PLA not sticking on glass nor previous layer (videos)

Hi,
I'm a beginner in 3D printing. Just bought a Kossel Mini from Think3DPrint3D. Build and calibration went fine. Smaller builds are fine. Trying to build their LCD display case, but on longer lines PLA is not sticking. Videos:

Not sticking to glass (+ PVA glue/water solution)
[plus.google.com]
Not sticking to previous layer
[plus.google.com]

Hotend temperature: 200 C (205 C for first layer)
Heated bed temperature: 70 C
Bed is covered with PVA glue/water solution (the only thing that worked for me to get PLA sticking on glass nicely).

Has anyone else seen something like this? Thanks

I have a T3P3 Min Kossel, which I upgraded to Duet electronics, and it prints very well. I suggest the following:

1. Use a lower bed temperature. 70C is above the glass transition temperature for PLA. I use 65C when printing PLA direct on glass (only works for some PLA filaments), and 55C when printing on solvent cement (should be OK for printing on PVA glue stick too).

2. Make sure you have done accurate delta calibration, with the bed and the hot end up to temperature. Then print a calibration spiral to make sure that the head is a uniform height above the bed.

3. Use lower printing speeds.

4. Your hot end temperature is higher than I use, although that shouldn't cause adhesion issues. I use 195C first layer and 185C for the rest.

5. The movement in your videos sounds rather scratchy, although I guess that might be because of the way Marlin drives a delta printer. Does the print head move easily with without those noises when you turn the motors off and move the carriages by hand?

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for your suggestions!
I lowered the temperatures:
Hotend: 185
Bed: 65
Used a bit more glue in my glue/water mix.
Turned "first layer speed" down to 30% from 50%.

Still, the problem persists.

At lower speed i get a strange vibration mid-line. Maybe end-stops are not properly calibrated, and motors are a tiny bit off sync?