Height to low on the printed objects

[AfTech54 0]

The height of my printed parts are 0,15-0.3 mm lower than the sketched expected height. I think I understand that it could be a difference of 0,15, but it shouldn't be more than that.
Could it be adjusted in Cura or do I have to add 0,15 mm extra to the height in my sketches?

 

I'm using Ender 3 and AddNorth's EPLA and have among others these (mm) settings in Cura:
Initial Layer Height = 0,25
Layer Height = 0.15
Top Thickness = 0,6
Top Layers = 4 (complies with 4 x 0,15 = 0,6)
Bottom Thickness = 0,6
Bottom Layer = 4 (complies with 4 x 0,15 = 0,6)
Initial Bottom Layers = 4 (4 x 0,25 = 1.0) 

 

Isn't the bottom thickness now 1,0 + 0,6 mm or is the "Bottom Thickness" just based on the 4 x "Layer Height"?
And why is it necessary to enter Thickness since it will be the product of "no. layers" x "layer height"

Edited January 23 by AfTech54
Added printer type

[Alain_D 5]

Did you adjust step/mm in your printer configuration ?

[Slashee_the_Cow 440]

It isn't necessary to enter thickness. You can just enter a number of layers and the thickness box will disable itself.

 

Initial Bottom Layers controls how many bottom layers are printed at the base of the model (i.e. right on top of the build plate) as opposed to bottom layers in other parts of your build. It uses the layer height which is currently in use, and only the first layer is taller, so 4 initial bottom layers = 0.25 + (0.15 x 3) = 0.7mm.

[AfTech54 0]

On 1/24/2024 at 12:38 AM, Slashee_the_Cow said:

It isn't necessary to enter thickness. You can just enter a number of layers and the thickness box will disable itself.

 

Initial Bottom Layers controls how many bottom layers are printed at the base of the model (i.e. right on top of the build plate) as opposed to bottom layers in other parts of your build. It uses the layer height which is currently in use, and only the first layer is taller, so 4 initial bottom layers = 0.25 + (0.15 x 3) = 0.7mm.

Ok, but it seems like I have 4 initial bottom layers. Should I alter that to 1 instead or will it be one layer what so ever?

As you see in the attached image, I have both "Bottom Layers" and "Initial Bottom Layers" in the settings.

 

And what about the low height problem, could I fix that in one way or another with the Cura settings.

[Slashee_the_Cow 440]

On 1/24/2024 at 2:55 AM, AfTech54 said:

The height of my printed parts are 0,15-0.3 mm lower than the sketched expected height. I think I understand that it could be a difference of 0,15, but it shouldn't be more than that.
Could it be adjusted in Cura or do I have to add 0,15 mm extra to the height in my sketches?

Worrying about top/bottom thickness actually has absolutely nothing to do with this. That just controls how many layers are printed with top/bottom fill in them. Cura should take the height of your model and round it to the nearest layer height, in your case with the settings you specified it doesn't round it to the nearest multiple of 0.15mm (like 30mm you'd think would be 30 ÷ 0.15 = 200), it takes the initial layer height into account, so 200 layers is now 200 x .15 + 0.1 = 30.1mm, the extra 0.1mm is initial layer height - layer height because that's how much it adds to the total). So when it's rounding, 199 x .15 + 0.1 = 29.95mm, which is closer to 30 than 30.1 is, so now it's only going to do 199 layers and you'll be 0.05mm short.

 

You can go to Experimental > Slicing Tolerance and set it to Inclusive. This makes sure your slice will be at least as big your model file is, rounding up instead of to the nearest number, not just when it comes to number of layers but also the size of parts in each layer, i.e. if your model has a part 4.1mm wide and you're using a 0.4mm line width, instead of rounding to the nearest number of lines (10 = 4.0mm, which is less than 4.1mm so it won't use it) it will round up to 11 lines (4.4mm) because it has to be at least 4.1mm. Using this mode is a bad idea if you're printing a model made of separate parts, because a gap may no longer be big enough (because the bit that goes into it rounded up).

 

If you need interlocking parts, you're better off setting the Slicing Tolerance to Exclusive. This makes your slice at most as big as your model, because it will always round down.

 

The default setting is Middle, which just makes it round to the closest number.

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It's also possible you have a hardware problem, as @Alain_D said, make sure the Z steps are set correctly on your printer, because if it's too low it'll make every layer a teeny bit shorter than it should be, which adds up over a whole print.

 

Also make sure your Z screw isn't too tight or too loose - turn off your printer and try to turn the screw by hand. You should be able to turn it by hand (which will make the X axis gantry move up or down) but if you move your fingers just a little bit it shouldn't wobble.

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But if you are wondering how the number of top/bottom layers works:

Bottom layers set to 4, initial bottom layers set to 2:

Looking at layer 3 we can see that it's only done two layers where it touches the build plate, layer 3 is just the walls.

 

Level 20, first layer which has something other than those three legs:

Level 24, we can see that it stopped printing the bottom on layer 23, so four layers (20, 21, 22, 23... can be a bit hard to get your head around remembering to count inclusively).

 

However if we only set thickness, not number of layers, it doesn't take into account the height of the first layer, it just does the number of layers anyway. Here I've set the initial layer height to 0.6mm so to reach 0.8mm it should only have to do the first two layers, right?

Nope. Layer 5 is the first layer without bottom layers. It just blindly follows the number of layers, which is based on the layer height.

 

On 1/24/2024 at 2:55 AM, AfTech54 said:

And why is it necessary to enter Thickness since it will be the product of "no. layers" x "layer height"

Actually Cura does it the other way around, when you enter a thickness it overrides any manually set layer values and calculates Thickness ÷ Layer Height to get the number of layers.

[AfTech54 0]

THANKS!

 

Now I think this old man understand the options to fix it and how the first layers are built.