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Another new user, trying to print with PETG  

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alan-bc
(@alan-bc)
Member
Another new user, trying to print with PETG

Short version:

Why didn't this stick to the sheet?  (See pic)

Long version:

Just finished my kit .. sat in the box for a year and a half as life got in the way.

Set it up, printed the tree frog using PLA, came out great!  Feeling pretty proud of myself.

Decided to try PETG .. actually have a genuine right now need for a PETG part.

Did the first layer cal on the smooth sheet over and over until I got it right.  Sadly, at that point, it WOULD NOT REMOVE.  After MUCH scraping, it came clean, but thank goodness the sheets are double-sided .. pretty sure I hooped that sheet.

Remembered that I'd ordered a textured sheet!  Did first layer cals until I got it right (I THINK), then started to print my part, more or less a block 5" x  3" x 1".

Prusa filament, Prusa settings. 6.5 hour printing time.

Started great!  Watched in fascination for 15 minutes, then came back to check every 30 minutes or so.  Then left it for a couple of hours and came back to a MESS.

Clearly, the print had warped, and the nozzle was dragging the part around.

What did I do wrong?  Alternately, how do I get PETG to stick to a bed to print, not warp, and then release afterwards?

Any thoughts GRATEFULLY appreciated.

Alan

Posted : 15/06/2024 3:30 pm
Eef
 Eef
(@eef)
Reputable Member
RE:

Let's look at the sunny side. You were able to print a couple of pieces right out of the bottle! Many of us (including me) have worse trackroads. 
- I see three issues: 
1. first layer, howto. 
2. difference between PLA en PETG. 
3. how to get it off the sheet (I did not work on that untill after 2-3 weeks 😉 ) 

Let's start with the second:
- PLA is a material that easily sticks to the sheet, and not to the hot nozzle. So you can go rather deep with the nozzle and kind of "iron" the PLA onto the sheet. 
- PETG is a material that likes the nozzle better then the sheet (as you have noticed, when it is really on the sheet it is hard to remove). So when printing this, it cannot be pushed on the sheet like PLA, because the nozzle, will collect all in a big clog. So the nozzle has to be higher then with PLA (about 0,2 mm) that way the nozzle makes as nice string what is laid on the sheet. So you can imagine that the temp of the sheet and the temp of the PETG is important, so the layers will stick together. (Also important that the PETG is dry (goes for all filaments) but PETG more then PLA). 
Because of these differences, there is possibility to save more then one sheet in the printer, with different Z-heights. 

2. first layer. 
The firstlayer from the menu is not perfect. It is good enough to see if the filament sticks to the sheet (corners are round or square). 
For the real work, this is my favorite: https://www.printables.com/model/251587-stress-free-first-layer-calibration-in-less-than-5/files

3. Have it more/less stick to the plate: 
- clean the sheet with dish-washing-soap. That is the best you can do. (sometimes I sand the sheet very light with a fine sandpaper. just to get the fine partikels of durt off). 
- for PLA this should be best. 
- for PETG (because it sticks to much, use glue-stick, hairspray or with glasscleaner. Just very lightly is enough. If the print sticks then the layer glue, hairspray etc will break and the rest can be washed off (with the dishwashingsoap). 

We will do what we have always done. We will find hope in the impossible.

Posted : 15/06/2024 7:54 pm
Diem
 Diem
(@diem)
Illustrious Member

(sometimes I sand the sheet very light with a fine sandpaper.

- but don't do this during your first year of ownership, we see too many ruined print sheets ... print yourself a *plastic* scraper and use that even though it can take more effort.  With experience you can try other methods.

Cheerio,

Posted : 16/06/2024 2:33 am
alan-bc
(@alan-bc)
Member
Topic starter answered:
RE:

Eef, thanks for the detailed reply!

Good news though.  Before getting your note, I decided to try again, doing another First Layer calibration with the satin (rough) sheet.

I lowered the extruder by an additional .25 mm, and then compared the "flags" printed by the calibration routines.  The first one still looked OK, but the second, printed with the lower extruder, was clearly better .. perfect, in fact to my inexperienced eye.

So I risked another six hour PETG print, and it turned out GREAT!  Not only better than expected, better than hoped for.  Frankly, I was astonished at how good it turned out.

Now, I'm not a total rookie when it comes to 3d printing .. I have two cheaper ones on the bench.  But neither have ever consistently turned out even acceptable parts.  Not once have I gotten a "good" part.

And that's why I bought a Prusa.  I just got TIRED of failure failure failure crappy part failure ... 

I decided to buy myself a "good" printer, and a bit of research suggested that Prusa were the best of the good.  They're certainly the most expensive of these home/hobby printers, but I felt that if they could actually produce good parts, it would be money well spent.

Well, it was absolutely money well spent.  I am quite simply delighted.

Thanks again for your note.  I've printed it off and added it to "my book" of 3d printing info.

 

Alan

This post was modified 1 month ago by alan-bc
Posted : 16/06/2024 2:51 am
Eef
 Eef
(@eef)
Reputable Member
RE: Another new user, trying to print with PETG

print yourself a *plastic* scraper and use that even though it can take more effort. 

Agree, that comes first. The sandpaper is only used when "I cannot see the partikels on the plate, but feel them when lightly moving with my fingertips + visible as little spots on a next print" And only very lightly!

We will do what we have always done. We will find hope in the impossible.

Posted : 16/06/2024 5:35 am
alan-bc
(@alan-bc)
Member
Topic starter answered:
RE: Another new user, trying to print with PETG

I'm going to try another print and see if I can replicate it.  Will just the right nozzle height, just the right bed and nozzle temp, and just the right cooling strategy give me a good print?  We'll see.

I will say that last time, the textured plate worked spectacularly well.  The previous print did not want to remove from the plate, until it was flexed.  Then it popped right off.

Posted : 16/06/2024 3:21 pm
John
 John
(@john-6)
Reputable Member
RE: Another new user, trying to print with PETG

With Petg the plate needs to fully cool down before trying to remove. 

i3 Mk3 [aug 2018] upgrade>>> i3MK3/S+[Dec 2023]

Posted : 17/06/2024 10:23 am
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