Offset planes

[cmmmike]

I am trying to do an offset plane. I have 5 points for Datum A. A1, A2, A3, A4,A5. A3,A4,A5, are all set to 13.97 below A1 and A2 is 4.14 above A1. When I set up my offset plane and then check my measurements to them they are off. Here are my measurements for them.

Measured Nominal

A1 = 0.005 0.00
A2 = 4.46 4.14
A3 = 13.765 13.97
A4 = 13.901 13.97
A5 = 13.550 13.97

In the box were I type in my offset I type in 13.97 for A1 and 18.11 for A2. I get 18.11 by adding the 13.97+4.14. Is this correct or am I way off. I hope this is clear on how I am doing it.

Thanks for the help

[Mike N.]

when using any plane (standard or offset) with more than 3 pts a "best fit" will be applied to the entire group of points.

If you want to find which points have the greatest deviation, select the 3 common 13.97 to level to and measure the others. This might show which ones altered your origin due to the "best fit" function.

[tking]

Mike is exactly correct, try it out with some gage blocks if you want to prove it to yourself. Fun, huh?

T. King

[johnboy]

When I'm working with 'uneven' datum points I make an offset point for each of the lower points the correct amount, then create a plane from them & the higher point(s).

[Matthew D. Hoedeman]

Well, the other option you have is if you are using DCC features ~ VECTOR points is you can use the same nominal for all the points and use a NEGATIVE ACTUAL stock thickness. Basically, find the 'highest' point and use that as the 'start' point, then use the negative actual stock thickness with a value equal to the offset distance. So, if you have five -A- points at various Z values (using Z just for ease) you would do this:

A1 Z12.345
A2 Z12.345
A3 Z10.345
A4 Z8.345
A5 Z6.345

For A1 and A2, use NO stock thickness, for A3 use a -2.0 ACT THICK, A4 gets a -4.0 ACT THICK and A5 gets a -6.0 ACT THICK, but they all get the same Z nominal, 12.345. Now, I'll admit, I have not tried this, but it should do the trick quite nicely. The ACT THICK is comped for by Pcdmis, but the nominal is not changed. When using a THEO thickness, the nominal changes but not the amount comped. Hey, what have you got to loose trying this? Just a probe, a head, a quill, etc., but it really should work.

[Jeffrey Lovely]

I like when people think outside the box
I like this idea !!!
sounds simple enough
I will use it next chance I get
Just to explain to the engineers
and see the confused looks

[Matthew D. Hoedeman]

Well, as you can probably deduce from my profile pix, I really don't fit in the box anyway, so if I want to think, I pretty much have to do it 'outside'. Now, it is breaktime and Lansing has a law against smoking inside a business, so it's smoke time and I'll be outside freezing my noonies off for MY smoke break!

[Jeffrey Lovely]

The smoke break signature goes with a saying
for those that have worked with me remember me by it
it was said when frustrated (hourly)
goes like this

Day in Day out
Stick it in pull it out
garbage in garbage out
when in doubt ship it out
Smoke break

When I yelled this out
we all would go on a smoke break
I miss being coorporate !!!