Intractable bed adhesion issues

[dramsey]

OK, this is ridiculous: over the space of a single day, I've gone from two weeks of printing PLA on bare glass with no problems over more than 100 prints, to being unable to print almost anything since nothing with stick to the effing bed, even with glue stick. Getting a good print now seems to be an issue of random luck and the whims of unknowable gods more than anything I'm doing.

Makergear PLA filament, the same spool I've been printing happily with pretty much the whole time I've had the machine. Bed temp lowered from the default 70 degrees to 60 and the extruder from 215 to 205 at the suggestion of forum members far more experienced than I.

Elmer's Washable School Glue purple glue stick.

Almost any time the head must make a sharp turn, such as reversing direction along a line:



...or sketching out the intricate outline of Ford's script logo:



...the filament peels off the bed and ruins the print.

I have checked head-plate clearance at 0.15-0.2mm across the plate, so at this point I'm kinda stuck. I really miss the "start the print and walk away" reliability I got used to and would love to hear any suggestions about how to get it back. Maybe I'll try blue tape next.

[Jules]

Whatever your Z-Offset is, move the bed closer to the nozzle by adding a negative -0.04 to that number. You need to smash the thread down just a little bit. Slow the first layer down to half of whatever you are using now for speed. (First layer speed.)

And you can take the bed temp back up to 70 if you are printing in a very cold room. (You have to be the one to determine what works for your situation.)

We're not there.

[jimc]

absolutely agree here. your bed gap is too big. you can easily see that in the extrusions. take a look anywhere where you have 2 side by side. there is a gap between them. this means that the extrusions arent being made wide enough. the extrusions are too round and sitting up too high on the glass. with the gap a little tighter, the extrusions will widen up and become slightly more flat. each extrusion should touch each other.

[dramsey]

Won't stick to blue tape, either. I'm beginning to think there's something wrong with this role of filament.

Giving up for the night. Not sure what I'm going to try next, since clean bare glass, glue stick, and blue tape all failed. Maybe I'll just wait until the PEI I ordered comes in.

(Thanks for the suggestions, though: I understand it can be almost impossible to diagnose problems like this remotely. Still: perfect operation to completely useless for no apparent reason in a single day is insanely frustrating.)

Ah, new info: I see jimc offers compelling evidence that my head gap is not correct. I suppose the Chinese feeler gauges I'm using could be off. Will try 0.10mm (indicated) gap tomorrow, since 0.15 is what I'm using now, and apparently that's too high.

[jimc]

feeler gauges are great for getting things real close but thats as far as it goes. proof is in the pudding. how the extrusions lay down is key and in the end thats what you have to go by. you need to adjust things a bit closer. as you get more experience you will instantly be able to watch the skirt printing and tell if your all set right. if not you can quick cancel, adjust and reprint. right now nothing is sticking because you have next to no bed contact. imagine a tennis ball sitting on your desk. while round it only contacts in a very small spot. now take the ball and push it down on your desk so it flattens out a bit. much bigger contact patch. if everything is correct you will be able to pop your print off the bed, look at the bottom and you should have 90-100% contact. it should be very hard to see the edges of the extrusions. should be a nice solid surface.

[dramsey]

Just to make sure we're on the same page: you're talking about the "Z Axis Origin Offset" setting in the G Code section of the process parameters, right? The setting below "Build Volume" and above "Homing Dir"?

[jimc]

you can adjust it there OR set it closer with the quick start app......if your using that OR previous models have the the z adjustment bolt. whatever is applicable to your machine.

[PcS]

.15 to .20 variance on bed level is too much. You need to relevel your bed and re adjust your z stop gap. What layer height are you printing at. If it is .2 or thinner it is no wonder. You could try .22 layer and 110 percent first layer as a quick and dirty work around. I see a lot of these threads and it seems people set the z gap for a .2 or .22 layer and then decide to print .1 layers. Anytime you drastically change a layer thickness your z will need to be readjusted by some means. Weather by by global off set , extrusion multiplier, z gap , or first layer height.

[Tim]

Won't stick to blue tape, either. I'm beginning to think there's something wrong with this role of filament.

Bear in mind that if this is a new roll/color/brand of filament, especially if it is a brand you haven't used before, then you can be having multiple issues combining to make life difficult. Fixing the gap to the bed is certainly the most important thing. But you may have to tweak your bed temperature, your extruder temperature, and/or calibrate the extruder multiplier as well to get back to the automatic print-and-go. You might also have exascerbated the situation by choosing a print with a lot of sharp travel reversals, which are always the most difficult to get to stick on the first layer. Making sure you are printing inner perimeters first, outer perimeters second can help, as the inner perimeter will likely have fewer sharp reversals. The outer perimeter is the one you care about, anyway. If the inner perimeter ends up with some defects, it won't show, and the print will probably recover after a couple of layers.

[Tim]

I see a lot of these threads and it seems people set the z gap for a .2 or .22 layer and then decide to print .1 layers.

It doesn't help, either, that Simplify3D uses a percentage layer height for the first layer. Setting a layer height of 0.1mm and then trying to print the first layer at, say, 90% just doesn't go over well. I've always found that the first layer prints best at about 0.2mm, and although it's a pain to readjust the percentage layer height by hand every time, it's kind of critical to remember to do it.