No Skin Combing

[Labern 774]

Just tried out RC11 and the No Skin combing feature.

The Item Im printing has a few holes in it.

I have noticed that it lays down the external perimeter of the print then travels to the holes with no retraction. then when its filling in the area it will retract.

Because of this i haven't found much of an improvement in quality as it oozes while traveling to the holes.

Is there a way CURA can detect multiple perimeters and retract while transferring to those?

 

[pm_dude 27]

Did you try with zhop? This way the hop will be triggered since its retracting so it doesn't scratch the surface anyway

 

[pm_dude 27]

also your minimum distance to retract might be too large. default is 1.5mm

 

[Labern 774]

I have tried both suggestion and put the minimum distance on 0mm and tried Z hop on 0.5mm.

neither of these helped as it still didn't retract.

hope this picture helps you understand more what on trying to explain.

 

[pm_dude 27]

ha yes I get it now.

 

[Labern 774]

If this can be fixed. Z hop on skin would also be a good feature.

 

[dirkdirk 5]

currently i am printing with this new feature. Works for me with combing+retraction at skin, but you still see some scratches.

 

..Z hop on skin would also be a good feature.

 

this would be really great!

 

[rpress 1]

The problem is that the "skin" surface is only the flat part in the middle, not the perimeters. The "No Skin" feature is meant not for the beginning of printing the layer, but meant so that after it prints the skin it won't ooze or scratch on it moving to the next point.

I suppose it could be made to add retracts on the bottom layer for the perimeters but at some point you have to ask yourself why use combing at all? You could also try increasing your travel speed.

 

[Labern 774]

I understand what you are saying about what the skin is. But I guess the goal is to print something with the least amount of defects as possible. But at the same time not have to many unnecessary actions that take up to much time.

so if you are only implement a feature that fixes the "flat part in the middle" to increase the appearance of the final print , but then the appearance is reduced by oozing on multiple perimeters. then you have only fixed some cases when all can be fixed if it retracts on perimeters also.

 

it won't ooze or scratch on it moving to the next point.

 

Well it will scratch unless you have Z hop turned on. and this is why Z hop on skin would be good.

 

but at some point you have to ask yourself why use combing at all?

 

So you don't get defects in the outer walls.

 

You could also try increasing your travel speed.

 

Travel speed is already set to 250mm/s

 

[rpress 1]

then you have only fixed some cases when all can be fixed if it retracts on perimeters also.

 

 

So you don't get defects in the outer walls.

 

I'm not sure I understand, so you want combing off for perimeters (retracts) but you want combing on for perimeters to eliminate defects? When you say outer walls you mean perimeters yes?

 

Well it will scratch unless you have Z hop turned on. and this is why Z hop on skin would be good.

 

Yes, of course "No Skin" with no z-hop will still scratch, but not ooze. But this "No Skin" setting will do a standard retract, including z-hop. So you already have z-hop on skin. Am I missing something here too? You want z-hop without retract on skin?

[Labern 774]

I'm not sure I understand, so you want combing off for perimeters (retracts) but you want combing on for perimeters to eliminate defects? When you say outer walls you mean perimeters yes?

 

I want retracts on for bottom and top surface for the perimeters, and combing on during the rest of the print so the side walls don't get defects.

 

Yes, of course "No Skin" with no z-hop will still scratch, but not ooze. But this "No Skin" setting will do a standard retract, including z-hop. So you already have z-hop on skin. Am I missing something here too? You want z-hop without retract on skin?

 

No, I don't want Z hop on during the entire print. Only while printing the top and bottom surface.

 

[rpress 1]

Retracts for everything on the bottom are doable with small changes.

But for the top it's a question of what is the "top"? For a square part it's easy, the top is the last layer, but what I think you mean is not "top" but any exposed flat surface. This is a skin. But for perimeters it's hard to decide when is the right time to modify behavior.

[Labern 774]

but what I think you mean is not "top" but any exposed flat surface. This is a skin.

 

I realise this, I was purely try to express myself so you would understand my request. Hence why I said Z Hop on skin earlier.

Ultimately it comes down to whether Daid thinks it's worth doing or not or if it's any benefit to anyone And if it's easy for him to implement. Because he is the mighty ruler of all things CURA.

If he doesn't like the idea or takes no interest then that's fine.

[rpress 1]

Maybe the RetractWhileCombing plugin will give you z hop for just the bottom. Or it could be modified, etc.

But for the perimiters next to skins this is much more complicated. And I suspect it has limited appeal for others; I have not found combing to affect my perimeters, but my stringing is nothing like yours.

[Labern 774]

I think that there maybe some appeal as there are guides into how to design things with holes so you don't have these issues. Yes I can try the plugin and redesign things to eliminate these issues but I saw a new feature that I thought could be improved further.

I'm no programmer so i have no knowledge of ease of implementation. That's why I asked here.

[jweaver 2]

I didn't even know that this option/feature existed.. But I just tried it out and am not sure I understand its use.

If I load a model lf a dice.. And look at the top layer.. With Combing set to "Off", i can see the tool path goes right over the holes in the dice.

If I set Combing to "All" the tool path travels around the holes.

When I set it to "No Skin", i would expect it NOT to comb on the TOP layer.. But when I look, its still combing and moving the tool around the holes.

So what exactly does "No Skin" do?

Jon

 

[rpress 1]

Yes it's not very clear what the skin surface is. Skin is only the flat infill on a horizontal exposed surface. So for your die, it will comb on the perimeters (the sides and holes) but not on the flat parts in between.

[randyinla 14]

@Labern: What are your retraction settings on your machine? I upped my retraction length to 5.35 and my retraction speed to 45mm/s and I don't get those "ooze-traces when combing" anymore like you show in your photo. The only scratching I get is from the head actually scraping over pre-laid down skin, not from plastic oozing out of the head during the move.

edit:

I also try to print as low a temperature as possible on a material by material basis to also minimize oozing during moves.

 

[Labern 774]

Its not retracting, thats the whole point of my question. It is only retracting while putting down the "pre-laid down Skin" but not the perimeter lines around it. Also you shouldn't need your retraction length that long. Maybe you bowden hose is loose?

 

[randyinla 14]

Ah. So it's not even attempting retraction over the 45 degree fill area, only on the borders? Hmmm It would seem that turning off combing for the skin surfaces should not turn off retraction all together. It should just go from one point straight to the next, regardless of holes in the path. I happened use the "no skin" combing feature for the print I made last night and did not notice such drooling while moving the head between cutouts on my first layer. But I have only upgraded Cura to 15.01, have yet to flash the U2 firmware. Perhaps that is why?

 

My bowden tube is snug, no movement whatsoever. I read a few posts when I first joined UM forum saying to increase the retraction length to help get rid of stringing. I played around with it for a while and found that 5.35mm @ 45mm/s works great for me. No stringing OR oozing during travels. My feeder doesn't grind away the filament, either, when I have a retraction-heavy print. I use |Robert|'s feeder and only had it grind away my filament when I had criss-crossed the material on the spool once, basically turning it into a knot. The only thing I hate about 5.35mm/45mm/s retraction is the sound of the feeder motor when it retracts. I have enclosed my U2 and added a front door for ABS prints, so it's dead quiet except for that "screech/screech" sound due to the high speed and length... but I LOVE the results of it, so I deal with it.

[Labern 774]

Ah. So it's not even attempting retraction over the 45 degree fill area, only on the borders?

 

Other way around. 45degree fill is retracting, borders is not retracting.

Haven't tried the 15.01 official release as it hasn't rolled out to me yet. im still using the RC11. when it does ill try it to see if its any different.

 

[randyinla 14]

I made a similar part to the one in your photo over the weekend and played with turning on/off combing for all or everything except skin and I saw no difference in printing. I had no lines or drools between perimeters as your photo shows. Even had my first line @ .3mm, which I never do. I wanted to make one giant hole in the center to kind of force a combing operation and try again, but I got too tired