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Sunday, 25 March 2012

Calibration continued

Having completed the mechanical calibration yesterday, it's time to move onto extruder/print calibration.

SIDEBAR: I suddenly realised I hadn't revisited the max values on all my axes after calibration, so here goes.  The approach used was to home all axes and then to move each axis in turn using the various increments until I felt comfortable that the maximum had been reached.  The values noted are:

  • X-axis - 170
  • Y-axis - 170
  • Z-axis - 100
I then changed the values in the configuration.h and reloaded the firmware.


Back to Slic3r
Having been reading quite a bit, I quite like the Slic3r is Nicer approach documented by RichRap, so will be following this.  He doesn't actually document this as a calibration technique, but for print improvement.  Well, why not do it in one.  I will be trying to combine his methods with the standard calibration (i.e. the objects chosen to print while following his article will be based on the calibration objects where feasible).  So, here are the steps followed:

Getting Slic3r running
  1. Download the latest version from the website. (at the time of writing this is v0.7.1) 
  2. Unzip to a convenient location (no setup required)
  3. You can run the slic3r.exe directly from the folder, but I prefer creating a shortcut on my Quick Launch bar as follows:
    1. Rt-Click the slic3r.exe file and drag it onto the Quick Launch bar.  When you let go, choose Create shortcut here from the context menu.
  4. Try it out.  You should get something like this:
Extruder Calibration
Having already done a mechanical calibration on the extruder, I decided to still follow RichRap's advice method and use this as the time to double check the values. I followed these steps:

  • Switch on the extruder heater
  • Mark the filament (a piece of tape will do)
  • Zero your measuring tool (or take a starting reading)
  • Make sure the heater is up to temperature (if not, wait!!)
  • Extrude 30mm, 5mm at a time with small pauses.  This is to ensure you aren't extruding too quickly.
    • Note the reading: 31.83
    • Measure again: 31.51
    • And a 3rd time for good measure: 31.10
    • Average: 31.48
    • New Steps = 608.519*30/31.48 = 579.91
  • If the results mean you need to change your config, then upload these changes using Arduino.
    • You should repeat the test to make sure it is now correct.
  • Don't forget to remove the tape from the filament.
Slic3r Print Settings Tab
I won't repeat the contents of RichRap's article, but will focus on the changes I make to the default settings.  These are:
  • Transform
    • no changes
  • Accuracy
    • Layer height - changed to 0.3mm based on his recommendation for a 0.5mm nozzle.
  • Skirt
    • no changes
  • Print Settings
    • Fill density - changed to 25% as I'll be testing things out and based on RichRap's article, this is a good general purpose value.
    • This version of Slic3r now has a Generate support material setting.
      • This looks like a useful feature to experiment with, even if using the same extruder.  I'll have a go sometime, but for now I left it switched off.
  • Retraction
    • Speed - I changed this to 16mm/s as this is what RichRap used with Sprinter firmware.  I may need to revisit this in the future.
Slic3r Printer and Filament Tab
  • Printer
    • Print center - 85,85
  • Filament (for the temperatures I couldn't use RichRap's suggestions as he uses PLA)
    • Diameter - 2.85
    • Temperature - 230  (based on this article)
    • First layer temperature - 215 (based on the same article as above)
    • Bed Temperature - 110 (based on the setting in Pronterface)
    • First layer bed temperature - 140 (based on Nophead's settings)
  • Print Speed
    • Perimeters - 65 (based on RichRap's "Normal" printing setting)
    • Small perimeters - 55
    • Infill - 80
    • Solid infill - 70
    • Bridges - 50 (RichRap uses between 35 & 70, so  I'll start in the middle - sort of)
  • Other speed settings
    • Travel - 150 (RichRap reckons a Prusa could get up to 200, mine is a Sells with a heavier X-axis, so I'll start with 150)
    • Bottom layer speed ratio - 0.35 (as per RichRap's article)
Slic3r Start/End GCODE
I decided to copy RichRap's Start/End GCODE settings as they make sense to me (this is copied directly from his article).
Here is the Start Gcode I use - (Suitable for a Prusa with heated bed)

G28                 ; home all axes
G92 E0 ;reset extruder
G1 E3 F1200 ;Prime extruder 3mm
G1 E2 F1200 ;retract extruder 1mm
G92 E0 ;reset extruder

And my End Gcode - 

G1 X12.0 F4000       ; home (almost) x - stops extruder crashing into frame if at very top of Z height
G1 Y170 F4000        ; move the print to the front.
M104 S0                   ; make sure the extuder is turned off.
M140 S0                   ; make sure the bed is turned off.
M84                          ; shut down motors.

So, let's print!
I downloaded WickedAndy's polycup as per RichRap's article and sliced it.  The resulting code said it would take around an hour to print, so I thought I would start with something a bit smaller.  I simply setting Slic3r to scale the object to 50% and tried again.  Result! ETA 12 minutes.

So I thought I would switch on the heated bed and hot end to get them warmed up first, but noted that now my heated bed isn't heating!!!

So, 2 steps forward, 1 step back.

  • First thing, test the output voltage. Check!
  • Next, check the PCB wiring. Aah!
    • Seems one of the soldered joints gave in.  Wonder if my solder is up to the job?
    • Anyway, re-soldered and let's try again.
Reload the settings in Slic3r (as I was messing with them), then try again. The settings of importance that I tweaked from my standard settings above are:
  • Temperatures:
    • Hot End - 230,230
    • Bed - 65,65 (it was taking ages to heat up and I got tired of waiting)
  • Scale - 0.5
  • Perimeters - 2
  • Fill - concentric
Here are some pictures of my very first print.  The cup is about 40mm diameter at it's widest.  The quality isn't fantastic (especially at the bottom), but considering the following I am very happy:
  • It's my first print, with no tweaking of the settings;
  • I scaled the item down the speed it up.  I don't think this item is really suitable for scaling like this as it makes the wall extremely thin;
  • I didn't wait for the bed to heat up properly.
That's me done for the day, I'm off to watch the Malaysian F1. (Having said that, I might print the odd other item in the interim)

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