Proper way to detail an ellipse

[jjellin]

Hello All,

I've created an ellipitical plate needed for an assembly. My probelm is what do I need to fully define it as a 2-D drawing that a machinist to understand. Right now all I have is the major and minor diameters and axes, as well as the overall centerpoint. If I gave this to a machinist would that be enough or do I need to find other points and radii. If so could someone lead me in the right direction of what I need to dimension.

Thanks,
Jason

 

[Rentapen]

Give em as much as there'll take. As least; Large & small radius and the center points of these. From each quad, X/Y dim @ 30 degree, 45 degree, and 60 degrees. Full size templets are the best or at least one quad.
Just Wandering.
The rentapen

 

[petersn]

Major diameter, Minor Diameter, location (and orientation), are all that I've ever used, and that usually gets the job done for me without any calls from the machine shop - I too was once 'skeptical' like you about 'will the machinist be able to do', but I've since found out they've usually been able to figure it out without any further input from me.
Good Luck - You might be pleasently surprised.

 

[gearguru]

The diameters should do it, they define the ellipse completely (next to the origin and orientation).
But I would also include the GD&T tolerance of the profile, if it has to match another part. Of course it all depends of what are you designing.
gearguru

 

[Curmudgeon]

I *really* hesitate to suggest this, but is it possible that you can live with a 'template' for the ellipse? In other words, what accuracy is required?
Could a simple (metal, wood, paper ?) template suffice?
If so, you can have a discussion with your better shop-guy(s) and have one template made up to meet your needs, and save a LOT of possible confusion.
Of course, if a template won't work, you may need to have a trained worker, or spend some training time on the workers (plural) that will need to do the job.

Curmudgeon

 

[jdsewell]

the only way that i know an elipse can be can is with a cnc or an nc with some pretty advanced controls. in either case, center point and diameters/radii would suffice.

 

[OldestToolDesigner]

Depends on what accuracy you need on the elliptical shape.

An approximate ellipse is obtained by using the major and minor radii and and the X and Y overall dimensions. Some blending may be required at the intersections of the radii. There is a standard drafting procedure for constructing and dimensioning these.

To obtain a true ellipse you have to project points from a circle and spline them. EG: Using basic descriptive geometry draw two views of the circle, plan and side ( a line), slice the plan with planes then project the intersections from the side view at the angle required to obtain the ellipse. Again, any descriptive geometry book should show this procedure.



Al Kirby
askkkf@avci.net

 

[SnowCrash]

Gee, I hope you are able to start this with a CAD file. Sw orks has the elipse as a sketch tool.
If you are making this piece with a CNC machine, output an iges file to the CAM operator. They should be able to program from this. Some machines will have the function built in.
If this is being done by a flame cutter, then do a plot on mylar.
If the poor sucker has to do this by hand on a milling machine, then use a spreadsheet to generate an xy table of values.
If sending this out to a blacksmith . . .

Crashj 'your lucky day' Johnson