Preferred PETG test pattern?  

RE: Preferred PETG test pattern?

The easiest method to do a Live-Z calibration for most is Jeff Jordan's "Life Adjust" procedure. He has provided pre-generated gcode, but you can use any sufficiently large print to do the same basic calibration if you want to use a different filament or nozzle configuration. In general, start high (less negative) and work lower (more negative) in large increments (e.g. 0.1mm) until the filament starts to stick on its own. When you've got your Live-Z setting adjusted properly, you should be able to gently rub the extruded lines on the PEI surface without dislodging them.  Then start lowering (more negative) the level until there are no gaps between layers. You should not be able to peel the lines apart after printing, but the top should be regular. 

Any suitably large 1st layer will suffice. You can use the Prusa logo print, or if you prefer, I've put together a customizable 1st layer print generator that will let you tweak it to your heart's content with any number and size of square or circle patterns. Samples are provided in a range of sizes for several printers.

RE: Preferred PETG test pattern?

Also - a test pattern good for PLA is also a good test pattern for PETG, ABS, ASA, PC, and any other plastic. No magic in the test coupon what so ever. Settings and Z-offset - CAN - matter, but generally, I leave the Z-offset settings the same and to date have never had issues. What works for PLA works just as well for PETG.

Some people adjust Z-offset to reduce adhesion, or because they feel their specific filament acts differently (materials properties and flow changes).  But pretty sure they only change the setting AFTER they understand why they need to change it.

RE: Preferred PETG test pattern?

@bobstro

Bob - I've already lost the link to Quentin's video. I think CSJ would benefit from watching it. 

RE: Preferred PETG test pattern?

one thing, if you will, to prevent your first PETG disaster - if you are using a smooth sheet, petG when the first layer is correct can stick so badly that it is impossible to remove the print without damaging the PEI.  This is important, please read it.

After you get the bed clean, before you print (and before the plate heats up - don't want you getting burned) a spray of classic blue windex - just a spritz, then wipe the plate with a paper towel - it will look like most of the windex is removed.  Then do your PETG print.

The windex is a release agent.  If you use too much, it will make getting a good first layer even more challenging - but it will give you practice in spotting a bad Z.

If you don't use the windex and you use the smooth sheet - AND you get a good sheet first layer (no lines showing below or above) you will be mad at Prusa again  (which is irrational).

RE: Preferred PETG test pattern?

Posted by: @dan-rogers

... a spray of classic blue windex - just a spritz, then wipe the plate with a paper towel - it will look like most of the windex is removed ...

Good advice up to where you wipe with a paper towel. All the paper towel is for is to spread the Windex around evenly so it wets the entire surface. Do NOT wipe the Windex off. You want to let the wet film of Windex dry on the sheet. A paint brush is better.

RE: Preferred PETG test pattern?

@tim-2

My goal is an even layer.  You cannot really "wipe it all off" - but if I leave too much on it is _much_ harder to get a first layer stick.  Just a bit is all you need is what I have found.

RE: Preferred PETG test pattern?

@dan-rogers

Very true.  I just try to leave it a little wet.  

RE: Preferred PETG test pattern?

The difference between Amazon Basics (Overture) PETG and Prusament PETG. The Amazon filament needs a clean sheet to stick, the Prusament needs the equivalent of non-stick to remove. So, ymmv.

RE: Preferred PETG test pattern?

@tim-2

That is a pretty good sum up.  I would Amazon is very similar if not identical to Polymaker, Overture, and Duramic.  

RE: Preferred PETG test pattern?

On the Prusament PETG versus Amazon petg - The prusament PETG prints at 250c - and the amazon at 240 (I print both frequently).  My experience is you get poorer layer adhesion if you print Prusament PETG below the 250 (first layer is 240, then subsequent layers are 250).

I also get almost no downside if I print generic or amazon PETG at a prusament PETG profile.  For my fishing lures I like that added layer adhesion and it helps with the water tightness.

RE: Preferred PETG test pattern?

OP - here is what a support pattern (interface) looks like when live Z is correct.  Note that the edges of the interfaces are not curled up, not smudging, and not slopped up.

RE: Preferred PETG test pattern?

Posted by: @tim-2

@bobstro

Bob - I've already lost the link to Quentin's video. I think CSJ would benefit from watching it. 

Here you go!

RE: Preferred PETG test pattern?

@bobstro

His video is very realistic.  You will have to redo parts many times to get them perfect.  

RE: Preferred PETG test pattern?

@All Many thanks! I want to follow up after I have played around and explored.

RE: Preferred PETG test pattern?

@cjshayward

Post a photo of a successful Layer One print.  That's the best way to let us know the progress.

RE: Preferred PETG test pattern?

I wanted to touch base.

When working with PLA, I stepped down by .200mm and got a successful-looking test print at -1.400mm.

When working with PETG, I stepped down by .100mm and have gotten to -1.900mm without an apparently successful test pattern. At a couple of points getting there, there were at least lines of resin along the initial motion by the near edge of the plate, and without anything approaching a square.

Ideas about what I might be doing wrong or what I might do differently?

RE: Preferred PETG test pattern?

No pictures, but good description.  Go lower.  If you used Windex, it will be more difficult to get a PETG to stick.  But once you get there you will know it.

RE: Preferred PETG test pattern?

@dan-rogers

And just to clarify:

"Go lower" means "go more negative," or do you mean "go closer to 0"?

RE: Preferred PETG test pattern?

@cjshayward

The difference between -1.400 and -1.900 is 0.500 mm.  Since you are trying to print a 0.200 mm layer (or maybe you're not) the nozzle will be underneath the print sheet. Well, since the sheet is solid, you'll be scratching the heck out of the sheet...

Have you read the printing handbook that comes with the printer so you understand what the layer one calibration is trying to achieve?

ps: CJ -- what you are describing is impossible without doing serious damage - hence the dubious nature of my reply. You are leaving out something that you are doing.  Like, are you performing a Layer One Calibration? Are you printing a test pattern? What settings are you using? Etc.