MK4 IS profiles defaulting to grid infill is a mistake  

RE: MK4 IS profiles defaulting to grid infill is a mistake

Wow, that's fascinating. I had black marks like the ones shown by @ph1nb above in a print yesterday and I wondered what could be the cause for that... I would never have thought that the infill type could be to blame, but I'll retry that print with gyroid infill at some time.

RE: MK4 IS profiles defaulting to grid infill is a mistake

@vextol

Your Overture PETG filament may need slower speed (lower volumetric limit in filament settings) or higher temperature -  even if it was not needed before IS (with slower speeds). There is no specific "Overture PETG" filament profile at the moment and "Prusa PETG" is meant mainly for Prusa PETG sold on Prusa3d e-shop.

Gyroid infill is printed much slower, so it will not show similar issues.

@PH1NB The issue on your photo is related to cooling. Printing PLA in an enclosure may be challenging.

RE: MK4 IS profiles defaulting to grid infill is a mistake

Well that's what was interesting to me because I've been printing IS since the alpha.  For now, I'm just going to stick with gyroid.

RE: MK4 IS profiles defaulting to grid infill is a mistake

Just had a particular experience with this.  I'm trying to print the parts for my MK 3.9 upgrade kit.

I had problems with the taller parts on my MK4, using a new roll of Polymaker PETG.  Mostly with the Structural IS profile.  They would reach a certain point in the print (1/2 to 3/4 done), and come lose from the bed. During the prints, lots of sound of the nozzle scraping against the infill.  I tried a few different print beds (textured, satin, even smooth PEI knowing it might stick 'too well', and blue tape.  They all came up from the bed at some point. Also tried another new roll of Jesse PETG, same thing.  I remembered this thread. Switched to gyroid, and finally got a finished print of the tallest part.

I also noticed gyroid only added a couple of % points of time to the print, so if this is what I have to do for reliability, there's no contest.

RE: MK4 IS profiles defaulting to grid infill is a mistake

I'm testing gyroid right now and I can already hear the nozzle hitting the infill over and over on my print. 🙁

RE: MK4 IS profiles defaulting to grid infill is a mistake

Do the same models print successfully when you choose the non-IS profile?

RE: MK4 IS profiles defaulting to grid infill is a mistake

re: "Do the same models print successfully when you choose the non-IS profile?"

They do print just fine. The really weird thing that I can't figure out is that a lot of models printed perfectly fine with IS but then got worse and worse. Same filament, same gcode, etc. It makes literally no sense.

RE: MK4 IS profiles defaulting to grid infill is a mistake

The other part of my ability to print the MK4 parts (along with switching to gyroid) was changing my Lift Z to 0.5 and retraction length to 1 mm.  YMMV (I'm using a CHT-like nozzle with the adapter if that matters).

RE: MK4 IS profiles defaulting to grid infill is a mistake

So even though gyroid will still make some noise when it runs over the fill I haven't had any failed prints or major shifts.  I'm still a bit confused as to why it printed just fine over and over and then started to fail using grid infill but for now I'm at least able to use IS with petg and gyroid infill.

RE: MK4 IS profiles defaulting to grid infill is a mistake

Well now it started doing the same shifts at the same height but even using different infill patterns.  I'm out of ideas and very frustrated.

RE: MK4 IS profiles defaulting to grid infill is a mistake

I've also recently experienced some very severe "infill lift" with the default Input Shaper profile. The attached image is an attempt to print the Prusa Enclosure transport handles using the default profiles. Setup:

• MK4 + Enclosure, 0.4mm brass Prusa Nozzle + silicone sock
• Prusament PETG Jet Black, dried and printed from a drybox
• 5.1.0 (final) + PrusaSlicer 2.7.0, with Prusament PETG profile
• 0.2mm Structural IS profile

I compared with the previous profiles and I noticed that 2.7.0's profiles reduced the PETG maximum flow rates and infill speeds. However, that did not eliminate the issue. It's possibly a little less severe after 2.7.0, but the default profile still results in nasty infill that causes nozzle scraping, and little fragments of PETG end up strewn all over the bed and around the printer, and a lot of bits also end up trapped inside the print. It's so bad that you can pick up the print, shake it, and it sounds like a maraca. I suppose that could be considered a feature if one wanted to 3D print some musical instruments, though. 🤣 

In the past I've switched to Rectilinear infill (which alternates directions) in some cases where scraping was an issue, but I have also used Grid infill plenty of times before with no issues. I suspect a lot of the problems here come down to the speed and volume at which the infill is being extruded with IS. Going fast is nice but I'd rather have the "structural" IS profiles focus on reliability.

At a small scale, here's what I think is happening: when the nozzle crosses the perpendicular lines of infill that were previously printed at the same layer, it effectively "cuts" or "wipes" the extrusion off the nozzle, and it causes a break that then results in the next "segment" of infill not connecting on the other side of the crossing and it doesn't bond properly at the start. With the higher speed, plus the higher viscosity of PETG, that would result in the little curls of filament that we see.

Anyway, there's definitely some tuning needed to the defaults here. IS is nice but we can't be sacrificing reliability for speed.

RE: MK4 IS profiles defaulting to grid infill is a mistake

Followup: multiple prints now with identical settings. The only thing changed was infill type to either Rectilinear or Gyroid. No failures, no infill lift, no maracas, and no "PETG sprinkles" all over the bed.

Basically, I think any infill pattern where the extrusions cross previous perpendicular extrusions at the same Z height is probably going to have problems at higher speeds, and that slower speeds could avoid "splitting" the extrusions. It looks to me like the speeds that IS enables are beyond that point. Of course different materials might also behave differently; lower thermal expansion and less stringing might both factor in to making PLA less susceptible to these effects, but it would require testing.

RE: MK4 IS profiles defaulting to grid infill is a mistake

I don't know if this will solve everyone's problems, but you can try editing the start gcode in prusaslicer to lower the temps for bed probing. I had lots of issues with petg bed adhesion and collisions. What I surmised was that the base layer was too high, which then caused filament to detach and collect on the nozzle, which then led to an eventual collision (usually with the infill). I suspected oozing during the probing process was causing inaccurate bed measurements. Now I have pla and petg probe temps 10c lower than their default and also start all non-prusa filaments with a .97 extrusion multiplier.  Since this change, I have not had a single failure on either smooth or textured sheets (which seemed more sensitive to the issue).

The default setting are 175 : 170. Since I am using a diamond nozzle, 10c may be too low for you. First try 170 : 165 on these two lines.

RE: MK4 IS profiles defaulting to grid infill is a mistake

Chiming in to report a similar issue using PETG with a 0.4 brass nozzle and MK4 IS 0.2 STRUCTURAL profile (with cubic infill instead of grid).

The outer walls are perfect, the infill is not and the nozzle rattles against it :\

RE: MK4 IS profiles defaulting to grid infill is a mistake

Where there any solutions to this in the end?

Latest firmware and still having the nozzle hit when using grid.

Is Gyroid the best way to go for now?

RE: MK4 IS profiles defaulting to grid infill is a mistake

I’m having these issues too. Perimeters and shells - fine. Flawless. When it starts to infill, it all goes to hell - either the extrusion doesn’t stick, nozzle catches and picks up previously deposited material, and I either get collisions causing layer shifts - or huge wads of plastic around the hot end.

In my frustration to solve this I updated to the latest firmware, and the did a re calibration. Which has now caused other issues as my printer will now no longer pass a Y axis check.

All parts / fasteners are tight. The belts pass the Prusa harmonic check for tightness. The pulleys are oriented correctly and fixed in place (no slop between the shaft and the pulley)

This printer is so frustrating. My mk3s was a complete workhorse. Since the upgrade, it’s now more of lame horse. 

Any help would be appreciated.

RE: MK4 IS profiles defaulting to grid infill is a mistake

I join the thread, I bought my first 3D printer with great enthusiasm, I opted for this brand so I could assemble it myself and learn a lot. Once assembled I encounter this error. The impressions are good but in the filling it sounds like a maraca. I hope I don't regret spending my money on this brand.

RE: MK4 IS profiles defaulting to grid infill is a mistake

Is this issue on the Github pages?

RE: MK4 IS profiles defaulting to grid infill is a mistake

Need to test without using IS - is this an issue only when using IS?

RE: MK4 IS profiles defaulting to grid infill is a mistake

I'm currently exchanging emails with support, they've acknowledged the issue and reproduced on their side; hopefully this gets the attention it needs.