Bad print quality after nozzle change attempt  

Re: Bad print quality after nozzle change attempt

[...] First I scratched the PEI sheet when attempting a print, because the nozzle was low. I attempted XYZ calibration, which went fine. When I did a First Layer calibration, the value of Z has changed from -700, before the nozzle removal to -450. This sounds like perhaps you didn't have the 0.50mm nozzle fully tightened. Your adjustment from -700 to -450 went "less negative" which means the level was raised. Presumably the nozzle is hanging lower accounting for the difference. With genuine E3D nozzles, my Live-Z adjustment is minimal when I do changes. I've had some cheap knock-off nozzles that require greater adjustments. Be sure you've heated the hotend up to ~250C when doing swaps. You need to be careful not to over-tighten the nozzle, but it should be snug with 2 fingers turning the socket wrench. Always re-calibrate your Live-Z when changing nozzles and monitor it carefully for a crash with the PEI bed.

The flow of material is normal, but there is a lot more stringing and the individual print lines break from time to time.
What can I do?What slicer and settings are you using? Did you make adjustments for the new nozzle?

I've put my notes on nozzle sizes and impact on settings here, changing nozzles here, and making changes in Slic3rPE here. Hopefully these will be useful.

I really regret attempting to change the nozzle. Don't! Changing nozzles really lets you do a lot of interesting things with the printer, and it's nothing to fear. Once you get the hang of the procedure and settings, it takes minutes to swap and be ready. Go slow, and be sure to keep notes as you go. Picking up an assortment of nozzles has really added to my enjoyment of my Mk3.

My plan is to do an acetone wash and reinserted it carefully.If you were using PLA, acetone may not do much. I've done the following with a badly clogged nozzle:

1. Find 2 pairs of pliers and a 1.5mm brass rod.
2. Firmly grasp the nozzle with pliers and hold it in front of a hot-air gun. Brush off any melted gunk in the threads and off the exterior with a soft brass brush.
3. Insert the brass rod into the nozzle and force any stuck filament through. Swish it around to pull out any loose gunk inside. This should clear most of it out.
4. Use some cleaning filament (I like eSun) into the nozzle while hot and push it until it starts oozing out the opening. Do this quickly since the filament will soften quickly.
5. Set it aside to cool.
6 Once cool, grasp the nozzle with pliers and the protruding filament with the other set of pliers.
7. Hold it in front of a hot air gun and immediately begin gently pulling the filament. As it softens, it should pop out in the shape of the nozzle interior and, if you're lucky, the opening.

This is basically the same as doing a "cold pull" with the nozzle removed rather than mounted on the hotend. Other folks have reported just using a blow torch to burn the filament out.

If you don't have the necessary tools, just set the nozzle aside and buy another. You can always get back to it later and new ones are under $10, $25 for hardened versions. I got my Mk3 in April and had a bad clog about 2 weeks in. I was rather upset, but set the clogged nozzles aside (I really made a mess of 2 of them). Just last week, I used this procedure to "reclaim" them. It was a good feeling getting completely past my failure and restoring the 2 lost cause nozzles to service.

Stay calm and you'll master this in no time. Printing different filaments with varying nozzles really opens up possibilities. Stick with it!

Re: Bad print quality after nozzle change attempt

Thanks man. I will reassemble the printer today and I will try and see what happens. I managed to clean some of the stuff, that was bothering me.
The print that failed was done perfectly with the same Gcode before the nozzle swap. As you stated most probably I didn't insert the nozzle deep enough, hens the difference in the Z height.

Re: Bad print quality after nozzle change attempt

[...] The print that failed was done perfectly with the same Gcode before the nozzle swap. As you stated most probably I didn't insert the nozzle deep enough, hens the difference in the Z height.
Oh, well there you go. You need to set up a slicer profile with the right nozzle settings, then re-slice it to produce new gcode.

Re: Bad print quality after nozzle change attempt

Afraid this is one of those learning experiences. Please don't take the following as criticism as that is not how this is intended.

This has nothing to do with the slicer and everything to do with the mechanical set up, relying on 'software' to fix a mechanical flaw is poor engineering.

Any time you touch your hot end with a tool of any sort you need to re-calibrate XYZ, then you need to calibrate the first layer. Before doing any of this you need to set the default height from nozzle tip to Pinda face as per the user guide (although I've printed a calibration plate with a 1mm step to make it less hit and miss), then and only then run the calibration. If you use a calibration tool on the Pinda even if you change the nozzle then set the Pinda height you can pretty much be sure that your live Z will be consistent.

You scratched the bed because the stored 'reference' heights were no longer valid, these only get stored after XYZ calibration.

I also recommend you check out the nozzle changing guide on the E3D site paying attention to the location of the heat break to get the initial tightening correct, don't cheat on this step, do it, do it and do it again until you're sure you've nailed it. Then you heat the nozzle, then you re tighten, then you set up the Pinda, then you recalibrate. Cheat on any of these steps and you'll pay the price either in failed prints or damaged hardware.

Once done by all means set up a 'wood' profile.