3D Printing Screw Threads

There are many ways to make screw threads in SketchUp. Here is one more using the Spirix plugin …

One of the aspects of SketchUp that makes circular objects such an issue in 3D printing is the use of line segments to approximate an arc. This is glossed over by the visual smoothing functions that make even relatively crude circles look smooth. While this is fine for visual aids and drawings, any circular arcs that will be 3D printed will need many more line segments than usual. However, this is not a problem if you are only making a single part here and there. A complete car with all of its mechanical details, for example, would not only be a very large model, but it would also not be suitable for 3D printing in the first place.

As an example, I chose to make a large 1" bolt about 2" long with an ACME screw thread. I also deliberately used 400 segments for each circle to show that oodles of points is not a problem (100 would have been more than enough). As per the usual SketchUp caveats, I constructed everything at 1000x scale.

I started by creating a profile of the thread I wanted and grouped the lines:

I traced around the trapezoid to form a closed loop:

Then I used the Spirix “Create Surface” function to create one revolution around the Z-axis while “rising” 0.140" (140 @ scale). Note that I specified 400 segments for this operation:

I then edited the resultant screw thread to “heal” both ends of the thread (this seals it and makes it water-tight):

I then made the group into a component and replicated it 20 times:

In order to create the body of the bolt, I added a circle at the base of the first thread (using 400 segments) and extruded it up to the bottom of the top thread using the Push/Pull tool and grouped it:


To add a hex head to the bolt, I created a hexagon from the center of the cylinder (note the interference patterns):

Extruding this with the Push/Pull tool and grouping it gives the final bolt:

In order to reduce the cost of printing this, I used the Offset and Push/Pull tools to inset the hex head and did the same with the cylinder from the bottom:


Using MeshLab to inspect it shows more visual interference, but this is no cause for alarm since each component is water-tight in its own right:

There is somewhere on the order of 50,000 polygons in this model, but the use of a component reduces the actual size quite a bit. The exported DAE file is only 660KB and the model file itself is only 604KB (see attached). However, when I uploaded the file to a 3D printing firm, it took quite a long long while for its slicer to digest it, but it finally gave their stamp of approval:

As I pointed out earlier, 400 points for a 1" diameter circle is way way overkill. But it illustrates the point that using a plethora of edges is not necessarily difficult to do when approached appropriately. As for performance issues, this was all done in less than 10 minutes on a netbook with an Atom processor and 1GB of memory running Windows 7 Home Premium and SketchUp 8.

Bolt model in SketchUp 8 format: bolt.skp (603.0 KB)

Spirix plugin: https://sites.google.com/site/spirixcode/code/spirix.rb

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I’ve always been a sucker for a well-turned screw thread. Modeling them was an early fascination for me in SU, as I know it is for many other geeks as well. Combine that with a geekish fascination for wrenching elements, and you have…Nuts to You:

-Gully

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All along since I started fooling around with SU ten years ago, it seems that minimalism has been the gold standard of good modeling practice: the fewest edges and faces that could produce an effective visual presentation was best, or to put it another way, all other things being equal, less was better.

Now, as 3D printing becomes more of a commonplace, the rules are all arsey versey. [scratches head; looks thoughtful]

-Gully

I hear you. From my perspective, we’ve come full circle. In 1980, I worked with a machine shop that was trying to sculpt aluminum using 3-axis CNC machines. A telephone shape could be modeled using b-surfs, but the point-to-point moves of a ball-end mill traversing that shape numbered in the hundreds of thousands. Anything less and the facets became very apparent. But that was due to the method of iterating across a mathematically smooth surface. Since that time, I’ve liked the approach of using polygons for everything. The processing is much more robust and efficient with only a little trade-off in accuracy. I find it ironic that the same segmented results that were the bane of machinists 35 years ago continue to plague us today in 3D printing. LoL

Here’s an example of a pendant I had printed in steel:

Yes, the old truths do not stand the test of time very well. Even overly detailed models are practical using the appropriate design techniques as shown in the thread. However looking at the images in the previous post it looks like the actual printing process still has to advance a bit further, no matter how brilliant the underlying design may be (it is!) even if Jim cheated bit with the thread detail (1). I suppose it will be a matter of a year or two for the technology to catch up :thumbsup:

(1) joking, of course! :innocent:

Hi jimhami42,
I’m looking for a simplest way to build a screw (better say a simply screw without complex surface)
I tried to use this method https://www.youtube.com/watch?v=IT5r3AQZBnw
but the result is not what i’m aspect.


some one can give me and hand?

What sort of screw are you trying to build? Is it intended to be used as a visual model? Or something that you will be 3D printing?

it’s part of a 3D model I want’t to build, just for example I wander to build a regulable table the screw it’s the core of movement system

       |

[ <==== ------- ====> ]

| (Regulation Screw)
------- (Movement Screw)
<==== ====> (Movement Direction)
[ ] (Table Parts)

I hope this can be useful to understand what I mean, it’s just a model i don’t need precision or perfect functionality of it.
Thanks for you kindly reply.

If you are looking for a way to make a lead-screw, here’s an approach that may work for you:

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So useful, perfect for my purpose.
Thanks a lot for your help :joy:

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Or try this method…

Hey guys, thanks so much for this post - found it so useful!! Just trying to figure out how I can taper that thread off? In my model (screen grab below) I want to taper the screw thread off at each end so that it blends somewhat into the parts of the model above & below the screw thread… Any clue how I could do this? I tried making a rounded prism that I could use solidtools to subtract from the thread component, however it stuffs up the geometry when I try this… Sorry if this is self explanatory - I’m pretty new to doing models of anything that isn’t rectilinear/a cylinder at most!
Screw%20Thread
Thanks in advance for your help!