Please help: Warping on the corners of my prints with Wham Bam flexible PEX bed

Hi there!

I am experiencing some warping issues on my prints at the moment, and I can't seem to solve them. I searched for solutions online and re-calibrated my printer three times but the issue is still there.
A few days ago, I changed the stock bed of my creality CR10s-pro (v1) for a Wham Bam flexible PEX bed. I installed it following the tutorial on the Wham Bam website, being careful to prepare the PEX with steel wool as best as I could as well as cleaning it with IPA and all seems good.I calibrated my printer and ran a few "first layer test" prints with black, GEEETECH, PLA filament, which I had used without issues before I changed my bed.
Although the calibration test prints were great, the following ones had quite severe warping on the edges. After ten or so layers, the corners of the prints start lifting from the bed. The print continued fine and still well-stuck in place, but it was quite ugly on the bottom. I tried solving the problem by re-calibrating and cleaning the printer and lowering the nozzle in order to "squish" more the first layer.

I print with the nozzle at 190C° (210C° for the first layer) and the bed at 70°C.

I don't know what to do to solve that issue.Does anyone have an idea that might help me?The picture attached is one of the back of one of my prints.
Thank you very much.

2 things.
1) Don't change printing temps mid flow. The hotter the pla the more it will shrink when it cools down. print the whole thing at 210 or 205 or 200. Changing temps is a youtube numpty thing that has no basis in reality.

2) your new bed is not as sticky to your filament as the old one was. Unfortunately long and silly names don't make a good printbed by themselves.

Get some print glue and use that on the new bed :-)
magigoo is pretty good.
Actually I've never come across any printglue that doesn't nail pla down like a limpet on steroids.

Thanks! I'll try without changing the temperature to see if it helps.

For the bed, I would be surprised if it was just that... although it might be. I have seen many videos and reviews and none mentioned having to use glue, nor did the installation tutorial. Wham Bam seems like quite a known and fiable system though...

it stands to reason if the prints stuck on the original bed put not on the "improved" thr likely cause is the bed so try reverting to the original !!

On the subject of print beds I have no specific knowledge of PEX as a bed material but when we set up our mini print farm 18 months ago because it was for commercial use we tested out a fair number of the print beds suggested on that mine of misinformation that is the internet and found few of them lived up to their hype in fact several of the most hyped ones we found plain useless. We ended up using Tufnol (Garolite in USA) with or without and adhesion promoter for almost all filament materials except those like Poly Propylene which pretty much only stick to themselves.

Well, that's disappointing... If I can't trust the internet, where can I find information ?

There is an old saying " If sounds too good to be true, it probably is too good to be true."

The in general the trouble with information on the internet is anyone can post their opinion as fact without offering proof!

the best print surface I've used is printbite, but cheap self adhesive PEI is a good alternative.

I also add the odd bit of print glue, for stubborn filaments: different filaments have very different sticking properties. So some generic print glue (not pva or hairspray) will just sort any issues.

As far as trusting the internet goes - use your noggin.
If a product is recommended by someone obviously being sponsored by the manufacturer - take the 'review' withn a large pinch of salt.
people like myself and gambo, who alas are not paid by anyone - will give you more unbiased advice based on personal experience.
Don't get me worng if anyone wants to send me free stuff - I'll definitely err on the side of positivety in any review :-)
But at the moment, I'm 4 for 4 with manufacturers promising to sedn me review printers and then no printer ever appearing.

And for the record - any review that states the product was given to the reviewer - has to be suspect.
Nobody wants to bite the hands that are feeding them.
Youtuber 3d print folk frequently say: 'we were not paid for this video'.
While also stating the printer was given to them for review. In my book that counts as payment.
So any review based on that relationship between reviewer and manufacturer, is suspect and can never be totally unbiased.

Evidence by all the glowing reviews of creality printers - versus the real world misery of many creality printer owners.

Any print surface that asks you to sand it before use - is just relying on the micro-pits you've just added to the plate to grip the filament. it's clearly not an actual chemical process.

A $10 sheet of pei, is my current go-to print bed of choice. Holds stuff when hot and lets go when cold - so you never need to remove the plate and flex it to remove print.

At some point I'll probably try gambo's garolite - but at the moment, I have no adhesion problems :-

Looking around - 3d printer adhesive is currently as rare as unicorn drool.
So send your ram.bam.mambo gexxy texk bed back, on the grounds it just does not work - and either go back to your original bed that worked (why change something that works ?)
or get one of these: https://www.ebay.com/itm/324305139528?hash=item4b8217b748:g:PowAAOSwHoNfal0 K

Amen to that !

I looked up what PEX is and unless there is another Polymer than the one listed in Wikipedia this stuff is just cross linked poly ethylene so it's good difficult to see what would stick to it chemically I'm puzzled.