I started with stock glue stick UHU and had good prints with very little to no warping. Then I started to get afraid of the glass chipping off while pulling up some of the prints where it seem fused to the plate(bed leveling issue probably.)The other issue was the clean up, I hated it. I moved on to the 3m painters tape medium adhesion, had great prints but after say 3 or so, a piece of tape needed replacement.Then sometimes I would have a heck of a time getting the damaged strip of tape off, it would mess up the bed leveling during the pull off. I moved on to use the 3m painters tape with low-medium adhesion and it peels off so much easier. But, I started to realize it gets air bubbles some times after a few prints and all you have to do is pull it up and smooth it back out. The more i use the printer the more I think 99% of the issues of bad prints I get are simply due to leveling  the bed correctly.

So far this is the rank of bed leveling techniques and method of getting the abs to stick for this noob.

Sticky
1. Glue UHU(I just bought the Elmers purple glue tonight, after another level i am going give it a test)
2. 3m painters tape Edge lock: low-medium adhesion
3. 3m painters tape Multi-Surface: medium adhesion
4. Bare Glass

Bed leveling(I think this is the far most important aspect of printing good quality)
1. Piece of paper
2. XYZ calibration
3. By eye during a single layer test print, adjust the level while its laying abs(Started experimenting with this)

...next 3 prints were on bare glass...worked fine. I am printing straight to glass, no rafts, ...

I get THICK Kapton from McMaster-Carr. I use this on my R2X's and they last months. Plus at .005" thick, it gives you a little 'give'.
(this ----> http://www.mcmaster.com/#2271k73/=vgrlg5 )

Just to make sure I'm understanding, are you printing to bare glass, or to Kapton tape?

First two prints were with very light uhu stick. Cleaned glass and next 3 prints were on bare glass...worked fine. I am printing straight to glass, no rafts, and using standard XYZ ABS carts.

I get THICK Kapton from McMaster-Carr. I use this on my R2X's and they last months. Plus at .005" thick, it gives you a little 'give'.
(this ----> http://www.mcmaster.com/#2271k73/=vgrlg5 )

I haven't printed many prints but I am quite impressed with this 'cheap' printer....

Jay

I was getting quite a bit of warping with uhu so I got some generic and still had issues. Lately I've covered the top hand hole and the front door hole while printing and it has helped greatly. I also don't clean the glue off after every print, just add more to cover the previous print spot.  I've noticed the print bed is cooler closer to the front, probably from the draft caused by convection currents when the top hand hole is open.

What is your bed temp? I print at 110 and as said previously use only Elmers Glue Sticks and have had no issues with lifting, curling, or separations. I also do not cover the unit or anything else. All I did is used the inserts for the hand holes and that was it.

I have found not cleaning the bed between each print had adverse affects as well. The glue does not bond as well with older layers of glue as it does with clean glass.

Did you see a difference between the white and purple? I tried both and they seemed the same, purple also wipes off with a wet towel and is a little easier to see where I've laid down. I generally run the bed at 100 - do we know what max recommended temps are for bed? Or for extruders for that matter - I worry about running at 250C regularly.

The extruder has a Teflon or PEET insert and should not be run nor have to run at over 240 for even the crappiest filament. I run at 210 to 225 max for all the filaments I have tried so far. As for the bed I run at and have always run at 110 for ABS and 80 for PLA. That includes all my previous printers as well. Those are somewhat standard temps for the industry. I however would not go over 150 as you will find the screws and nuts get hot enough to damage the insets they are in and cause the nuts under the bed to free spin and make adjusting impossible.

Mine got up to 180 once because Repetier Host locked up with the heater on. Since it was locked up it was not controlling the heat as it should so the bed as well as the extruder where on runaway. The only thing that alerted me was the smell of ABS that is too hot. Once I power cycled the printer, the extruder was at 310 and the bed at 180. Not sure why the firmware safety did not kick in unless maybe it was the firmware that locked up instead of the Host. Anyways that high temp caused the nuts to melt the inside edges of the recesses the nuts sit in so they would free soin when trying to adjust the bed.

Because of this little mishap is why am moving to a more proven board and firmware as well as the PICO hot end that is safe as and can take as high as 500C.

Also for pla i printed on bare glass at 50c with zero issues.

This was the case for Kapton and blue tape. Once I went to the Elmers whit glue sticks and a bed temp of 110 I have not had any more lifting or delaminations.

Couple questions:

- how easy is it to remove the Kapton tape when I do want to run PLA?
- what about other filaments (mainly HIPS, but also Ninjaflex, Nylon, etc)
- is this a better choice for adhesion-problematic prints (e.g.: tall prints with a small base)

I use blue tape for abs. And blue tape with glue stick for large planar surfaces (also brims help). For pla I use blue tape with airspray for planar surfaces or just 50-60C with glue stick for less stressfull surfaces.

For PLA you should just be able to use hot dry and bare glass. If your bed is calibrated properly. This was one of the reasons PLA was adapted to printers in order to remove the need for glue, tape, and so on.

Originally I was using the Uhu glue stick and bought a 12 pack off amazon pretty cheap.  The glue stick works pretty well, I've had some issues of prints warping/dislodging if I didn't clean the bed or if too much old glue had piled up.  I usually cleaned it with isopropyl alcohol, some paper towel and a razor to scrape.

Last night I tried some acetone "glue"; a splash of acetone in a mason jar with abs trimmings to melt down and paint on the bed with an acid brush.  Once the acetone evaporates (which helps clean the bed) it leaves a very thin layer of abs for the print to easily stick to. The result was very nice.  I tried it with my problematic filament that usually lifts and dislodges and had no issues, resulting in a pretty clean print.

Glue stick was nice and I still have half a box of sticks left, but it can be difficult to work with, whether it be trying to break the print loose from the bed or washing off the remnants of glue from the bottom.
The acetone glue seemed to dislodge easy enough when I got a blade under it and there shouldn't be a need to clean the bed as often.

Hope that helps!