TRUE POSITION

[A Disho]

I am runing 3.7 ,I have a slot checked with the following results, True Position is required for this slot, my boss insist that the true position for this slot will be within spec,
GD&T ON THE BLUE PRINT CALLES: on length 44.25mm. / loc. / 2.0/A/B M / C M/
: on width 17.82mm./loc./2.00/A/B M/C M /

BOTH B & C in max. material condition


AX NOMINAL +TOL -TOL MEAS DEV OUTTOL
X 3670.737 1.000 1.000 3671.699 0.962 0.000 --------#
Y -572.777 1.000 1.000 -571.891 0.886 0.000 --------#
Z 1748.644 1.000 1.000 1748.684 0.040 0.000 ----#----
D 17.820 1.000 1.000 17.962 0.142 0.000 -----#---
L 44.250 1.000 1.000 44.346 0.096 0.000 ----#----

would you please, show me how to fill up TRUE POSITION FEATURE WINDOW.
WICH FEATURE TO BE CHECKED IN THE FOLLOWING :

IN AXIS : FORM OR PRAD - - - - - - ?
IN TOL. BESIDE ENTERING THE +1 , -1 WHAT AXES . DF , ALL , D1 D2 -------?
MATERIAL CONDITION : CHECK MARK FOR USE DATUM
DEVIATION : -----------?
FOR AXIS FEATURES ------?
DIM. INFOR --------?
ANALYS ------ON OR OFF ------?
Please, explaine as for a bigner ?

Thank you in advance,

[bw_bob]

Your boss is correct. The TP will be in tolerance. If your using the X,Y locations then your TP will be 2.606
The tolerance is 2.0 an you get 1.142 for -B- and 1.096 for -C- ....bonus for a total of 3.238 TP

Now as for using the TP function i always check the slot back to -B-,-C- and calculate by bonus tolerance seperately and then put into feature TP.

[bw_bob]

I just thought about this and had to post. Its a little off subject. You have a TP of 2.0 with the chance of getting 4.0mm bonus for a total of 6.0 TP

I could make that part using a skill saw,drill & drill bit and measure with tape measure.

I could then sell all the cmm's and go to Burmuda for a month...ya thats it.

[chris conley]

1

[John Kingston]

I'm at home and don't have a calculater handy, but you appear to be in tolerance. the formula is 2*(sqrt(Xsq +Ysq)). I'm too lazy yo do the math right now.

[thenettrainer]

Here's a cool way to calculate Position (NOT True Position! There's no such control characteristic called True Position) . . .

If you need to quickly know if you're "ballpark" in tolerance . . .

Pos=2L+1/2S meaning . . . 2x the larger deviation, plus 1/2 of the smaller.

EX: XDev=0.017 YDev=0.008 ... 0.017x2=0.034 1/2x0.008=0.004 = .038
EX: XDev=0.0068 YDev=0.0126 . . . .0252 + .0034 = .0286

NOTE: Only works if you double the LARGER and half the smaller.

Comes from an "old school" shortcut to calculating hypotenuse . . .

(2L+1/2S)/2 where L=long side and S=short side.

You'll find you can get within about .0005 of the actual using the shortcul.

I'm NOT implying you should use this as an actual result!!! I'm saying . . . you can calculate Position in your head in a few seconds, and be really close to correct, to 4 decimal places!