cz position of holes ?

Hi,

what is the best way to get the position of a hole pattern to Datum A ?

2 holes with fcf | ⌖ | Ø 0,3 | A ask for the distance between them, but | ⌖ | Ø 0,3 CZ | A connected to 4 holes ?

attached a simple illustration.

yellow plane: Datum A

blue hole: Datum B

green hole: Datum C

4 holes : | ⌖ | Ø 0,3 CZ | A

- the part is 3mm thick sheet metal
- pc dmis v2017 r1

Attached Files

Matthew D. Hoedeman over 1 year ago

Since the CZ (common zone) only uses the "A" datum, after you are aligned to ABC and you measure the 4 holes, do a BEST-FIT, ROTATE & TRANSLATE using those 4 holes and then report the positions.
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MaLux over 1 year ago

thank you for the fast answer
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MaLux over 1 year ago in reply to Matthew D. Hoedeman

sorry i have more questions... i have no experience with best-fit and positioning :>
i have not tested it yet, but when the best fit alignment is done after the ABC alignment... i use the "xact measure position" on each of the 4 holes for it´s own, or one with all 4 holes selected ?

i set the fcf as given in the drawing | ⌖ | Ø 0,3 CZ | A and let the settings how they are ? (ISO Standard , Alignment: Datum Reference Frame, Fit to Datums, Perpendicular to centerline ?!)
"Alignment: Datum Reference Frame & Fit to Datums" must be turned off to not overwrite the best-fit ?
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MaLux over 1 year ago

weeks later i got time to try the best-fit

is it correct to use best-fit min/max in this situation ? that´s how i understand the help file...
2 holes are measured GX the other 2 GG

when the best-fit is done the easiest way is to create a legacy position and select each hole for itself and activate the perpendicular to centerline checkbox, so that it is using the aktiv (best-fit) alignment and checks the x,y deviation for the position ?

- one more question: in which case is it required to dimension an element group from a hole pattern instead of the holes itself ? how would the drawing look like ?
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vpt.se over 1 year ago

If you are using XactMeasure or GeoTol, the bestfit is taken care of in the evaluation. If you are using legacy, you need to do the bestfit manually.
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MaLux over 1 year ago in reply to vpt.se

so in the case of XactMeasure or GeoTol i select all 4 holes at once (for the CZ) set Ø 0,3 and datum A, with the other settings at default (ISO Standard + Perp. to Centerline) the result should be the same as bestfit + legacy ?

do you know which best-fit method is used in this case?

thanks for this tip
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vpt.se over 1 year ago in reply to vpt.se

The bestfit is probably Gauss (LSQ).
No, the result might not be the same as legacy due to differences in calculating datums and datum fit (legacy VS Xact and GeoTol).
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