a time, to ensure that:- All intended features of the model are present and fully printed.- No unintended features are present.- Supports, if requested, are going to be printed.- All faces have solid continuous edges.- No errors are shown. Some slicers will indicate errors in their mesh as colored areas in the simulation.Step 5. Print the 3D ModelChoose the material and color of the model from the filaments available for your printer. PLA is the preferred material at MPL. Changing the filament on the printer is a fairly simple process and the manufacturer’s instructions must be followed.Before starting to print the model it is advisable to confirm that there is sufficient filament on the spool selected. Typically the slicer software will indicate, along with the print time estimate, the length and the weight of the filament required for the model. FDM filaments are typically purchased in 1 kg spools, and quantities of filament are practically measured by weight – not length.Once the .gcode file has been created by the slicer it may be transferred to the 3D printer. This may be accomplished by using a SD memory card or by a network connection.The printer will require some warm-up time to melt the filament in the nozzle and heat the bed of the machine. The heated bed improves adhesion of the extruded filament on the bed. Some machines/users apply tacky glue to the bed to also improve adhesion. This is typically done when the model has little surface area in contact with the bed and rafts have not been used.Print time may be from 20 minutes to 20+ hours depending upon the size and complexity of the model. Safety considerations must be given to leaving a working and hot printer unattended for long periods. MPL stipulates that their printers are not to be run unattended.Once printed, the model is allowed to cool before it is removed with a palette knife from the bed. Any supports and rafts are removed by cutting the excess material away. The model may be cleaned up with fine grained sandpaper. is a good resource to understand types of printing issues, including under extrusion, pillowing, stringing and warping and how to adjust the parameters in the Cura slicer software to correct them.Detailed 3D printing is not easy. It is part science and part art/craft.Costs:? For 3D printing, MPL charges $1.00 + $0.25 per 10 minutes of print time. See; On-line 3D printing services are available. You send/upload the corrected .stl model to them, they send you a quote and, when printed, they return your model by mail. Costs are based upon print technology used, material to be printed, weight of print material used, time to print and costs of shipping. - design and make is an iterative process!Resources - for Ultimaker printers and software. - all things Sketchup. – all things 3D printing. - generic printing guide. - generic printing guide. - essential explanations of 3D printing.Filament Weights and Lengths HYPERLINK "mailto:info@" \t "_blank" GlossaryPrinting TechnologiesFDM – Fused deposition modelingSLS - Selective laser sinteringSLA – StereolithographyDMLS - Direct metal laser sinteringEBM – Electron beam meltingLPBF – Laser powered bed fusionSLM – Selective laser meltingDLP – Digital light processingMaterialsPLA – Polylactic acid or Polylactide. Preferred material. Dimensionally stable. Good finish. Biodegradable. Use PLA unless a very strong reason exists not to.Wood – PLA base combined with cork, wood dust, etc. to provide look and feel of wood.The following materials require fume extraction for printing;ABS - Acrylonitrile butadiene styrene. Stable. High impact strength. TPU 95A – Thermoplastic polyurethane. Qualities of rubber and plastic. PC – Polycarbonate. High temp resistance. Strong and rigid. Transparent.CPE – Co-polyester. High temp resistance. Strong.Nylon – Polyamide. High temp resistance. Super strong.HIPS – High impact polystyrene. Susceptible to warping.File types (from Wikipedia).stl - describe only the surface geometry of a three-dimensional object without any representation of color, texture or other common CAD model attributes. An STL file describes a raw, unstructured?triangulated?surface by the?unit?normal?and vertices (ordered by the?right-hand rule) of the triangles using a dimensionless three-dimensional?Cartesian coordinate system..obj - file format is a simple data-format that represents 3D geometry alone — namely, the position of each?vertex, the?UV coordinate position?of each texture coordinate vertex,?vertex normals, and the faces that make each polygon defined as a list of vertices, and texture vertices. Dimensionless..dae – Digital asset exchange. Uses the XML COLLADA?(COLLAborative?Design?Activity) interchange?file format?for interactive?3D?applications..gcode - which has many variants, is the common name for the most widely used?numerical control?(NC)?programming language. It is used mainly in?computer-aided manufacturing?to control many types of automated machine tools.OtherCAD – Computer aided designCAM – Computer aided manufactureNC – Numerical control. An early form of C – Computer numerical controlXML – Extensible markup language. File format for text based database using tags to define objects and the data for an object.ASCII – American Standard Code for Information Interchange. ASCII numerical codes represent characters in the text files used by computers. ................
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