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?
How to make a curvy worm gear?
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?
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
@Bajicoy wrote:
I can make a straight worm gear simple enough...
Is this supposed to be an example?
I see significant interference between gears???
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. 😞
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.
Accepted solution
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!
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
