hotend leveling

[green eggs]

I'm looking for suggestions on how to lower the 2nd nozzle a little further than is allowed by the demonstration in the video and the printed instructions that I'm following for the Rostock mini g2s pro. Here's the video segment https://youtu.be/VCa_Bvx8OWs?list=PLODC ... ejQ&t=1214 for reference. My experience mimics the video's, in that I did a minor adjustment, then a more serious adjustment involving removing the heating rod and rotating 180+ degrees, but I still need another 1+ mm or so.

Editing for brevity: I suggested that I checked over my assembly to see if I missed a washer or plate calibration etc, and became concerned that the diagonal rods might be of different lengths (say 1mm) according to crude measurements. I'd considered putting a washer or two between the hotend to counter-tilt the spider, but wasn't sure if that was wise, or would even buy anything.

[Mark]

you can level them like this, there's two nuts on each of the hotend. You can heat up the hotend to about 200 degrees and then unscrew the upper nut, then you can rotate the threaded tube to level the two hotends. And remember to heat up the hotend before you do this, cause if there's still filament left inside the hotend then you might broke the threaded tube. And sometimes you need to remove the heating cartridge to make more room for you to adjust it.

[green eggs]

Thanks Mark,
Are you saying that the 200 degrees will allow some freedom of movement that I don't have at room temperature? I'm already able to loosen the top nut and partially rotate the hotend, but the block bumps into the other which I suspect it will continue to do at 200 degrees. At this point in my initial setup, I haven't (yet) used printer filament.

[green eggs]

As an update to this topic, I found that the diagonal rods vary in length by 1.5 mm or so based on some crude measurements. I suspect this caused the tilt of the spider since when calibrating near the smooth Z rod, I needed to relax the upper limit screw by quite a bit (say 2mm) to clear the pad. I'm now concerned that I can't win with a tilted spider. If I make the hotends even in one position, they'll be uneven in another position further or closer to the smooth Z rods. I've read elsewhere on this forum that another user has actually witnessed that condition.

Edit: In hindsight, I think the limit screw was irrelevant. It seems that once the diagonal rods are attached, the tilt of the spider is pretty much determined regardless of raising and lowering of an individual pair of rods. Before I adjusted the arm lengths, I had some success in minimizing the tilt and also directing the remaining tilt to be side-to-side rather front to back which caused difficulties in leveling the nozzles. It seemed that averaging the arm lengths helped; that is, placing the longest and shortest arms on the diagonal close to Z and then alternating short, long around the circle. Ultimately, making the rods the same length was my favored solution.

[Mark]

the diagonal rod is glued into the ball bearing holder, how about heat it up a little and melt the glue and then adjust the length? will it work?
And you can compensate the settings here in the configuration.h tab:
#define DELTA_DIAGONAL_ROD 196 // mm

[green eggs]

I meant to reply in the forum that heating for about 30 seconds on a stove filament was enough for me to twist with pliers. One was stubborn and would not go below 197mm (mid-eye to mid-eye), so they all were adjusted to agree with that length. I placed all 6 diagonal rods on the shaft of a snug fitting screwdriver and placed another snug-fitting shaft through the other set of eyes to make sure they were all in agreement. I switched the order around to make sure they were truly even. I adjusted the firmware to use 197 mm. It seems like things are calibrating well now.

[Mark]

good job. So how's the result? could you print a better object?

[green eggs]

Thanks, I've been able to use both extruders to print the test files in the tutorial that look like 4 chess-board squares and they look pretty good, so I'm happy about that. I'm sure I'll learn more, but for now, I adjusted slic3r's extruder2 to use offsets of about: x=1.6 and y=26.8 to minimize the seam between extruders. Thanks again for the tips.