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Calibrating a Dual-Extruder 3D Printer

Calibrating a Dual-Extruder 3D Printer

I think we can all agree that auto-calibration (of the two extruders) is an awesome feature in dual extruder 3D printers.

No doubt: More and more printers now have auto-calibration and if you are in the market for a new printer with two extruders, check out the new Airwolf 3D AXIOM DUAL Extruder 3D Printer.

But ... there's no need to throw out your trusty 3d printer from a year or two ago just because it requires manual calibration.

Why?

Because in this post we'll share our Hotel-Card-Calibration Technique -- an easy-yet-powerful trick that we have been using for years with our Felix 2.0, one of the early dual extruder 3d printers.

Leveling vs Calibration

Before we get started, let's quickly clear up the terminology.  

Leveling refers to the process of adjusting the z-axis distance between the nozzle (or multiple nozzles) and the print surface.

Calibration on the other hand is the process of adjusting the nozzles of a dual extruder to be at the same vertical distance from a given point of the print bed (but not necessarily close enough or level with the bed).

For dual extruder 3D printers we start with calibrating the extruders before we level them to the bed.

Clear as mud? Then let's go ...

What's so difficult about calibrating the nozzles of a dual extruder 3D printer?

Compared to a 3d printer with a single extruder, calibrating the two hotends of a dual extruder printer adds another challenge as both nozzles need to be at the same distance with virtually no tolerance.  If the nozzles are calibrated differently by as little as 50 Microns (=0.05mm) it will most certainly ruin your print, because of two issues:

  • Depending on the thickness of the layer, the nozzle that is closer to the print bed may "scratch" over the layers printed by the other nozzle, and potentially drag plastic away from the bed
  • Even if this not a problem, you will most certainly experience issues with getting the print to stick to the bed as is common when the distance between nozzle and bed is too large

After struggling with this issue for a while and being unable to fix it by following the manufacturer instructions for calibrating the print nozzles of my Felix 2.0, I found the trick described below. It works consistently, although the print heads naturally move over time and you will have to recalibrate on a regular basis.  

If you don't have a Felix 2.0...

Obviously the instructions won't work exactly as pictured, as the extruders on your printer will be different. But aside from finding the right screws to loosen and the method of raising/lowering the print bed, you can absolutely apply our Hotel-Card-Calibration technique.

Felix 2.0 Print Head

Start With Clean Nozzles

Before you start, make sure that no dried plastic is sticking to the tip of the nozzle.  The nozzles will be calibrated by touching a surface so even a tiny amount of filament from your last print will mess up the result.  I found it easiest to use tweezers to pull off the plastic as the nozzle is cooling down -- just after it stopped oozing but before it cooled down and the plastic hardened.

Loosen The Nozzles

I found that the easiest way to give the nozzles of the Felix 2.0 just a little wiggle room is to loosen the two screws of the front fan a little bit. A couple turns of each screw should be enough. Be sure not to unscrew them entirely!

Felix 2.0 - Loosen Nozzles of dual print head

Adjust the Height of the Print Bed

For this step use a plastic card. We prefer old hotel key cards as we always find one of those laying around in the office. Whatever you use, be sure not to use a card with raised numbers such as a credit card -- obviously you'll want a flat surface!

Before we get started a word of warning: DO NOT do this step directly on the print bed, you may damage the protective surface if your bed is covered, or even worse, the bed itself.

With that in mind, it's time for our ....

Hotel-Card-Calibration Technique

Card to calibrate Felix 2.0 Print Head

Place the card underneath the the print head and slowly move the print bed up.  This should be done manually by turning the z-axis and not by using the motor (in fact your printer should be turned off during the entire procedure).

Once the nozzles get near the card slowly continue to move the bed up until you can see that BOTH heads are pushed up ever so slightly.  This will ensure that they are now level with each other.

Lastly, with the bed in this position, tighten the two screws to lock the nozzles in this position.

Felix 2-0 ajdusting the print bed with card

Don't forget to move the bed down by manually adjusting the position along the z-axis.  

That's it -- now you are ready to calibrate the distance between the nozzle(s) along the entire surface of the print bed as you usually would!

Good luck & Happy Printing!


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