POINTDATA QUESTION (scanning)

[george frick]

when doing a linear closed scan i was wondering why the reports
always read a deviation when the axis is set to zero. in other words
the y axis is set to zero, the hits are at y axis zero but the reports
always show a deviation anywhere from .0001 to .006. i know if i do
an individual vector point and set the x or y axis to zero the report
reads zero. b&s mistral,ph10t,tp20. i'm thinking that this is because
we're not using a true scanning head like the sp600. or am i off base?

[Matthew D. Hoedeman]

Well, do you have your vectors set for a ZERO (or 1) for the axis you want to stay at zero? They can wander off, ya know. Also, do you use SNAP point when doing the individual points? That will make the zero/zero-vector point show a result of zero.

[george frick]

Well, do you have your vectors set for a ZERO (or 1) for the axis you want to stay at zero? They can wander off, ya know. Also, do you use SNAP point when doing the individual points? That will make the zero/zero-vector point show a result of zero.

vectors are correct & and i don't always use snap when taking individual vector points

[george frick]

well i guess nobody has any input on this- does anyone here use scanning?

[JamesMannes]

well i guess nobody has any input on this- does anyone here use scanning?

George,

I do scanning with an SP600. Can you posta little snippet of code so I can get a better idea of what you're doing?

[robehor4]

I scan nearly every day. I have not seen the types of results you have though.
I use SM25 head and or TP 20. Are you useing models?

[Randy P]

I just ran scan w/50pts across my table top and get no dev at all.

[robehor4]

Why closed scan and not open?

[george frick]

I scan nearly every day. I have not seen the types of results you have though.
I use SM25 head and or TP 20. Are you useing models?

yes we are using models- quality engineer says it has something to do with the cad=part.
i just don't know for sure. project is assigned to engineering. i was just reviewing the cmm
program and noticed the slight deviation in the "locked" axes (z/x,z/y). no one else here will
admit "i just don't know". that is a career killer at large companies like general dynamics-
so everyone knows a little about something and a lot about nothing.

[robehor4]

I never use CAD = Part

Here is an example of my generic startup. Since I use an external alignment for the machine locator I use a generic point with offset dimensions to the part Zero. Once I align this as XYZ zero it moves the point to CAD XYZ zero without useing CAD = Part


STARTUP =ALIGNMENT/START,RECALL:,LIST=YES
ALIGNMENT/END
MODE/MANUAL
FORMAT/ ,OPTIONS, ,HEADINGS, , ;MEAS,NOM,DEV,TOL,OUTTOL, ,
LOADPROBE/TM25-20-TP20-3X30X17
TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0
RECALL/ALIGNMENT,EXTERNAL,a1,LOCATOR:a1
$$ NO,This program was created on 01/03/07 by Rob Horne. Print Revision # 2753563 Program Revision #1.
C1 =COMMENT/YESNO,NO,Do you Wish to See Set Up Sheet?
IF/C1.INPUT == "YES"
EXTERNALCOMMAND/DISPLAY ; F:\QC\SETUPSHEETS\2753563.BAT
END_IF/
C2 =COMMENT/YESNO,NO,Do you wish to Calibrate probe?
WORKPLANE/ZPLUS
IF/C2.INPUT == "YES"
COMMENT/OPER,NO,Please be sure sphere is in normal Location for calibration!!!!!!
AUTOCALIBRATE/PROBE, PARAMETER_SET=ALL-TIPS-WITH-DEFAULTS, QUALTOOL_MOVED=NO,
SHOW_SUMMARY=NO, OVERWRITE_RESULTSFILE=NO
END_IF/
L1 =LABEL/
C3 =COMMENT/INPUT,YES,'Work Order\PO # ?'
C4 =COMMENT/INPUT,YES,'Clock #?'
C5 =COMMENT/INPUT,YES,'Serial #'
COMMENT/OPER,NO,Machine about to go into DCC Mode.
,Do you wish to continue?
,Please be sure probe is clear!!!!!!!!!!!!
MOVESPEED/ 50
TOUCHSPEED/ 2
PREHIT/ 0.5
RETRACT/ 0.5
FLY/ON,0.1181
DISPLAYPRECISION/5
MODE/DCC
F1 =GENERIC/POINT,INDEPENDENT,RECT,$
NOM/XYZ,0,0,0,$
MEAS/XYZ,3,0,6.1,$
NOM/IJK,0,0,1,$
MEAS/IJK,0,0,1
A2 =ALIGNMENT/START,RECALL:LOCATOR:a1,LIST=YES
ALIGNMENT/TRANS,XAXIS,F1
ALIGNMENT/TRANS,YAXIS,F1
ALIGNMENT/TRANS,ZAXIS,F1
ALIGNMENT/END

[Inspector Gadget]

Is this a 2d or 3d surface and what version are you using? The numbers seem too high for normal positioning error.