Printing small objects with a bowden extruder 2


Today I tried printing a small Marvin KeyChain because someone at RepRap forums started a thread about problems when printing such a small object.

Marvin 1

Marvin 2

Marvin 3

 

I wanted to see what kind of success will I have after calibrating and tuning my Rostock Mini for over a month.

First I tried slicing with Slic3r 1.1.4-development version :

  • Repetier Host 0.95F
  • Slic3r 1.1.4-dev
  • Clear PLA 1.75 mm
  • layer height 0.18 mm
  • layer width 0.48 mm
  • 50% feedrate (reduced from 100% at layer 50)
  • temperature reduced from 185C to 180C at layer 50
  • additional 120cm fan blowing over the bed (activated at layer 50)

2014-06-26 10.51.15

2014-06-26 12.30.15

 2014-06-26 12.33.38

Then I tried slicing the object with KISS 1.1.0.14 :

  • Repetier Host 0.95F
  • KISS 1.1.0.14
  • Clear PLA 1.75 mm
  • layer height 0.18 mm
  • layer width 0.48 mm
  • 25% feedrate (reduced from 100% at layer 24)
  • temperature reduced from 185C to 180C at layer 18
  • temperature reduced from 180C to 175C at layer 47
  • additional 120cm fan blowing over the bed (activated at the first layer)

2014-06-26 12.32.29

2014-06-26 12.32.48

2014-06-26 12.33.29

I was changing settings mid print as I was observing what is happening and quickly spoted a cooling problem. The object is so small  that the layer doesn’t have time to cool and another hot layer is layed on top and then another…and so on. Quickly the whole object turns soft like piece of soft rubber and I tried to eliminate that by changing the temperature, feedrate and adding extra fan.
One fatal mistake was made with the use of Clear PLA as it’s the worst choice when doing experiments like this – it is clear and you can’t see anything.  I tried spray painting both robots with red paint and made it only worse, spraying added tiny drops and the paint filled some holes too much. Those two robots ended up looking reaaaally ugly, don’t look at them please.
So I changed the fillament to Gray PLA an tried again.

Slicing the object with KISS 1.1.0.14 :

  • Repetier Host 0.95F
  • KISS 1.1.0.14
  • Gray PLA 1.75 mm
  • layer height 0.18 mm
  • layer width 0.48 mm
  • 50% feedrate (reduced from 100% at layer 1)
  • 25% feedrate (reduced from 50% at layer 6)
  • temperature reduced from 185C to 180C at layer 6
  • temperature reduced from 180C to 175C at layer 11
  • additional 120cm fan blowing over the bed (activated at the first layer)

2014-06-26 15.57.41

2014-06-26 15.58.022014-06-26 16.01.072014-06-26 16.02.312014-06-26 16.03.00

2014-06-26 16.03.23

This one turned out pretty good, no overhang isues but it has some other problems. It looks like it has curly hair under the helmet and you can see some curles sticking from under the helmet on his right side and the center. It also has a visible vertical seam visible in the last picture.

Lessons learned:
  • must buy a camera , lousy phone cam I am using makes grainy pictures and makes good prints look ugly
  • don’t use Clear PLA for experimenting
  • must mount a proper cooling fan, the cheap small 40mm fan I am using now makes almost no difference
  • the new Slic3r 1.1.5 stable is out! must install
  • still haven’t solved ‘curly hair’ issue
  • an overhang has nothing to do with bridging, they are seen as completely different things by the slicing software

Slic3r and Kiss gcode file used.

UPDATE: Solved my ‘curly hair’ problem. As my friend ,the computer programmer, likes to say : It’s a feature, not a bug 🙂
Was looking at gcode and discovered that the path is wrong (like one way street sticking out) at the exact spots where my curls appear:

Marvin curls

Marvin-curls-26-6-2014-2The easiest solution in this case would be to manualy correct the gcode. But I am lazy and just peeled off those curls with a fingernail as they are easy to remove when the object cools off 🙂

The next day I started reading a very interesting topic on Reprap forum and couldn’t stop. This topic lead me to another and another and at the end I tried printing even smaller objects. Read these words of wisdom or save them for later as they contain detailed explanations of extrusion process :

X Y resolution – 8 micron details

As to my results printing even smaller objects? I was amazed this is posible:

Small Kitten and SquirrelSmall Kitten and SquirrelSmall Kitten and SquirrelSmall Kitten and Squirrel

Still slicing with Slic3r 1.1.4-development version :

  • Repetier Host 0.95F
  • Slic3r 1.1.4-dev
  • Red PLA 1.75 mm
  • layer height 0.18 mm
  • layer width 0.48 mm
  • measured again and changed filament diameter from 1.65 to 1.70 mm
  • 25% feedrate (reduced from 100% at layer 2)
  • temperature reduced from 185C to 156C at layer 2
  • additional 120cm fan blowing over the bed (activated at layer 2), BUT the fan is not the same as in previous prints,it’s blows much,much stronger

Lessons learned:

  • the smaller the object the more important it is to have proper cooling
  • also very important is to set the right filament diameter, small flowrate errors can ruin the print at such a smale scale
  • use Tantillus calculator to calculate the right extrusion width and height,  I couldn’t dream of such results before using it , thank you Sublime !

Files used:

 

 

 

 

 

 

 

  • Bryan Smith

    How did you calibrate your printer?? I am studying videos and all say when pressing Home button that booms are supposed to return to top position
    mine fly down against my print bed

    any suggestions?