Independent Bottom and Top Thickness

[Nicolinux 288]

Hi,

in Cura one can set the bottom/top thickness. The top thickness is very important in order to achieve a great surface quality. So I tend to print almost everything with 1.2mm bottom/top. The problem is, bottom thickness of 1.2mm is almost always a waste of printing time and material. The bottom most layer is already flat because it sticks to the bed and the rest of the bottom layers just pile up and add to the printing time. These layers are inside the model and will never contribute to surface quality.

So it would be great to specify bottom and top thickness independently. That's especially important for objects with large flat bases (like vases or architectural objects).

 

[Daid 303]

The bottom thickness is also used for bridges and steep overhang, so then it's more important then you would imagine.

The engine already support 2 values. But I do not want to add a 2nd setting in the GUI.

 

[Nicolinux 288]

The bottom thickness is also used for bridges and steep overhang, so then it's more important then you would imagine.

Ok, understood. Didn't think of that.

The engine already support 2 values. But I do not want to add a 2nd setting in the GUI.

Why not? Add it to the full settings or do you fear to become Slic3r?

 

[Daid 303]

Ok, understood. Didn't think of that.

Why not? Add it to the full settings or do you fear to become Slic3r?

Yes.

 

[eldrick 64]

One more vote for separate Top and Bottom thickness: I have a small structural piece where the product needs a strong bottom to hold a threaded insert, but a thick Top causes a bulge halfway up the piece where the infill ends and a hollow section begins.

 

[gr5 2,003]

That sounds wrong. That sounds like pillowing. Pillowing can usually be fixed with more layers. Please post a photo. Here is information about pillowing (post #10):

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/?p=17300

 

[IRobertI 516]

No, I don't think he's referring to a bulge at the top but rather at the side of the print. Similar to that thread a while back with the little cube puzzle where there was an indentation on the shell where the print transitioned from one shape to another. I'll see if I can find it and edit in a link.

If I'm understanding correctly his print has a thick bottom, a hollow(ish) section, a solid section and then a hollow section. The hollow sections might be shrinking slightly and the thick solid section is bulging outwards slightly. Either because it is extruding a bit more plastic that is squishing out to the sides or because it's resisting shrinkage better than the hollow sections.

 

[eldrick 64]

An image of one of the produicts is at: http://www.fencing.net/forums/attachments/5936d1392842643-melting.jpg

The flat end needs a few solid layers, for the threaded insert that is melted into place. The first half-inch from that end is 50% infill around the insert, and needs a solid layer or two at the inner end for best strength. The 35mm in the "bulb" is hollow, with 1/8" walls.

If I specify 1.25mm for the Top/Bottom, then Cura puts a 1.25mm layer at the top of the infill, and this does not shrink as much as the infill or hollow sections, leaving a raised band on the outside where the Top has been filled in.

Does anyone know exactly what the Expert settings for Solid Infill Top and Solid Infill Bottom do? Could that be a solution?

 

[gr5 2,003]

I couldn't see the picture. It wants me to create an account on the fencing site. When I got to the part where it wanted my email I gave up.

I would expect solid infill layers to shrink *more*, not less. I'm wondering if there is a different issue - maybe related to a heated bed or fan issue as I've seen that cause what looks like shrinking but is something more complicated.

To post a picture click on GALLERY in the top left corner of this page. Then click the blue UPLOAD button. After uploading make a new post and click "My Media" next to the smiley face.

 

[eldrick 64]

Sorry about that. Here's the image:

These were made with Kisslicer.

 

[eldrick 64]

Also, I noticed that on the Basic panel, one sees the label: Bottom / Top Thickness, so I tried entering 1.25/.5 and it at least stayed there in the entry box. Does anyone know if this actually works to give independent thickness?

 

[rgharris 0]

Also, I noticed that on the Basic panel, one sees the label: Bottom / Top Thickness, so I tried entering 1.25/.5 and it at least stayed there in the entry box. Does anyone know if this actually works to give independent thickness?

 

I don't know how Cura specifically works, but I would be worried that it would interpret this to mean 1.25 divided by 0.5 = 2.5, rather that two values.

 

[Daid 303]

Also, I noticed that on the Basic panel, one sees the label: Bottom / Top Thickness, so I tried entering 1.25/.5 and it at least stayed there in the entry box. Does anyone know if this actually works to give independent thickness?

 

1.25/.5 = 2.5

You can do math in settings :-)

 

[neoxm3 0]

One more vote for separate Top and Bottom thickness: I have a small structural piece where the product needs a strong bottom to hold a threaded insert, but a thick Top causes a bulge halfway up the piece where the infill ends and a hollow section begins.

 

i also vote for that, i think is very important top and bottom can be set with diferent numbers,,,

 

[eldrick 64]

What exactly does Solid Infill Top and Bottom in the Expert settings do?

The Help says "Creates a solid top surface" but that leaves a lot out.

How many layers? And how does this interact with the thickness of the bottom of the piece? Does it create a solid top surface on infill if the infill is contained within the piece, but open to a hollow area above it?

 

[IRobertI 516]

This is what the help popup says for me. Is that not what it says for you?

How many layers depends on your "Bottom/Top thickness" setting and your layer height setting. Thickness/layer height = number of layers.

And the answer to your last question is yes, if I understand it correctly.

 

[eldrick 64]

OK - thanks.

My questions were whether this interacts with the Top/Bottom thickness, but careful observation while printing reveals that the internal upper surface (at the bottom of the bulb) is treated as an external periphery, and gets the thickness set as Shell Thickness.

 

[illuminarti 18]

No. Shell thickness determines the number of loops around the outside of each layer. Turning on solid top and/or bottom causes solid layers to be printed wherever the solid model lies over empty space (bottom) or under empty space (top).

In either case, the number of layers printed is determined by the Bottom/Top Thickness setting (which should be an exact multiple of the layer height).

 

[eldrick 64]

In this case, I'm pretty sure that the Shell Thickness controls, as the interior is open to the outside thru the 8mm hole into which the threaded insert fits.

 

[illuminarti 18]

I'm not sure what the geometry looks like that you're talking about, since it's inside the shape, and I can't see it. But I'm pretty sure that what I said above is correct. Shell thickness affects the number of loops around the outside of each layer. Top/Bottom thickness determines the number of solid layers laid down where infill meets the outside other than in the x-y plane. Bottom thickness (in particular) is what causes Cura to generate the 'extra 100% infill' that gets put inside the perimeter of sloping shapes, to better support the layers above.

 

[gr5 2,003]

bottom/top are the solid *diagonal* infill layers. For this grip the "top" doesn't really occur because you have shell all the way except maybe the last layer where there might be some diagonal fill.

You can see what all these do for your particular part by slicing it in cura and looking at the results in layer view.

 

[wallan 0]

One more vote for separate Top and Bottom thickness: I have a small structural piece where the product needs a strong bottom to hold a threaded insert, but a thick Top causes a bulge halfway up the piece where the infill ends and a hollow section begins.

 

You have my vote as well.

I have great succes printing abs on slurry with open bottom exept for getting holes on my figurines shoulders etc.

i did thought of those areas as continued shells and did not realise that it was the top settings that could be the problem. Or at least it could be the problem if latest suggestions to my problem are correct. I still have to verify it by doing a print.

I want to keep bottom open while still closing the top and without getting less undercut abilites.

Maybe a simple checbox for not creating a bottom when its the builplate layer.

Except for wanting an open bottom for acces,saving time and filament a bottom also makes a deformation on the figurine as it seems to either not follow the shape correctly or possibly shrinks more.

[tosha_r 0]

Hi,

I am new with ultimaker 2 and 3d printing. I have a question:

If I uncheck in the expert settings the solid infill top and bottom I realize (layers view) that neither the bottom and top layers appear as 100% infill.

Therefore if I uncheck this two boxes, the parameter bottom and top thickness does not make sense?

I hope you can help me

 

[gr5 2,003]

Therefore if I uncheck this two boxes, the parameter bottom and top thickness does not make sense?

 

Yes, correct. Many parameters are not used. For example if you disable brim, it still shows brim parameters but they are ignored.

 

[Daid 303]

https://github.com/daid/Cura2/blob/master/Cura/machine/fdmprinter.py#L31