8 Color Rocket

by ykratter May 28, 2016
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How did you get your printer to use the purge wall properly?

The wall (or cylinders - you can use many shapes) should be positioned next to the printed object where the printing head starts each layer, usually behind or in front of the printed object.
This way , the purge wall is built from the color transients and by the time the hot end moves to the actual objects layer, you've got the desired color mix.
I stopped using the wall shape and moved to using cylinders, takes much less material and faster.
The purge wall/cylinders/shape should have a constant width and depth no matter the size of the object (the only difference is the height that should be identical to that of the object) that is because you only need to get the minimum amount of filament for the right color change which is not a function of the objects size, just the extrusion filament length of the mixing process.
Hope I understood your question... :-)

I think I understand what you are saying.....so for this 8 color rocket, do you have 8 separate purge cylinders? Or just one? I've had problems with the print and purge object being printed in the correct order.....

Probably better if you start with the square pillars, just to get the hang of it.
You can try learning from this:

-I've inclouded the purge towers in the stl for this model
You might need to turn it about 180 deg - depending on your printer/firmware, so that each layer printing starts at the purge tower
Also see the attached files for clarification


Okay, so I have downloaded your GyroThingy and observed what you have done. But for the life of me I cannot seem to duplicate your results....Ive imported the objects in different orders, placed them in various positions, even placed the purge rings on the same coordinate system and grouped all of them together, and still I cant seem to control the order in which it prints each layer so that the purge objects are printed before the part at all times. I even made sure that the purge area is greater than the part on every layer. as it seemed to have prioritized the larger areas first....what am I missing?

Try printing two small cubes one behind the other, not working? try printing them one beside the other.
The printer should always start a new layer on the same cube, shouldn't it? the "first" cube should be the direction of the purge tower.
Maybe I've assumed that your using the same slicer as I do ?
I'm using Slic3er Ver 1.2.9 (inside Repetier-Host V1.6.1)
If not, check where to set the slicing to prioritize the direction of building layers (I think there might be a way...)
As I understand it its all about the slicing, It makes a file which is a road map for the printing head, this is where the order of layers is determined to my understanding.

Thanks, I'll try it, but this is the least of my problems, if you watch closely you can see that I get a weird "wavy" texture in all rounded objects, this is the real mystery :-)

I had that same problem with the ripples on curved surfaces, but when I switched from repetier firmware to marlin, they went away.

(does Marlin mix colors?)

...I eventually found out the reason - 'maxStartFeedrate' - should be between 20-40 and I had it on 0!

I found out this somewere:
..." so my assumption is that your maxStartFeedrate = extruder start speed is set 0 or very small for your printer. Normal values would be 20-40 since extruder has nearly no mass it can start very fast. But with low setting it enforces low speed where not needed. Then speed is increased to minimum speed as it seems instead of 0 from computation.

So increase extruder start speeds and the problem should be gone. Never thought of that.

Morpheus69Morpheus69 October 2016 edited October 2016 Posts: 0
YES !! It is gone. It is the first test, but i think is solved. Thank you very much.
I this point i want understand if is it my mistake...( i forgot to set right value ?) or my printer is "strange" and it wants a non zero value...

Comments deleted.

Hi, If you setup the firmware with software retract you can avoid the stringing completely. The software retract will retract all extruders at the same time.

I found out I was just printing in a higher temperature than needed - lowered the pla temp to 195-200 and lost all strings.