why no top on spiralized vases

[derPotz 0]

Hey, I'm probably not the first asking for a function to make top layers while using spiralize mode. A closed vase so to say... I have to print bottles and jars a lot and often it would be awesome to have the nice,smooth and fast spiralzed surface AND a closed top though. I understand that the platform is moving down gradually but cura is also able to print the bottom in steps... why not the top ? For other stuff there are a million settings...

(btw: "Change at Z" won´t let you change that...) . Miss I something here or where can I propose that feature?

Thank you guys for any hint.

_L

[derPotz 0]

anybody...?

[Slashee_the_Cow 270]

Spiralise doesn't support horizontal surfaces, since it's specifically for printing just the outline. Probably more importantly, spiralise doesn't let you use supports since it's just doing one continuous movement, if it had to stop and move to print a support it would create a Z seam, which would defeat the purpose of spiralising.

 

You can create a closed object, but the top can't be a flat surface, and it would need to be pretty steep since you have only the adhesion of the filament to support itself as it gets smaller (so moving in by less than your line width each layer... time to get the giant nozzle out).

[derPotz 0]

Hey slashee-

thanks. But ... - using the spiralize mode you are able to define how many layers of the bottom the printer should do in normal horizontal printing mode. Only then it switches into spiralizing. Why can´t it switch back into normal horizontal printing mode for the top layers?  For the small bottle mouths I wouldn´t need any support...). Is just a programming issue, isn´t it?

_L

[Slashee_the_Cow 270]

5 hours ago, derPotz said:

Why can´t it switch back into normal horizontal printing mode for the top layers?  For the small bottle mouths I wouldn´t need any support...). Is just a programming issue, isn´t it?

Could it be technically be done in programming? Probably, maybe even in a plugin.

 

But I don't think it's implemented at all because I'm not sure there's a printer and material around that can do a 90° overhang with no support. It would succumb to gravity and fall straight down before there was even a remote chance it would adhere to a wall directly beside it.

 

The closest I can think of is if you use incredibly thin layers and incredibly chunky walls and add a small bit on top which goes in at a very sharp angle, something like this:

I still doubt that would print successfully though. Your best bet is probably to print a top separately and glue it on.

[derPotz 0]

Hey -

the nice thing about bottles is the relativley narrow mouth opening. No problem without support- 5 layers are enough most of the time to have a plain top surface (the first ones will hang a bit - but since it is closed then you wouldnt even  see that.For larger opening it is also just a matter of how many layers until it gives you a nice plain surface on top.

[Slashee_the_Cow 270]

18 minutes ago, derPotz said:

5 layers are enough most of the time to have a plain top surface (the first ones will hang a bit

Remember that in your model file, any top surface has to be raised to print, it can't be equal height with the top of the bottle, because after the base, spiralise will only print a single wall per layer, regardless of what's in the model.

[derPotz 0]

8 hours ago, Slashee_the_Cow said:

Remember that in your model file, any top surface has to be raised to print, it can't be equal height with the top of the bottle, because after the base, spiralise will only print a single wall per layer, regardless of what's in the model.

Yes yes - I know how it is right now. I just wonder why a very useful setting can´t be added to spiralize mode...

[Slashee_the_Cow 270]

10 hours ago, derPotz said:

I just wonder why a very useful setting can´t be added to spiralize mode

Because it's physically impossible. You can't spiralise if you have to build supports, and you can't have a top without support because if you try and print next to a wall with nothing below, the filament is just going to go straight down, not adhere to a wall next to it.

[Slashee_the_Cow 270]

Okay, experiment time! (if you dare)

 

Here's an STL file containing a small cylinder with a rim overhanging at the top.

If you can print this as a regular model (not spiralise), without support and have the rim print fine and stay in place, I will tip my hat to thee, fine sir, madam or otherwise. It is designed to be printed at 0.2mm layer height and 0.4mm line width. I don't mind what material you use.

cylinder_with_rim.stl

[43915 16]

Of course it will be next to impossible to print a model with a rim like that, since the printer has to print a circle in mid-air. But that's completely irrelevant to his request.

 

He wants to print completely closed off top layers, which means that it would only print straight lines between two points of the circular wall. And that is definitely possible if you have a fine tuned printer.

 

If Cura would have the same settings for top layers as it does for bottom layers, so that you'd be able to define a thickness/number of top layers, you would be able to get an acceptable result on models like bottles with a narrow top. The first layer will most likely look bad, but on the 3rd/4th/5th layer it will look good.

 

Just for fun I modeled a cylinder with 0.4mm wall thickness (1 line) and 0.8mm closed off top (4 top layers @ 0.2 layer thickness), 30mm diameter. I printed it with my UM2+ which is far from well tuned and with a PLA filament that has given me some trouble so far, and it still came out fine. Slow print speed, relatively high fan speed, tuned the temps a bit.

 

Sure, the first top layer looks horrible. But the second one covered the whole surface pretty well, the third layer looked okay-ish and the fourth and final layer looks perfectly fine. Make it 5 layers just to be safe and you'll never notice the bad first layers. Since you won't ever see the first top layers it won't be a problem at all.

And even then, the nozzle on my badly tuned printer only connected with the wall on like every 5th-6th turn on the first layer and it still came out fine. If you have a well tuned printer which manages to connect most of the lines there won't be any problems at all.

 

I'll switch to another filament and give it another go to see if I can get even better results, and perhaps post some images later if you don't believe me.

[derPotz 0]

Slashee_the_Cow - I see what you mean -and it really comes down to what our colleague 43915 above tested - (and I am about to...) In the settings of the top you can define extra skin wall count. If thats more than one it will print a wall parallel to your original... into the air. (In your test file it creates a rim with 8 or so...) But if put to zero and increasing the "overlap of top and wall" it should be fine (see attached pic)

Also I normally take the 0.8mm nozzle so I get a less wobbly bottle.

Testprint outcome see second pic.

Anyone knows where can I propose that... 😕  Can other slicers do that? It would be a great material saver in a lot of cases where you could print without infill...

[43915 16]

I think you can suggest it on this page:
Issues · Ultimaker/Cura · GitHub

 

If I remember correctly you can post a new issue there and choose between bug report and feature request, that's probably your best bet.

[43915 16]

Here's a test print I did with a better quality PETG filament. I had some pretty severe under extrusion because of a partial clog in the nozzle, but despite that it came out just fine apart from the walls, which aren't the focus here anyway.

Even the first top layer it printed looks pretty decent from underneath, it connected every single line to both sides and by the time it finished the 4th layer you can't even tell that it's hollow 3 layers down. Just some under extrusion still visible, which has nothing to do with the way the model was printed.

 

With an unclogged nozzle and a decently tuned printer you'll be able to get great results, without a doubt. Definitely not "physically impossible".

 

[Slashee_the_Cow 270]

And this is why I love saying "this can't be done", brings in the masses to show how it's done. I'll amend my point to "there's no way a slicer can guarantee it can be done and it will only work for small gaps", how's about that.

[43915 16]

It will not only work for small gaps, it's just easier with small gaps. I'm certain that you can use this method for at least medium sized parts as well if you do some tuning.

 

And on that note there are a lot of other features that the slicer can't guarantee that they can be done other than in specific instances, so I don't see how this feature would be any different in that aspect. Spiralize mode on it's own already requires specific types of models to work well, so I'm sure that another feature like this, that you have to enable manually, won't hurt anyone.

[derPotz 0]

Slashee_the_Cow --    I heard about the forum trick to troll your own question with a different username just to lure others into the discussion 😁  - so thanks...

 

43915  ✌️

[Slashee_the_Cow 270]

1 minute ago, derPotz said:

Slashee_the_Cow --    I heard about the forum trick to troll your own question with a different username just to lure others into the discussion 😁  - so thanks...

I wish I was that smart. I promise you I'm not 43915 (my other usernames in various places are at least as wacky as Slashee the Cow, except I don't use them enough to bother with a website I never update).