Need a bit help here

maurice_rietveld · May 3

Hi All i wanna build 2 kind of things for my childerens marble track. Well i try different things i made a lot already but kind of this pices i can not make it… seems that i do something wrong and i dont know what it is… Can someone plz help me a bit out here :)

this is the first one the circle of the ball track is 25.8, 3mm from the sides and 6.3 mm from the bottom.. i can make it in tinkercad but onshape is a bit different haha also i nwanna make this piece and have a link for that one :)

https://cad.onshape.com/documents/7fd4ecdd33e2c563ee82d4e8/w/171d0d2568cb9c494e79d005/e/5420bbbb94df4451fe384d0e?renderMode=0&uiState=6815e5236540381ed896033c

Thanks already!

EvanReese · May 3

Fun project! If you're going to be making a lot of these kinds of add-ons (or at least plan to lie to yourself about how you'll totally get to it someday), then you should use a Variable Studio to put in major dimensions, like ball diameter, clearance, wall thickness, and so on. That will make sure any dimensions that use those are exactly the same and let you update them all at once across all of your parts if you need to. For example, you might get a few prints in before deciding you need a little bit more clearance. That change would be easy.

Here's an approach to the first part, and I included an example Variable Studio for you. https://cad.onshape.com/documents/a2d2a8c97bfbbddebeb09af8/w/abd723e7810da80eca81c9cf/e/f97fbd0cb8b1d4d2e3af6a69

What's your issue with the loop model you linked? Seems usable to me.

maurice_rietveld · May 6

Hi @EvanReese ,

The problem with the loop is that the ball stuck if its going up, the track is smaller over there. the loop needs to be a bit smaller so the ball hold the speed when it is going in now the loop is a bit to big so sometimes the ball is falling down.

maurice_rietveld · May 6

https://forum.onshape.com/discussion/comment/116764#Comment_116764

The problem with the loop is its a little to high, and when the ball go's up the bal stuck on the sides so the track is smaller when it go's up… :)

jelte_steur814 · May 7

you're quite close already.

add some direction control for the sweep and it'll work.

sweeps are often self interfering when the path takes bends that are too sharp. So that may be something to look out for when making changes

https://cad.onshape.com/documents/8500ecbf5292df35d2b8decf/w/821d0bbe175672fc8fd07004/e/875e54b8dc2fbad19adb7a9a?renderMode=0&uiState=681b0459a5712a4a971dadbc

MDesign · May 7

https://forum.onshape.com/discussion/comment/116868#Comment_116868

His issue is the ball gets pinched when it rolls up the slope. The sweep tool is not maintaining this dimension shown by these two points. The source dim is 25.8mm, but this is 21.2mm

MDesign · May 7

And even smaller at the peak.

MDesign · May 7

https://forum.onshape.com/discussion/comment/116822#Comment_116822

I suspect your tinkercad model has the same issue. Can you verify that?

MDesign · May 8

@maurice_rietveld You can mitigate some of this pinching by providing more profiles along the curve by using loft with a path, instead of a sweep. But you will need to adjust some dimensions to keep it from self intersecting..

jelte_steur814 · May 8

@MDesign : You're right.

another (more laborious way) that does provide good results (I believe) is to derive a routing curve, create a boundary-surface as a helper to create the sweep: like this (blue helper surface to use in the sweep as "lock profile face".

so the blue surface has to point in the direction the ball needs support fom the track.

https://cad.onshape.com/documents/8500ecbf5292df35d2b8decf/w/821d0bbe175672fc8fd07004/e/875e54b8dc2fbad19adb7a9a?renderMode=0&uiState=681c5a370a6369260851d8a3