3D Printing

A place where current 3D printer users can document the process of 3D printing.

Introduction MakerBot Replicator

The printer currently being used in the physics lab Dennis 128 is a MakerBot Replicator. The Replicator can print both ABS and PLA filament, and has a build volume of 8.9" L x 5.7" W x 5.9" H. ((255x145x150mm) It also comes equipped with a dual extrusion system to be able to print objects in two colors.

Makerbot Replicator product page and full system specs

Software

A very user-friendly program to use to communicate with the Replicator is MakerBot's own ReplicatorG, which can be found as a free download here: http://replicat.org/download. There are installation instructions included on that website, as additional downloads are required (Python and some drivers).

3D Modeling

All programs mentioned are free.

OpenSCAD

Open source. Programmatic 3d modeling. Very precise, units in millimeters.

Preparing a model in OpenSCAD for printing

• You’ll need:
  • http://replicat.org/
  • http://www.openscad.org/

• render and compile with OpenSCAD with F6
• export to stl,
• open that stl in ReplicatorG
• center the object and put on platform if necessary

generate gcode

• recommended settings: left extruder, 15% infil, .20 layer height, 35 extruder and motor speed
• Wait.
• After the file is generated go to the gcode tab and modify the numbers on the lines M104 should be 230 and M109 should be 128, i.e.:

M104 S230 T1 (set extruder temperature) M109 S128 T1 (set HBP temperature)

• export file to disk

Blender

Open source. The best open source modeler out there, very powerful, hard to get to be precise for engineering centric designs. After exporting a model to an .stl you'll want to run the model through Netfabb which will check to make sure the model has no holes or connected meshes that share a single edge.

Google SketchUp

Maintained by Google, tutorials available.

Thingiverse

3D models can be uploaded and downloaded online through a free website called Thingiverse.

ReplicatorG

ReplicatorG is the main interface between the 3D model and the printer. Since 3D models are usually .cad, .obj, or .stl files, the printer cannot directly print them. ReplicatorG uses a tool called Skeinforge to take the 3D model as a .stl file, and turn it into gcode. Skeinforge slices the model into layers and determines what paths the extruder needs to take for each layer based on the parameters set in ReplicatorG. The resulting file is a .gcode file, which can be printed directly from the computer if connected via USB. To print without connecting a computer, the .gcode file needs to be converted to a .s3g file and saved to an SD card, as discussed below.

Interface

ReplicatorG will display a 3D interactive preview of the open .stl file. The column on the right offers some options on how to orient the model on the actual build platform. Some of these options include moving, rotating, or scaling the model before it is printed. It has default "snap-to" settings to center the model on the platform, and move it so that its bottom most side (the first layer) is laying just on the surface of the build platform. A model that lies below the build platform will result in an error and will not print correctly, and a model that lies above the platform will print with severe warping, since the first layer of plastic will have nothing on which to adhere.

Converting to gcode, and Print Settings'

Once the model appears in the preview the way it is intended to be printed, it can be converted to gcode by either clicking on the icon at the top of the screen with an arrow and a sheet of paper with a 'g' on it, or clicking on the button on the column to the right labeled "generate gcode." A new window will pop up with settings for how the model is to be printed.

• Slicing Profile: It is best to use Replicator Slicing Defaults, since the machine being used is a Replicator.

• Extruder: Since the Replicator has a dual extrusion system, either the left or the right extruder can be used.

• Raft/Support: Depending on the shape and orientation of the model, a raft and/or supports might be necessary to print. Objects with flat bottoms and no overhangs do not require a raft or supports. A raft should be used for objects with a rounded, curved, or otherwise nonuniform bottom, or for an object with relatively little surface area on the bottom. The raft will add a stable, flat bed of plastic on which the printed object can adhere. If the object has overhangs, or very steep vertical curves, supports will be needed in addition to the raft. Supports are essentially pillars of plastic printed under the overhangs or curves so that the overhangs have something to rest on as they are being printed. The supports and rafts can be cut away from the final product after it has finished printing.

Printing and General Maintenance

• Do not set the extruder temperature too high or it will reduce the coefficient of friction on the filament and the stepstruder to a point where it cannot extrude anymore.
• Makerbot people recommend cleaning the printer after about 50 hours of printing or so
• If your model has trouble sticking:
  • Clean the plate.
  • Make ABS goop and paint a thin layer on, this will help the filament stick to the plate more easily.

Post-Processing

Turn off the printer and take your print off the plate. Depending on the surface area covering the plate this could be difficult, easiest to wait for the plate to cool completely. Gently use a flat head screw driver if necessary, be sure not to rip the kapton tape. With a knife or razor you can trim down the sharper edges if necessary. If there are tears in the model that might compromise the integrity of the model you can use acetone to weld the model back together. You can get acetone from the chemistry department.