Introduction to 3D Printing
##What is a 3D Printer?
3D printing is a revolutionary manufacturing process that emphasizes rapid prototyping and iterative design. With the help of 3D printers, users can easily convert their 3D models into a physical product by a process called 'additive design.'
##Types of 3D Printers
The most common 3D printers utilize one of two technologies: FDM (Fused Deposition Modeling) or SLA (Stereolithography) printing.
###"So what's the difference?"
FDM printers are the most common 3D printers available today because they're cheap, simple to operate, and cost-effective. It's easiest to think of a FDM printer as a hot glue gun that constructs a model layer-by-layer by tracing the shape of your object while depositing material onto the print bed, slightly raising it's Z-axis after the layer is complete, and starting the process over until you have a finished product
SLA printers operate almost the same as an FDM printer, but rather prints your product upside-down using a combination of special resin and a laser diode. A SLA printer begins by soaking the print bed in a vat of resin while a laser diode traces the shape of your design. After the layer is completely traced, the model ever-so-slightly moves it's Z-Axis and then repeats the process after the layer solidifies.
##Getting Started
The Edge currently offers students, faculty, and staff access to the following four FDM printers, all with varying specifications and abilities.
The twins. By far our most popular printers, both printers deliver printed objects with a maximum balance of both quality and time efficiency.
- Print volume is 152mm x 152mm x 158mm (6in x 6in x 6.2in)
- Average print time is anywhere from 4-12 hours depending on the model.
Compatible Materials: 1.75mm or 3mm ABS, PLA, HIPS, PVA, wood filled filaments, Polyester (Tritan), PETT, bronze and copper filled filaments, Polycarbonate, Nylon, PETG, conductive PLA and ABS, UV luminescent filaments, PCTPE, PC-ABS, Alloy 910.
The big horse of our 3D printing fleet. Use of the Taz 5 is generally limited to printed objects that require a very minute level of detail, or for prints that will not fit within the print dimensions of our other printers.
- Print volume is 290mm x 275mm x 250mm (11.4in x 10.8in x 9.8in)
- Average print time is anywhere from 4-12 hours depending on the model.
Compatible Materials: 1.75mm or 3mm ABS, PLA, HIPS, PVA, wood filled filaments, Polyester (Tritan), PETT, bronze and copper filled filaments, Polycarbonate, Nylon, PETG, conductive PLA and ABS, UV luminescent filaments, PCTPE, PC-ABS, Alloy 910.
The unloved child. Prone to breaking, the Makerbot Replicator 2 was one of the first consumer-viable 3D printers for home use, and as such is considered a relic compared to our Lulzbots. Prints using this machine are usually only attempted under special request or as a last resort for time-sensitive deadlines.
- Print volume is 284mm x 155mm x 152mm (11.2in x 6.1in x 6in)
- Average print time is anywhere from 1 hour to Eternity depending on the model and the alignment of the stars.
Compatible Materials: 1.75mm PLA
##Workshop Overview
In our two hour workshop we'll get you started with 3D printing by introducing you to the various technologies involved. We'll give you an overview, talk about our 3D printers and freely available software tools you can use to design your own parts, and then finish by working to design a simple keychain with your name on it using the online tool TinkerCad.
A 3D model is typically represented by the computer as a series of interconnected triangles which make up the 3D "surface(s)" of the object. There are various ways of creating 3D models. There are expensive Computer Aided Design (CAD) tools which give very high precision and advanced capabilities necessary for engineering businesses. These days there are an increasing number of [Tools](3D Printers#Software) available to make designs. The common interchange format for 3D models is called an STL File. STL stands for STereoLithography. These files represent the surface and volume of the object you'd like to print. These can be hand-drawn in software or developed based on data or code.
There are many sites where you can download 3D models of objects scanned or designed by others, some include:
- The British Museum
- The Smithsonian
- Thingiverse
- [The NIH 3D Print Exchange] (http://3dprint.nih.gov/)
- [The NASA 3D Resources Repository] (http://nasa3d.arc.nasa.gov/models)
In order to print a 3D model on a 3D printer, it is necessary to take the 3D model and turn it into a series of 2D slices of the underlying 3D object. This is largely automatic in most easy to use 3D printing software, but it is important to understand that a lot of the settings that control the quality and speed of a print are applied at the time that the model is sliced. As 3D models can represent any imaginable usage of 3D space, there can be limits to what is physically printable. To help alleviate this, some slicers will print what is called "support material", this is sacrificial material (material you'll remove after the print) which is just there to help the printed part not sag under its own weight while it is being printed. Remember we're dealing with molten plastic here. Tweaking of slicing parameters is a pretty advanced topic. However, when you're done slicing a model you produce a GCode File. GCode takes the STL file and translates it into specific movement commands on the 3D printer. So a GCode file is really specific instructions to a specific printer that describes all of the movements it should make to reproduce the part(s) that you'd like printed. These days there are classes of printers that speak similar versions of GCode, but there is enough variation that you need to make sure you're producing the appropriate kind of GCode for the printer you'll be printing on.
Because we're building up a hot material in successive layers, it is possible for our material to not cool fast enough before the next layer is deposited. In these cases the pull of gravity on the object could cause the object to sag during the print. Cura has an "Overhangs" view which can help us make a determination if the overhangs in our project are severe enough for us to need to address them. Depending on the type of object you're building you can address some overhang issues by how you orient the part on the build platform. Some designs can be rotated in such a way that all overhangs are eliminated. If you are not able to eliminate overhangs and you think based on looking at the slice view that there will be problems with sagging, you may need support material, talked about in the next section.
Support material is material that is laid down in order to support areas where there might be sagging. This material can be removed after the build by breaking it away using small tools like pliers, dental pics, emory boards etc. It can be quite tedious to remove support material, so it isn't always worth doing. Another consideration is whether or not support material will be deposited in an area where it might be impossible to remove. Depending on your design, this may or may not be an issue. Although we do not have the technology in this lab, it is possible to use a special kind of filament on a dual-extruder 3D printer, where one material is say PLA and the other is ABS plastic, and through a chemical process the PLA could be removed leaving only ABS. In our lab, you'll have to clean the parts yourself if you choose to use support material. Support material does make it possible that would otherwise be impossible to print because of sagging that would take place in the hot material.
Filament is extruded plastic which is extruded at a uniform size and wound to a spool. These spools can be loaded into the 3D printer which will then extrude them. Slicing software will often let you set the particular type of Filament you're using (choosing from common types). Here at The EDGE we tend to use PLA filament as it has lower odor (because it is derived from Corn), but our printers are capable of printing with a wide range of filament types. It is possible to print with ABS and HIPS filament at the EDGE as well, but we recommend you begin with PLA. PLA filament has one down-side, it can become exceptionally brittle and will sometimes break mid-print. To aleviate this do not use the feeder tube (on the Lulzbot TAZ 5) and just allow the extruder to pull directly from the spool. Before you start a print job on your own it is always a good idea to look at the spool and make sure your GCode and printer settings are appropriate for the type of filament you've chosen. When you have selected a filament color and type, you always want to double-check that the temperature you have configured is appropriate for the filament you're loading. If the temperature is too hot you could cause a poor and messy print, if it is too low the filament will not extrude and you could gum up the extruder mechanism. Lets learn more about the extruder.
The extruder is a mechanism which feeds filament through a nozzle on the "hot end" in order for it to be deposited in layers. The extruder works using a pair of wheels, one with a rough groove with barbs that can grip onto the plastic and an idler wheel which serves to press the filament into the teeth. The Lulzbot printers and the MakerBot have slightly different extruder designs, but the common feature is that there is a locking mechanism which needs to be released in order to load/change filament. The extruder uses a stepper motor, and idler wheel and a hobbed bolt to feed the filament through the extruder and press it through the hot-end.
This is the extruder assembly:
A hobbed bolt:
The Lulzbot printers have heated bed assemblies, these help with the initial adhesion of the part to the bed, and they also help with part removal when the print job is over. Depending on the type of filament you're using, various bed temperatures can be set during the print and during removal of the part from the bed. Following these guidelines for the filament you're using will help you to ensure high-quality prints.
Cura is a piece of software that can take STL file(s) and prepare them for printing on the Lulzbot Printers. The MakerBot has a different piece of software called MakerBot Desktop which serves a similar function but gives you less control over the print parameters. CURA will help us to slice, add support material and print most simple STL models we might want to print. It does not allow for very detailed editing of the STL file but will allow us to make orientation changes and some simple geometric mirroring operations. In it's simple mode you can select from High Quality, Normal Quality and Low Quality prints, select presets for HIPS, PLA and ABS filament, and print support material and a brim (a halo of pre-printing in the shape of the print job to prime the extruder). It can also be switched to an advanced mode, enabling more advanced settings. This software is Open Source and free, you can download it to your laptop and be able to come to the lab with Gcode that is ready to print.