<p>There are 3 effects at work, and you misread your micrometer: the measurement is 19.35 in the picture.</p>
<h1>You have a little lip</h1>
<p>There's a little lip at the top and bottom of the print. You'd need to clean that up with a sharp knife or sandpaper. That is the biggest part of the error you measure.</p>
<h1>Movement errors accumulate</h1>
<p>Errors also collect on the center of holes due to the order in which walls are usually placed, resulting in outer walls having the correct diameters but inner holes having a small offset.</p>
<h1>Plastic shrinks when it cools</h1>
<p>A smaller part of the error is the plastic shrinking as it cools, but that can be compensated for by the slicer - if your printer allows for it: Under Materials, there is a <code>Shrinkage Ratio</code> setting.</p>
<h1>There's compensation for that in Cura</h1>
<p>The option is under Shell and called Hole Horizontal Expansion. Setting that value to 0.6 mm to 0.7 mm should solve the hole sizing error.
<a href="https://i.sstatic.net/l0g2l.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/l0g2l.png" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2021-01-01T17:29:31.743Z
The error here is way too large to be shrinkage with PLA, especially as it's a thickening of the part not thinning. I'd suspect loose belts here.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2021-01-02T12:35:47.027Z
I read 19.3 mm from my micrometer, proper value (will not argue about 0.05 mm). On this side of 3D print there is no "elephant foot". I am still missing 0.7 mm (or 0.65 mm with your readings).
Jan Kowalski
CC BY-SA 4.0
2021-01-02T19:19:07.227Z
So there is no little lip and I think that PLA does not shrink that much. 0.6 mm is a lot when working with holes as big as 5 mm for example.
I guess my problem is "Movement errors accumulate". Is there a way to improve that?
Jan Kowalski
CC BY-SA 4.0
2021-01-02T23:39:25.270Z
@JanKowalski usually try to use multiples of wall thicknesses to get that small... or you might compensate by demanding a slightly larger hole...
Trish
CC BY-SA 4.0
2021-01-01T15:07:24.817Z
2021-03-03T10:15:56.627Z
2021-03-03T10:15:56.627Z
Trish
<p>I have problem with my Ender 3. Whenever I print, I have proper outer dimensions (accuracy usually better than 0.1 mm, sometimes a bit worse), but every hole, pit or any inside dimension is inaccurate (0.6 - 0.8 mm never less or more).</p>
<p>I have tried extruder calibration. Calibrated extruder voltage and e-steps (in Ender firmware), but this does not change a lot.</p>
<p>Here you can see test dimensions I modeled:</p>
<p><a href="https://i.sstatic.net/fR5Bw.png" rel="nofollow noreferrer" title="Test dimensions"><img src="https://i.sstatic.net/fR5Bw.png" alt="Test dimensions" title="Test dimensions" /></a></p>
<p>And it will come out with these dimensions:</p>
<p><a href="https://i.sstatic.net/RPRtY.png" rel="nofollow noreferrer" title="Resulting dimensions"><img src="https://i.sstatic.net/RPRtY.png" alt="Resulting dimensions" title="Resulting dimensions" /></a></p>
<p>Aaand the final print looks like this:</p>
<p><a href="https://i.sstatic.net/HjodB.jpg" rel="nofollow noreferrer" title="Final print"><img src="https://i.sstatic.net/HjodB.jpg" alt="Final print" title="Final print" /></a></p>
<p>As you can see, my estimation (second picture) was almost perfect. 19.3 mm and results are weirdly consistent. Always holes are 0.6 - 0.8 mm smaller than holes in model.</p>
<p>Do you have idea why this is happening?</p>
<p>Specs:</p>
<ul>
<li>Printer - Ender 3 with original circuit board</li>
<li>Printer software - Marlin 2.0.5</li>
<li>Model cutting software - Cura 4.8.0</li>
<li>Modelling software - Fusion 360</li>
</ul>

CC BY-SA 4.0
2021-03-03T10:16:16.230Z
Found a solution in Cura
Trish
CC BY-SA 4.0
2021-03-04T12:43:21.747Z
What's your line width?
If the wall width isn't a multiple of your line width you can end up with a bigger or smaller wall width depending on the way the model is sliced. It shouldn't cause a big error but maybe it adds to something else.
Yareon
<creality-ender-3><calibration><extrusion><dimensional-accuracy>
Incorrect inner dimensions of 3D prints with Ender 3
Jan Kowalski
# Incorrect inner dimensions of 3D prints with Ender 3

(Asked by: username_0 on 2021-01-01)

I have problem with my Ender 3. Whenever I print, I have proper outer dimensions (accuracy usually better than 0.1 mm, sometimes a bit worse), but every hole, pit or any inside dimension is inaccurate (0.6 - 0.8 mm never less or more).

I have tried extruder calibration. Calibrated extruder voltage and e-steps (in Ender firmware), but this does not change a lot.

Here you can see test dimensions I modeled:

[![Test dimensions](https://i.sstatic.net/fR5Bw.png "Test dimensions")](https://i.sstatic.net/fR5Bw.png "Test dimensions")

And it will come out with these dimensions:

[![Resulting dimensions](https://i.sstatic.net/RPRtY.png "Resulting dimensions")](https://i.sstatic.net/RPRtY.png "Resulting dimensions")

Aaand the final print looks like this:

[![Final print](https://i.sstatic.net/HjodB.jpg "Final print")](https://i.sstatic.net/HjodB.jpg "Final print")

As you can see, my estimation (second picture) was almost perfect. 19.3 mm and results are weirdly consistent. Always holes are 0.6 - 0.8 mm smaller than holes in model.

Do you have idea why this is happening?

Specs:

* Printer - Ender 3 with original circuit board
* Printer software - Marlin 2.0.5
* Model cutting software - Cura 4.8.0
* Modelling software - Fusion 360

**Tags:** creality-ender-3, calibration, extrusion, dimensional-accuracy

> **Comments:**
> **username_1**: Found a solution in Cura  
> **username_2**: What's your line width? If the wall width isn't a multiple of your line width you can end up with a bigger or smaller wall width depending on the way the model is sliced. It shouldn't cause a big error but maybe it adds to something else.  

---

## 1 answers

### Answer by username_1 on 2021-01-01. Score: 1

There are 3 effects at work, and you misread your micrometer: the measurement is 19.35 in the picture.

# You have a little lip

There's a little lip at the top and bottom of the print. You'd need to clean that up with a sharp knife or sandpaper. That is the biggest part of the error you measure.

# Movement errors accumulate

Errors also collect on the center of holes due to the order in which walls are usually placed, resulting in outer walls having the correct diameters but inner holes having a small offset.

# Plastic shrinks when it cools

A smaller part of the error is the plastic shrinking as it cools, but that can be compensated for by the slicer - if your printer allows for it: Under Materials, there is a `Shrinkage Ratio` setting.

# There's compensation for that in Cura

The option is under Shell and called Hole Horizontal Expansion. Setting that value to 0.6 mm to 0.7 mm should solve the hole sizing error.
[![enter image description here](https://i.sstatic.net/l0g2l.png)](https://i.sstatic.net/l0g2l.png)

> **Comments:**
> **username_3**: The error here is way too large to be shrinkage with PLA, especially as it's a thickening of the part not thinning. I'd suspect loose belts here.  
> **username_0**: I read 19.3 mm from my micrometer, proper value (will not argue about 0.05 mm). On this side of 3D print there is no "elephant foot". I am still missing 0.7 mm (or 0.65 mm with your readings).  
> **username_0**: So there is no little lip and I think that PLA does not shrink that much. 0.6 mm is a lot when working with holes as big as 5 mm for example. I guess my problem is "Movement errors accumulate". Is there a way to improve that?  
> **username_1**: @username_0 usually try to use multiples of wall thicknesses to get that small... or you might compensate by demanding a slightly larger hole...  

---

