3D printed threads in Fusion 360

[SimEyeSee]

After being inspired by @Josh-3D intro on how he makes a 3D printed thread, I have been thinking about ways to have more control over a 3D printed thread. I dived into it last night and figured out a very effective and relatively easy way to have full control over the shape of the thread.

First use the coil feature to make a thread that extends farther than the top and bottom of the cylinder. For the coil, use the Triangular(External) type and Section Position Outside, make the Diameter of the Thread slightly smaller than the cylinder, so that you can combine the thread and cylinder bodies if needed. Make it a New Body, which is important for a few of following steps.

Make the coil extend far enough on both ends of the cylinder so there is a small space between the ends of cylinder and the coil, as shown below.

Make a sketch on the bottom end of the coil to adjust the thread to the shape that you want. The 50° interior angles makes the slope 40°. I first tried 45° but I felt it made the thread too short for this particular part, and I think 40° will likely be good enough for printing. In the sketch, I added a fillet to the end and both sides of the base of the thread to round it out.

Use the sweep feature to adjust the shape of the thread. It is important to select the “Path + Guide Surface” type or it is likely that the sweep won’t properly align with the coil. Select the outside edge of the Coil triangle for the Path, and the top side (bottom should also work) of the coil triangle for the Guide Surface. Use the New Body Operation to create the thread.

Hide the Body of the original coil and the new Thread will be visible.

Use the split tool to cut the excess thread that extends past the top and bottom of the cylinder. Select the Sweep Thread as the body, and select the top surface as the splitting tool to remove the excess thread at the top (Make sure Extend Splitting Tool is selected), and the bottom surface to remove the bottom excess. Then just hide the new bodies that are created after the two splits to remove the extra thread. The picture below shows the Split being applied to the excess bottom thread.

After cutting the excess thread, part of the edge of the thread at the top and bottom is sharp. Sometimes a fillet can be added, but other times it fails. Sometimes if the “Constant” fillet doesn’t work, the “Chord Length” will work, other times, none will work. I have tried a few alternate ways to round the sharp edge, but nothing worked properly.

This is what the thread looks like when completed.

[SimEyeSee]

I’m going to slightly modify my answer later today. I wasn’t able to fillet the base of the thread with my original answer, but my adjusted approach should work

[user_3026326371]

I do threads for many years in Sketchup - worst program for 3D printing needs most say but does what I need.

Whenever I create a thread from scratch I use a spiral with the matching pitch and extrude the thread profile around it.
Results in a very nice control of the amount of triangle in the resulting model - Sketchup does not do true circles, only line interpretations.
I abuse this ‘flaw’ to use a number of sides that is doable in terms of print resolution.
Tiny edges and such are smoothed out by the slicer, means there is no need to start with 180 sides for a 6mm bolt…

Getting a thread profile that not just works on screen but is properly printable is not impossible, quite easy actually if you know how your overhangs turn out when printed.
What often is not though if creating longer threads by simple stacking sections.
If you encounter geometry issues when stacking your thread to get the required length try this:
Check where this is a proper junction point - like for those vertical lines over the pitch in your image.
Make this height the first cut and move up vertically to get to the next line in the same spot for the second cut.
Like this you have perfectly matching geometry.
In fusion though you can create custom threads with a few clicks, might be worth checking these tools to create some profiles for your printing needs ?

[SimEyeSee]

Which tool in Fusion are you referring to for getting custom threads in a few clicks?

The thread tool in Fusion has a few options, but unless there is a setting I didn’t notice, all of them have an angle of approximately 30° which easily fails when 3D printed. A small layer height can help prevent failure, but I wanted a thread that can be printed with regular print settings.

[Josh-3D]

This makes me want to dive in a little more again. I get a little frustrated with Fusion sometimes because it feels so… constrained. Haha. I want to go through your whole approach here though and see. There’s a few things you mentioned that I hadn’t considered/thought of.

The threads tool in Fusion 360 is… expansive but limited. Ha. I wish there was a thread tool that gave some ability to customize a few aspects beyond just selecting standardized sizes. I feel like I’ve gone through all the options it provides, and there’s just no specific plastic/print friendly threads.

Oddly enough creating threads in something like 3dsmax is pretty simple in comparison. Well, I mean plastic threads. Machined threads would be a little different.

[SimEyeSee]

I modified my answer. instead of the Intersect Sweep, I used the New Body Sweep and then hid the body of the coil because I couldn’t make the fillets at the base of the thread work with the Intersect Operation. So now both the edge and base of the thread is rounded.

[user_3026326371]

Here is some vids that might help better than what I can explain it…

How to add Custom Threads to Fusion 360! | Fusion 360 Tutorial

In case you wonder about the missing angles :
The minor and major diameter together with the pitch result in the angle.
So if you need a specific one and have no DIN reference or such you need to do a bit of math.

And here a guy nicely explain some design options :

Custom threads in Fusion360 (multi start thread, custom profile)

Might still no be ideal for everyone but those two vis should get you going

[SimEyeSee]

Thanks! I didn’t know you could do that.

[SimEyeSee]

It gives your alot of control. That is much better than doing it manually.

Here is a description of what you can control.

Sample XML with Functional Parameters:

<?xml version="1.0" encoding="utf-8"?>
<ThreadTable version="1.0">
  <ThreadType>
    <Name>Metric 3D Printed Plastic Threads</Name>
    <CustomName>Metric 3D Printed Plastic Threads</CustomName>
    <Unit>mm</Unit>
    <Angle>45</Angle>
    <SortOrder>26</SortOrder>

    <ThreadSize>
      <Size>1.0</Size>
      <Designation>
        <ThreadDesignation>1x0.44</ThreadDesignation>
        <CTD>1x0.44</CTD>
        <Pitch>0.44</Pitch>

        <Thread>
          <Gender>external</Gender>
          <Class>h14</Class>
          <MajorDia>1</MajorDia>
          <PitchDia>0.82</PitchDia>
          <MinorDia>0.64</MinorDia>
        </Thread>

        <Thread>
          <Gender>internal</Gender>
          <Class>G14</Class>
          <MajorDia>1.0</MajorDia>
          <PitchDia>0.85</PitchDia>
          <MinorDia>0.66</MinorDia>
        </Thread>
      </Designation>
    </ThreadSize>
  </ThreadType>
</ThreadTable>

Explanation of Functional Parameters:

1. <MajorDia>:

   • Effect: Defines the major diameter, which is the largest diameter for external threads and the smallest diameter for internal threads.
   • Explanation: This parameter controls the outermost dimension of the thread, ensuring that external threads fit into internal threads of matching diameters.

2. <MinorDia>:

   • Effect: Defines the minor diameter, which is the smallest diameter for external threads and the largest diameter for internal threads.
   • Explanation: This governs the innermost part of the thread profile, playing a critical role in ensuring the threads mate properly without excessive gaps or friction.

3. <PitchDia>:

   • Effect: The pitch diameter is the diameter where the thread’s profile is equally thick on both sides.
   • Explanation: The pitch diameter is crucial for achieving the correct fit between internal and external threads. It determines how tightly the threads engage and the overall strength of the threaded connection.

4. <Pitch>:

   • Effect: Defines the pitch, which is the distance between adjacent thread peaks (or valleys).
   • Explanation: The pitch determines how fine or coarse the threading is. A finer pitch (smaller number) results in more threads per length, while a coarser pitch (larger number) results in fewer threads per length, which can affect both the strength and ease of printing or machining.

5. <Angle>:

   • Effect: Specifies the thread angle, which is the angle between the sides (flanks) of the thread.
   • Explanation: This angle is typically set at 30° for most metric threads but can vary. In the sample, it’s set to 45°, which affects the overall thread profile and can make threads easier to print or manufacture, particularly with plastic materials.

Summary:

In this XML sample, the functional parameters that influence the actual thread geometry are:

• <MajorDia>: Controls the outer diameter.
• <MinorDia>: Controls the inner diameter.
• <PitchDia>: Determines the fit and strength.
• <Pitch>: Controls the distance between threads.
• <Angle>: Determines the thread flank angle.

[SimEyeSee]

I am putting together an XML file of 3D printable threads with options of tight or loose tolerances. The options will show up in Fusion’s thread tool.

[SimEyeSee]

I forgot to link this post to my post of thread definitions for Fusion.

3D Printing Thread Definition for Fusion Thread Tool

I created an XML file that can be imported into Autodesk Fusion to make threads for 3D printing available in Fusion’s Thread tool. The threads are made with a 45° angle instead of the standard 30° angle used for Fusion threads, and I adjusted the pitch and diameters and tested printing to make it ideal for 3D printing, at least I think it is ideal. You can’t add a fillet in the Fusion Thread definition file, so I add a fillet after using the Thread tool. I will describe the steps I use for makin…