Hi. I'm new to PC DMIS (fresh from a class). We are using 15.1 and have a Romer Arm, currently with a 3mm probe. Here's what I was asked to measure:
A row of 70 drilled holes (.25" dia, spaced 1.5"). This row was placed in the .31" thick material with no reference is an edge, datum or otherwise. There is no design print. It's just a row of holes. The Engineer wants hole spacing (I've done that). He also wants to know if the holes are in a straight line. He wants the deviation from each hole center point to a line created between the first and last hole centers. So, I constructed a BF line between the first and last holes. Then I measure from that line to each hole center. Problem is this.. I would expect to see zero for the distance between the line and the first and last hole centers. But I am seeing 0.0392" for both.
I aligned the material multiple times and this does not seem to significantly impact the results (Plane, Circle, Circle; Plane Cyl, Cyl; and currently at Plane, Line Point).
I appreciate greatly the assist and any suggestions that may come for the forum.
Plane level and origin Z
first circle origin X and Y
Last circle create line from first circle one to this hole
Alignment Plane level
rotate line Y about Z or X about Z (not sure how you got it laid out)
Origin Plane Z
Origin First hole X and Y
create your circles in between make sure each hole your "X" direction reads "0" in THEO
and "Y" direction reads 1.5 then the next hole 3 the next 4.5 etc.....THEO, or vise versa again unsure how this is lined up.
Then go back and run the program
I would make sure you created a 3D line. Also. For consistency, check all your holes at the same -Z- value. As a sanity check when completed you can also create a line from ALL of the circles and then use a straightness callout to see what that line looks like.
Thanks Kirbster. My Alignment looks OK with the Plane, Line, Point I have now, but I'll go back and check one of my previous Plane, Circle, Circle alignments per your notes. My "X" increments by 1.5 and my "Y" though ranges .639 at hole 1 to .561 at hole 71
Here is a snip of the current alignment.
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Hi Schlag,
I changed my Constructed Line to Circle dimensions from 2d to 3d and the results changed dramatically to more what I expect (a few thousandths off vs. 30+). The results did not change when I changed the constructed line from 2d to 3d. So was my main problem a 2d vs 3d issue?
Can you provide guidance when I would select 3d vs 2d for a constructed line or a dimension? I should recall this from training but do not recall an emphasis on this.
3D looks at the distance of centroid to centroid. Just, "how far apart are these 2 points in space?"
2D is workplane dependent. In the ZPLUS workplane, any deviation in Z is ignored. The measurement will happen perp/parallel to X/Y (as you select) when measuring the distance between 2 features.
There is a 2nd option for 2D distance, "To Feature". To use this, you must select your 2 features being measured, and then a 3rd feature to measure relative to (perp or parallel). This can be a plane or line (lines are line, cylinder, slot, cone, and circle**). You could create a line from hole 1 to hole 70, and use that as feature 3 to measure 2D distance from hole 1 to hole 70 perp/parallel to the line.
**I have no idea how a circle is used as a line, it's vector, like a cylinder? Not sure.
The help menu is pretty decent at answering some of these questions. Just open the Distance dialog window and hit F1.
Constructed lines depend on what you need, and are also workplane dependent. If your holes are (0,0,1) but at a 45 degree angle from X and you make a line in XPLUS or YPLUS, then your line will be parallel to X or Y, and .7071 times the length of hole 1 to hole 70.
He also wants to know if the holes are in a straight line.
Well the only reason, I'm not satisfied is you specifically stated the engineer wanted to know how straight the holes were, you are not doing that. Unless you misworded your original statement. If your basing this off a different alignment. Then no they probably aren't straight to an edge. But straight to themselves, leaving him/her scratching his/her head, probably making unnecessary changes.