<p>Teardrop shape
ere is a feature there which is inside of the part which you cannot see otherwise. By turning it, you should be able to decipher what these features are for and therefore should be able to</p>

CC BY-SA 4.0
2019-12-28T20:23:16.280Z
Welcome to the stack, but able to do.... what? Your answer is breaking off. You can [edit] it and add to it.
Trish
CC BY-SA 4.0
2019-12-28T18:37:33.050Z
2019-12-28T18:37:33.050Z
Xian Xian
<blockquote>
  <p>Item 1) The holes are not round. Why???</p>
</blockquote>

<p>Two things about this. First, the print is upside down. The holes are not round to accommodate the fact you cannot print a round hole unsupported. If you try to print the circle unsupported, when you get to the top portion, it will sag until the print catches up to it. By that time, the circle is flat at the top and you won't be able to fit whatever you were trying to fit into it (without some post processing). Printing the V-ish looking part at the top will ensure you'll be able fit things through it you meant to fit through (sorry if that's redundant). If you'd like to know more, take a look at the following Maker's Muse video:</p>

<p><div class="youtube-embed"><div>
                <iframe width="640px" height="395px" src="https://www.youtube.com/embed/j6508J94VsA?start=0"></iframe>
            </div></div> </p>

<blockquote>
  <p>Item 2 ) There are some little squares inside the piece which i don't know if they are there for some structural reason</p>
</blockquote>

<p>To be very honest with you, I don't know why the little squares are there either, however, I believe you can answer this part for yourself.</p>

<p>I think the answer lies in the part, meaning, if you can manipulate the 3d design in whatever you're using to design it, you can look into the part and see what's going on with it. It appears there are dashed lines in the center parts, which would make me believe these are <em>hidden lines</em>. There is a feature there which is <em>inside</em> of the part which you cannot see otherwise. By turning it, you should be able to decipher what these features are for and therefore should be able to discern what the small squares a for as well. If, after you've looked the part over completely you cannot discern a purpose for the squares, don't design them into your part. It may just be they are an artifact of the design itself and doesn't provide anything worth repeating in your own design. Bottom line, don't get hung up on the minute details which in the end don't mean a thing.</p>

CC BY-SA 4.0
2019-12-18T15:03:43.883Z
I'm not convinced about the hole shape.  It's easy to have the slicing software put supports inside the hole so the top is properlly shaped.  THese look a lot more like they're designed for a non-rotating, "keyed" item to be inserted.
Carl Witthoft
CC BY-SA 4.0
2019-12-18T22:04:21.397Z
Great video, good to link it related to the design questions of the OP (has been a while that I saw it), but the flat spot in the hole is not related to printing orientation, this piece can be printed with the holes down to the build plate.
0scar
CC BY-SA 4.0
2019-12-19T17:06:02.140Z
@CarlWitthoft both probably? a Teardrop shape can be used to make parts "self clamping" to some degree.
Trish
CC BY-SA 4.0
2019-12-17T22:45:17.210Z
2019-12-17T22:45:17.210Z
Pᴀᴜʟsᴛᴇʀ2
<p>I am attempting to build a 3D printer using the <a href="https://github.com/gregsaun/prusa_i3_bear_upgrade" rel="nofollow noreferrer">Bear Upgrade</a> for guidance.</p>

<p>However, I want to modify some of the parts. I am basing the modified parts on the original designs.</p>

<p>I would like to understand the reason behind some design details presented on the original designs so that, if necessary, introduce them into the new designs. </p>

<p><a href="https://i.sstatic.net/XTG3N.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/XTG3N.jpg" alt="example of design with details I don&#39;t understand the reason behind"></a></p>

<p>Item 1) The holes are not round. Why???</p>

<p>Item 2 ) There are some little squares inside the piece which i don't know if they are there for some structural reason </p>

<p>Please use <a href="https://github.com/gregsaun/prusa_i3_bear_upgrade/blob/master/full_upgrade/for_mk3/printed_parts/step/y_idler.step" rel="nofollow noreferrer">this link</a> to the piece depicted above. </p>

<p>Here is a drawing of the full assembly, showing that this piece is the y axes linear rods holder:</p>

<p><a href="https://i.sstatic.net/rOAzb.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/rOAzb.jpg" alt="enter image description here"></a></p>

<3d-design><diy-3d-printer><fusion360>
Help needed to design 3D printer part
Albaguti
# Help needed to design 3D printer part

(Asked by: username_0 on 2019-12-17)

I am attempting to build a 3D printer using the [Bear Upgrade](https://github.com/gregsaun/prusa_i3_bear_upgrade) for guidance.

However, I want to modify some of the parts. I am basing the modified parts on the original designs.

I would like to understand the reason behind some design details presented on the original designs so that, if necessary, introduce them into the new designs.

[![example of design with details I don't understand the reason behind](https://i.sstatic.net/XTG3N.jpg)](https://i.sstatic.net/XTG3N.jpg)

Item 1) The holes are not round. Why???

Item 2 ) There are some little squares inside the piece which i don't know if they are there for some structural reason

Please use [this link](https://github.com/gregsaun/prusa_i3_bear_upgrade/blob/master/full_upgrade/for_mk3/printed_parts/step/y_idler.step) to the piece depicted above.

Here is a drawing of the full assembly, showing that this piece is the y axes linear rods holder:

[![enter image description here](https://i.sstatic.net/rOAzb.jpg)](https://i.sstatic.net/rOAzb.jpg)

**Tags:** 3d-design, diy-3d-printer, fusion360


---

## 2 answers

### Answer by username_3 on 2019-12-17. Score: 4 | Accepted answer

> Item 1) The holes are not round. Why???

Two things about this. First, the print is upside down. The holes are not round to accommodate the fact you cannot print a round hole unsupported. If you try to print the circle unsupported, when you get to the top portion, it will sag until the print catches up to it. By that time, the circle is flat at the top and you won't be able to fit whatever you were trying to fit into it (without some post processing). Printing the V-ish looking part at the top will ensure you'll be able fit things through it you meant to fit through (sorry if that's redundant). If you'd like to know more, take a look at the following Maker's Muse video:

> Item 2 ) There are some little squares inside the piece which i don't know if they are there for some structural reason

To be very honest with you, I don't know why the little squares are there either, however, I believe you can answer this part for yourself.

I think the answer lies in the part, meaning, if you can manipulate the 3d design in whatever you're using to design it, you can look into the part and see what's going on with it. It appears there are dashed lines in the center parts, which would make me believe these are *hidden lines*. There is a feature there which is *inside* of the part which you cannot see otherwise. By turning it, you should be able to decipher what these features are for and therefore should be able to discern what the small squares a for as well. If, after you've looked the part over completely you cannot discern a purpose for the squares, don't design them into your part. It may just be they are an artifact of the design itself and doesn't provide anything worth repeating in your own design. Bottom line, don't get hung up on the minute details which in the end don't mean a thing.

> **Comments:**
> **username_4**: I'm not convinced about the hole shape.  It's easy to have the slicing software put supports inside the hole so the top is properlly shaped.  THese look a lot more like they're designed for a non-rotating, "keyed" item to be inserted.  
> **username_5**: Great video, good to link it related to the design questions of the OP (has been a while that I saw it), but the flat spot in the hole is not related to printing orientation, this piece can be printed with the holes down to the build plate.  
> **username_2**: @username_4 both probably? a Teardrop shape can be used to make parts "self clamping" to some degree.  

---

### Answer by username_1 on 2019-12-28. Score: 0

Teardrop shape
ere is a feature there which is inside of the part which you cannot see otherwise. By turning it, you should be able to decipher what these features are for and therefore should be able to

> **Comments:**
> **username_2**: Welcome to the stack, but able to do.... what? Your answer is breaking off. You can [edit] it and add to it.  

---

