First off, thanks for all of the help on bed leveling- I think I am getting it dialed in after a lot of experimentation. It seems my glass bed does have some slight variations.

Before I was "smashing" prints on the bed to get them to stick. I have always had a problem with adhesion. I had it on the stock TEVO sheet on the printer, I had it on a PLA sheet, and now I am having it on a Creality glass bed with some fancy coating that is supposed to lock the print down.

When the bed does hold the print it seems to do it well (you actually have to wait for it to cool down) but getting the print to stick is hit and miss.

This is a calibration where it is not "smashing" the print on the bed. No stickage. Some spots may hold, but eventually one string doesn't, it balls up and drags around, and then catastrophic failure.  One is a standard 0.2mm first layer, the other is the recommended 0.3mm in Cura.

I've tried printing at 60c, 70c, 75c. I've tried leveling the bed from 0.03mm to 0.1mm. 0.1mm seems to be where my 0.2mm layers do not get smooshed.

Here is a Calibration Cat that I have tried to print 10 times this morning with no adhesion. (Sorry for the black on black, it is what I had loaded.)  I do a skirt since I like to "prime" the extruder a bit before it hits the actual print.

0.2mm first layer. Got to the top section, filament balled up despite being able to print the skirt beyond there.

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0.3mm first layer

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I just use Glass (level the bed after its heated) and mist it with Aqua net hair spray. Once every 10-20 prints I clean it with rubbing alcohol.
But I mist it before every print, it evaporates while the bed is heating up.
To get my prints off I use the putty knife and it it with a small hammer to brake it free. I dont use a brim or raft in my prints just a skirt to prime the nozzle.

Update: I decided to do another print with the bed z-level at 0.02.  That tweak seems to have the rear of the print seating properly.

We will see how the Calibration Cat comes out. I wanted to test some other tweaks I did to the printer over the weekend, I printed some belt tensioners, dialed in the y-axis carrier wheels and added 2020 corner brackets to parts of the frame.

... and regarding "smooshing", PLA  wants to be smooshed a bit on the first layer. You can overdo it & it will still stick & print.  If your trace starts looking transparent, you are overdoing it & you need a bit more headspace. (this is all easier if you are using the control panel to change Z offset instead of using the wheels - an advantage to having something like mesh leveling enabled).

Thanks- I do think I need to check out a video on e-steps.  I never did any extra calibration on my extruder (or other axises) out of the box so I will check that. I am seeing the first later pretty oozy.

I also see I turned off z-hop due to the time it adds, I think there was a custom setting to only do it on the top layer so z would still be an issue if it is dragging.

I am just so delighted to have prints on the bed outside of 4" dead center thanks to your suggestion on mesh bed leveling, and we see here what difference 0.02mm can make so that was surely a factor.

I just went through the same thing. I finally made it work after watching this video

Well, that was short lived.  I got a couple good prints using more of the bed, then I went to print dead center and taller and three times in a row it knocked the print off the bed despite having a skirt.

I think I am going to have to put this thing away for awhile.  I really wanted to get in to 3D printing, but this printer is so wildly inconsistent I've wasted four full weekends screwing with it. Every time I think I have it dialed in, within a print or two everything is off.

Either I got a lemon or I am too hamfisted for this hobby.  I've repaired watches, I've rebuilt motors, I've hand soldered PCBs, but I can't print a kazoo on a 3D printer.  

Part of me wants to put a BLTouch on this money pit since I can't level the bed for anything, and the other part wants to donate it to the local Makerspace and be done with it.

I wanted to get more of a "kit" so I would understand the mechanics of the thing, and I sure do now after all the tweaking.

But part of me wonders if I should have got an Ender or a Prusa.

I am sure I will be messing with it again next weekend as always. But it would be so nice to just be able to load a print, walk away, and actually make stuff.

You know, it is in the corner on an external wall by a window. Maybe I will fire it up in the warm basement just to see if it does better there.

Part fan you say? I have not tweaked that before.

Running 50% on it now to see how it looks. From here it looks "wetter" and less stringy like most prints have been today. Maybe that brim will hold down better, too.

I also slowed it down a bit to 50mm/s, at 60mm/s it was really hammering that small, tall part. (Think an oval tube.)  It actually shook one of the bed adjusters loose it was jarring so much.

Stick with it. The initial hump can be frustrating, but once you get over that it gets really easy really fast. VERY handy hobby when you get a handle on it.

You printing PLA right?
I always use blue tape for PLA, its always just worked. Might do a small print on glass if being lazy, but dont trust PLA there for anything big.
You can wipe the blue tape with some rubbing alcohol to make it stick more. Use sparingly though, too much and the surface on the tape will be blue after you jackhammer it off the bed

Some use fancy sprays or goops and have luck. Aqua Net super extra hold is PVA based as is the clear elmers school glue (seems like these always have some purple on the label or cap).
Im not a fan of these because they can be messy, but might be worth a shot before throwing in the towel.

Part got a little further, but started to wobble a bit, there seems to be some contact that starts rocking the tube when it is about 2" high.

I tried to blue tape the brim down but there was just too much wobble and the part started looking bad.

Then I tried a print another part, on the bed that I just leveled before the last part with a perfect brim, and the bed seems to be too high.  

I can't keep bed level for more than one part.  I leveled it about 10 times today, it is getting a little old.

After bed levelling 11, it won't stick again, where a dinky little part did before.  This thing is possessed.

3 of the 9 points had shifted enough to either not let the shim under it, or there was totally free play.  

Example:

I am trying to print this.  https://www.thingiverse.com/thing:3114202

I level the bed. (0.08mm shim) I print 2 each of the washers and caps. Perfection.

I try to print the kazoo body 4x today, each time it eventually fails about 1/4 of the way through.  (Nozzle starts hitting the part and wobbling.)

Oh well, let's print something flat and small.  https://www.thingiverse.com/thing:1977933

No adhesion.

Weird, everything was 100% perfect an hour ago, you printed 2 perfect 4mm thick washers.

Fine, I will set the bed z +0.02 to push it up.  No adhesion.

Fine, I'll level the bed for the 10th time today.  3-4 of the 9 points need a 4-5 click tweak to fix.

I feel like I am printing on a liquid mercury bed or something.

I have a TEVO Tarantula Pro. I followed the ruiraptor YouTube instructions since the included PDF was seriously lacking.

I feel I set it up right (checking for square and level on the frame, etc.) and their Facebook group has people posting amazing stuff but for me it is level, tweak, eventually get a good print, and the next with the same settings and calibration is a mess. It is wildly inconsistent and I spend more time trying to get a decent print than I do actually printing.

When setup right, they will do the same thing, every time.
Im guessing you have something too loose, too tight, hanging up, etc.

I think you should take the little nuts off the screws that hold the z nut on. This will free it up and you can move it around and make sure it is smooth and free.
I cant remember how they come, but the z nut needs to be under the bracket, then just drop the screws in through the top. (no nuts)
It will print fine like this, and also has the added bonus of coming apart in a crash instead of damaging stuff.

The coupler on the stepper screw. Make sure set screws are tight, and there should be a tiny oring in there between the motor shaft and z screw.
The screw should sit down on this oring, and you can even pull up on the coupler just a lil before tightening the set screws for the z screw to give a lil preload.

If you have the support bracket for the z screw up top, take it off.
Pretty sure Tevo only puts it in there because so many people that dont know wtf they are doing think they just gotta have it

What printer?
On my Monoprice some times the z gets out of alignment and I use a glue stick or chap stick between the bed and the Z. Then manually turn the motors to level the Z.
It turns out I had a bad plug on the stepper motor and 1 in 100 prints it would get out of alignment.
are you sure the Z axis is parallel with the bed?

@oetkbyetdia

You have a lot of experience w/ the Tarantula Pro, so I'd like to try your z-axis suggestions.

First, you can ditch the bracket with the bearing on the top rail and just let everything lower be free?

And are you saying on the bracket attached to the x-axis (that has the threaded brass guide), remove the bolts on the back and let it free ride with just the screws holding it?  That is interesting that Z will still move up and down without them.

Any benefit to inverting the z-axis now that I have firmware that will support that?

Any other tips would be appreciated. I plan on checking the steps for x, y and z and extruder next weekend.

I am still concerned about the bed. I hope I didn't mess it up putting on and remove a very sticky PEI sheet.  (Warped the bed?)  My main pain point is the constant need to level the bed, and when I do mesh leveling some areas will be +, some -, and it can get up to a 0.7 correction in some spots, on some days...  The inconsistency of levelling is what's getting me.  "Level once every month or so" where for me it is "level every print and it's still a 50/50 shot".

You can always move to solid bed mounts and an ABL or Bltouch. Fairly easy to install. You still have to calibrate them and you'll need to adjust your z offset when changing filament types (PETG doesn't need the smoosh that PLA likes for instance) but they're nice once dialed in.

With something like octoprint you can even have it generate a 3d map of your bed so you can see how even or uneven it is and where. When I first fought with it I shimmed the worst corner up with washers. Now my bed is very close to level.

How do I do this in OctoPrint?
Never mind I found the plug in. Thanks for letting me know about that .

Ya, been doing this for a few years now. Enough that when I put my Tarantula Pro together, I didnt even look at the instructions

Ditch the bracket and let it freeball. It is a perfect world solution for a problem in an imperfect world, and just doesnt do what people think.
No z screw is perfectly straight, not on these hobby grade printers from any mfg.
Constraining the free end is only forcing this error into the z nut.
Leave that end free to basically absorb the error, and it wont force the issue so much at the z nut.

And sounds like you got the screws in the z nut part right also. It should just sit on there with gravity keeping it tight, if it doesnt, you have probs elsewhere.
Its hard to explain all the benefits of doing this, but one of the main ones is the decoupling part. Makes maint easier and a layer of safety in a crash.
If you want to get fancy, print one of these up and install it. Does the same thing, but locates the z nut much better than just the screws hanging out in there without the nuts on them.
Z Nut Thing

I dont see any benefit to inverting Z. The OG Tarantula came with the motor at the top and everybody thought they needed it on the bottom.
I dont think it makes a difference either way if setup and adjust well, and never mess with them.

I dont mess with xyz step, only e.
Trying to achieve perfection is a great way to learn more about these things. Its fun, its frustrating, but you will learn. Just be creative and try different things.
In the end I pretty much just accepted that these things (all of them) are only capable of a certain precision for reasonable amount of tail chasing and head on wall beating.
Anymore I just do everything by eye. If it looks good and it works good, no need to put the calipers on it.

Def want to figure out what is up with that bed. Inconsistency is usually an assembly or setup prob though.
Have you checked the wheels yet? Its rare, but every now and again you run into one that is deformed (like tilted off axis).
Put the nozzle at x0 edge of the bed and about .5mm from touching. Any z works here, whatever is easiest for you to see if it changes.
Now run y all the way back and all the way forward a few times while watching the nozzle gap closely.
The nozzle gap should be the same from one end of y to the other.
If you see it opening and closing every 1.5" or so, you have a wheel problem.

Never had any probs with the glass on my OG Tarantula or Flash.

I run max tension on the springs. Basically run them down to just about coil bind, then adjust the z stop so I only have to back them off as little as possible to level.
Running loose springs will let the bed shift when y changes direction (ghosting) and can also cause the adjusters to loosen during a print.

Shit loads of ways to skin these fkn cats though

@oetkbyetdia

Thanks for the continued tips for the TTP. I will ditch the top Z bracket and dismiss flipping the axis. I'll look in to printing that Z-gimbal thing as an upgrade.

I'll also do the steps calibration for e to make sure extrusion is in top shape.

I'll check the bed level while moving the y-axis, it seemed to run smoothly on the rail while checking it last time but I'll double check closely for a wheel problem.

@The_Beer_Slayer

I would like to hear more about the fixed bed mod.

I am going back and forth on the tension for the bed level screws. I used to set them in the middle and adjust, but one print one went loose and threw everyting off. (Maybe my jerk is too high after the firmware flash?)

One suggestion on a forum was to crank them down hard, so I did. This morning I ran a straight edge across the glass bed and I can see a little space in the middle with the corners very tight. I loosened them up and it diminished the bowl for the most part. Not much, but I am finding 0.02mm is the difference between working and failing.

Running mesh bed leveling it seems like fixed would just solve a lot of problems, as long as I got it within 1-1.5mm across the board to allow enough adjustment in the mesh level routine.

Does anyone have a favorite adjustable z-stop for the rail? I really want to print one of those since I have adjusted it so many times in trying to get things figured out.

Thanks- I can make something similar work!

I almost got a set of 25mm aluminum spacers to really tighten things up but those are essentially free.