Filament sticking to nozzle on first layer

I’ve had a Taz 6 since November and have gotten some great prints with it. I love not having to manually level the bed or clean the nozzle, but my one constant frustration has been with the fail rate of the first layer.

I find whenever I’m starting a print I have to do 3-4 attempts before getting a successful first layer (actually on starting my 6th attempt on a print right now, but 3-4 is average), whether I’m using nGen, HIPS, Polylite PLA, or a few other sample filaments I’ve tried out. Either the filament just creates a blob around the nozzle not sticking at all, or it will stick to the bed but the loose end is stuck to the nozzle so as it moves it pulls the filament up and I’m frantically trying to cut it free.

I’m just not sure whether I’m doing something wrong or if that’s just the way it goes with these printers. Before my Taz 6 I was using a Makerbot Replicator 2, and there were definitely a lot more headaches with it, but I was really hoping the Taz would be a bit more reliable than it’s been so I could focus on designing things rather than hovering over my printer to make sure it works properly.

I’m going to take a guess that you need to adjust your z-axis offset – sounds like you’re a bit too far from the bed and aren’t getting good adhesion of that first layer. There could be any number of things wrong, but if you’re getting this on multiple types of filament, I’m thinking that’s ruling out temperature-related problems.

Another possibility is that your PEI bed surface isn’t doing its job – it may have picked up a coating of oil or something like that, either in manufacturing or perhaps it’s a simple as someone touching the bed just after putting hand lotion on their hands (in my case, it was removing a part after I’d unpacked some steel stock – the steel was coated with a protective oil, and the smears from my dirty hands were quite visible once I knelt down to view the bed at just the right angle). Clean the bed with rubbing alcohol, and a 3M (plastic) green scrubbing pad… and if you have a hardware store nearby, you can try some incredibly-fine sandpaper (4000 grit) to lightly scuff up the surface.

I’ve both a mini and a taz – and while I’ve encountered the symptoms you’ve described, it happens so infrequently I honestly cannot remember the last time I had the first layer detach. The “blob on the string” I do see more often, but it seldom causes a problem (the blob might be loose, but the string is usually stuck nicely to the bed, and seldom gets in the way of the print).

Thanks for the reply mwester. I’ve tried cleaning the bed multiple times with isopropyl alcohol wipes, and have been using glue stick when recommended (ie. with nGen filament) so I’m going to try out your first suggestion of adjusting the z-offset.

I’d read on here (or maybe on that someone who was having even worse bed adhesion than I am had emailed Lulzbot support twice about it and received the conflicting recommendations of adjusting the z-offset and to never touch the z-offset. So, guess I’m gonna be messing with that z-offset and hoping for the best!

I hv been having similar issues as the ones described here.
-The first issue I had was bed leveling. The nozzle was dirty and when the Taz executed the wiping and probing, there was excess pressure which cased slight deflection on the bed, causing the nozzle to be too close to the bed impacting material flow. To fix this I now raise the extruder, heat up the nozzle, with a leather glove clean the head and rub with a non-conducive scotch britte to clean it. With this, the nozzie just lightly touches the contacts in each corner and keeps an acceptable distance to the bed not to impact material flow.
-2nd issue was that I was using a low temp for the material. I’m too inexperienced here. What I did was to load the material on the extruder, heat up the head to 190 degrees… go to Movement/Extruder and push some material through the nozzle. I kept raising the temp and pushing material till I got a good flow of material. That was the temp I used for the next run.
-3rd issue was the first layer settings. Experimenting, with some friends help and watching videos I did the following changes: moved the first layer speed to 50% (more time to extrude that initial critical layer), increase the skirt lines from 1 to 3 (more time to prime the nozzle), cut the fan to 0% for the first layer (less impact on temp), raised temp for the first 2 layers +5 degrees above the rest. With this I got good priming on the nozzle prior to start printing and a slower/higher quality first layer.

After doing 1-3 I run a test on a BlueTape and I got a great print.

Now onto the bed/PEI:
Due to the adherence issues, I followed the recommendations to clean the PEI. Using a mix of 1:9 Isop Alcohol/water mix, wet the bed and sand with 1500-2000 grit (Lulzbot tech team recommendation). Sand thoroughly and clean again with the same solution. I did this yesterday after my print and I’m going to try a new print today now on the PEI and not on the Blue Tape. Will report back. A few days ago my PEI was showing a ton of bubbles, I’m wondering if that’s the issue. My machine is basically new, I hv run just 4 prints total… :slight_smile:

Will write back after testing the PEI today.

Keeping the bed clean (I use 70% isopropyl alcohol) and the nozzle clean are crucial to getting good adhesion on the first layer. While Z-offset may need to be adjusted, there are other things (many of which have already been mentioned) to try.

In Cura, Print Setup, change from Recommended to Custom. In the search box, type “initial layer”. These are all the parameters you can adjust in addition to “Z-offset” that might help get that perfect first layer. Mouse over each parameter to see the help.

I agree with the recommendation to increase the skirt lines. I use a minimum of 3 lines and increase the minimum distance from 250 to 750. You can also move the skirt farther away from the print. I can usually tell if the first layer is going to be successful in the time it takes to print the skirt. If the bottom surface of the printed object is small, I may switch to a brim instead of a skirt.

Thanks for reminding me about those settings. I know I’d played with the speed of the initial layer and had some success, but a few months back I remember setting the initial layer height to around 0.4mm and that print worked on the first try. Definitely worth me exploring more of those settings!

I’ve tried this and actually had the most success adding about 5-10 lines of brim, even with large bases that would be very unlikely to come off. Unfortunately I found with the skirt that even if it sticks down, when it moves to the actual part it often does the thing where the loose end sticks to the nozzle creating a loop of filament that pulls itself up as the print head moves. This is only made worse when the part I’m printing has multiple points of contact with the bed.

This sounds like it might be a temperature issue. Try reducing the temperature by 5 degrees at a time.

It might also be a retraction issue so type “retract” in the Search and increase the Retraction Distance by .5 mm at a time, Retraction Speed by 5-10 mm/sec.

Last thing I’d try is reducing the speed of the initial layer.

Great advice posted. Here’s a few more tips to try, but the real key is to get good adhesion to the PEI.

Start the first layer a few degrees (3C) higher than you would normally extrude. If you get good adhesion to the bed, the hotend should be able to melt its way through the first layer rough spots.

Check that the autolevel discs are clean, and check for bubbling of the PEI that may cause any unevenness of the bed.

Could also be overextrusion… adjust the flow rate or multiplier in your slicer.

Keep working on roughing up the surface of the bed. Try a green scrub pad in a cross-hatch pattern. Parallel and perpindicular doesn’t hurt either.

I was having the same problems a little while ago. My solution was probably a combination of adjustments. Here’s my list:

  1. Reduced the speed of the initial layer to 25mm/sec.
  2. Increased inital layer bed temperature by 5 degrees.
  3. Reduced initial layer height to 0.2mm.
  4. Set the Z Offset on the fly by printing a large perimiter and using the onboard screen. Go to TUNE, scroll down to Z Offset and rotate the knob whilst carefully watching the extruded line (needed my glasses for that one!) I go for a half squished line. Then once it starts filling in the first layer, I adjust it so that I get a solid fill without over squishing (I think that the technical term for it :slight_smile:)