Vertical Ridge on Petg  

RE: Vertical Ridge on Petg

I can’t see the retraction holes.  Is this hollow?  It looks to me like the change or line is cased by the transition from the layers from the base to hollow section, but I would need to see the other side to confirm it.  

RE: Vertical Ridge on Petg

@cwbullet

Yes that is correct about where the change is. Yes it is hollow. I couldn't show the retraction holes because I could only upload one image. So here is the image of the retraction holes. That ridge by the way, goes all the way around the box. It was printed at 230c on 1st layer, then 235 on the rest.

RE: Vertical Ridge on Petg

The ridge you see if caused by the transition.  There are other threads on this topic that have compensated for the transition.  I have never seen the need to do so.  

Link that might help:

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-how-do-i-print-this-printing-help/any-tips-to-get-rid-of-the-bulge/

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/getting-bulge-ridge-when-printing-large-flat-areas-that-are-walled-in/

I would focus on one problem at a time and not make a bunch changes at one.  

RE: Vertical Ridge on Petg

@cwbullet

Ok thanks. I will check those links and see if I can find a solution. I've been printing mostly ABS on another printer up until now, but now I have the mini I figured it would be better suited to Petg or PLA, with no enclosure. Have never had that problem before though, so hope it can be fixed somehow.

RE: Vertical Ridge on Petg

@cwbullet

OK, I had a read thru those posts and subsequent other posts. It seems that that bulge problem they are having is a bit different to my straight out X and Y dimensional increase, above the solid bottom layers. But there was some discussion about thermal expansion, which gave me a clue at what I should be looking for. In my case it seems I have thermal shrinkage, as I found out when I got the callipers out and discovered the bottom slab before the walls started, was 0.3mm smaller in diameter than the slicer said it was. The side walls were 0.05mm oversize in diameter. So now I have something to work with, maybe bed temperatures, layer widths, etc. Or maybe extrusion, but I haven't found a way to change extrusion half way thru a print with Prusa slicer. But I could just use the live adjust in the tuning menu, as a last resort.

RE: Vertical Ridge on Petg

If it is hollow, how thick are the walls and how big is your model?

Are the higher layers oversized or shifted? The shift can happen, when you have loosen screws on the pulley.

I would suspect also something related to extrusion. Temperature ? What mark of PETG do you use?

Even Prusa has two different filament profiles for PETG - Prusa PETg and Prusament PETG with different extrusion temperatures.

RE: Vertical Ridge on Petg

@zoltan

No the walls are perfectly parallel all the way up and are 3mm thick. The shift in dimensions is imediately after completion of the boxes floor layers, then doesnt change all the way to the top. Im still going for shrinkage, also because Im using Polyfilla Petg and I mistakenly followed Prusa slicers recommended heat settings for generic Petg (85-90) for bed temperature, when Polyfilla specify a bed temperature of 70-80C. So Im going to drop the bed temperature down to see if I can prevent the shrinkage. Some people are getting away with as low as 60C for the bed on the textured PEI. The box is only 45 by 35mm, so probably not prone to warpage.

RE: Vertical Ridge on Petg

I actually agree with @cwbullet, this is just another incarnation of the bulge issue. I've seen this many times on models similar to yours, regardless of filament type used.

RE: Vertical Ridge on Petg

@fuchsr

Well look Ive pretty much solved the problem. Coming from Simplify, Ive never had this problem and am now convinced this is a bug with Prusa slicer, (nobody on all the posts Ive seen about the bulge issues has solved the problem) where because it has so many extra features like multiple different layer widths, etc, it just comes down to having to fine tune various settings at different layer heights. I put a height range modifier in at the transition point to decrease perimeter layer widths. Also increased extrusion to 1.02 from 0.95 for the bottom layers. Changed bed temperature down 10C, which made no difference at all. Also decreased extrusion down to 0.95 for the perimeters above the bottom slab.(so annoying that the slicer doesnt allow programmed extrusion multiplier changes at different layers. You can do this live so why not in the slicing. This is where Simplify has the advantage with split processes).  So after all that I ended up with a barely visible ridge that was caused by a 0.1mm undersize of the base slab. The top perimeter width was exact to 0.01mm. Now I still need help with the perimeters not meeting up with each other and leaving a gap. I set the seam position to the rear to observe this problem more closely and ended up with a slot down the back side. This not an extrusion problem and I cant find any way in the slicer to close it up, but havent tried extra restart yet. Any ideas on a fix for this? I forgot to mention that I also tried different nozzle temperatures to get a better flow at lower layers, but it had no effect.

RE: Vertical Ridge on Petg

@rick-7

If you think this is a bug, I suggest you report it on Github.  

https://github.com/prusa3d/PrusaSlicer/issues

RE: Vertical Ridge on Petg

If you have available Prusa or Prusament PETG I would recommend to print out of it an see how this behave.

Do you have previous good experience/reference with the  Polyfilla Petg  filament you are using with MINI yet?

Google was not able to find for me any reference on Polyfilla Petg

RE: Vertical Ridge on Petg

@zoltan

No don't have any of that filament because I'm in Australia and the freight costs would be too high to get it. I've only had the mini a few days and that cost me about $130 Aus dollars to freight it here. But I have done some good prints of other small models with the Poly Petg, including some temperature test towers with bridging that turned out alright. It's specifically an issue I found on many posts where people are printing flat surfaces near hollow walls.

RE: Vertical Ridge on Petg

@rick-7

I would see if you can find a brand that is available world wide.,  

RE: Vertical Ridge on Petg

Probably eSun or similar CHinese brand, they are available in US, EU and should be available down there in Australia too.

RE: Vertical Ridge on Petg

@crawlerin

Good choice.  

RE: Vertical Ridge on Petg

Posted by: @cwbullet

@crawlerin

Good choice.  

Sorry, I stepped aways and it timed out.  I meant to add that I have the in stock if you want someone to test print with you.  

RE: Vertical Ridge on Petg

@cwbullet

Well I've been using Polyfilla for years and it's a good quality brand for all filament types, but definitely not as cheap as overseas brands. I buy it locally from an importer and have tried other cheaper brands sold in Australia, but had issues with the the cheaper ones producing bad results, mainly due to the filament not being consistently 1.75mm in diameter all the way thru the roll. Besides that I can't see how a different brand would make a difference to that ridge problem.

And by the way, I'm assuming you guys are using Prusa slicer as your main slicer, so I'm surprised no one shot me down for complaining about the slicers inability to change flow rate during a print. When in fact you can insert a custom M221 gcode in the preview to change flow rate at different layers. I had forgotten to try it for the mini because I had previously already tried that, but it was when slicing a print for a Flashforge printer that doesn't use Marlin firmware, so it didn't work.

So one last issue is the seam crack shown on the image, where the perimeters aren't joining up. There are no retractions all the way up so that is not the cause. I can't find any settings to fix this. Any ideas?

Or should I raise this issue as a new topic?

RE: Vertical Ridge on Petg

@rick-7

I have no issues with Prusa Slicer.  On some prints, I get the issues you described.  I pretty much accept it until PS 2.4 is released. 

RE: Vertical Ridge on Petg

@rick-7

Which FW version are you on?

Can you share pls your .stl file? We can try on our slicers and printers.