How to model this part....

[egoaudio]

Hello there, 

I am trying to make an improvement to my baby gate where i add a latch to keep a door open. The attached image is the part I am trying to replicate/add onto. 

I've tried a few sketches to cut the teeth into the top of the cylinder and from the side using the extrude feature with taper but it does not get it exactly like the part. 

Any ideas will be greatly appreciated! I'm just a hobbyist who 3D prints some useful things for home. 

Thanks,

Erik

[davebYYPCU]

For the first tooth, Extrude with taper, should work, 

another way, is the single tooth profile, and a second sketch with the tracks to Sweep with Guide Rail.  Top view defining the taper like spokes in a wheel.  Do one then circular pattern, the rest.

I think it is called a Hirth joint, search in here you will find some other threads about it.

Might help...

[egoaudio]

Thanks, Dave. Extrude with taper leaves some high areas that don't fully look like the part (see image). 

I will try the other way with rails. I haven't used rails yet but I will look into it. thanks!

[davebYYPCU]

Your pic, is plain Extrude, can’t see any taper.

The taper angle is half of the top view rails angle.

To keep the top of the tooth parallel to the valley, it would be a Patch Loft.

Are you adding the tooth, or cutting the Valley?

[egoaudio]

I think I see how I've messed up. I can add taper to my profile cut and it should work (3rd attachment)?

[davebYYPCU]

You are closest with the 2nd picture, but way off with the other two.

Your triangle, outside the cylinder, attached to the two top lines, and Sweep along those two top lines towards the middle.

Might help....

[egoaudio]

in that scenario you describe, how do you get it to sweep to the point in the middle of the part? it looks like everything is pointing to the very middle of the part (the axis) but how could I sweep the triangle to the center axis of the part? wouldn't I need to have a small sketch in the center?

Thanks, Dave.

[davebYYPCU]

Sweep starts at the profile, and goes as far as you want, factor 0 to 1, of the length of the path, 

However, the triangle is being scaled as it moves so right in the middle, it will be reduced to a point.

If you are looking for constant height, it has to be loft cut with two different triangles on each side of the rim, aligned with your top rails.

Might help....

[mavigogun · Accepted solution]

One Solution, using Patch.   It seemed to me securitizing the photo the teeth might feature a pitch, describing a very shallow cone shape/up-slope toward the center- ergo, my solution.    I worked out what I wanted to do as I was doing it- so the use of Sketches is a bit of a mess- still, the How of it is pretty clear in the attached design.

[egoaudio]

Both you and Dave have been a big help! Really appreciate you both taking the time to assist. I will be practicing later this evening to make sure I get it right. 

Happy holidays y'all!

[chrisplyler]

An easy Extrude method is in this video... although depending on exactly the profile of the teeth you need, you might be better off defining (accurately dimensioning) the triangle in a sketch on a plane tangent to the outside of the cylinder and then lofting it in to the center point.

[egoaudio]

THanks, Chris. but I don't think  you can loft to a line from the tooth profile tangent to the circle. I can loft to a point but cannot loft to a lint in the axis of the part..... so the tooth has a pitch to it which aI may or may not want. 

I think Patch will work but I can't combine the patch bodies to my other body (circle) yet. 

I would love to do it the way you've decribed because I think it's simpler but how to loft to a sketch line/axis?

[TheCADWhisperer]

See these >>threads<<.

[mavigogun]

---

@egoaudio wrote:

I think Patch will work but I can't combine the patch bodies to my other body (circle) yet. 

---

Stitch the Patch surfaces until transformed to a solid BRep, then Combine.    Those Patch surfaces necessarily must fully enclose a volume with an inside and outside for the transformation to occur. 

[chrisplyler]

@egoaudio  that's right, you cannot loft to a line in Model space. The work-around is to set up a smaller triangle at a smaller radius to loft to instead of lofting all the way in to the center. It looks something like this:

[egoaudio]

Fantastic video! I dig it. Thanks, Chris.