Please, this is the 7th try, how to awoid this

I've been trying a lot of thing, how thef f**k do I avoid this thing...
PLA printing at 235C, bed at 70C and a speed of 45 mm/s

You have to check you initial bed leveling and 0 Z starting point. Probably you Z 0 point at the start is too high.
Despite that, you are way too high regarding temperatures.

Hm, what effect does the leveling have here? It does stick well to the tape, the problem is that the warpage makes the tape lift from the bed...
I had to increase the temp because of the extruder having problems pushing the filament through

Most people print PLA at between about 190 and 205 degC. If you have to push it up to 235 then I suggest there is something wrong with your hot end and/or thermistor. 70 deg C bed temp is way too high for PLA IMO. You could print PLA on blue tape with no heated bed. Generally you use build tac or blue tape with an unheated bed. Generally you only need a heated bed if printing on glass or glass covered in Kapton tape (note I say generally because someone is bound to do something different). Try printing with blue tape and the heated bed turned off.

Could also do with a bit more info. Do you have a cooling fan blowing on the print? If so, when does it turn on? What nozzle size are you using? What layer height are you using? What extrusion width are you using? Do you use different settings for the first layer?

Edited 1 time(s). Last edit at 05/01/2016 04:12PM by deckingman.

Hi and thanks for the reply!
Please have a look at attached images of my settings (using Cura). The only thing that differs is the speed (which the Prusa I3 I have does not use so I have to tune that manually on the printer, currently running at 38 mm/s)
I have no cooling fan blowing on the print, I did bought a fan to be mounted on the printer to do that, could that resolve these kind of issues ?

Yesterday I bought another roll of filament (was using cheap china-PLA before) and with this one I can lower the temperature a bit. Started at 200 but that makes the extruder having problems pushing it through so I increased it to 209 and that made an even flow at least and the quality of the print is really good, except for the same kind of warpage as you see in my first image.

ello,
Odd you using painters tape with a heated bed, folks generally used painters tape on a cold bed. but the 45 C is to low for PLA, you want it between 55-60 C.

kapton tape for PLA, but my best result for bed adhesion been the use of "prit stick" although it got a tendency to discolour the first layer but sticks great.

Edited 1 time(s). Last edit at 05/03/2016 01:47AM by jinx.

I'm using an aluminiumbed. Should I use it with tape and no heat, or without tape and heated ?

I've always had trouble with prints lifting on a cold bed with PLA, and PLA doesn't hold for long an a heated bare aluminium, but apply some glue stick it will.
but for what you have at hand leave the tape on and turn the bed up to 55 C should be fine.

I have tried with tape and heated to both 45 and 70 with same result so I don't think that will solve it...

I mostly use tape with a heated bed for PLA. I just use some sandpaper on the tape to provide a decent amount of friction for the first layer.
I run PLA on my DaVinci Duo 2 @ 205 & 50 for the first layer then raise the bed to 60 after that. Really the thing that makes the job is the
1st layer, if you cant get that down correctly the rest of the job will sacrifice IMHO. Try reducing the speed on the perimeters and 1st layer
in Slic3r. If you do try glue try the Purple Elmers Glue Stick, it works good for the longer length jobs which is where I see the most warpage.

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I don't think you see the problem here. The item printed sticks fine to the tape. It is the tape that doesn't stick to the bed after a while. Probably because of the way the PLA reacts when it's cooled (or hardened).
I know it's hard to tell in the image, but the problem I have is not the PLA sticking to the tape, it's the tape sticking to the bed that is the problem. It seems to be a result of the PLA retracting when cooled down ?

Edited 1 time(s). Last edit at 05/03/2016 09:39AM by Cannehag.

Quote

it's the tape sticking to the bed that is the problem.

lol I thought it was the print lifting looking back at the pic not all the strips bubbles up? tried replacing just those strips fold them around the edges of the bed, take a spare bit of tape try and transfer some of the tacky stuff by dabbing it? then lay down a fresh strip.. about all i can think off.
does the tape itself come with a low tack backing.

take a wet wipe to the bed could be there some grease on that part of the bed? after that am all out of ideas

I had a similar problem to you, large surface area prints in PLA would warp and actually lift the tape away from the bed. I'm using a cheap no-name brand of tape, and apparently using real 3M blue tape works much better. You could also try sticking the tape down by using PVA under the tape, or using multiple layers of tape as it will adhere to itself better than glass/aluminium.

In the end, I switched to PVA glue (wood glue), mixed in water to make a milky consistency (roughly 2 parts water, 1 part glue) and then paint it on bare glass. This works pretty well, especially if you layer up the glue mix 3 or 4 times. Prints come away easily, no warping and you only have to splash some water on to 'renew' the surface and smooth over any lump or parts the print pulled up.

Also, it sounds like your thermistors may be off, so you think it is 70c but actually its 60c. Filament with an uneven tip also sometimes won't go through your hotend I've found. so make sure to neatly trim the end of filament before using it.