Straightness

[tnguyen]

Hi. Could anybody instructs me how to measure a line to apply for Straightness dimension ?.
I read in the Manual Referrence. It says the line for straightness should have 3 points minimum. Do I have to pick up 3 points for a line or pick up 3 single points, then construct a line ?
Before comming up this question, I ve already tried it, the straightness result was 0.00. I wasnot sure it was right . I need a expert from this forum to give me a confident answer.
Many thanks

[ag1979]

Straightness

You can use both options. Either measure individual points and construct a line, or measure a line. The more points that you use the more accurate reading you will get. For your straightness of 0, there is the possibility you measured a line that was that straight. You could always test to make you your dimension is giving you an answer besides zero. Just measure your two hits on an actual straight line and a third off the line.

[Matthew D. Hoedeman]

YOU MUST also make sure you are in the correct workplane if you just go a measure a line. For instance, if you measure a line that is in reality (wht a concept) in the Z+ workplane, but you measure it in an X or Y workplane, it will report a straightness of zero since it was not done in the correct workplane. Workplane really effects your measurements in a case like this. IF the line is NOT in a workplane, you will need to measure the plane it lies in, then after you measure the line, change the parameter from WORKPLANE to FEATURE, then enter in the feature ID of the plane you measured.

[Paul Sarrach]

If he constucts it, should it be a 2d or a 3d line?

[tnguyen]

Thanks you very much for your quick respond

[Matthew D. Hoedeman]

Good question! Are there any more? No? Class dismissed!

Well, it might depend on what type of points he collected and where they are in relationship to datum planes and stuff like that. If you make a 3-D line, then your straightness will actually end up being a 3-D dimensional value, since the line is now 3-D. However, unless he IS in a workplane and CAN be in that workplane, he will not get good data constructing a 2-D line. You can not tell Pcdmis to construct a line in a 'feature plane' in the same way you can tell it to measure to that feature, like in my first post, you would have to make an alternative alignment to do that. Also, I am not sure if SNAP points will have an effect on this either.

Personally, if I could be in a workplane, I would measure it as a line, if I had to construct a line, I would do it 2-D, but I would make an alternative alignment so I could construct IN a workplane.

[John Kingston]

Good question! Are there any more? No? Class dismissed!

OO! OOO! I have a question Mr. Hoedeman! Aren't you going to assign any homework? I think you forgot to.

[Matthew D. Hoedeman]

Hahahahahahahhahahahahahahahhhahahahahahahhahahaha hahaaa

OK, for tonight, I want to all to find out how many ounces in a 12 ounce can of beer actually come back out the other end when your body is done with it. Now, this may take some time, but I do NOT want you to just ignore this assignment! It may take many beers to get a good over-all average return, so I expect 3-page papers on the re-issuance of beer in the morning from EACH AND EVERY ONE OF YOU!

[Paul Sarrach]

Personally, if I could be in a workplane, I would measure it as a line, if I had to construct a line, I would do it 2-D, but I would make an alternative alignment so I could construct IN a workplane.[/quote]

Teacher, Teacher, When you say an alternative alignment, are you refering to,f it is not in a normal X, Y Zworkplane?

[Matthew D. Hoedeman]

Yes Paul, I am, if it is NOT in a normal workplane.

[Jeffrey Lovely]

what type of an alignment?
iterative ,321 best fit
where is zero
mid line , end one or end 2
2d 3d
workplane
and its only monday

[Matthew D. Hoedeman]

I would only create a LEVEL alignment for the construction, then create and dimension, then go back to the regular alignment, NO CAD=PART for the 'level' alignment.

[Jeffrey Lovely]

I would measure 3 circles 2 ends 1 mid
create alignment
and apply MMC
Just to see the look on the engineers face
when I tell him its ok per MMC

[John Kingston]

Hahahahahahahhahahahahahahahhhahahahahahahhahahaha hahaaa

OK, for tonight, I want to all to find out how many ounces in a 12 ounce can of beer actually come back out the other end when your body is done with it. Now, this may take some time, but I do NOT want you to just ignore this assignment! It may take many beers to get a good over-all average return, so I expect 3-page papers on the re-issuance of beer in the morning from EACH AND EVERY ONE OF YOU!

But I don't drink canned beer. Bottles, sometimes they are 16 ounce. Is that OK teach?

[Jeffrey Lovely]

How many shots of beer is that ?