DogBone is a program that creates custom tool paths for Fused Filament Fabrication 3D printers (also known by the trade marked term FDM). The motivation for creating this program was to allow the user to independently adjust as many printing parameters as possible for the purpose of researching and characterizing each parameter's effect on a part's properties.

Version 1 can only toolpath single profile parts (parts which can be extruded). Version 2 can also toolpath STL files.

Through the parameters.py module you can adjust a large group of printing parameters. Most parameters can be adjusted for each individual layer. The program contains some methods to make it easier to print multiple parts.

NumPy

After downloading the zip file and extracting it in an appropriate location either open the parameters.py file in your preferred Python IDE or with a text editor (I prefer Notepad++)*. The user adjustable printing parameters are broken into five sections:

• Part
  
• Layer
  
• File
  
• Misc
  
• Printer
  

Parameters which are in Python lists [enclosed in square brackets] can very varied between either parts or layers depending on which parameter set they are located. For part parameters the longest list determines how many parts are printed all other parameters a cycled until the longest list is exhausted. For layer parameters the parameters are cycled until the specified number of layers have been printed.

Part parameters are parameters that are constant throughout a single part but can change between parts (except for outline). The longest list of part parameters determines how many parts will be created. The part parameters are:

• outline
  
• solidity ratio
  
• print speed (mm/min)
  
• shift X
  
• shift Y
  
• number of layers
  

The outline of the part to be made. An outline must be of type Shape. The doneShapes module contains several methods which return pre-defined shapes. Only one outline is allowed.

Solidity ratio is used to calculate the extrusion rate for each layer.
extrusion_rate = solidity_ratio*layer_height*nozzle_diameter/filament_area

Print speed is how fast in millimeters per minute the print head moves while printing. It seems most slicing software uses mm/sec but the G-code the slicing software sends to the printer is still defined in mm/min so that is the default I have chosen.

To print multiple parts without them attempting to occupy the same space you must use Shift X and Shift Y. These shifts are absolute shifts (they are not relative to the previous shift). Since it does not make sense to have two parts printed in the same location at least one of these two parameters should be the longest list of part parameters and therefore will determine how many parts are printed.

How many layers are printed in the part. The layer parameters are continuously cycled until this number is reached for the part being printed. They are then reset for the next part.

Custom infill patterns can be designed for the part. The pattern must be of type LineGroup. The pattern is extended by copying the design and then connecting the start of the first line in the copy to the end of the last of the original and saving that as the new original. This process is repeated until the design is sufficiently longer than the outline. This whole new line group is then copied and translated in Y by pathWidth until a full field is created. Please read the comments in the InFill module for more details.

Layer parameters are unique to each layer of a part. Each list of parameters is cycled until the Number of Layers for the part is met. The lists are then started over at the start of the next part. The layer parameters are:

• Infill Angle (degrees)
  
• Path Width (mm)
  
• Layer Height (mm)
  
• Infill Shift X (mm)
  
• Infill Shift Y (mm)
  
• Number of Shells
  
• Trim Adjust (mm)
  

The angle of the infill for the part. Zero (0) degrees is in the positive X direction with the angles moving around in the counter clockwise direction.

The distance between the centerlines of two adjacent passes. This is an orthogonal distance, not a normal distance. If you had a zig-zag infill pattern v^v^v^v when that pattern is turned into a field it would only be shifted in the Y direction by path width. If the angle were 90 degrees that would mean a path width of 1.0mm would create a normal distance of 0.707mm which will then effect your solidity ratio.

Sometimes when the infill is created it is not centered properly in the shape or you may want to do testing that creates beads which sit in the valley of the lower bead instead of directly on top of it
O O O O O
O O O O O
O O O O O
vs
O O O O O
. O O O O
O O O O O
Infill shift X and Y are hacks used so you can adjust the infill to fine tune your pattern.

The number of shells you want around the part. Shells are created by a normal offset pathWidth away from the previous shell/outline. Version 1 of the program does not handle shells very well. When two non-adjacent lines cross (like when the gage section of a dogbone tensile specimen crosses before the grips are fully filled) it pretty much blows up. Sometimes is gets mad even when that doesn't happen. Version 2 of this program uses Shapely to fix this problem. Keep in mind that to tool path the infill properly a trim shell is created by the program. For example if three shells are prescribed a fourth trim shell is created inside the third shell to properly trim the infill. If this extra trim shell has problems, Explosion.

• outputFileName - The name of the output Gcode file
• start_Gcode_FileName - Name of the file which contains all of the starting Gcode commands
• end_Gcode_FileName - File with end Gcode commands

• filamentDiamter (mm)- The diameter of the incoming filament.
• nozzleDiamter (mm) - Nozzle outlet diameter

These are parameters used by the printer while not actually printing

• RAPID (mm/min) - How fast the printer should move when not printing
  
  • The RepRap wiki (9 July 2016) says "The RepRap firmware spec treats G0 and G1 as the same command, since it's just as efficient as not doing so." I strongly disagree with this statement. A G01 is a feed command and as such needs an F value to know how fast to move. A G00 command should be a rapid command where the printer knows its max velocity and therefore does not require an F feed rate. Because of the RepRap design choice G00 needs a feed rate command requiring the programmer/operator to know each individual machine's max speed and creates larger programs by needing the additional text on every G00 line. How is that just as efficient?
• TRAVERSE_RETRACT (mm) - how far to retract the filament to prevent nozzle drool when traversing around the part.
• MAX_FEED_TRAVERSE (mm) - if the move to the next printing position is less than this value the head is not lifted up, no filament retract is performed, and it is moved at the print velocity.
• Z_CLEARANCE (mm) - Relative clearance height to which the head is moved when traversing the part.
• APPROACH_FR (mm/min) - Speed the printer should move when approaching the part. A slightly slower speed helps prevent hard crashes and allows the filament more time to move forward in the nozzle in preparation for printing.

If you have Python and the appropriate dependencies installed you can use Notepad++ to edit the parameters.py files and then run the program with Python. To do this in the menu bar select Run-> Run (F5) type the following:

<your python path>\python.exe -i "$(FULL_CURRENT_PATH)"

<your python path> is the actual path to python. For me Python was in my Anaconda3 folder. FULL_CURRENT_PATH is a variable in Notepad++ so type that exactly. On my computer the full command was:

C:\Anaconda3\python.exe -i "$(FULL_CURRENT_PATH)"

Now select save. For a command I chose ctrl-r and hit ok. Now you can edit the parameters.py file, save the changes (if you do not save the changes then it will run the old changes, which can be confusing) and finally hit your hot keys (ctrl-r). Notepad++ will call Python and run your program.