Rope/wire cable/chain in motion?

[KMoffett]

Is there a way to 3D model a flexible part like rope, wire cable, or chain? Think of it actually moving in a linear to rotary to linear manner around a pulley in a GeoMagic assembly.

Ken

 

[bigseb]

For a chain, you need to model one link then open an assembly window and add however many links you want. Create axis as your straight section and constrain the links to the axis and to each other. Similar process for around the pulley. Rope, being made of one single piece as opposed to segments must be modelled accordingly.

I modelled a chain on my manual pallet stacker. Have a look there.

 

[KMoffett]

Thanks!

 

[Lew_Merrick]

Sebastian,

But how do you constrain it such that (using rollerchain as an example) mates to the sprockets, yet moves between them in straight lines?

 

[bigseb]

Oops just reread this thread and realised I didn't see the 'in motion' bit. My reply above was for constraining a static chain.

My apologies.

 

[RCH_Projects]

Is there a way to 3D model a flexible part like rope, wire cable, or chain? Think of it actually moving in a linear to rotary to linear manner around a pulley in a GeoMagic assembly.

Ken

Only with the API.

Use an angle constraint on one sprocket and use increments in the API to rotate relative to a plane.

For each link create a set of constraints that alternate between link to link (plane) aligned, tangent to tooth(teeth) on sprocket (or a "hidden" pulley overlapping the sprocket).
Ripple the contraints (suppress / un-suppress) as the angle on the pulley is updated.

Depending on your approach and degree of program sophistication you could drive other sprockets (if you include suppressed / unsuppressed constraints to them and keep track with the program).
Perhaps use the angle constraint plane and an axis on every n'th link.

The 3DS assembly update will be slow so something as simple as Excel or MS free VB will suffice (unless these are slowing down the API and I don't know).

You can save snapshots if you have software to string them into a movie.
It will put out as much effort as you put into it but there is no "Geo-magic" to spare.

I am battling round-robin constraint fails on a challenging design anyway, so if you give it a go it could get rough.
For just a few links of movement you might use manual increments for a faster one time project.


From "Can't get a simple constraint to work"
viewtopic.php?f=10&t=16263

Keith
Try making the third constraint between an edge and a face, this may work around any slight misalignment between the parts. Remember that computers are digital, decimal numbers are approximated to a lot of decimal places to a base 2 number. While GD tells you that the angles are 90 deg, they are really a digital approximation of 90 deg in radians to base 2. If the approximations are rounded to a slightly different number you will get over constraints, hence using an edge instead of a face can overcome this. You should always try to design your constraints to avoid this rounding problem, eg. do not constrain a cube inside a cube by 3 faces.

Jim

I may apply this (avoid faces) to my current application to see if it helps.

Motion 2 is supposed to have 2D contact but with other considerations the outlook is dim from overhead considerations.