[Shanghyd]

This question is sort of a g-code question. Its more about x and y coordinates but this was the nearest forum that the question fit so here goes.

I am cutting a .250 hex on the end of a piece of bar stock. The stock is held in a 4 jaw scrolling chuck. I have chucked up a piece of stock and mounted a universal indicator on the spindle. I found the center of the part and set x and y to zero. Stock size is .750
I am starting on the left side of the part, cutting a flat, moving down and right to cut the first angle...see picture for the path.


Here is the coordinates that I am using. I'll add my logic in quotes.
I'm using tool compensation to the right.
Z 1.0 (get above clamps and chuck)
X -.250 (x zero is center of part. Move to the left of the part center)
Y +.500 (move past the part in the + y direction)
Z -.250
X -.250 Y-.1443 (move to point 1 in the pic)
X -.1443 Y -.250 (cut first angle down and to the right)
X +.1443 Y-.250
X +.250 Y0.00
X +.1443 Y+.250
X -.1443 Y +.250
X -.250 Y +0.00 (might throw out this last move)

I don't have the exact code. I wrote that by memory.

Here are the resulting measurements:
Viewing the hex from the top the flats are located at 9&3, 1&7, 5&11
I start cutting flat 9 then, 7, 5, 1, 11, 9. 9 is done halfway again to get the little corner.

Across flats 3-9 = .500
Across flats 1-7 = .495
Across flats 5-11 = .505

I checked for backlash by putting a dial indicator on the spindle and programmed the table to move the X axis .010. I checked the result, then moved it back .010. The dial indicator was perfect. Same thing with the Y axis

Anyone have any ideas? Hopefully its my poor programming skills.

[dcoupar]

I think your numbers are wrong. At some point (6 and 12 o'clock) you need to take X to center. Maybe you could post "the exact code".

[CNCRim]

Hey Shang, If you want I can quickly weap up a toolpath for you, just tell me the tool diameter and the hex dia

[Shanghyd]

Thanks!
The tool diameter is .250
The hex is .500 across the flats and .577 across the points

[CNCRim]

%
O0000
N100G20
N102G0G17G40G49G80G90
(1/4 FLAT ENDMILL TOOL - 1)
N104T1M6
N106G0G90G54X.2058Y.5451A0.S2139M3
N108G43H1Z.25
N110Z.1
N112G1Z-.5F6.42
N114X-.0107Y.6701
N116G3X-.0375Y.5701R.2
N118X.0625Y.3969R.2
N120G1X.3125Y.2526
N122G2X.375Y.1443R.125
N124G1Y-.1443
N126G2X.3125Y-.2526R.125
N128G1X.0625Y-.3969
N130G2X0.Y-.4137R.125
N132X-.0625Y-.3969R.125
N134G1X-.3125Y-.2526
N136G2X-.375Y-.1443R.125
N138G1Y.1443
N140G2X-.3125Y.2526R.125
N142G1X-.0625Y.3969
N144G2X0.Y.4137R.125
N146X.0625Y.3969R.125
N148G3X.1625Y.3701R.2
N150X.3357Y.4701R.2
N152G1X.1192Y.5951
N154G0Z.25
N156M5
N158G91G28Z0.
N160G28X0.Y0.A0.
N162M30
%