Monday, December 26, 2011

Start and End Alterations

So now that I have all the minimum end-stops installed and working, I am able to do more automation and get closer to a "plug and play" print experience. I did this by changing some Skeinforge settings and adding code to the start.gmc and end.gmc files.
Skeinforge Adjustments:
I wanted to print in the middle of the bed so I activated Multiply and enter the bed's center coordinates.

If the names of the alteration files should be different than the default they can be change under the Skeinforge Preface tab.

Alteration Files
If you are using pronterface/sfact they should be here: ...\Pronterface\sfact_profiles\alterations\. If you are using only skeinforge they are here: ...\Pronterface\skeinforge\skeinforge_application\alterations\. My goal on writing these little snippets of g-code was to automate the things I have to do every time I print.

Right now I am using PLA and it tends to ooze out of the hot end between prints. So, before each print I want to prime the extruder. It seems to work best if it is primed in two steps with some delay in between. The extruder works on an absolute filament distance so, unless you know the current absolute distance, it needs to be reset in-order to move it a relative amount.

G92 E0 ;reset extruder position distance =0
G1 E10 ;Prime extruder 
G28 ;Go Home ( woot! +1 for end-stops!)
G1 E20 ;Prime extruder 10mm more (10+10=20)

I am still tweaking this and it seems as it is never perfect but I enjoy the automation as it is still better than nothing.

Most of the things I print now are 1 each so at the end of each print I want the following:

Retract the extruder by 20mm to prevent ooze
Maneuver the platform to a place where the part can be taken off
Disable stepper so I can move axis by hand and also saves power
Turn off bed heater
Turn off extruder heater
Turn On Cooling Fan (set skein forge "Cooling" not to turn it off at end)


G92 E0 ; reset Extruder counter
G1 E-20 F900 ;Retract extuder 20mm at 900mm/min
G28 X0 Y0 ;Go Home but keep Z height
G92 X0 Y0 Z0 E0 ;reset all locations and  extruder 
G1 Y80 F3000.0 ; Move platform so part can be removed
M84 ;disable steppers so they dont get hot during idling
M140 S0 ;turn off bed heater
M104 S0 ;turn off extruder heater
M106 S255 ; Turn on cooling fan

To make sure the code is going to be used, the g-code can be examined in a text editor. After skeining, the g-code is in the same directory as the yourPart.stl file. There are two versions. The yourPart_penultimate.gcode version is the one with the comments and is easier to read . The Alteration code should be included and wrapped in  <alteration> tags. Such as:

G92 E0 ;reset extruder position 
G1 E10  ;Prime extruder 
G28 ;Go Home
G1 E20  ;Prime extruder 

The start.gmc and end.gmc should be at the start end of the file as expected. If not make sure the files are in the proper directory(SFACT uses same directory names) and the files are named properly.

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