2018 R2: Offset a datum in Xact

[BIGWIG7]

Morning,

I have a part that the machine shop left .010'' material on the primary datum plane surface.

How do I offset that plane in XACT so that true position compensates for that material that is going to be removed at the next op?

I have tried creating an offset plane that compensates for the .010'' but when I report the position of the feature using that plane, the nominals change as well and my readings for the tp are the same.

thanks.

[Schlag]

Create an offset plane. Define that plane as a datum. Use that datum in your feature control frame.

[BIGWIG7]

Create an offset plane. Define that plane as a datum. Use that datum in your feature control frame.

so I did that and it just offset everything and the results are the same as the nonoffset datum.

[KIRBSTER269]

Is this your Primary Plane? It still will level based off the hits from your original Plane it will just offset the plane. nothing will change. What exactly are you trying to accomplish?

[BIGWIG7]

Is this your Primary Plane? It still will level based off the hits from your original Plane it will just offset the plane. nothing will change. What exactly are you trying to accomplish?

trying to show that if the machine shop takes off exactly .010 material from that plane the part will be good.

[RIDER]

Have you tried... Assign a variable for PLN1.Z-0.01. Create a generic plane with actuals ( pln1.x, pln1.y, variable). Use the generic plane as your datum definition.

[Sora5]

Change the nominal of your constructed offset plane to be .01 inward.

[vpt.se]

...or just change the nominals for the toleranced feature in the TP when using the offset datum plane. Make sure you do not update nominals for the actual feature (autocircle/measured circle).

[KIRBSTER269]

What I'm trying to gather from your info is first, is your plane the Primary, or secondary? If it's primary, you take a plane, construct an offset plane from that plane, and you call hole positions?<<< Offsetting your primary plane won't change because technically those holes are perpendicular to the plane, your constructed offset plane is based off of hits from actual existing plane it is still leveling based off of that plane except the origin is now .010 further down not changing anything, except where the origin of Z is located. unless of course the holes or features are parallel to that plane then things can change showing .010 difference, so I guess my question is what does this plane control? Leveling? or Position? If it's Primary, the only thing it can control of other features for position is in the Z direction, therefore if it's a hole perpendicular to that plane, well then it controls perpendicular to "Z", if it is secondary, it can only control either the "X" or the "Y"

[KIRBSTER269]

BIGWIG7 answer the questions, you turdlicker

[UseAsIs]

>the nominals change as well and my readings for the tp are the same.

I believe you can key-in the nominals in the "nominals" tab in Xact. Is this something you've looked into already?

[BIGWIG7]

What I'm trying to gather from your info is first, is your plane the Primary, or secondary? If it's primary, you take a plane, construct an offset plane from that plane, and you call hole positions?<<< Offsetting your primary plane won't change because technically those holes are perpendicular to the plane, your constructed offset plane is based off of hits from actual existing plane it is still leveling based off of that plane except the origin is now .010 further down not changing anything, except where the origin of Z is located. unless of course the holes or features are parallel to that plane then things can change showing .010 difference, so I guess my question is what does this plane control? Leveling? or Position? If it's Primary, the only thing it can control of other features for position is in the Z direction, therefore if it's a hole perpendicular to that plane, well then it controls perpendicular to "Z", if it is secondary, it can only control either the "X" or the "Y"

the plane being offset is the primary datum

I created an offset plane. what happens is that the nominals and the measured values also move and so I am left with the same tp measurement as the nonoffset plane.

the plane controls leveling.

[KIRBSTER269]

And so you will end up with the same true position. As I explained above, moving your plane won't change anything. It's a useless step that you're trying to do. I was just trying to understand what you were trying to accomplish. I believe if you want to check best leveling, I would create a plane (if possible) from the bottom, for the simple fact when the machinist takes off the .010 material, it will need to be parallel to the bottom, for that plane is what they are going to lay the part down in the machine to cut the .010 off of the top plane, and/or even make your offset plane from there, just as Schlag described. Still won't change anything.
P.S. your still a turdlicker

[Matthew D. Hoedeman]

I'm guessing that you will also want to check this thing after they remove the extra stock.

SO.....

Try this:

Put an INPUT comment at the beginning of your program asking for the amount of stock left on your primary datum plane feature.

Then use that input value as the ACTL_THICKNESS for the points that measure the datum plane for the alignment.

It should then self-adjust for the amount of stock left on the datum plane and not screw up your nominals and can be used for stock on or stock off.

[KIRBSTER269]

Or, How about the existing plane (hopefully an auto plane) if your using a CAD model. Click on the surface, offset your "Z" to plus .010, move your points around where you want them to hit (going to to see a big gap between the points and CAD model) F10 Change your Check distance to at least .025 or more, create alignment Leveling "Z" and Origin, put your cursor after the alignment. Go to Operation/Graphic Display Window/Transform. Move your CAD model .010 up in the "Z" so you can make your auto features based off of the model and whether you have .010 material or not, after the CMM levels and Origins to "Z" all your features circles, cylinders and such will be at the right level.

[KIRBSTER269]

When you run with the extra .010, it will look weird on your model, without .010 it will look normal on the CAD, but like I said before who cares the model is useless after creating the program. actually might not

[BIGWIG7]

I'm guessing that you will also want to check this thing after they remove the extra stock.

SO.....

Try this:

Put an INPUT comment at the beginning of your program asking for the amount of stock left on your primary datum plane feature.

Then use that input value as the ACTL_THICKNESS for the points that measure the datum plane for the alignment.

It should then self-adjust for the amount of stock left on the datum plane and not screw up your nominals and can be used for stock on or stock off.

I'm going to try this.

I know I wasn't totally clear at the beginning, but this part does not have a conventional datum structure where I can easily offset a surface and all the corresponding measurements are just off by .010.
it's a pretty complicated part with some complex geometry and profiles and I need to know that if the .010 material is removed all the features stay the same.

[KIRBSTER269]

Well that's why I said work from the bottom for your Plane. If they are drilling holes and such before establishing your Datum Plane.<<<stupid. Then you establish the plane that your machinist is going to load the part on. That way if your features aren't perpendicular or parallel to that plane then cutting the extra .010 or less or more. wouldn't be a waste of time. Sometimes you have to think for the machinist.