RepRap Mendel

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How To Use the 3D Printer

Contents

1. Get a 3D Model (.stl file)

You can download an STL file, scan an object using a 3D scanner, or create one using a 3D modelling program.

Places to download 3D models from:

Ask Ben about his 3D scanner: good for scanning small objects.

Photofly converts photos to 3D models: good for scanning large objects. http://labs.autodesk.com/technologies/photofly/

3D model editors:

Sketchup doesn't support STL file format natively. You have to use "Import" and "Export". On Import, it's important to hit the Options button and set the units appropriately.

2. Print the STL file

This actually requires several steps:

  • Convert the STL file to GCODE.
  • warm up the printer
  • print the GCODE

Here are some all-in-one programs that handle these tasks:

2.1. Convert the STL file to GCODE

A GCODE file contains opcodes that directly controls the behaviour of the 3D printer at a low level. The conversion from STL to GCODE is non-trivial, and there's a lot of fiddling you can do during the conversion that will improve the print quality.

You can print several objects at once, which means loading several STL files, positioning each object on the print platform, then generating GCODE.

Instructions for Mendel Host Software:

  • see above
  • according to Kevin, the STL file needs to be manually edited before being loaded, to uppercase all the ‘e’s in the exponential-notation numbers
  • according to Kevin, the GCODE file needs to be manually edited after generation, to replace the M109 (set temperature and wait to stabilize, which unfortunately often waits forever) with M104 (set temperature).

ReplicatorG and PronterFace use SkeinForge for GCODE generation. Not tried yet. Skeinforge docs: http://fabmetheus.crsndoo.com/wiki/index.php/Skeinforge

You specify the material when you generate GCODE. We currently have ABS. PLA is the other popular material, which we can mail order if there is interest.

  • PLA is claimed to warp less during printing, and smell better (fumes less toxic). The printing temperature is lower. It's biodegradable. It's more brittle, and very hot water will melt it.
  • ABS (what we have) is stronger, less brittle, more durable, has a higher melting point.

You specify the temperature when generating GCODE. Kevin has had success printing at 220 degrees (ABS) -- he manually edits this into the GCODE file using WordPad.

  • Lower temperatures are preferred for: small printed areas, large overhangs, or other situations where faster phase change is beneficial lower temperatures are preferred. Lower temperatures also reduce swell inside the extruder and decrease the extrusion after feedstock drive is stopped.
  • Higher temperatures allow the build material to flow into printed areas and extrude faster, and bond to previously extruded stock faster. At the same the filament becomes more viscous and more plastic evacuates the extruder after drive is stopped. A fan can help the plastic solidify faster and improve performance.

Lots more parameters to tweak.

2.2. Warming up the printer

2.3. Printing the model from the generated GCODE

Appendix (other topics and notes)

New hotness, recommended by Josef Průša, one of the RepRap core developers: Sprinter is a new generation of firmware for reprap. This is the 1st firmware that has native support for SD card, and extreme acceleration. This firmware can run a printer at up to 300mm/s, which really changes the quality of a print. Sprinter has been tested and works on Gen6, Ramps, and Sanguinololu.

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