Calibrating the Prusa i3

March 18, 2014 3D Printing

The Makerfarm Prusa i3 is pretty much ready to go upon assembly, however, there is still a little bit of work to do in setting up your extruder and heated bed.  I won’t claim to be any expert in this, but wanted to post a few tips that might help people get set up even faster.

Tip #1: Bed Leveling

I’ve done some reading around on the topic, and I don’t think there’s any way around this… leveling the bed is a pain in the ass.   The Makerfarm Prusa i3 comes with the “Bed Leveling Kit” which includes springs and socket cap screws for providing some adjustability of the bed above it’s platform.  Additionally, since the Z carriage is dependent on two screw drives to raise and lower, it also requires leveling.  Here is a quick overview of the steps:

  1. Use a level to make the Z-carriage horizontal with ground.
    A_DSC_0137
  2. The back right corner of the bed is home, so make sure that a nylon spacer is installed in that corner.
    A_DSC_0127-2
  3. Then use an extra spacer as a guide to adjust the springs in the other 3 corners.  This gets us a bed that is more or less level with the platform.

    • Use spacer as a guide.

  4. Adjust the Z-home position to be about the height of a piece of paper above the glass.  Do this by modifying the position of the Z-stop screw and then pressing the Z-home command in Pronterface until the correct height is achieved.  Once set, finger tighten nuts on either size of the screw so that it does not move.

    • Use a piece of paper as a height guide. The nozzle should be just barely touching the paper. When you can move it with slight resistance, it is at the correct height.

  5. Now, adjust the screw in the front-right corner of the bed until the Z home position is just above the glass
  6. Adjust the front -left corner to the correct Z-height.
  7. Adjust the back-left corner to the correct Z-height.
  8. Position the print head in the center of the glass bed, and test the Z-home position.
    A_DSC_0125-2
  9. Repeat steps 5 throught 7 until all corners and the center of the bed are at the correct height.

Tip #2: Extrusion Calibration

This is a simple test to make sure that the factory installed settings for the extruder are on target.  Using a set of calipers, create a thin mark to measure out 10mm of filament.  Make sure your extruder is up to temperature, then extrude 10mm of filament.  Inspect the mark and your measure point for accuracy.  In my case, the extruder was spot-on.

  • Mark off 10mm of filament with a marker.

If you extruded too much or too little, RichRap made a good blog post explaining what to do.

Tip #3: Printing Temperatures

After these adjustments, I was ready to begin printing the “Test Cube” geometry, which is just a cube, 24mm on each side.  So, I produced the GCode in Slic3r, and got everything set with the factory temperatures input at 80 degrees C for the bed and 205 degrees C for the extruder.  Quickly after beginning the print, however, I realized something was wrong when my test print detached from the bed and became a rats nest of plastic as it got moved around underneath the extruder.  Figuring it must have been an anomaly, I retried it, with the same result.  At this point I noticed that the bottom of the test prints were curved.  When I ran another test print, I noticed that the upper right corner looked like this:

A_DSC_0035

At this point, I realized that the heat settings for either the bed or the extruder were not properly matched, making my print warp as it cooled.  So I dropped the bed temperature to 60 degrees C, with no luck.  I tried extruding at 190 degrees C, and that didn’t help either.  I went through a few iterations:

A_DSC_0039

After a bit more experimentation, I finally landed on a bed temperature of 70 degrees C, and extruder temperature of 205 degrees C (see update below).  The prints were uniform, and I was able to get a full cube.  Using my calipers, I measured it and came up with the results below the pictures.

  • Full test cube.

Direction Nom. Dimension [mm] Actual Dimension [mm] Difference [mm] Differenc [in]
X 24.00 23.90 0.10 0.004
Y 24.00 23.95 0.05 0.002
Z 24.00 23.53 0.47 0.019

So, while the X and Y directions appear to be relatively accurate, the Z direction is about 0.02″ off.  For now, that’s good enough for my purposes… maybe in the future I’ll work on doing some further calibration.

UPDATE:

After a lot of trial and error, I am now printing with a bed temperature of 65ºC and an extruder temperature of 185ºC.  I believe that extruder temperature fluctuations due to drafty printing rooms caused me to require a higher temperature.  I have since built a printing enclosure and can now print much more reliably than at the time of this writing.

This article has 12 comments

    1. moczys@gmail.com

      Hi Joe! I’m not quite sure what you mean by “extruding too fast”. The extruder is controlled by the gcode that your slicing program outputs. In my case, I use Slic3r, and haven’t yet played with the other slicing programs. In Slic3r, however, there are several things you can do to control the extruder. First, make sure you set the program to run in “Expert” mode using File>Preferences. Extruder settings are found by clicking on the Printer Settings tab up top, and then click on Extruder 1 in the window on the left. Here you’ll be able to set some of the parameters that the slicing program uses to calculate how fast to extrude, and when/how far to retract. Additionally, by clicking on the Filament Settings tab, you’ll get some options where you input the filament diameter, and the Extrusion Multiplier.

      If you’re talking about oozing, where the nozzle is leaking out extra plastic while it is moving around… try playing with the Retraction speed and length in Printer Setting>Extruder 1. I have read on other blogs/forums that the motors used on the Makerfarm Prusa i3 had some issues with not being able to retract at the speeds you input into Slic3r. For PLA, I set mine to retract 1mm at 10mm/s and it seems to help limit the amount of oozing.

      If you’re talking about actually extruding too much filament… then you’ll want to go into the Filament Settings tab and change the Extrusion Multiplier. First, make sure your filament diameter is correct so that the program is calculating the correct volume of plastic. Next, if it is still outputting to much plastic, then you might want to dial back the Extrusion Multiplier to 0.95 or 0.9. You may have to do a couple iterations of changing this number to get it to work the way you want.

      Hope this helps!

  1. John M

    Hello I hope this message reaches someone that can help. I’ve searched and can’t seem to find what I’m looking from. I have a Prusa I3 that I have just assembled and if i use the Slic3r retraction settings at all it just prints excess globs of filament in any spot that is supposed to retract. From what I can tell, the motor is not retracting at all and when it goes to normalize, since it wasn’t retracted, it spits out filament. I’ve read that the speed is auto set too high and I’ve gone down to as low as 7mm/s and it still does the same thing.
    Also, none of the manual extraction buttons in Repetier host or Pronterface seem to actually retract the filament. It’s like it’s basically another extrude button.
    I’m really new to this and would love any input. Thanks
    John

    1. moczys@gmail.com

      Hi John! Is the printer laying down filament correctly otherwise? The retraction speed issue you mentioned is a good thing to check first. I believe I have my retraction currently set at 10mm/s and 1mm, but it sounds like that’s not the problem. Printing at too high of a temperature can cause oozing… for PLA I print at 185 deg C extrusion temp and 70 deg C bed temp. For the last issue you mentioned, about the manual extrusion… that sounds like you might have something wrong with your extruder stepper. You might want to check the wiring on the stepper to make sure they’re connected properly. Sorry I can’t be of more help!

  2. peter burgess

    hi john just finish building my geeetech prusa 13 x when using home button setting the extruder carriage moves away from the stop switch to the opp side of the carriage and I have to press reset to stop it. all plugs are in the right sockets and the end stop do not appear to be working I am total new boy to 3d printing so any help you can give me would be of much help ie how to set up xyz etc thank you

    1. moczys@gmail.com

      It depends on how you’re controlling the printer. If you’ve got the Makerfarm Prusa i3 model that I do, running Marlin firmware, you’ll use the control potentiometer to select Prepare>Move Axis>Extruder, and then turn clockwise (I think) to extrude filament. The menu tree can be found here: https://github.com/open3dengineering/Prusa-i3/blob/master/Firmware/Marlin/Marlin/LCD%20Menu%20Tree.pdf

      If you’ve got a different setup, however, I can’t help you, sorry!

  3. Rob

    I am confused about the temperature calibrations. From initial assembly, the test print and several for my first 5-6 prints, It was running with the stock 60 degree bed and 200 degree extruder. The prints all came out great.

    the last few attempts have broken free on their own yet were still listed at the same temperatures. I changed the tape on the bed and still the subjects break free. I recalibrated the bed clearance several times over. the problem is still there so I went back to the basic test objects. Testing the cube, 95% of the first layer is sticking but there are some spots that fail. The readings now are telling me that it is printing at 50!. is this something that I change in the printer settings or the object properties when i slice it?

    Should I order a better plate?

Leave a Reply

Your email address will not be published. Required fields are marked *