Additive Manufacturing (AM) in a Nutshell Spring 2016 Nick Meisel Additive vs. Subtractive Manufacturing Traditional subtractive manufacturing involves the removal of unwanted material from a block of raw material until you arrive at the desired part geometry. Additive manufacturing (AM) involves the selective layerwise deposition of material until you arrive at the part geometry. The main advantages of this layerwise approach are i) greatly reduced scrap/waste and ii) the ability to create virtually any geometry imaginable. General Additive Manufacturing Process Flow The general AM process involves converting a digital CAD model to a physical 3D object. To do this, CAD models must be transformed into STL files for printing (under Save As or Export in any CAD program). STL files create a triangular mesh based on the surface geometry of the part. This.STL file can then be used in any 3D printing software/printer. 3D Printing vs. Additive Manufacturing You re likely hearing about 3D printing everywhere, but may not have heard of the term additive manufacturing before. The terms are more or less synonymous (3D printing is simply the catchier public term for AM), but AM is the official standard term for the technology. The term is meant to emphasize that the technology is being used to create end-use products now (and thus is a manufacturing process), instead of simply creating prototypes. Types of Additive Manufacturing There are 7 main categories of AM processes, which all have their unique pros and cons. Some are powder-based, while others are based on filament or liquids. Some can process metal materials, while other focus on polymers. The seven types are i) material extrusion, ii) material jetting, iii) binder jetting, iv) vat photopolymerization, v) powder bed fusion, vi) directed energy deposition, and vii) sheet lamination. The process that you re most likely to encounter is material extrusion (a.k.a. fused deposition modeling). This process can be likened to a robotic hot glue gun; a plastic filament is fed through a heated nozzle and then extruded onto a build tray. The nozzle draws each layer of the part out of the molten plastic. The process is very useful for quick prototyping, due to its relative robustness and the cleanliness of its operation. When creating the part, an extrusion printer will automatically create support material, which is a sacrificial scaffolding to support any overhangs during the build process (the support is manually removed at the end of the print)
Design for AM Because of the layerwise nature of AM, it is possible to create printed parts of seemingly infinite complexity. However, there are still certain manufacturing concerns to be aware of. These two areas form the crux of the concept of design for additive manufacturing (DfAM). 1. Opportunistic DfAM. This realm includes innovative, big-picture design concepts that relate well to the opportunities of AM. This includes complex lattice structures (for lightweight, yet strong products), topology optimization (only using material where it is most needed in a product), mass customization (creating highly individualized products for each user), and printed assemblies/part consolidation (reducing the number of assembly steps necessary in a manufactured product). 2. Restrictive DfAM. This realm includes all of the limitations that a given additive manufacturing process places on a design (while AM is powerful, there are still design restrictions). This includes minimum feature size (what s the smallest size feature that my printer can actually create), anisotropic effects (since the printer creates in layers, parts are inherently weaker when loaded perpendicular to the layers), support material concerns (can the support material actually be removed without damaging the part), and surface finish concerns (curves are always better defined when parallel to the layers). General Build Guidelines The following are some tips to help your students determine how best to orient their parts for printing: 1. Build time. All 3D printers are slowest when moving in the z-direction. Because of this, to get the fastest build time, the shortest dimension of the part should be placed along the printer s vertical, z-axis. 2. Geometric Quality. The majority of printers have their highest print resolution in the X-Y build plane. Because of this, any important curves should be oriented parallel to the build plate, otherwise the curve will show stair-stepping. 3. Material Quality. Because of the layerwise approach inherent in AM, parts will often exhibit anisotropic material properties, especially in the z-direction. Because of this, printed parts will usually be strongest when loaded in the X-Y direction. 4. Support Material Use. To simplify post-processing (and decrease build time and material consumption), you ll want to select a build orientation that limits the number of overhangs; this will reduce the need for support material. The general guideline is that angled faces greater than 45 degrees from horizontal will not require the use of support material (the self-supporting angle ). Want to Learn More? Students and faculty members have access through the PSU library to a digital copy of Additive Manufacturing Technologies: 3D Printing, Rapid Prototyping, and Direct Digital Manufacturing by Gibson, Rosen, and Stucker. This book contains much more information on the basics of AM.
Using the PSU Maker Commons Spring 2016 Nick Meisel Adapted from information found at help.solidworks.com and makercommons.psu.edu What is the PSU Maker Commons? Maker Commons is a university-wide initiative to enrich the teaching and learning experience through 3D printing, rapid prototyping, design thinking and direct support for students, faculty and staff. They provide an open access 3D printing service based on MakerBot technology that allows any member of the Penn State community to print on-demand. Currently, use of the Maker Commons is free for students. Creating an.stl File 1. Once you ve finished creating your CAD model, click File > Save As. 2. Select STL (*.stl) for Save as type, then click Options. 3. Select from the options described below, then click OK. Option Description Output as Select either Binary or ASCII as the file format. Binary files are smaller than ASCII files, but they are not supported in some other systems. Select the type supported by the target system. You can leave this at its default value. Resolution Unit. Select the unit of measure. Important: make sure that this is set to the same units that you designed the part in! Controls the tessellation of non-planar surfaces for Stereolithography (STL) output. A lower deviation setting produces a more finely tessellated STL file. Files generated with higher accuracy settings (increased tessellation) are larger in size and slower to generate. Coarse or Fine Preset resolutions. For the purposes of EDSGN 100, you should be able to just use the Fine Setting Show STL info before file saving Displays a SolidWorks dialog box (when you click Save in the Save As dialog box) that contains the following information: Triangles (number), File Size, File Format, and the directory path and file name. Preview Displays a faceted model preview in the graphics area and displays the Triangles (number) and File size information in the Export Options dialog box. Do not translate STL output data to positive space Save all components of an assembly in a single file (assemblies only) Makes exported parts maintain their original position in global space, relative to the origin. You can leave this at its default value. Saves the assembly and its components in a single.stl file. When printing an assembly, this box should be checked (you want just one.stl file).
Option Check for interferences (assemblies only) Output coordinate system Description Performs an interference check on an assembly document prior to saving. Export of an assembly with coincident or interfering bodies to a single.stl file produces a file that may be unsuitable for some rapid prototyping systems. It is recommended that you check for interference between the components prior to saving the assembly document. For more information, see Interference Detection. You can leave this at its default value. Select a coordinate system to apply for export. If you select -- default --, no transformation matrix is applied. You can leave this at its default value. 4. Click Save to export the file. Creating a.makerbot File To create a.makerbot file, first open the MakerBot desktop software (can be downloaded for free from http://www.makerbot.com/desktop). Once the software opens, the first thing you will need to do is make sure that the right printer type is selected. To do this, click on Device at the top of your screen. Then go to Select Type of Device and choose Replicator (5th Generation). Once you have selected the proper device you can now import your model. To do this, first click on the Prepare tab from the list of icons at the top of the interface.
Next you will need to add your 3D model to the build platform. To do this, click on the Add File button that appears just below the Prepare tab that you just clicked on. Now you can select the file you wish to add. Note that the MakerBot Software will only take three types of files,.stl,.obj, and.thing files so your model will need to be in one of these formats. Once you find the file you wish to add, click Open.
Your file will then appear on the build platform in the software. To help ensure you have a successful print, you will want to make sure that your model is in the proper place on the build platform before you prepare it for printing. In order to do this, there are some quick changes we can make by using the tools that appear on the left hand side of the interface. First we are going to make sure that our model is in the center of the platform and that it is sitting on the surface of the platform. To do this, double click on the Move Objects icon which is the second icon on the left hand side that looks like four arrows. When you do a window should pop out from the side of it.
Click the On Platform button to move your model all the way down so that it is touching the build platform. If you do not do this and your model is sitting above the build platform, it is likely that your print will fail. Next you can center the model by clicking the Center button. The final change we need to make is accessed by clicking on the Rotate Objects icon which is directly below the Move Objects icon.
In this window you will need to click on the Lay Flat button. This will rotate your model to a flat surface to help ensure that the model is laying flat on the build platform. Next you will need to check the settings that you would like to have for the print. Click on the Settings button at the top of the screen. A window will pop up where you can change the settings of your print. For the most part, you will not want to change anything on this screen. However there are a few items that you will want to be aware of. These are the Quality, Raft, and Support settings.
You can leave these on the standard settings however you will need to decide whether or not you will need to turn the supports on for your print. If you are unsure whether or not your need them, it is better to go ahead and turn the Support setting on just to be safe. Once you have finished changing your settings you can press ok. Once you have finished changing your settings, you can click OK to close the window. The final step will be exporting your print file. To do this, click on the Export Print File button located in the top left corner of the interface. In the window that appears, give your file a name and select where you would like to save it. Then press the save button in the bottom right hand corner of the window.
Once you do, the MakerBot software will process your file and when it is finished, your model will appear as a.makerbot file in the place where you saved it. You can now take this file and upload it to the Maker Commons software in order to start your print. Best Practices for Preparing a Print Make sure your model is centered and actually on the platform in the Makerbot Desktop position settings. Make sure your model is oriented correctly on the MakerBot platform. If your print is tall, you may want to re-orient the object to lay flat so it will need less support while printing. Make sure Raft is turned on in Makerbot Desktop settings before you export. The raft provides a consistent base and keeps your object from slipping during printing. Make sure Support is turned on in Makerbot Desktop settings before you export. If your object has any area that is supposed to exist over empty space, turn this on. Without support the print is almost certain to fail and you will end up with a spaghetti print. You may also have to go into custom settings and add Extra Support, Breakaway Support and/or Bridging if you have a particularly challenging object. Make sure your Quality setting is set to Low or Standard. We do not recommend changing this to High unless you have printed a working low resolution print. The build volume on the MakerBot printers is 9.9 inches L x 7.8 inches W x 5.9 inches H. Print submissions cannot exceed this size or they will not be printed. Submitting Your Print General Information. Go to http://makercommons.psu.edu/3d-print-request-submission/ to begin the submission process. Start by filling out an appropriate Project Name to describe your print submission. Please do not select a deadline. The Maker Commons will not be able to honor deadline requests.
Filament Information. Our MakerBot Innovation Center only prints PLA filament. Please select which color of filament you would like to have your print to be printed in. If the selection is left on Any Color, Maker Commons consultants will choose the first available printer for you. Only upload.makerbot files, which have been compiled using the MakerBot Desktop Software. The Maker Commons is unable to print any other file types and these submissions will be deleted. Upload Files. You are also given the option of uploading multiple.makerbot files to a single request. We do not recommend this as the interface makes it unclear how many files have been uploaded and requests could be lost. Please submit individual requests for each.makerbot file you would like to print. After you have successfully uploaded a.makerbot file, you may see an option to change the quantity of prints. Due to high demand and limitations of the MakerBot Innovation Center interface, we are not able to honor quantity requests. Each submission will be printed one time. If you need multiple prints of a single model, you can either submit it multiple times or place duplicates of the model on a single build plate in one.makerbot file. Instructions and Notes. The Maker Commons is unable to assemble any parts and will have to ignore any assembly instructions uploaded to this section. Submission. Click the Next button to review your submission details. When you have confirmed that they are correct, please click the Confirm button. You will receive an email that acknowledges your submission and will receive another email when your print has been approved and entered into the queue for a printer. Want to Learn More? All of the information presented in this document (and more) can be found on the official Maker Commons website (makercommons.psu.edu).