Dimension a spline on a drawing

[grunt58]

What is the correct way to dimension a spline on a drawing? While not that important (for me right now) as the CAM software will generate the path from the 3D model. Im just curious as to how it would be done if there was no model to generate the path and programing was done from just a drawing.

Points and angles?

Inspection is for another discussion...

Thanks

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[ewh]

A series of points.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[TheTick]

Whatever it takes to adequately define the geometry. It could be the defining points. It may include the curvature and/or angle at the endpoints, or even at points in the middle.

The math behind B-spline definition is well-documented, not hard to unearth with Google. I wouldn't recommend using that for inspection or definition purposes, though.

 

[grunt58]

The question came up from the way I got the spline. I copied entities from an existing solid model that Im designing around. The resulting spline had no points like if I sketched a spline so I'm nut sure how one would dimension that on a drawing. I guess I would put points on the drawing a define their location. Again this is all in house stuff and only in the quoting phase. Just curious more than anything.

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[KENAT]

Not a direct answer but maybe look at the use of model based dimensioning for this application? You can still have a partial drawing with reference to the model for the nominal/basic geometry.

There have been several threads about this if you're interested.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[JonSelby]

Really you should be specifying the spline in accordance with the standard to which you are working.
In the past I've used BS A19:1941 and recall using a note with something like "SPLINE 1/4" x 36 TO BS A19:1941". This standard is now obsolete and times have moved on ...

It also depends on how you are going to check the spline. If using a gauge its probably ok just to reference the standard. If using other inspection methods you probably want to note some of these ... number of teeth, pitch angle, dimension across flats, OD, ID, dimensions "across wires", radii.

The best thing I've ever come across for splines is Scwhanog Splining:

http://www.schwanog.com/produkte/produkt.php?id=75&Serration

The splines produced are utterly true (no twisting), spot on accurate and very quick to machine. See attached info!

Jon

Medical Design Eng - Glos. UK
NX 6.0.4.3 / TCE V10.0.3.8.6

 

[ewh]

Okay, now I'm confused...
I was under the impression that the OP was in regards to a b-spline curve (a sometimes random appearing series of points connected together), and not a gear tooth.
Perhaps the OP need to clarify.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[grunt58]

Wrong spline. A multiple radius curve; not a spline on a shaft.

Took me a minute to understand why you posted the link....

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[dgallup]

In the aircraft industry they just hold up cutouts to see if it's the right shape. Not sure how they figure out how much deviation is OK.

 

[ewh]

Depends on which segment of the industry. Most of it is MBD for such lofted surfaces today.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[fcsuper]

This thread is very similar: [thread559-269352]

Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion

http://groups.yahoo.com/group/solidworks & http://twitter.com/fcsuper

 

[ewh]

Eerie, ain't it? ;-)

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[grunt58]

Guess others are new to splines like me. We don't get into contoured shapes so this was something new.

I ended up dimensioning points.

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