Constructed Cone HELP. (CAD File Attached)

[jshields]

The attached part has a conical profile that I need to construct a cone from. I will use this cone axis to align my Y axis to for my machine alignment then will measure with more points to report the form of said cone. I measured vector points for the machine alignemnt and constructed a cone which constructed in the correct direction, but with incorrect dimensions both from the CAD model and the measured. I know the model is correct as I created it. The cone should have a 15° included angle (7.5° per side.) Nonetheless I used that to align my axis and began a measurement routine. Measuring the vector points for the cone and constructing the second time either fails, or creates a cone with an axis in the Z when is should be in the Y.

I would appreciate any help from someone who has knowledge of constructed cones.

DCC Gage running PC-DMIS 3.5 MR2

[JamesMannes]

How many points? you need at least 9 (3 levels of 3) to get a good vector. Also, the workplane you are in is important. With a "Y" vector, you need to be in the "Y" workplane.

[John Kingston]

The order you pick the points that construct the cone is important. How many rows of points are you using? Try at least 3 and pick level 1 going CW, level 2 going CCW, then level 3 going CW. I don't use cad, and have to calculate my vectors. You may want to double check your vectors, as I understand it they are not always picked up correctly from the cad model.

[cmmguy]

If I needed to align to a cone axis, I might be inclined to measure three circles and create a 3D line through them and use that as my axis...

[jshields]

I had tried changing my workplane to Y-Minus and even Y-Plus with the same results. I am measuring 6 points for the alignment measurment and 16 points for the final measurement. I will try to get 9 for the alignment, but when I hade more than 6 before it would fail. I think maybe I am not getting them all in the same row closely enough. As you can see from the picture I only have about .375 aound the rim to measure on. My last gig was on a 2.5meter x 7meter dual arm Vento measuring truck frames, these small parts are giving me a headache.

[jshields]

Do you guys think I should change my workplane BEFORE measuring the vector points that I am using to construct the cone, or just before the construction of the cone?

[Matthew D. Hoedeman]

Do you guys think I should change my workplane BEFORE measuring the vector points that I am using to construct the cone, or just before the construction of the cone?

Vector points are plane-independant. There is no workplane for a vector point. HOWEVER, I would also do it as 3 circles as was suggested, then do a 3-D line through the centers of the circles. As for the DCC cone, I would NOT use an AUTO-FEATURE cone but a learned DCC cone, 3 levels, 4, 5, 4 hits per level.

[jshields]

I'll try it both ways on the alignment and see which works best. As far as the measurement, I only have cad here and not cad++ so I do not have many auto features, only point, circle, and cylinder so I will be doing it by construction. Thanks for the help!

[Matthew D. Hoedeman]

I'll try it both ways on the alignment and see which works best. As far as the measurement, I only have cad here and not cad++ so I do not have many auto features, only point, circle, and cylinder so I will be doing it by construction. Thanks for the help!

If you can construct a cone, can you not also measure one (NOT using auto-features)? If you can measure a cone in manual mode as a cone, you can measure one in DCC mode and it becomes what most call a 'learned' feature, ie, a DCC feature VERY simular to an auto-feature. This is the best way to measure a cone from what few I have had to do and from what I have read on the various boards.

[jshields]

I can measure a cone. The only reservation I have doing that is that the nominals wil be set by the feature which I will then have to change. I rarely ever do that type of measurement except in manual as I trust the math more.

[jshields]

Problem solved! Thanks guys, I rearranged my points to where they were all parallel to the X axis and that worked much better. I also used "find" for the Z component of the vector points, then "find vector" to reset the vector for each point. Worked like a champ!