How to enlarge threads for 3D printing?

[Anonymous]

I've figured out thread modelling, and thanks to this excellent post I know how to chamfer the ends of a threaded portion, but I can't figure out how to slightly enlarge internal threads to allow for 3D FFD undersizing.

On my FFD printer, holes tend to be just slightly undersized (thread slump, imprecision, etc.), so I've found that if I upscale the internally threaded part by about 10%, I get good engagement.  Thing is, I don't want to upscale the whole part -- just the threading.

How?  Thanks.

[JFKANSAS]

I'd think of this in terms of trying to imitate injection molding by instead 3d printing the part. Generally threads in injection molding aren't molded. They are either tapped afterward, or the screw is just inserted into the plastic and the threads are formed by the screw.  

[Anonymous]

Hi, have you tried nonuniform scaling of the body, to enlarge the threaded hole radially but not longitudinally?  Also, to apply scaling specifically to one section of a body, you should be able to split the body along some planes into separate bodies.  I haven't worked with threads yet, but would be interested to also try Push/Pull to see how it modifies the threads.  Let me know if it works or need some help.

Jesse

[hato54]

I use to do that in my printer software (Makerbot desktop) even if the whole body is resized.

[HughesTooling]

One thought how about making a separate boss with the scale added then copy it to the correct points in your model and then use Combine. You could even make the bosses in a separate file and insert them.

Mark.

[prainsberry]

I think one approach you could take would be to make just the threaded area into a seperate body.  Then scale just that body.  Here is a quick video showing a simple approach.

http://youtu.be/BtyFdWCLhO4

I'd be interested to hear more about how you use this technque with your printer and if it is successful.  I am looking at some different things around desigining for 3D Printing right now.

[Anonymous]

Really appreciate the walkthrough -- I'm (obviously) just learing Fusion 360 so the narrated walkthrough was extra helpful.  I will try this out when I'm back at that workstation this evening.  (Just to verify: the threads scaled with the containing object?)

SLA would probably yield better results on both total dimensional precision and feature precsions, but what I have is FFD.  My findings across about 20 experiments this weekend are that I may or may not need to scale the screw part down slightly (or the nut part up), but I definitely need a deep thread engagement.  The most success I had was with M7x1, but I'm not getting enough thread engagement for good hold.  (M7 is the largest I could go for the application I was working on.)

(Let me see if I can add a picture...)

Here's my parts; I'm getting the best detail (again, working around the limitations of FFD printing) by printing the bolt-part as shown, and the receiving part flat on the selected face.  Edges and threads are pretty clean, and engage well -- until I really crank down on it, at which point they slip.  I'm thinking of combining your scaling with using an Acme thread as my starting point, perhaps pullingthe thread face.

Failing that, I may try just crafting an extra-deep thread from a coil primitive.

[Anonymous]

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@JFKANSAS wrote:

I'd think of this in terms of trying to imitate injection molding by instead 3d printing the part. Generally threads in injection molding aren't molded. They are either tapped afterward, or the screw is just inserted into the plastic and the threads are formed by the screw.  

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In this case (admittedly, it's a bit of an exercise) I'm actually trying to form the complete functional part via printing. My initial approach was actually a nut slot for drop-in hardware -- but I decided to try to think printable. See the picture I posted below for the current state.

[Anonymous]

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@Anonymous wrote:

Hi, have you tried nonuniform scaling of the body, to enlarge the threaded hole radially but not longitudinally?  Also, to apply scaling specifically to one section of a body, you should be able to split the body along some planes into separate bodies.  I haven't worked with threads yet, but would be interested to also try Push/Pull to see how it modifies the threads.  Let me know if it works or need some help.

Jesse

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Not yet (tried non-uniform scaling), because I couldn't figure out scaling at all until prainsberry's video. I had gotten as far as splitting the body; that allowed me to have the required 6mm shaft and move up to a 7mm threaded section.

In re. pulling the thread face, I've only played with that for a few seconds, but it yields... odd results.  (If somebody figures this out, please chime in.)

[Anonymous]

In re. pulling the thread face, I've only played with that for a few seconds, but it yields... odd results.  (If somebody figures this out, please chime in.)

[Anonymous]

[Merged with previous.]

[prainsberry]

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@Anonymous wrote:

 (Just to verify: the threads scaled with the containing object?)

If you follow that method in the video, just the new body with the threads would be scaled. Then you merge it back into the unscaled rest of the body.

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