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## Inventor General

Valued Contributor
Posts: 89
Registered: ‎11-26-2008
Message 1 of 12 (439 Views)

# Shortest distance across irregular surface

439 Views, 11 Replies
11-19-2012 07:38 AM

Quite often I need to measure shortest surface distance between two points (electrical tracking diatance) as in pic below. I can do it iteratively by taking a range of slices out of the part (2nd pic) and measuring the cut edge length but it's quite meticulous and time consuming. Anyone have a better/easier/faster way to do this? .ipt attached.

Thanks,

Jon.

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Message 2 of 12 (423 Views)

# Re: Shortest distance across irregular surface

11-19-2012 08:40 AM in reply to: Cnoj

I get error that file not checked out to me, but -

Not sure what the red and green cylinders are for.

Create axis through surface at desired point.

Create workpoint at intersection of surface and axis.

You can now measure distance between these workpoints.

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Message 3 of 12 (409 Views)

# Re: Shortest distance across irregular surface

11-19-2012 09:05 AM in reply to: JDMather

Does the check-out error stop you from opening the file? I just use Save As to remove check-out flags if I can open them.

The red/blue cylinders are the points I'm trying to measure between. If they were electrical terminals at high PD then electricity would 'track' across the surface taking the shortest path betwen terminals.

I don't fully understand your solution but it sounds like it would measure a straight line distance. I need the length of a curvy path following the surface.

Also I should add that my cutting solution from first post isnt ideal as it can only find paths that stay on a single plane, which won't always be the case.

If you can open my model and move the EOP down you should see my single plane attempt.

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Message 4 of 12 (398 Views)

# Re: Shortest distance across irregular surface

11-19-2012 10:21 AM in reply to: Cnoj

Cnoj wrote:

If you can open my model and move the EOP down you should see my single plane attempt.

I can open the file just fine.  There is nothing below the EOP in the file you attached - so I didn't understand what you were trying to do.  I thought you were after a straight line distance.

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Posts: 89
Registered: ‎11-26-2008
Message 5 of 12 (389 Views)

# Re: Shortest distance across irregular surface

11-19-2012 10:53 AM in reply to: JDMather

Sorry about that. Here's the correct part file.

WP3_offset param adjusts the angle of the 'measurement cut' which I'm using to get an edge to measure the length of.

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Posts: 89
Registered: ‎11-26-2008
Message 6 of 12 (350 Views)

# Re: Shortest distance across irregular surface

11-20-2012 06:41 AM in reply to: Cnoj

Here's another one. Pretty obvious that the shortest surface path from red to blue will not lie on a single plane.

Any ideas how you could plot/measure it?

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Message 7 of 12 (340 Views)

# Re: Shortest distance across irregular surface

11-20-2012 07:11 AM in reply to: Cnoj

if it's an obviouse "as the crow flies" straight line between 2 points along/around an object then could offset a plane above the points, create a 2d sketch with a line joining the 2 points, then 3d-sketch and intersect that line with the object to give you the creepage-path along the surface.  Use measure loop to get the length.

But... if it's something like the 2nd example where the shortest path isn't necessarily obvious (presumably direct to the "finger" and then around it instead of over the top) then i think you'll need to be creative and draw the expected path on the 2d sketch before intersecting in the 3d sketch.  Can't think of an obvious "minimum distance between 2 points but following a surface" which is what I believe you're after.

However it's done it's going to be an approximation as there's probably too many variables in the real-world which would affect the creepage-path (surface contamination/humidity/etc.)

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Posts: 692
Registered: ‎10-23-2012
Message 8 of 12 (330 Views)

# Re: Shortest distance across irregular surface

11-20-2012 07:23 AM in reply to: sam_m

Create plane, project cut edges, measure loop?

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Message 9 of 12 (322 Views)

# Re: Shortest distance across irregular surface

11-20-2012 07:35 AM in reply to: sam_m

"Can't think of an obvious "minimum distance between 2 points but following a surface" which is what I believe you're after."

That's exactly what I'm after, Sam_m. I'm not at all worried about real world stuff, just cad world for now

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Message 10 of 12 (315 Views)

# Re: Shortest distance across irregular surface

11-20-2012 07:43 AM in reply to: LT.Rusty

Rusty, it's not a simple cut with a plane tho.

Look at the cylinder with a finger example picture - a straightforward cut would cut the finger in half and provide a "shortest path" going up and over the finger (red path in drawing)

But, if you were an ant wallking from the red to blue points you'd walk in a straight line to the finger, to a point tangential with the path, then around nearly 1/2 the finger's circumference, to a point tangential to the straight-line to the blue-point - isn't that the shortest path? (green path)

(sorry for crude quick drawing - hope it makes sense...)

----------
but please understand that the solution may not be the answer you're wanting to hear...

If you have found any post to be helpful, even if it's not a direct solution, then please provide that author kudos - spread that love

Lithium - helping nntp users with mania, depression and headaches

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