First layer: how to get skin/infill/whatever it's called printed BEFORE holes circles

[jrobin28260 0]

Hi all,

 

I'm living a nightmare each time I have to print a part in which there is holes in the first layer: those tiny holes are always printed failed before doing the rest of the infill, making them horribly looking and/or way too big at the end (because what you see in green into the attached picture never succeeds to print correctly). I had this issue tens of time, making me cancelling and retrying again and again the first layer, putting tons of stick glue for nothing and this is getting me so mad I was about to throw the printer away by the window ^^

 

How to get the infill, skin, whatever it's called, BEFORE these holes circles ?

 

Thank you in advance, this would change my life!

 

SupportWatchCrobe.stl

[Gero 47]

There is no feature to turn the skin before the walls. The skin layers are printed best after the walls. I would say that you might have some adhesion issues here.

I have to option in mind here: try some settings to make the adhesion for the first layer easier. Try a higher first line height (like 0.25mm) and an increased first layer with (like 120%). Print the first layer slow (20 or even 15mm/s). I kinda guess from experience that your nozzle is carrying the first printed hole line away?

 

Second idea: remove the bottom layers (by setting them to 0) and check infill before the walls. This way you might not have a 100% solid bottom layer, but the infill structures, so you achieve somehow what you want... 

[jrobin28260 0]

Hi Gero,

 

Thanks for the answer, then I'm only interested in the second idea. You saved my day 😀 Top bottom thickness and layers set to 0, the infill (which was top/bottom, yellow) turned orange (infill) and is now done BEFORE the tiny circles 👍

 

I spent months trying everything I found and everything you wrote in the first idea, which is letting Cura attempting to print tiny isolated circles first, with unnecessary high probability of failure, and try every possible workaround and tuning for this to fail less... but this fundamentally is the wrong way and today was the last straw on the camel's back 😁 my printer was about learning to fly.

 

Part of the problem also is: between 2 circles, the printer is leaking half of its material on the travel, so that there is missing material at arrival. There is "Retraction extra prime amount" but this amount is fixed and is only about travels with retraction. Even with combing off I still have some travels without retractions... so it's a double failure.

 

I believe with a solution to this part of the problem, even tiny isolated circles would have a better chance of success.

 

I'll post there my parameters once they will be fine,

Thanks again!

[jrobin28260 0]

So here is the set of customized parameters I use (and now it's giving good results!)

• Wall Line Count: 3
• Optimize Wall Printing Order (so that the 3 circles outlines are done all at once on the same circle before going to another circle)
• Top/Bottom thickness / layers: 0.00mm, 0 (Gero's tip to permit "Infill before walls" option to apply from the first layer: thanks a lot!)
• Infill density: 100% (for parts like empty cases / mounting plates this is usually fine)
• (Infill before walls should already be checked)
• Enable Retraction (permits to avoid leaking too much material on travels between things to print)
• (Retraction extra prime amount : 0 mm³ is fine with PLA on my printer but in case of leakage, you may try to put something here so that enough material is pushed on arrival to compensate the leak)
• Combing mode : Off (so that most travels are done using straight line + retraction, so it prevents unnecessary material leakage during travel - but if there is some, it's more visible).

This still makes first layer usual tuning important but at least, tiny holes on the 1st layer aren't a nightmare anymore. As usual, fine bed leveling (for those who are lucky enough to have a really flat bed), glue stick or spray, thick first layer (so that missing material length on arrival is as short as possible) and Initial Layer Flow > 100% if necessary (slightly pincushion shaped bed) are my usual hacks to work around the many imperfections of the process and this printer.

 

Unfortunately, for parts on which 100% infill density isn't an option, setting Top/Bottom thickness / layers to 0 may not be possible, causing small holes circle to be printed isolated on the plate before their surrounding.

In this case: The combination of "Optimize Wall Printing Order" with 3 outlines wall, Enabling Retraction and Combing mode OFF may reduce the failure rate despite this problematic print order

Edited May 10, 2021 by jrobin28260