Help with PP/PE warping

[Reinier1994]

Sorry for the late reply. Thank you all for your insights and information. I've started printing and I'd like you to see some results so you maybe can share some tips on how to improve the print quality.

Biggest issues right now:

- Corner warping/shrinking. PE-HD shrinks a lot, and on straights the welding gun can just push the raised layer a little bit, and improve adhesion. In corners the product falls inwards, resulting in a lower height and circumference. This results in the next layer being laid down aside, so there's no adhesion, and every next layer gets even worse.
- Bed adhesion. This is not a huge issue, but the first layers need to be pre heated by a heat gun. Warping isn't a big issue, the vacuum table actually holds down the ground plate the entire time.
- Print speed and filament feed. Since the project's goal is to recycle PE-HD waste, it's not a solution to lower the print speed for a better quality. There has to be a way to print at around 20-30 mm/s with the best quality possible.

My settings I have been playing with right now are:
- Air temp (of the welding gun blower) : 180 C . Since the air doesn't really do anything, usually the air gun heats the welding surfaces, but the previous layer is always hot enough to bond with the next one. This is the lowest possible setting without disabling the wlder.
- Extruder temp: 200-240 C. I've been trying to get it as low as possible, so if I turn up the welding speed, it doesn't collapse due to the high heat.
- Layer height. I start with a layer height of 2mm, with the first one being pushed on the bed (25% first layer height) and ending at 3 mm. The next process has layers of 4 mm, starting at 3 mm.
- Extrusion speed. Since it's a welding gun, I cannot give an exact number, but it's around 1,0 kg/h.
- Filament width is 4mm, and the extruder has a nozzle of 8mm. Since this is a welding gun, I have no access to smaller nozzles. I think a smaller nozzle will result in a significantly better result. I want a small extrusion, being pushed to the side so the material is as curved as possible on the sides, so it can release it's heat.
See this album for a lot of pictures:

http://i.sli.mg/a/sluwww

As you can see, the first finished product (the tub) went pretty well. This design was meant to be wide in the middle, and smaller on the top and bottom. Only downside is that the print speed was 10mm/s so it takes up to 6 hours to finish. This is not a valuable result :P.

As for now I'm not in the position to buy a heated bed or chamber, but I can ask to mill a welding shoe with a smaller nozzle.
Thanks everyone in advance for your replies and insights.