Metric screw thread model for 3d printer

[Anonymous]

Hi,

I'm brand new to Inventor and the first thing I'm trying to do is create an M4 screw thread that I can print on my 3D printer. I've followed some tutorials and think I'm 90% of the way there. I've been able to print a screw thread but my measurements aren't wuite right as the M4 nut does not screw on without a lot of force.

I'm trying to relate the measurements from this site  http://www.metrication.com/engineering/threads.html to my 2D sketch and then the appropriate settings on the coil but I can't work out how to do it. Screenshots of my 2D and 3D sketches are attached.

I'd be grateful for any pointers.

Thanks,

Aaron

[mcgyvr]

post the ipt file...

images don't help us look at the details/dimensions of your sweeps..

However does your printer even have the resolution required to print a m4 thread.. (I bet not) so you will have to adjust the profile to adapt to your printers resolution..

[JDMather]

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@Anonymous wrote:

... I've followed some tutorials ...

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Can you give the url to those tutorials here?  From the screen captures you posted - that doesn't look even close to the correct way to model threads.

Attach your *.ipt file here as suggested and end all doubt.

[Anonymous]

.ipt file attached.

My printer (Ultimaker 2) has a resolution of 20 micron and I have printed a m4 bolt I found on thingiverse that works alright.

This is the tutorial I watched https://www.youtube.com/watch?v=N52CBNo96As but as I said I'm brand new to this and am struggling to correlate the measurements from the thread specification to inventor.

Thanks.

[Anonymous]

I'll chime in!

So I can't open your part file because it is in 2016 and I'm in 2015. But I did look over your images and I watched a good bit of the tutorial video. Frist thing I feel compelled to touch on is that in the tutorial, the user patterns a sketch feature. This isn't recommended (at least not by me... and many others). Instead, moving forward, try to pattern 3D features and not the sketch entities that created them. This keeps your sketches simple and makes the pattern easier to manipulate.

Also, in every diagram of thread I've seen, the profile is parrallel to the centerline of the shaft. I'm sure there may be other ways? But if you had to do it the way you show, then I'd say the difference between the image you posted and the image the user shows in the tutorial video is the pitch of the coil. That's what's stopping you from getting that result.

[dag_h]

I've never modelled threads myself, but from skipping about in your linked video, it doesn't strike me as the way to go about making metric threads. There might be a way to use the method in the video to produce what you want, but I can't think of it.

Try modelling the shape above the table you linked to earlier, then use the coil function about the axis of the bolt.

The below yielded something that resembled a correct result for me, though the "bolt" was hollow, and would need trimming the top and bottom.

[JDMather]

That "tutorial" is absolute garbage and will not result in a correct thread profile.

Before I create a video of how to do it correctly - do you really really want a 4-pitch thread as shown in the video, or do you really want a single thread?  (I have never ever seen a fastener that small with multiple thread pitches.)

[Anonymous]

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@Anonymous wrote:

...do you really really want a 4-pitch thread as shown in the video, or do you really want a single thread?...

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This really is an important question. I made a quick demo video assuming that what you really want is single pitch threads, but if you needed 4 pitch, I would only need to change a couple of things about mine and I can show you what I would change if that were the case. But since I highly doubt it is, here's how I've come to model threads:

It should also be noted that the ends of the shaft are typically chamfered (as in I can't think of a time that they're not but can't garuantee that they alwasy are) but I don't show that here. All you would have to do is apply a chamfer before the coil and you're good.

[JDMather · Accepted solution]

Here is my example with thread modeled specifically for 3D printing.

I used 0.1 as my process tolerance, you can adjust depending on your printer.

Turn on your sound.

Note the 0.1 clearance I cut from the Ø4mm and added to the cutting tool to remove extra material from the thread form for 3D printing.  Adjust this number as needed for your printer.

[dag_h]

Well, that was a much simpler and more beautiful way of getting there. I'll hopefully manage to modify my workflow to something like that, if a similar challenge appears at work.

One nitpick though, the Dmaj of 4 mm seems to extend only out to the flat peak of the sketch the OP linked to, not the peak of the V. I made the same error when making my own sketch. Just something for the OP to take into consideration when modelling his own solution.

[Anonymous]

Great tutorial, thanks a lot (one very minor point which I "think" is incorrect is that the very first rectangle is created with a 4mm height when it should be 2mm since the revolve operation will make the shaft diameter 4mm, of course I could have just mis-interpreted something).

I've been tweaking and printing for the last couple of days to test out printing different thread sizes.

Printing long m4 threded shafts did prove to be problematic as the plastic filament warps pretty badly. I switched to m6 instead which works better. I've attached a picture of a m6 screw thread printed with PLA based on the technique in the tutorial. The nut is a tiny bit loose so I'm still mucking around to see if I can improve it.

One thing of note for anyone else visting this forum thread is that printing such small tolerance shapes with hot plastic is tricky. The same print with PLA and ABS plastics results in a usable thread on the PLA and not the ABS. I suspect this is down to the ABS not contracting as much as it cools resulting in a thread slightly to thick for the nut.

[JDMather]

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@Anonymous wrote:

.... I "think" is incorrect is that the very first rectangle is created with a 4mm height when it should be 2mm since the revolve operation will make the shaft diameter 4mm, of course I could have just mis-interpreted something). 

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What does this symbol Ø mean to you?

Go back and watch from 1:27-1:35 again.

[JDMather]

Internal threads for 3D Printing.

Adjust the clearance to for your printer and desired fit.