Alignment question

[dtmtim]

Okay - sanity check here ... The goal here is to rotate the part around the origin to a point. BTW the origin is set to the center of a cylinder. I'm not sure why this is not working ...

This is the current location of this vector point from the CAD model.
DIM LOC1= LOCATION OF POINT PNT1 UNITS=IN ,$
GRAPH=OFF TEXT=OFF MULT=10.00 OUTPUT=NONE
AX NOMINAL MEAS
X -1.29350 -1.29356 ----#----
Y 0.00000 0.00012 ----#----
Z -1.11020 -1.12008 #--------
END OF DIMENSION LOC1

I have to rotate the alignment so the Z value of this vector point matches the nominal of -1.1102.
I constructed a BF line from the vector point to the origin to check the angle I was getting ...

DIM ANGL1= 2D ANGLE FROM LINE LIN2 TO XAXIS ,$
GRAPH=OFF TEXT=ON MULT=10.00 OUTPUT=BOTH
AX NOMINAL MEAS
A -40.63921 -40.88884 <-------- This measured value actually trigs out to 40.8889 but should be close enough ??? The nominal angle is correct.

A4 =ALIGNMENT/START,RECALL:A3,LIST=YES
ALIGNMENT/ROTATE,XPLUS,TO,LIN2,ABOUT,YPLUS
ALIGNMENT/ROTATE_OFFSET,40.63921,ABOUT,YPLUS
ALIGNMENT/END

Here is the location of the same vector point after the alignment. Notice the z value of the point is still not correct.
PNT2 =AUTO/VECTOR POINT,SHOWALLPARAMS = NO
THEO/-1.2935,0,-1.11018,0,0,1
ACTL/-1.29365,0.00014,-1.11439,0,0,1
TARG/-1.2935,0,-1.11018,0,0,1

I also tried a best fit alighment using only the vector point and selecting rotation only but that didn't work either. Can someone please enlighten me as to the correct procedure for this?

Thank you!!!

t.

[Wingman]

Okay - sanity check here ... The goal here is to rotate the part around the origin to a point. BTW the origin is set to the center of a cylinder. I'm not sure why this is not working ...

This is the current location of this vector point from the CAD model.
DIM LOC1= LOCATION OF POINT PNT1 UNITS=IN ,$
GRAPH=OFF TEXT=OFF MULT=10.00 OUTPUT=NONE
AX NOMINAL MEAS
X -1.29350 -1.29356 ----#----
Y 0.00000 0.00012 ----#----
Z -1.11020 -1.12008 #--------
END OF DIMENSION LOC1

I have to rotate the alignment so the Z value of this vector point matches the nominal of -1.1102.
I constructed a BF line from the vector point to the origin to check the angle I was getting ...

DIM ANGL1= 2D ANGLE FROM LINE LIN2 TO XAXIS ,$
GRAPH=OFF TEXT=ON MULT=10.00 OUTPUT=BOTH
AX NOMINAL MEAS
A -40.63921 -40.88884 <-------- This measured value actually trigs out to 40.8889 but should be close enough ??? The nominal angle is correct.

A4 =ALIGNMENT/START,RECALL:A3,LIST=YES
ALIGNMENT/ROTATE,XPLUS,TO,LIN2,ABOUT,YPLUS
ALIGNMENT/ROTATE_OFFSET,40.63921,ABOUT,YPLUS
ALIGNMENT/END

Here is the location of the same vector point after the alignment. Notice the z value of the point is still not correct.
PNT2 =AUTO/VECTOR POINT,SHOWALLPARAMS = NO
THEO/-1.2935,0,-1.11018,0,0,1
ACTL/-1.29365,0.00014,-1.11439,0,0,1
TARG/-1.2935,0,-1.11018,0,0,1

I also tried a best fit alighment using only the vector point and selecting rotation only but that didn't work either. Can someone please enlighten me as to the correct procedure for this?

Thank you!!!

t.

Can you draw a pic? NOt sure EXACTLY what you are trying to do.

This is just a stab but from the text/ explanations it looks like you are capturing an angle (actual Angle) but rotating a Nominal Angle. You will always have deviation. You need to rotate to a feature or capture the actual angle if you require the feature to be exact.

[Wes Cisco]

Well it is hard to tell from your description, esp. w/o a sketch, but I'll take a few stabs at helping you.

1) sometimes it is easier to use the compliment of the angle. Instead of 42.3 degrees you might rotate 47.7 degrees. 90-42.3=47.7

2) Use your graphics window to watch the rotation when you create the alignment. This can help you figure out how to get the correct alignment.
HTH

[dtmtim]

Alignment Question

Basically all I need to do is rotate the alignment until the point checks correctly. This point is being used to clock the rotation of the part. Each method I use gets it close but not close enough. I am using a CAD model but cannot post it. After each alignment I am using Cad = part. Then I re-check the location of the datum point (there should be no deviation from nominal). It seems simple ... maybe I'm just brain dead this morning ...

[Wingman]

If you have a flat surface where you can get a true vector try this:

Level to the surface you need SET. Take a few points on the surface and create offset points from them (positive Z your required setpoint).
Create a line through the Offset points and the Datum Origin and Rotate to it (X Axis)

Your sample points should be correct. Any deviation from points should be due to out of square and form.

As an alternative you can align as you are doing to get 'close' then do the offset points from that alignment instead of the actual surface normal vector.

HTH,

[dtmtim]

The surface I'm trying to rotate to is only .060" X .100" so there is not much area there to level to. Also, the primary datum is a cylinder I am already leveled to. I don't think I can level to another surface without over-constraining the part. I can understand why after I rotate then re-hit that point I am getting some error because I'm not really hitting the part at the same location I was before.

Can you explain wht you mean by offsetting the points?

The only other thing I can think of to do is to have a loop that keeps rotating until the point measures correctly.

[cmmguy]

Is this point on a surface or the center of a feature?

what is the value that you want the point to report(after aligning??

[Wingman]

The surface I'm trying to rotate to is only .060" X .100" so there is not much area there to level to. Also, the primary datum is a cylinder I am already leveled to. I don't think I can level to another surface without over-constraining the part. I can understand why after I rotate then re-hit that point I am getting some error because I'm not really hitting the part at the same location I was before.

Can you explain wht you mean by offsetting the points?

The only other thing I can think of to do is to have a loop that keeps rotating until the point measures correctly.

Aligning to the surface to create the offset points is not a problem because it is only a temporary Datum designeg to put the offset point exactly where they need to be.

You can still level to it and create the offset points. Then recall your original alignemt BEFORE you construct the line.

Or, you can do the alignment your way and get glose. THe only error you will have is a small cosine error. There is no PERFECT solution as there is no PERFECT part.

Again, my response is Old School and there may be a simpler automatic solution. But, to create an offset point you make SURE you are in a correct alignment (very, very close will be OK). Measure a POINT. Construct an Offset Point using the point you just measured and an offest value of (I think it was 1.012 or something like that). This should put the point in a level plane with the Origin if all your stuff is square. Do a couple of them if you want or you can just do one in the center of the pad.

Once you create your Datum Line through this point the Original Point HAS to be in the exact correct place.

[#2#]

I'm lost. Based on your sketch, you measured the cylinder and leveled to the cylinder (good) and set it as the x,z orgin (good). Now, you want to rotate to some line between the cylinder and pnt 1 (or 2). I'm not sure where the point is coming from. Is it a measured point? constructed point?

[dtmtim]

Is this point on a surface or the center of a feature?

what is the value that you want the point to report(after aligning??

The point is on a surface. It's a small rectangular pad on the part.

I want the Z location of the point to match the nom. (-1.1102)

Thanks!

t.

[dtmtim]

I'm lost. Based on your sketch, you measured the cylinder and leveled to the cylinder (good) and set it as the x,z orgin (good). Now, you want to rotate to some line between the cylinder and pnt 1 (or 2). I'm not sure where the point is coming from. Is it a measured point? constructed point?

The point is a measured point on the part. A Vector point on the CAD model. I need to rotate the alignment until the Z value of that point matches the nominal value of -1.1102.

Thanks!
t.

[dtmtim]

Aligning to the surface to create the offset points is not a problem because it is only a temporary Datum designeg to put the offset point exactly where they need to be.

You can still level to it and create the offset points. Then recall your original alignemt BEFORE you construct the line.

Or, you can do the alignment your way and get glose. THe only error you will have is a small cosine error. There is no PERFECT solution as there is no PERFECT part.

Again, my response is Old School and there may be a simpler automatic solution. But, to create an offset point you make SURE you are in a correct alignment (very, very close will be OK). Measure a POINT. Construct an Offset Point using the point you just measured and an offest value of (I think it was 1.012 or something like that). This should put the point in a level plane with the Origin if all your stuff is square. Do a couple of them if you want or you can just do one in the center of the pad.

Once you create your Datum Line through this point the Original Point HAS to be in the exact correct place.

Thank you - I love old school - trouble is I'm still relatively new to PCD. Especially since I only use it a few days a month. It looks like this solution is basically reducing the amount of error because the angle of the line I'll be rotating to is much smaller. Does that make sense?

t.

[#2#]

Ahhh, I see now. I was trying to do something similar quite some time ago. Mine was for aligning to a line from a point on the end of a cart tube to the theorhetical point where a wheel would touch the ground. I gave up. I'll be interested to see if you come up with anything.

[cmmguy]

Align to the point through the origin.
Save the distance between the point and the origin to a variable.

Then rotate the alignment by the inverse Sin of (1.1102/Distance)

[dtmtim]

Ahhh, I see now. I was trying to do something similar quite some time ago. Mine was for aligning to a line from a point on the end of a cart tube to the theorhetical point where a wheel would touch the ground. I gave up. I'll be interested to see if you come up with anything.

The only thing I have now is to keep doing the same thing over and over again. Touch the point, create a line, rotate the alignment. Each time the error gets smaller and smaller. I'm thinking this could probably be done in a loop until the difference between nom and measured is zero.

t.