Constrains qeustion - Spheres and holes

[OpticMech]

I’m new to Inventor, just got Version 6.

I am having trouble with a constraint problem.

I work allot with lenses, so a sphere locating on a hollow cylinder (a spacer) is a common occurrence, to properly space two lenses. I have not been able to constrain this geometry.

I assume the same would be true of a ball on a plate with a hole in it. Say the ball had an Dia of 5 and the hole has Dia of 2 the ball would fall into the hole up to the cylinder diameter and have a specific height off the top of the plate. How would I set this type of constraint?



Thanks

 

[Courtancer]

You could try a tangent constraint. If you click on the "place constraint" button, under the "type heading, go to the 3rd button across which says tangent and then click on your surfaces.
I hope this works for you.

Andy

 

[OpticMech]

I think I tried every possible tangent combination possible. I had limited success with putting a chamfer on the hole/cylinder (tangent of a cone to a ball), but if the radius of the ball greatly exceeds the Dia of the hole the ball hovers above the pane it should be dropping into.

I also tried a fillet on the hole edge, but Inventor wouldn't allow me to apply a tangent constraint to the torriod.

Any other ideas out there?


-d

 

[cadranger]

You need to mate the centroid of the sphere (you're talking round like a ball bearing here, right) to the center of the hole at the surface or one of the holes if goes right through the part. This will show up as a little green dot. Next you can mate one of the origin planes of the sphere to the surface where the hole breaks out. You can adjust the offset of this constraint with any value in the edit box.

 

[autocol]

okay, this will be difficult to explain, and i don't have inventor here at home so i can't even try it, but give this a shot:


model your sphere as a revolution, making sure you projected the origin point of the part file onto the sketch so the sphere is definitely locked onto the centre of it's coordinate system.

whack another sketch on the xy plane, and slice graphics. use project geometry to project the outer "circle" of the sphere onto your new sketch.

draw a line from the centre of that circle to the perimeter, vertically downwards.

draw a line from the centre of the circle to the perimeter, on an angle down to the right. continue drawing from that point, horizontally to left, to join your vertical line somewhere.

you now have a right angled triangle in the lower right hand quadrant of your sketch, yes? if not, yell back and i'll post an image for ya on my site when i actually try this!


okay, the dimension of the horizontal line is related to the diameter of the hole you want to drop the ball into, to be precise, it's half (or equal to the hole's radius, if you prefer)... entering that dimension will lock the vertical position of that line.

use that line to create a workplane in your sphere part.


finish edit.


constrain.


simmer and repeat


as i mentioned, this is only in theory, i haven't tested it, so ask away if i either a) explained it poorly, or b) explained a method that doesn't work

 

[OpticMech]

Autocol,

Thanks, real close too the solution my reps came up with, only I do it all on the base sketch making the right triangle out of construction geometry.

I know I should’a posted the answer as soon as I got it, but it was one of those got the answer and ran with it.

Regardless, yours was the only answer in this forum that was on the mark.

Thanks!

OpticMech