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Cheat Sheet

3D Printing For Dummies

From 3D Printing For Dummies by Kalani Kirk Hausman, Richard Horne

3D printing starts with a virtual 3D model that is transformed into solid form one layer at a time. Each layer is built on top of the layer before, creating a solid form representing the virtual 3D model in all of its complexity and detail without requiring additional forms of machining and treatment necessary in traditional manufacturing. You can build your own 3D printer using the open-source self-REPlicating RAPid-prototyping (RepRap) family of designs. Check out these helpful articles to guide you toward selecting the right RepRap design for you.

Deciding on a RepRap of Your Own for 3D Printing

When it comes to 3D printing, selecting a RepRap printer for personal use begins with an analysis of your particular need in terms of the type, size and other qualities such as turnkey off-the-shelf or build-it-yourself creation. Total cost is also a factor, along with source licensing preference such as the determination of open vs. closed source technologies.

Some of the RepRap designs include:

  • Mendel, Prusa Mendel, Mendel90, Prusa i3: One of the more common branches of Cartesian design, this printer has spawned many variations including the miniaturized Huxley.

  • Wallace and Printrbot: Common educational-sector alternatives for kit construction.

  • MendelMax: This is the derivative of the Prusa Mendel that's an example of Cartesian RepRaps.

  • Ultimaker: A box-frame RepRap using Cartesian movement.

  • Tantillus: A miniature box-frame RepRap which has the most 3D printable parts of current RepRap variations.

Several RepRap options exist beyond the standard Cartesian format, including:

  • Rostock, RostockMax: A Delta-format RepRap printer that provides a tall build volume. The RostockMax is a laser-cut kit form that we will build here as an example of Delta RepRaps.

  • 3DR: An alternative delta-style RepRap designed by Richard Horne, based on the Rostock format with inspiration from the Tantillus for self-replication.

After identifying the type of printer, you will need to select the proper type of plastic filament you wish to print with and the components that will be used in building the printer itself, including the framework, extruder, build plate, control electronics and software that will be used.

Understanding RepRap 3D Printer Control Electronics

A RepRap 3D printer is an example of a purpose-built robot, using the popular open-source Arduino microcontroller at its heart together with stepper motor controllers, motors, and sensors to control its movements. Some custom 3D printer boards have been created to integrate an Arduino's functions and the related items typically found on a 3D printing "shield" that attaches to the basic format. Some of these options include:

  • RAMPS: The original Arduino shield designed for multiple stepper motor control and management of the extruder and built plate heaters.

  • RAMBo: A modular all-in-one combination of the Arduino board and RAMPS shield.

  • Sanguinololu: A popular build-it-yourself all-in-one board integrating both microcontroller and stepper motor controllers

  • Minitronics: A reduced size variation of the Sanguinololu.

  • RUMBA: A modular integrated board with modules supporting LCD panels, external memory cards and other add-on capabilities.

  • ELEFU-RA: A developer integrated electronics set that can plug in standard ATX computer power supplies

  • Megatronics: The "big brother" of the Minitronics board, which allows the use of higher-temperature thermocouple thermal sensors in place of the more common thermistor type sensors.

Many components have multiple options such as the selection of contact switches or magnetic hall-type sensors for the end-stops or the use of different fans to meet the type of plastic you are using. Even the type of motor controllers and wire connections (soldered vs. crimped) will affect options available upon completion of your RepRap.

Assembling the RepRap Extruder and RepRap Upgrades on a 3D Printer

Once the framework for a 3D printer has been assembled and the electronics selected, the final component needed is the extruder and hot-end that melt and deposit plastic to create your object. The extruder slides the plastic filament incrementally into the heated hot-end, where it pushes a small amount of the molten plastic out with each step. The extruder can be made in many ways, including:

  • Geared: Some extruders include additional gears to slow the advance of filament with each step to gain greater control, and to increase the force with which the filament can be advanced into the hot-end.

  • Hobbed: Smooth plastic filament can be held by the extruder using interlocking gears or a hobbed bolt (one with teeth cut along the axis around the bolt's girth) to hold the filament against an idler wheel so its advance and retraction can be carefully controlled.

  • Bowden: This type of extruder forces the filament through a tube connecting the extruder and hot-end rather than forcing the filament directly into the hot-end, separating the two and allowing the hot-end to be lighter without the directly attached extruder motor for non-Cartesian formats.

  • Syringe: For designs like the Fab@Home printer or RepRaps equipped with Richard's Universal Paste Extruder, a syringe can be used with a constrained strap to incrementally extrude paste or gel materials instead of the usual melted plastic.

  • Multi-color: Advanced extruders include multiple gearboxes and motors to advance multiple filaments into the hot end at the same time. By varying the rate of each color using additional electronics, the end result is a multi-colored print that varies throughout.

  • Dual: A common variation with more limited color mixing involves a dual extruder, which is simply two extruders side by side. This is useful for prints that include PVA (polyvinyl alcohol) or other soluble support material integrated into the same print as the object filament material.

Identifying 3D Printer Software and Machine Calibration

The software chain for a RepRap 3D printer begins with the products used to create and prepare the virtual 3D model for printing. However, once an object model has been created or obtained, the model must be processed through several steps before the solid object is created by the RepRap printer:

  • Support: Unlike granular binding systems, fused plastic extruders cannot deposit plastic in mid-air and have it remain there. For overhangs and wide spans, support material must be added to the design and later removed after printing.

  • Raft: Depending on the type of material and build plate used, it may be useful to add a raft or flat printed layer that forms a base on the build plate for your model. As in the case of support, the raft is later removed in finishing the object.

  • Fill: Because additive systems like the RepRap are unaffected by complexity, it is possible to define any solid object as a solid outer shell and an interior space that can be completely solid (100% fill), empty (0% fill) or some midway point in which a regular pattern of thin walls provide support with voids interspersed. The amount of volume that includes plastic is defined as its "Fill" and allows you to produce the same object printout using far less plastic than solid equivalents.

  • Slicing: The virtual model is calculated as a series of layers, with each slice then translated into codes that will direct the printer to move a particular distance while extruding or not and then again, until that layer is done and the z-axis can be moved to the next layer with the process begun again. This code is called "g-code" and many slicers can add support and raft elements automatically, along with an automatic "fill" pattern to reduce the amount of plastic needed for each print.

Once your model has been prepared and sliced, a few final details are handled by the printer control software. Settings for the hot-end and heated build plate will control the melted plastic viscosity and layer adhesion, while the movement rate of the extruder will control the thickness of the extruded material and the rate of the printer's movement. Additional factors can be adjusted for finer control of each feature.

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