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I upgraded to a dual Mk9 extruder, and quickly discovered how critical it is to get the ends of both nozzles exactly level with each other -- that is, equally distant from the build plate at all times. Otherwise the lower one will crash against the plastic just extruded by the higher one.

So, what's a good procedure for getting the nozzles accurately level? About all I've figure out is to move the heads down close to Z=0, and then run X and Y back and forth and eyeball and adjust; then move even closer to Z=0 and repeat. Is there a better / more efficient way?

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    $\begingroup$ Do you have a bubble level? $\endgroup$ – Daniel M. Jan 19 '16 at 11:09
  • $\begingroup$ Several; hadn't thought of that. Interesting. $\endgroup$ – TextGeek Jan 19 '16 at 13:35
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    $\begingroup$ When I get home I'll write up a proper answer if nobody beat me to it. Basically, use a bubble level to get the nozzles as level as you can and then use an index card with the nozzle close to the bed to fine-tine it. $\endgroup$ – Daniel M. Jan 19 '16 at 13:46
  • $\begingroup$ Does your machine not have a leveling routine? MakerBot machines have it built in the firmware to move to various points around the build plate so you can adjust the knobs. Easier than jogging it around manually lol $\endgroup$ – tbm0115 Jan 19 '16 at 19:58
  • $\begingroup$ Since I built this one from scratch, that would be a "no". :) But I haven't had any trouble getting the bed level; it's the relative heights of 2 different nozzles that I'm finding tricky. $\endgroup$ – TextGeek Jan 20 '16 at 4:21
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  1. Make sure that the bed is level. As the saying goes, a level bed is next to godliness or something like that. Pay extra attention to the direction the nozzles are offset by (if one nozzle is offset on the X-axis, pay extra attention to the bed leveling along the X-axis). This can be done with just one nozzle and a business card or piece of paper.
  2. Use a bubble level to get the nozzles about right. Move your z-axis up a bit and put a bubble level against the nozzles. Adjust as necessary so it's exactly level. The nozzles should be level enough that the bubble stays in the middle.
  3. Fine-tune it with a business card. When you home the z- axis, you should be able to just fit a business card under both nozzles with a moderate amount of resistance. Don't force the card. If sliding the business card under produces a different amount of resistance for one nozzle than for another, adjust the nozzle a tiny amount. You can also use an index card or playing card.
  4. Once it passes the card test, try a test print. If it doesn't work, make sure your bed is level, your nozzle offset is correct in the slicing software, and try calibrating with an index card again. If the nozzles become way off, try the bubble level again.

As for physically adjusting the level, another answer suggests shims made from aluminum foil, which work well. Personally, my extruder was off-level by almost exactly 1mm, so a pair of washers worked nicely for that.

Happy printing!

Leveling with a bubble:

Almost level, sorry for the bad lighting

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Two good options for ROUGH alignment:

  1. For threaded thermal barrier type extruders: use a leveling jig like this while the extruders are disassembled: http://www.thingiverse.com/thing:23013
  2. For straight-shaft thermal barrier type extruders: Carefully level the bed to whichever nozzle is lower, using your preferred piece of paper / business card / feeler gauge. Then stick the same paper / leveling tool under the higher nozzle, release the set screw or clamp on the tube, and drop it down to rest on the leveling tool. You can also use a printed jig if your thermal barrier tubes are stuck and need some force to move.

The best and easiest way for FINE alignment:

Shims.

Just stick some folded-up aluminum foil (or layers of Kapton, or whatever) under whichever end of the cooling bar is lower, and tighten the screws holding it onto the carriage. Re-adjust as needed until perfectly level. This is ten times more accurate and much easier than trying to get precision alignment of the thermal barrier tubes in the bar itself.

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