3D printing at CABE

3D Printing is an exciting new technology that can enable modelmaking and design that was previously out of reach for most students. Any shape that you can dream up and draw in Computer Aided Design (CAD) program, you can 3D print.

History

The first 3D printer was invented in MIT for Rapid Prototyping purposes. The goal was to make an object directly from CAD (also and MIT invention) without the constraints of CNC milling (MIT again.) The first commercial machine was shipped in 1986 and used a liquid photopolymer and laser to produce solid objects. This is the same technology that our Formlabs machines use.

In 2008 a new market was invented with the low cost Material Extrusion 3d printer. Thanks to some expiring patents, Makerbot produced a $750 3d printer made from laser cut plywood and open source tools. That consumer market steadily grew and has provided us with two of the finest open source 3d printers in the world: the Ultimaker 2+ and the Lulzbot Taz6.

The 3D Printing Process

3D CAD and printing process

3D printing involves taking designs from your mind and putting them into the computer via CAD. Then you create instructions so a robot can produce that design from undifferentiated material. Ideally, you start on paper with concepts and dimensions. Then, you use your favorite CAD program to draw your design in 3D with accurate dimensions. Any CAD will do, but solid modeling programs work best. Once your design is ready for the first prototype, you output a Standard Tessellation Language (STL) file that describes the relative shape of your design. That STL file is opened in the 3D printer's control software where you can make decisions about its construction like quality, density, and material. The control software outputs a set of instructions, a.k.a. GCODE, that is loaded into the machine to start the print. After some startup checks, the 3D printer will produce your design on its own. The machines lays down material one layer at a time, incrementing the height of your object layer by layer to produce the full size model. Once the print is done, there is some post processing required to make your model finished and accurate.

In the image above you can see the process of taking Jefferson's new logo with gradient and making a 3D printed model. In the top left corner, the CAD file is shown with a slight curve designed in to mimic the logo's gradient. In the bottom right is a screenshot of the 3D printing software Cura showing the toolpaths the 3D printer will use to make the model. Finally in the bottom left, you can see the completed 3D print.

Our Machines

We have 13 Ultimaker 2+'s, 4 Lulzbot Taz6's and 2 different Formlabs machines. They use two different technologies: Material Extrusion and Vat Photopolymerization. These are ASTM terms and can be a bit confusing.

Material Extrusion

Material Extrusion

With this process, the Ultimaker or Lulzbot extrudes molten material out of a small, heated nozzle based on your instructions. This mechanism is the similar to a hot glue gun, but the placement in 3D is what the robot offers. In the case of these machines, the material is a 3mm wide filament of thermoplastic Polylactic Acid (PLA.) PLA is very easy to print with and is non toxic. This machine moves in 3 axes: XYZ. Specifically the nozzle moves along 2 axes with the build plate and print on the third axis. The printer can place material anywhere in the build envelope as needed to produce your model. Our machines also have a heated glass build plate. Hot glass at 70°C is adhesive to PLA, but cold glass is not. When your print is done, the part should pop right off the bed. 

Vat Photopolymerization

 

Vat Photopolymerization closeup

This term is more difficult. The Vat in Vat Pho. refers to the pool of liquid material that the machine uses for stock. This material is a photopolymer, a liquid resin that turns into a solid when exposed to light. In this process the model is produced with an ultraviolet laser drawing each layer into the liquid. The UV begins the polymerization process, linking fluid monomers into long, solid, polymer chains. The chemistry is harder to grasp than simple melting plastic, but the results are fully dense objects of a higher quality. In our machines the vat has a window on the bottom and the laser shines up through this window into the vat. After each (XY) layer, the model is peeled off this window vertically (Z axis) into the air, and the machine prepares for another layer. 

There is a higher safety concern with this process. The uncured liquid resin is toxic to us. When handling the printer before or after a print, latex gloves need to be worn. The post processing of the finished parts also involves isopropanol with dissolved resin, so safety goggles are required. It is extra important that you do not use these machines without training, so the access to our Formlabs printer room is restricted until training is complete.

Specifications

ultimaker2plus.png

Ultimaker 2+

Build volume: 223 x 223 x 205 mm

Layer resolution: from 600 micron to 20 micron

Taz 6

Lulzbot Taz6

Build volume: 280 x 280 x 250 mm

Layer resolution: from 500 micron to 50 micron

form1plus.png

Formlabs Form 1+

Build volume: 125 x 125 x 165 mm

Layer resolution: from 100 micron to 25 micron

form-2-printer.png

Formlabs Form 2

Build volume: 145 × 145 × 175 mm

Layer resolution: from 100 micron to 25 micron