Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: cdewen on December 15, 2010, 09:01:24 AM

Pardon the newbie question, but I can't figure out why I get the error msg, "Tool Radius greater than approachLine 1", when I load this Gcode:
G91.1 G17 G41 P0.250 F10
G1 Z1.0000
M30
I presume I'm being warned of a collision problem, but I can't figure out why.
TIA
Charley

You have to apply the G41 on a feed line e.g. G01 G41 X10. P.25
Graham

Graham:
I've been enlightened ;D
Thanks!
Charley

I wonder if I can't get a little more education. With the tool at X0 Y0, this works fine:
G01 G41 X1 P.25
but this produces the tool radius error message again:
G01 G41 X2 P.25
Charley

what are you trying to do, using G41/42 is not a simple one line command there is more to it than that. Post a sketch of what you want to machine then we can tell you how to proceed.
Graham

As Graham stated, you need at least two lines of gcode to use G41. And that's before you even start to cut your part. You should be moving to a specified position before calling the G41. The comp is applied during the move from that point to the next one.

I appreciate the offers of assistance.
I'm trying to make a fairly simple part  cutting a roughly 2"x3" rectangle (more or less) out of sheet brass. One side has rounded corners, and the other is completely round. Top and bottom are straight. I'm frustrated at the results, not just with the error msg.
Here's one of many versions of Gcode that I've tried:
N010 G91.1 G17
N020 G1 G41 X0.1 P0.125
N030 G1 Z+0.0500
N040 G1 X+0.0000 Y+1.1111
N050 G1 Z0.0050
N060 G2 X+0.0000 Y1.1111 I0 J1.1111
N070 G1 Z+0.0500
N080 G1 X+1.0000 Y0.9675
N090 G1 Z0.0050
N100 G1 X1.7500 Y0.9675
N110 G2 X2.0000 Y0.7175 I0 J0.25
N120 G1 X2.0000 Y+0.7175
N130 G2 X1.7500 Y+0.9675 I0.25 J0
N140 G1 X+1.0000 Y+0.9675
N150 G1 Z+0.0500
N160 M30
Line N020 is a dummy that I've had to throw in to get rid of the error msg.
I don't know where the top and bottom intersect the arc, so I try to cut them separately. Mach3 doesn't seem to want to do this. When I run this code, it cuts the N040N060 arc, but then goes to X500 somewhere, rather than X+1.000. It cuts the rest of the bottom, side and corners correctly, but then stops on the top in the X_500 area. I'm sure it's trying to help, but I don't understand how to control it.
Charley

Here are a few help sheets I did for the chaps at work, it gives examples of how to do some basic gcode programs to do simple jobs, its all in metric but the principals are the same.
Graham

Graham:
Thanks! I'll be studying it in detail this evening.
Charley

Not sure if you wanted that "trapezoidal" shape. I changed it to a more rectangular shape with parallel sides.
Try this.
N010 G91.1 G17
N011 G0 Z0.05
N012 G0 X.5 Y1.3 (Move to start of leadin)
N013 G41 P0.125
N020 G1 X0.1 Y1.1111 Z.05 (Ramp Down While applying comp)
N040 G1 X+0.0000 Y+1.1111
N060 G2 X+0.0000 Y1.1111 I0 J1.1111
N100 G1 X1.7500 Y1.1111
N110 G2 X2.0000 Y0.8611 I0 J0.25
N120 G1 X2.0000 Y+0.8611
N130 G2 X1.7500 Y+1.1111 I0.25 J0
N140 G1 X+1.0000 Y+1.1111
N150 G1 Z+0.0500
N155 G40
N160 M30

Not sure if you wanted that "trapezoidal" shape. I changed it to a more rectangular shape with parallel sides.
Try this.
[snip]
Thanks, Gerry. The part has to be 1.935" top to bottom, though; the only critical X axis position is that the arc must be 1.1111 from X0 Y0. My problem here is that I don't know where the top & bottom lines (at +0.9675) intersect the arc on the end. I figured I could cut the straight lines and the arc separately, making the straight lines longer than necessary. If I cut the arc first, I can't get the cutter to go to the X1 position in line N080. For whatever reason, Mach3 executes N090 somewhere around X.5.
Charley

My problem here is that I don't know where the top & bottom lines (at +0.9675) intersect the arc on the end.
You can't write the correct code if you don't know that. Gcode just specifies coordinates. If you don't know what they are, then you can't write the code correctly. You're trying to run before you can walk. First, do an accurate drawing and calculate all your coordinates.

Gerry:
Having walked for a number of months, this was to be my first run. I've been doing cutter compensation manually, and thought it time to try doing it the right way.
I didn't consider a drawing necessary, as just cutting a straight line through the arc puts me in a waste area  no need to know exactly where to stop. Not an economical, elegant way of doing things.
Thanks for your help.
Charley

If you want to do separate moves with cutter comp, then you need to turn comp on and off for each move, and each should have it's own leadin and lead out move. Otherwise, it won't work right.

Gerry:
You got me thinking about my high school geometry. The intersection of the straight side and the arc'd side occurs at 1 radius (1.1111") and at Y=0.9675"  that's two sides of a right triangle. No problem. They intersect at X=0.5463".
Thanks, again.
Charley