# G68 problems

• posted on March 21, 2009, 6:46 pm
Awl --
If I do G68 X0Y0 R+45. G0 X4.Y0,
No problem. The endmill goes 4 linear inches at a 45 deg. angle from x0y0 in E0.
If I do
G68 X5.Y0 R+45. G0X4.Y0,
the endmill just goes to x4. in E0, and stops, whereas I thought it might
wind up at an x 4 linear inches at a 45 deg angle rel. to x5.y0 in E0.
It seems I can only issue a g68 X0Y0, and if I want the coordinate rotation to indeed be at x5. in E0, then I have to make and execute a fixture offset of 5. in x at, say, e11.
THEN, in E11, I can execute the g68, with proper behavior: At X5.Y0 in E0 (or x0y0 in E11), the endmill will go 4 linear inches (or whatever) at 45 deg.
Am I missing something, or is this the way it is? It does seem a little problematic to "just" issue a g68 x5.yo R+45., because this almost implies a new offset, without really having specified one.
Iny experiences? Or is everyone in cadcam heaven over here??
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• posted on March 22, 2009, 4:24 pm
Aight, here's what works and what doesn't work. On a fadal cs-88.
This works: N2.001G69
N2.01G0X-3.Y0E0 ( just an arbitrary move
N2.02E11 ( a must
N2.1G68X0Y0R+45.E11 ( this second E11 is also a must!!! x,y must be zero
N2.11M0
N2.2G1X4.Y0F100. ( x4 is now 4 linear inches along a +45 deg line, from the "origin" established by x0y0 AT E11, which is equivalent to x4.y0 in E0. See below.
N2.201M0
And, of course, g68x0y0R+45. by itself will properly send the em at 45 deg from the E0 origin.
This dudn't work:
N2.001G69
N2.002G0X4.Y0E0
N2.1G68X4.Y0R+45. ( here, trying to establish the point of rotation *with the em physically being at that point*; of course, it also does not work if the em is elsewhere.
N2.11M0
N2.2G1X4.Y0F100. ( this now sends the em 4 linear inches at a 45 degree angle, but from x0y0 at E0!!!!!!
N2.201M0
A'ight, speriment over.
It appears G68 can/will work, as long as you are careful specifying offsets (redundantly, apparently), and use only X0Y0.
The fadal manual gives their usual bullshit laadeedaa. Clearly whoever wrote that effing manual never used/proved the machine.
Altho this is apparently moot for all the bigdick cadcam peeple here....
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• posted on March 23, 2009, 1:18 pm
On Mar 22, 11:24 am, "Proctologically Violated©®"

thanx for the info; I printed it out and put it in my cnc book if I ever get to need it.
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• posted on March 24, 2009, 3:46 am

thanx for the info; I printed it out and put it in my cnc book if I ever get to need it. ============================================
You mean, you too are cadcamless????!!!! goodgawd....
I got another trick, that makes this "version" of g68 a bit more useful.
Since the fadal cs-88 version seems to be so highly dependent on formal offsets in the offset table, it would be nice to be able to manipulate those offsets more easily.
G10 allows you to do just this, by modifying your fixture offset table *from within the program*. iow, you can send values to the fixture offset table!
This is esp. useful if you are doing g68s that may depend on other geometries/point locations, as I am doing.
Basically you do
G10 L2 Pxx R1+xx R2+yy,
where L2 tells g10 to address the fixture offset register, Pxx (say, P6) is offset 6, and R1 is the x value, R2 is the value. So, for P6, you can now say,
E6 G68x0y0R+45.E6
It is important to be judicious about one's choice for the values put in E, as the point of rotation can make subsequent moves quite a bit easier than other choices, depending of course on the existing geometry, moves, etc.
Thus, G68 would seem to be acting as another kind of G52 offset, but with a twist.... <G> And only with x0y0 at some E.
AND, shortly thereafter or whenever, you can execute another G10 at P6, with diff. R1s, R2s, and execute a different g68, say, e6 g68x0y0R+80.E6,
where E6 now has different values than the previous g10.
And so on. Or use offset 7, or whatever. I find using just one offset number to hold changing offsets specifically for g68s keep things a little neater.
G10 allows you do do a bevy of writes *and reads* via different Lxx's, to fixture offset tables, tool cal tables, and some other shit I didn't fully grok.
Not bad for a whining hack matchining cadcamless pyooter-hating effing home-moaner, eh??
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• posted on March 24, 2009, 1:43 pm
On Mar 23, 11:46 pm, "Proctologically Violated©®"

No I'm not without cadcam, but that does not prevent me from learning either. And I always try to learn from the best. Thanks.
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• posted on March 25, 2009, 2:18 pm
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• posted on March 25, 2009, 4:22 pm
On Mar 25, 10:18 am, "Proctologically Violated©®"

I understand your G68 explanation completely. It could be very very useful in some setups- although none of my previous my cnc managers would've allowed it to be tried on any parts ( understandibly, safe and dumb costs less ).
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