MK3: Nozzle seems far too high above the bed?  

Re: MK3: Nozzle seems far too high above the bed?

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Re: MK3: Nozzle seems far too high above the bed?

it says right on you're LCD that Z is at 0.15mm which is what it is when it's homed... it's never Z=0. Move to Z=0 then check.... also it will be Z=0 + first layer height when printing... if Z=0 is 0.1mm from bed, it will be 0.3 when printing a first layer height of 0.2mm...

Also adjusting live Z should be from the calibrate menu, if you adjust while printing something else it seems to adjust "relative" to the previous live-z from the calibration menu and saves like that and each print it will get lower or higher and really messes you up.... maybe that's not the case with MK3 but it does this on my MK2s with latest firmware....

Re: MK3: Nozzle seems far too high above the bed?

it says right on you're LCD that Z is at 0.15mm which is what it is when it's homed.

That's my point, it should be at 0.15mm but I can easily fit a 0.75mm card under there with room to spare. I don't get why it would be so high above the bed by default. I get having to fine tune the Z using Live Adjust Z, but it calibrates Z to almost a full mm above it should generally be. Could there a problem with the PINDA?

Re: MK3: Nozzle seems far too high above the bed?

If you have Live Z set = 0, you should have a large space under the nozzle. (Nearly a 1mm per your drag test which indicates -1.115mm).

If you have Live Z set to your = -1.115, then the nozzle is nice and low - as your test prints showed (since they squished at -1.150).

This all seems normal to me. This is the purpose of setting the Live Z so the machine knows the distance from the electrical PINDA position to the nozzle tip.

Please post photos of your calibration surface at the -1.150 and let us see how it works.

Re: MK3: Nozzle seems far too high above the bed?

If you have Live Z set = 0, you should have a large space under the nozzle. (Nearly a 1mm per your drag test which indicates -1.115mm).

I don't understand this. If Live Z is 0, and I home the nozzle, shouldn't it be at 0.15mm rather than at nearly 1mm?

Re: MK3: Nozzle seems far too high above the bed?

If you have Live Z set = 0, you should have a large space under the nozzle. (Nearly a 1mm per your drag test which indicates -1.115mm).

I don't understand this. If Live Z is 0, and I home the nozzle, shouldn't it be at 0.15mm rather than at nearly 1mm?

Only if your Live Z is set correctly. If your Live Z is set to zero, there should be a gap.

Think of it this way. The machine knows where the PINDA is because it measures the PINDA to BED distance when does the Z-Cal. (This is approx due to different PINDAs and beds).

But it has now way to know where the nozzle is relative to the PINDA. Did you put it lower or higher? How could it possibly know? So in step 3 of that post, you get it approximately correct by doing the drag the paper thing. The paper is approximately 0.15mm. The printer thinks its at 0.15mm. You adjust Live Z until you feel the paper drag a bit. Now the nozzle is approximately at 0.15mm while it thinks it is at 0.15mm. Now printer knows approximately where the nozzle is relative to the PINDA. The value can vary quite a bit depending on how low your PINDA is. If you adjust you PINDA, the Live Z will need to be adjusted. You can think of the Live Z as the adjustment to let the printer know where the PINDA is relative to the nozzle. It is not quite that simple, but you can think of it that way.

Sadly, that is not good enough. Why? Well, what really matters is that filament squishes out at a nice flat way. That depends a bit on the viscosity of the filament (thus PLA and PETG and ABS will all have different settings), the specific part of the nozzle that was dragging above. Step 6 is designed to get this set very very accurately, which makes the filament adhere much better to the bed, and prevents a lot of failures.

Does that help?

Re: MK3: Nozzle seems far too high above the bed?

Got it, thanks! Your post helped me understand exactly what I was doing in terms of calibration, rather than just following the instructions and hoping for the best.

It's weird that I set my PINDA to a height of approximately 0.5mm (I stacked five sheets of paper under it while the nozzle was touching the bed and then pushed the PINDA down onto the paper) but I still had to set a live Z of -0.98 after doing an auto home and doing the "single sheet wiggle test".

Then, when doing the first layer calibration, I had to drop the live Z down to -1.2 before I got a good layer. At first I kept messing about in the 0.9 range, and had poor results - almost all squares consisted of loose strips. Eventually decided to go the reverse route: I dropped the nozzle down to where it is just barely off the bed and the extruder starts clicking because it can't deposit filament anymore. This was somewhere in the -1.4 range. Then I slowly raised the Live Z value, lifting the nozzle until filament started coming out and the layer it was printing started feeling smooth. This was around -1.2. I measured the printed sheet with my calipers, and presto: 0.2mm thick.

Still confused about the fact that I had to go so far over the "something might be wrong" number of -1.0 though.

Re: MK3: Nozzle seems far too high above the bed?

Got it, thanks! Your post helped me understand exactly what I was doing in terms of calibration, rather than just following the instructions and hoping for the best.

It's weird that I set my PINDA to a height of approximately 0.5mm (I stacked five sheets of paper under it while the nozzle was touching the bed and then pushed the PINDA down onto the paper) but I still had to set a live Z of -0.98 after doing an auto home and doing the "single sheet wiggle test".

Then, when doing the first layer calibration, I had to drop the live Z down to -1.2 before I got a good layer. At first I kept messing about in the 0.9 range, and had poor results - almost all squares consisted of loose strips. Eventually decided to go the reverse route: I dropped the nozzle down to where it is just barely off the bed and the extruder starts clicking because it can't deposit filament anymore. This was somewhere in the -1.4 range. Then I slowly raised the Live Z value, lifting the nozzle until filament started coming out and the layer it was printing started feeling smooth. This was around -1.2. I measured the printed sheet with my calipers, and presto: 0.2mm thick.

Still confused about the fact that I had to go so far over the "something might be wrong" number of -1.0 though.

There is a lot of variability in this number. Nothing is wrong. Think of it this way, if there is a 10% difference in the sensitivity of the PINDA sensor, or in the depth of the metal in the bed, there could be very large variability in the calculated distance. You only really care about three things:

1) The PINDA triggers reliably during the calibration at the beginning of each print. (If not you need to lower it.)
2) The PINDA is high enough not to drag on a print - even if the print curls up a little bit. (If not, you need to raise it.)
3) The Live Z is set such as you get a good clean first layer - with the adhesion that goes with that.

The actually measurements are just to get you into the ball park. Don't obsess on them.