Using a cone for an origin

[pgardner]

When checking the location of several cones in a plate, the engineer asked to reference from a certain cone. After setting the X-Y origin as asked, the output for this datum cone is not 0,0. Anybody have an explanation for this? Thanks, Pete

[Matthew D. Hoedeman]

Is this due to a re-check or are you measuring the cone, aligning to it, then dimensioning the cone? Are you measuring it in DCC mode?

[pgardner]

The cone is measured in DCC, then aligning to it, and then we are dimensioning the cone.

[bw_bob]

Are you leveling or just setting orgins ????

[Matthew D. Hoedeman]

Yep, the order in which you DO the alignment will also have an effect on the results. For example, if you origin XY to the cone THEN level to a plane, it WILL change the location of the cone, if it is NOT 100% perp to the plane.

[pgardner]

Sorry, I'll give you more details. All features are measured in DCC. Each cone is theoretically perpendicular to the leveling plane. The alignment is leveled to the plane and rotated using the long side of the part. Each cone is then measured. Prior to outputting the desired measurements, the alignment is reset using the same plane and line with the datum cone as the x-y origin and the leveling plane as the z origin. The x-y output for the datum cone after this re-alignment is 0.001, 0.0001; not 0,0.

[#2#]

Sorry, I'll give you more details. All features are measured in DCC. Each cone is theoretically perpendicular to the leveling plane. The alignment is leveled to the plane and rotated using the long side of the part. Each cone is then measured. Prior to outputting the desired measurements, the alignment is reset using the same plane and line with the datum cone as the x-y origin and the leveling plane as the z origin. The x-y output for the datum cone after this re-alignment is 0.001, 0.0001; not 0,0.

Looks like your cones aren't perpendicular to your plane. The numbers your are seeing are the location of the vertex of the cone. If you want the location where the cone intersects the plane, you need to construct a point or circle where the cone intersects the plane and dimension that.

[pgardner]

Goodluck, That sort of makes sense to me, but if the x-y output of the cone is at the cone vertex, wouldn't the software use that point for the origin and reset it to 0,0?

[#2#]

Goodluck, That sort of makes sense to me, but if the x-y output of the cone is at the cone vertex, wouldn't the software use that point for the origin and reset it to 0,0?

You are correct.

I think the problem lies in the alignment. When you do the alignment do you level first and then transfer the axis as Matt sort of suggested?

[pgardner]

Yes, I always level and then transfer the axis, then set the origins.

[#2#]

Hmmmm,

Did you execute the entire program after creating the dimension? I have had cases where alignments didn't 'show up' for one reason or another during a partial execution.

[pgardner]

Yes, that's the first thing that I checked with the programmer. She has since tried the same thing on a new part in a new program with similar results.

[cmmguy]

Are we positive that the vertex of the cone is where the X/Y/Z point of the cone is located? When you specify the nominals it is not to the vertex...

[pgardner]

cmmguy, I was trying to find that info in the manual, but didn't see anything. As a check, I just set the cone to x-y-z = 0, and when I did that, the graphic display window indicates that the vertex is the x-y-z position. At least the red alignment icon seemed to be where the vertex would be. It definately was not within the measured area of the cone.

[cmmguy]

It sounds like when you are reporting the location of the cone, the vertex point is being projected to the Z origin plane and the slight skew of the cone is showing up there. Try constructing a point where the cone and plane intersect and use that point for each cone to do these measurements that you are trying and see if that makes a difference.