topic Re: How to make a curvy worm gear? in Fusion Design, Validate & Document Forum

How to make a curvy worm gear?

Bajicoy — Tue, 05 May 2020 22:00:50 GMT

I am stumped, which is rare, Fusion normally handles any idea I throw at it like a champ. I can make a straight worm gear simple enough but I am having trouble getting the teeth to curve around the gear body like a globoid or double enveloping worm gear for that sweet sweet optimal surface contact. Any ideas or is fusion not ready for this kind of stuff?

Re: How to make a curvy worm gear?

Bajicoy — Wed, 06 May 2020 01:35:05 GMT

I did the math and put tooth profiles around the gear body every 90 degrees, then I tried using the 3D sketch tool of moving an arc but I couldn't snap it to any of the 2D sketches. help?

Re: How to make a curvy worm gear?

davebYYPCU — Wed, 06 May 2020 02:54:38 GMT

You can only snap to articles in the same sketch.

Create a 3d sketch while editing it,

Create > Project > Include 3d Geometry,

Select the common point on each tooth from those other sketches.

Hide source sketches and finish destination sketch.

Might help....

Re: How to make a curvy worm gear?

Bajicoy — Wed, 06 May 2020 19:02:06 GMT

Sweet, include 3D sketch is so powerful, I did have to double the number of planes but so far coincidenting arcs around the new projected points of the teeth is working, dunno what I am going to do next exactly but baby steps, I'mma get that curvy wormy

Re: How to make a curvy worm gear?

Bajicoy — Wed, 06 May 2020 19:45:31 GMT

Unfortunately, the rails are not considered smooth so the sweep dead stops every quarter rotation, rip me, it was all looking pretty good so far, maybe I need to try some other line tool than the arc

Re: How to make a curvy worm gear?

davebYYPCU — Wed, 06 May 2020 20:50:01 GMT

I haven’t tried to make Tangent arcs, do that,

i would use Fit Point spline with just four points per revolution.

Use a helper line at start and finish position, to create Tangent Constraint there.

Sweep will be Path, Rail, and Guide surface to prevent the tooth rolling along the rail.

Might help....

Re: How to make a curvy worm gear?

TheCADWhisperer — Wed, 06 May 2020 20:48:45 GMT

@Bajicoy wrote:

I can make a straight worm gear simple enough...

Is this supposed to be an example?

I see significant interference between gears???

Re: How to make a curvy worm gear?

Bajicoy — Wed, 06 May 2020 21:09:27 GMT

I am running into a sweep bug with splines where the sweep will not complete at 1.00 distance but will complete at 0.95-0.96 depending on the path and rails I select. Additionally the sweep does not follow more than a single path or rail and at the two unmanaged rails the profile changes from a sweep to an uncontrolled loft.

I then tried making a loft and it will generate a yellow path complaining about "Modeling Error: the rails cannot be tangent to the profile" and refuses to generate.

This is the closest I have gotten to a completed curvy wormy by abusing the sweep tool but the teeth profiles on the worm are very inconsistent. I think I have just about given up on the sweep tool at this point and I am out of ideas how to fix this. 😞

Re: How to make a curvy worm gear?

etfrench — Wed, 06 May 2020 21:11:00 GMT

Here's how I would do it. @TrippyLighting will appreciate this method 😀

Re: How to make a curvy worm gear?

Bajicoy — Wed, 06 May 2020 21:13:17 GMT

Thanks DavebYYPCU! Sorry for the slow reply, the spline helped make some excellent rails, just running into trouble with the sweep keeping a consistent profile along the path and guide rail.

Re: How to make a curvy worm gear?

Bajicoy — Wed, 06 May 2020 21:15:31 GMT

Hi TheCADWhisperer, the straight worm gear was the closest I had gotten to making a worm gear, I probably should have posted some proper curvy wormy pictures but I was being lazy and this was the least I could do to show I wasn't trying to make another straight wormy. 😛

Re: How to make a curvy worm gear?

TrippyLighting — Wed, 06 May 2020 21:20:41 GMT

Yes, I do. Thanks!

A good while ago someone posted a question about how to model involute gears, which also pointed to that site.

That particular model created a quad mesh and I've added it to my todo list of things to check.

It is often stated that Sub-D meshes modeling tools are not precise.

It would be interesting to see how much deviation there really is between an accurately developed mesh/T-Spline model and a CADmodel. I would predict less than 0.001mm. Good enough for most machining and definitely accurate enough for 3D printing.

Re: How to make a curvy worm gear?

Bajicoy — Wed, 06 May 2020 21:20:58 GMT

Thanks @etfrench , still learning the ways of the forum, I was really interested in otvinta and other guides but they tended to ignore how to make multi threaded curvy worms. I have a 20 tooth drive pinion and a 2 tooth wormy for a cool 10:1 gear ratio. It does help make me better understand the math I just guess-timated on for my tooth profiles lol

Cool to be getting replies on this stuff, I was worried I would go weeks in the dark 😄

Re: How to make a curvy worm gear?

Bajicoy — Wed, 06 May 2020 21:51:48 GMT

I got me a bug to report to fusion, maybe, idk, welp, time to play with lofts

Re: How to make a curvy worm gear?

Bajicoy — Wed, 06 May 2020 23:29:47 GMT

Got it!!! I made several lofts and then cleaned the rest up, woo, that is one sexy curvy wormy, I am treating myself to some ice cream, cheers all!

Re: How to make a curvy worm gear?

al28975 — Tue, 26 May 2020 22:35:02 GMT

This particular design may be impossible to assemble. Tooth pressure angle is usually little higher than the worm enveloping angle for assembly and for driving efficiency.

Easy way to model Globoid worm (I have gotten this program for free):

https://grabcad.com/tutorials/globoid-worm-in-inventor

Re: How to make a curvy worm gear?

Bajicoy — Wed, 27 May 2020 13:48:41 GMT

Assembly was possible and you're right that tooth pressure is not even. I had to do quite a bit of eyeballing to reduce backlash from milometers to micrometers and it is still significantly sub-optimal. Thanks for posting the update to the globoid excel sheet! I saw earlier it was only for solidworks and could not figure out the math to use the demo so I am happy to see fusion 360 support. Where can I download the excel sheet to give it a try? I couldn't find the link on spiralbevel.com.

Re: How to make a curvy worm gear?

al28975 — Wed, 27 May 2020 14:13:32 GMT

It used to be free demo downloads at spiralbevel.com
The 3d tooth surface is generated in Excel as igs. Then you import igs
tooth surface into Inventor or SolidWorks or other CAD and split your gear
blanks - cut teeth. It is convenient when you move between jobs with
different CAD but Excel remains the same. Can model gears in any CAD.

Re: How to make a curvy worm gear?

Bajicoy — Wed, 27 May 2020 18:27:27 GMT

cool, excel download link?

Re: How to make a curvy worm gear?

blaisebarrette — Wed, 27 Mar 2024 15:35:14 GMT

Hi all.

I may have found an easy way to design a globoid worm gear. It's not the exact perfect throated worm gear design. It couldn't be assembled unless the worm is split in half when 3D printed and both half would be assembled over the gear.

As I said, not perfect but the key thing here is that it's easy to design and repeatable!
The eureka to this idea is to sweep the profile of a gear in a circle while giving it a twist.

The path is the large circle. The smaller circle will be used to extrude the worm so this is where you experiment with overlap etc... I only go half distance because Fusion will throw an error if I go full circle. Twist angle is 360 divided by the number of teeth so that they match later when you do a circle pattern of two.

You can then do a combine cut to carve the worm.

There is still a bit of work to doo. There is interference between both parts.

So the next thing to do is a combine / intersect, keep the tool and create a new component containing the resulting bodies.

I only kept the two largest ones (in the center) and remove all the other ones.

I did a circular pattern on the two remaining bodies to the number of teeth and combine cut on the gear.

At this point all is left to do is add some tolerance. I opened the Offset command and widow dragged over the worm to select all carved faces and did a negative offset of the amount of tolerance I thought made sense.

Thats it!

Here is a link to the file if you want to check it out.

https://a360.co/4awr3uE

I have no doubt that this technique can be largely improved upon. Hopefully, this will inspire some of you to push it all the way to the perfect globoid worm gear!

- Blaise

(view in My Videos)