<p>I would like to thank @hfcandrew and @MagWeb for their in-depth explanations:</p>
<ul>
<li><p><a href="https://forums.autodesk.com/t5/fusion-design-validate-document/creating-a-two-part-mold-from-organic-mesh-bone-sample/m-p/12672056#M316180" rel="nofollow noreferrer">Creating a two part mold from organic mesh (bone sample)</a></p>
</li>
<li><p><a href="https://forums.autodesk.com/t5/meshmixer/newbie-questions/m-p/10351368/highlight/true#M3435" rel="nofollow noreferrer">Meshmixer: Newbie questions</a></p>
</li>
</ul>
<hr />
<p>Quoting from the original forum post:</p>
<p>Here's how I do moods from shapes like this needing curved parting lines:</p>
<p><a href="https://i.sstatic.net/7hJzK.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/7hJzK.png" alt="Ohne TitelX.png" /></a></p>
<p>Step: Finding the parting line of the shape:
MM's Overhangs shader (drag the sphere with the red bottom onto your object) is pretty useful if it is set to paint regions at its max angle. You can modify this angle in <strong>Analysis</strong> &gt; <strong>Overhangs</strong>. Set AngleTresh to max (89°) and cancel the tool. MM remembers this setting to use it for the overhang shader:</p>
<p><a href="https://i.sstatic.net/FIkm2.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/FIkm2.png" alt="Ohne TitelXX.png" /></a></p>
<p>Now drag this shader from <strong>Shaders</strong> onto your object.</p>
<p><a href="https://i.sstatic.net/44bcn.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/44bcn.png" alt="Ohne Titel X2.png" /></a></p>
<p>Use <strong>Edit</strong> &gt; <strong>Transform</strong> to rotate the object to an orientation where you get a meaningful border of red/white. You want to find a position where there are no white islands within a red area or red islands within white.</p>
<p><a href="https://i.sstatic.net/BU6zZ.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/BU6zZ.png" alt="Ohne Titel X3.png" /></a></p>
<p>Now using the ViewCube switch to Bottom view. Make sure that you do not navigate for the following: Go to <strong>Select</strong>, select something (which region doesn't matter at all) and do <strong>Modify</strong> &gt; <strong>SelectVisible</strong>:</p>
<p><a href="https://i.sstatic.net/u5uDj.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/u5uDj.png" alt="Ohne Titel 2.png" /></a></p>
<p>Run <strong>Modify</strong> &gt; <strong>SmoothBoundary</strong>. At its default settings, it will create a face group too:</p>
<p><a href="https://i.sstatic.net/eK9tj.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/eK9tj.png" alt="Ohne Titel 3.png" /></a></p>
<p>Now you've found the parting line.</p>
<ol start="2">
<li>Design a parting surface:</li>
</ol>
<p>From above you've got a face group. We want to use its boundary to deform a plane primitive:</p>
<p>For easier view drop the first shader from <strong>Shaders</strong> onto your object.</p>
<p>Go to <strong>Edit</strong> &gt; <strong>CreatePivot</strong>. Set <strong>PlacementMode</strong> to <strong>SnapToGroupBorders</strong>. Double-click at the group boundary several times to get pivots at that boundary like this:</p>
<p><a href="https://i.sstatic.net/vFMDn.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/vFMDn.png" alt="Ohne Titel 4.png" /></a></p>
<p>When done go to <strong>Select</strong> and double-click the face group to select it. Run <strong>Edit</strong> &gt; <strong>FitPrimitive</strong>. By default, it will insert a square object. Set a high <strong>MeshDensity</strong> and make sure to check <strong>CreateNewObjects</strong>. Scale up the object using the transform widget. It needs to be about two times its fitting size:</p>
<p><a href="https://i.sstatic.net/gqq6j.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/gqq6j.png" alt="Ohne Titel 5.png" /></a></p>
<p>Accept. Now there should be a FitPrimitive1 object in your scene. Leave <strong>Select</strong> and hide the shape object.</p>
<p>Activate the plane and select all of it (<kbd>Ctrl/kbd&gt;+<kbd>A</kbd>). In <strong>Select</strong> go to <strong>Deform/Wrap</strong>.</p>
<p>In <strong>Wrap</strong>, double-click next to a pivot to create a red sphere. Drag this handle to the pivot to make it snap to it. Do the for all pivots to deform the plane:</p>
<p><a href="https://i.sstatic.net/OVEJ3.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/OVEJ3.png" alt="Ohne Titel 6.png" /></a></p>
<p>After accepting <strong>Wrap</strong>, you should discard all pivots. You may make them visible in the ObjectBrowser by clicking the pivot icon in the bottom-left of the browser. You may now show the source shape to check the parting surface:</p>
<p><a href="https://i.sstatic.net/HMXP2.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/HMXP2.png" alt="Ohne Titel 7.png" /></a></p>
<p>Next is to construct the molds from that.</p>
<ol start="3">
<li>Construct solid molds:</li>
</ol>
<p>At first, we need to create an offset shell from the source shape. Its <strong>OffsetDistance</strong> will define the width of the flanges later on. I use <strong>Edit</strong> &gt; <strong>MakeSolid</strong> in Accurate mode which allows me to add an offset:</p>
<p><a href="https://i.sstatic.net/p4iq1.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/p4iq1.png" alt="Ohne Titel 8.png" /></a></p>
<p>Drag the transparency shader onto this result (top-right in <strong>Shaders</strong>) and make a copy of the parting surface:</p>
<p><a href="https://i.sstatic.net/7oiH3.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/7oiH3.png" alt="Ohne Titel 9.png" /></a></p>
<p>SelectAll of one <strong>FitPrimitve</strong> an use <strong>Select</strong> &gt; <strong>Edit</strong> &gt; <strong>Extrude</strong> to give it a thickness including the ghost shell to one side.</p>
<p><a href="https://i.sstatic.net/4ENTw.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/4ENTw.png" alt="Ohne Titel 10.png" /></a></p>
<p>Do the same on the other <strong>FitPrimitive</strong> with a negative offset</p>
<p><a href="https://i.sstatic.net/FBEgB.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/FBEgB.png" alt="Ohne Titel 11.png" /></a></p>
<p>Make a duplicate of the source shape. Hide all objects but one pair of source shapes and <strong>FitPrimitive</strong>.</p>
<p>Activate the extruded <strong>FitPrimitives</strong> as the first and hold down Shift</kbd> one source shape as the second object. Run <strong>BooleanDifference</strong>:</p>
<p><a href="https://i.sstatic.net/Iliyh.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Iliyh.png" alt="Ohne Titel 12.png" /></a></p>
<p>Do the same with the second pair.</p>
<p><a href="https://i.sstatic.net/902d9.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/902d9.png" alt="Ohne Titel 13.png" /></a></p>
<p>If the molds' sizes are bigger than your printer's volume it's to cut the halves. To do this <strong>Edit</strong> &gt; <strong>Combine</strong> both halves to one object for now and run <strong>Edit</strong> &gt; <strong>PlaneCut</strong> at <strong>Slice(KeepBoth)</strong>:</p>
<p><a href="https://i.sstatic.net/prawl.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/prawl.png" alt="Ohne Titel 14.png" /></a></p>
<p>Run <strong>Edit</strong> &gt; <strong>SeparateShells</strong> to split all of the mold's parts again.</p>
<hr>
<p>From this point, I modified the technique described for my case.</p>
<p>I had to re-mesh and smooth edges quite a few times in Meshmixer to obtain a completely solid object without any holes, which enabled me to make a boolean difference.</p>
<p>Here is my re-meshed bone and the plane cutting through it:
<a href="https://i.sstatic.net/BUske.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/BUske.png" alt="Bone with plane cutting through" /></a></p>
<p>I made two copies of the fit primitive, and extruded them in separate directions:
<a href="https://i.sstatic.net/aHB61.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/aHB61.png" alt="Raw extruded mold" /></a></p>
<p>While this is not an elegant solution, I sculpted each mold piece to have a thicker mold that I can cut into orderly pieces, so I can print and compress the bone cement in between.</p>
<p><a href="https://i.sstatic.net/un0Tn.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/un0Tn.png" alt="Green monster mold of nightmares" /></a></p>
<p>I cut a few planes through the mold, obtaining this orderly shape.
<a href="https://i.sstatic.net/uQ2oN.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/uQ2oN.png" alt="Note the bone within the mold" /></a></p>
<p>Now to print it:</p>
<p><a href="https://i.sstatic.net/UVQ5C.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/UVQ5C.jpg" alt="Separate pieces" /></a></p>
<p><a href="https://i.sstatic.net/NYA1S.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/NYA1S.jpg" alt="How they fit" /></a></p>
<p>Obviously, it would be better to create some mechanism to improve alignment(Ball/hole or some pins?).</p>
<p>But here is the end product, not dried yet:</p>
<p><a href="https://i.sstatic.net/BdaI1.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/BdaI1.jpg" alt="End product 1" /></a></p>
<p><a href="https://i.sstatic.net/m4kcN.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/m4kcN.jpg" alt="End product 2" /></a></p>

CC BY-SA 4.0
2024-04-09T07:04:21.323Z
Please [edit] and include the relevant part of the link, if possible. However, in Magweb's answers alone, there are 28 images spread over 5 posts/steps - so probably not feasible.
Greenonline
CC BY-SA 4.0
2024-04-09T07:07:47.643Z
Nice of you to come back and post an answer, however, at SE we expect answers to be self containing, not link only. As links on the net tend to rot, we need a summary of the answer in the link which will be retained on our own servers. Please [edit] your answer with a summary from the link, pictures are welcomed and can be inseterd to be hosted from our own image servers (also retained with the SE site).
0scar
CC BY-SA 4.0
2024-04-09T09:02:03.857Z
I assume that the hfcandrew post is [this one](https://forums.autodesk.com/t5/meshmixer/newbie-questions/m-p/10339395/highlight/true#M3424)? Is that the correct post? That is just one animated gif, so it would be possible to post that - however, the image is too large to post (exceeds 2MB), I have just tried it. I have also tried to [resize the image](https://apple.stackexchange.com/q/351578/100490), but not had much luck. I guess this will have to be a link only answer. +1 anyway, for coming back with the answer :-)
Greenonline
CC BY-SA 4.0
2024-04-09T11:59:18.967Z
I modified my answer using a combination of the original post and my own production process. Hopefully, this will help anyone who is trying to print a bone/organic material two-piece mold. Thanks for the pointers.
Bilal Bahadır Akbulut
CC BY-SA 4.0
2024-04-09T12:15:42.873Z
Excellent, thanks for updating the question! Hint, you may want to loo up non-planar printing, this may help create better molds if they have a shallow indentation!
0scar
CC BY-SA 4.0
2024-04-09T06:38:40.163Z
2024-04-09T14:13:13.303Z
2024-04-09T14:13:13.303Z
Bilal Bahadır Akbulut
<p>I have an STL file of a bone, and I want to create a mold to fill in with bone cement for a drilling exercise.</p>
<p>However, a midline cut through the mold doesn't work as the bone is atypically shaped. I would like to create a plane that follows either one of the bone's surfaces to create a mold that separates well.</p>
<p>Shape of the bone</p>
<p><a href="https://i.sstatic.net/v7xP3.png" rel="nofollow noreferrer" title="Shape of the bone"><img src="https://i.sstatic.net/v7xP3.png" alt="Shape of the bone" title="Shape of the bone" /></a></p>
<p>This doesn't work, as you might expect:</p>
<p><a href="https://i.sstatic.net/wKjrV.jpg" rel="nofollow noreferrer" title="This doesn't work, as you might expect"><img src="https://i.sstatic.net/wKjrV.jpg" alt="This doesn't work, as you might expect" title="This doesn't work, as you might expect" /></a></p>
<p>It should look like this:</p>
<p><a href="https://i.sstatic.net/2QFR0.png" rel="nofollow noreferrer" title="It should look like this"><img src="https://i.sstatic.net/2QFR0.png" alt="It should look like this" title="It should look like this" /></a></p>
<p><sup>Image source: The third photo from <a href="https://3dprint.com/61320/cranioplasty-3d-printed-molds" rel="nofollow noreferrer">Cranioplasty Welcomes 3D Printed Molds for Reconstructive Surgery in Russia</a></sup></p>

<3d-models><fusion360><medical>
How can I create a mold for an atypical shape for 3D printing using Fusion 360?
Bilal Bahadır Akbulut
# How can I create a mold for an atypical shape for 3D printing using Fusion 360?

(Asked by: username_0 on 2024-03-27)

I have an STL file of a bone, and I want to create a mold to fill in with bone cement for a drilling exercise.

However, a midline cut through the mold doesn't work as the bone is atypically shaped. I would like to create a plane that follows either one of the bone's surfaces to create a mold that separates well.

Shape of the bone

[![Shape of the bone](https://i.sstatic.net/v7xP3.png "Shape of the bone")](https://i.sstatic.net/v7xP3.png "Shape of the bone")

This doesn't work, as you might expect:

[![This doesn't work, as you might expect](https://i.sstatic.net/wKjrV.jpg "This doesn't work, as you might expect")](https://i.sstatic.net/wKjrV.jpg "This doesn't work, as you might expect")

It should look like this:

[![It should look like this](https://i.sstatic.net/2QFR0.png "It should look like this")](https://i.sstatic.net/2QFR0.png "It should look like this")

Image source: The third photo from [Cranioplasty Welcomes 3D Printed Molds for Reconstructive Surgery in Russia](https://3dprint.com/61320/cranioplasty-3d-printed-molds)

**Tags:** 3d-models, fusion360, medical


---

## 1 answers

### Answer by username_0 on 2024-04-09. Score: 3 | Accepted answer

I would like to thank @hfcandrew and @MagWeb for their in-depth explanations:

* [Creating a two part mold from organic mesh (bone sample)](https://forums.autodesk.com/t5/fusion-design-validate-document/creating-a-two-part-mold-from-organic-mesh-bone-sample/m-p/12672056#M316180)
* [Meshmixer: Newbie questions](https://forums.autodesk.com/t5/meshmixer/newbie-questions/m-p/10351368/highlight/true#M3435)

---

Quoting from the original forum post:

Here's how I do moods from shapes like this needing curved parting lines:

[![Ohne TitelX.png](https://i.sstatic.net/7hJzK.png)](https://i.sstatic.net/7hJzK.png)

Step: Finding the parting line of the shape:
MM's Overhangs shader (drag the sphere with the red bottom onto your object) is pretty useful if it is set to paint regions at its max angle. You can modify this angle in **Analysis** > **Overhangs**. Set AngleTresh to max (89°) and cancel the tool. MM remembers this setting to use it for the overhang shader:

[![Ohne TitelXX.png](https://i.sstatic.net/FIkm2.png)](https://i.sstatic.net/FIkm2.png)

Now drag this shader from **Shaders** onto your object.

[![Ohne Titel X2.png](https://i.sstatic.net/44bcn.png)](https://i.sstatic.net/44bcn.png)

Use **Edit** > **Transform** to rotate the object to an orientation where you get a meaningful border of red/white. You want to find a position where there are no white islands within a red area or red islands within white.

[![Ohne Titel X3.png](https://i.sstatic.net/BU6zZ.png)](https://i.sstatic.net/BU6zZ.png)

Now using the ViewCube switch to Bottom view. Make sure that you do not navigate for the following: Go to **Select**, select something (which region doesn't matter at all) and do **Modify** > **SelectVisible**:

[![Ohne Titel 2.png](https://i.sstatic.net/u5uDj.png)](https://i.sstatic.net/u5uDj.png)

Run **Modify** > **SmoothBoundary**. At its default settings, it will create a face group too:

[![Ohne Titel 3.png](https://i.sstatic.net/eK9tj.png)](https://i.sstatic.net/eK9tj.png)

Now you've found the parting line.

2. Design a parting surface:

From above you've got a face group. We want to use its boundary to deform a plane primitive:

For easier view drop the first shader from **Shaders** onto your object.

Go to **Edit** > **CreatePivot**. Set **PlacementMode** to **SnapToGroupBorders**. Double-click at the group boundary several times to get pivots at that boundary like this:

[![Ohne Titel 4.png](https://i.sstatic.net/vFMDn.png)](https://i.sstatic.net/vFMDn.png)

When done go to **Select** and double-click the face group to select it. Run **Edit** > **FitPrimitive**. By default, it will insert a square object. Set a high **MeshDensity** and make sure to check **CreateNewObjects**. Scale up the object using the transform widget. It needs to be about two times its fitting size:

[![Ohne Titel 5.png](https://i.sstatic.net/gqq6j.png)](https://i.sstatic.net/gqq6j.png)

Accept. Now there should be a FitPrimitive1 object in your scene. Leave **Select** and hide the shape object.

Activate the plane and select all of it (`Ctrl/kbd>+A). In Select go to Deform/Wrap.`

In **Wrap**, double-click next to a pivot to create a red sphere. Drag this handle to the pivot to make it snap to it. Do the for all pivots to deform the plane:

[![Ohne Titel 6.png](https://i.sstatic.net/OVEJ3.png)](https://i.sstatic.net/OVEJ3.png)

After accepting **Wrap**, you should discard all pivots. You may make them visible in the ObjectBrowser by clicking the pivot icon in the bottom-left of the browser. You may now show the source shape to check the parting surface:

[![Ohne Titel 7.png](https://i.sstatic.net/HMXP2.png)](https://i.sstatic.net/HMXP2.png)

Next is to construct the molds from that.

3. Construct solid molds:

At first, we need to create an offset shell from the source shape. Its **OffsetDistance** will define the width of the flanges later on. I use **Edit** > **MakeSolid** in Accurate mode which allows me to add an offset:

[![Ohne Titel 8.png](https://i.sstatic.net/p4iq1.png)](https://i.sstatic.net/p4iq1.png)

Drag the transparency shader onto this result (top-right in **Shaders**) and make a copy of the parting surface:

[![Ohne Titel 9.png](https://i.sstatic.net/7oiH3.png)](https://i.sstatic.net/7oiH3.png)

SelectAll of one **FitPrimitve** an use **Select** > **Edit** > **Extrude** to give it a thickness including the ghost shell to one side.

[![Ohne Titel 10.png](https://i.sstatic.net/4ENTw.png)](https://i.sstatic.net/4ENTw.png)

Do the same on the other **FitPrimitive** with a negative offset

[![Ohne Titel 11.png](https://i.sstatic.net/FBEgB.png)](https://i.sstatic.net/FBEgB.png)

Make a duplicate of the source shape. Hide all objects but one pair of source shapes and **FitPrimitive**.

Activate the extruded **FitPrimitives** as the first and hold down Shift one source shape as the second object. Run **BooleanDifference**:

[![Ohne Titel 12.png](https://i.sstatic.net/Iliyh.png)](https://i.sstatic.net/Iliyh.png)

Do the same with the second pair.

[![Ohne Titel 13.png](https://i.sstatic.net/902d9.png)](https://i.sstatic.net/902d9.png)

If the molds' sizes are bigger than your printer's volume it's to cut the halves. To do this **Edit** > **Combine** both halves to one object for now and run **Edit** > **PlaneCut** at **Slice(KeepBoth)**:

[![Ohne Titel 14.png](https://i.sstatic.net/prawl.png)](https://i.sstatic.net/prawl.png)

Run **Edit** > **SeparateShells** to split all of the mold's parts again.

---

From this point, I modified the technique described for my case.

I had to re-mesh and smooth edges quite a few times in Meshmixer to obtain a completely solid object without any holes, which enabled me to make a boolean difference.

Here is my re-meshed bone and the plane cutting through it:
[![Bone with plane cutting through](https://i.sstatic.net/BUske.png)](https://i.sstatic.net/BUske.png)

I made two copies of the fit primitive, and extruded them in separate directions:
[![Raw extruded mold](https://i.sstatic.net/aHB61.png)](https://i.sstatic.net/aHB61.png)

While this is not an elegant solution, I sculpted each mold piece to have a thicker mold that I can cut into orderly pieces, so I can print and compress the bone cement in between.

[![Green monster mold of nightmares](https://i.sstatic.net/un0Tn.png)](https://i.sstatic.net/un0Tn.png)

I cut a few planes through the mold, obtaining this orderly shape.
[![Note the bone within the mold](https://i.sstatic.net/uQ2oN.png)](https://i.sstatic.net/uQ2oN.png)

Now to print it:

[![Separate pieces](https://i.sstatic.net/UVQ5C.jpg)](https://i.sstatic.net/UVQ5C.jpg)

[![How they fit](https://i.sstatic.net/NYA1S.jpg)](https://i.sstatic.net/NYA1S.jpg)

Obviously, it would be better to create some mechanism to improve alignment(Ball/hole or some pins?).

But here is the end product, not dried yet:

[![End product 1](https://i.sstatic.net/BdaI1.jpg)](https://i.sstatic.net/BdaI1.jpg)

[![End product 2](https://i.sstatic.net/m4kcN.jpg)](https://i.sstatic.net/m4kcN.jpg)

> **Comments:**
> **username_1**: Please [edit] and include the relevant part of the link, if possible. However, in Magweb's answers alone, there are 28 images spread over 5 posts/steps - so probably not feasible.  
> **username_2**: Nice of you to come back and post an answer, however, at SE we expect answers to be self containing, not link only. As links on the net tend to rot, we need a summary of the answer in the link which will be retained on our own servers. Please [edit] your answer with a summary from the link, pictures are welcomed and can be inseterd to be hosted from our own image servers (also retained with the SE site).  
> **username_1**: I assume that the hfcandrew post is [this one](https://forums.autodesk.com/t5/meshmixer/newbie-questions/m-p/10339395/highlight/true#M3424)? Is that the correct post? That is just one animated gif, so it would be possible to post that - however, the image is too large to post (exceeds 2MB), I have just tried it. I have also tried to [resize the image](https://apple.stackexchange.com/q/351578/100490), but not had much luck. I guess this will have to be a link only answer. +1 anyway, for coming back with the answer :-)  
> **username_0**: I modified my answer using a combination of the original post and my own production process. Hopefully, this will help anyone who is trying to print a bone/organic material two-piece mold. Thanks for the pointers.  
> **username_2**: Excellent, thanks for updating the question! Hint, you may want to loo up non-planar printing, this may help create better molds if they have a shallow indentation!  

---

