On 4/11/24 14:50, John Dammeyer wrote:
Where I'm still having trouble is understanding the compromises.
Using G02 I,J motion it's possible to specify a feed rate and spindle RPM that
remains constant regardless of the spiral diameter. This approach generated by
the CAM software does a number of segments. But since a spiral is continuously
changing the radius doesn't this approach still create a blocky segmented
series of lines? Shouldn't there really be more like a new line for every say
one tenth of a degree of rotation?
%
N1 G17 G21 G40 G90
(2 1/2 Axis Profiling)
N2 T1 M06
N3 S2000 M3
N4 G0 Z11.35
N5 X-6.795 Y-2.3642
N6 G1 Z5. F745.1
N7 X-4.971 Y3.7182 F372.5
N8 G17
N9 G02X2.9354Y7.9767I6.0824J-1.824 F279.4
N10 X0.0086Y-11.1633I-3.0663J-9.3249 F372.5
N11 X-4.8878Y12.9255I-0.3348J12.4739
N12 X10.8896Y-12.3617I5.6431J-14.0447
N13 X-16.8958Y8.9702I-11.9852J13.1505
N14 X21.6077Y-2.7715I18.1973J-9.3286
N15 X-23.7802Y-5.6409I-22.9524J2.6529
N16 X22.4641Y15.1503I24.9984J6.2225
N17 X-18.2168Y-23.5731I-23.4829J-16.0603
N18 X12.0427Y30.2156I18.8718J24.7892
N19 X-3.5415Y-35.0813I-12.341J-31.5628
N20 X-6.7258Y37.3924I3.4567J36.4587
N21 X17.9557Y-36.5564I7.1836J-38.6957
N22 X-29.1519Y32.2355I-18.7497J37.6857
N23 X39.2113Y-24.4201I30.2257J-33.1012
N24 X-47.7931Y-8.2457I-40.4241J24.6445
N25 G1 X-49.1271 Y-2.0374 F745.1
N26 G0 Z11.35
N27 M30
%
On the other hand with the rotary table the motion is continuous for both axis.
G00 G49 G40.1 G17 G80 G50 G90
G20
(2 1/2 Axis Profiling)
M6 T2
M03 S2000
G1 F100 A3600 X60
G00 Z0.2362
M5 M9
M30
However the F100 is a joke because my A axis can't run more than 7 ipm or so.
I have faint memories of that from a previous discussion on how to set up the A
axis. My INI file says
DEFAULT_ANGULAR_VELOCITY = 90.00
MIN_ANGULAR_VELOCITY = 0
MAX_ANGULAR_VELOCITY = 180.00
I think that's in degrees per second because at a G01 F6 A3600 it takes 2 seconds to
do one revolution. Now that's still plenty fast if we are slotting with a 3mm or
0.118" end mill. However the problem of SFM is now in the picture. Again, a
custom G-Code solution would likely be to do something like the following.
G01 F6 A360 X10
F5.5 A720 X20
F5 A1080 X30
And so on... Picking both X resolution and A distance to create a closer to
ideal SFM. I don't know if there is a G-Code that states the F rate for the A
axis is in degrees per minute so it's some sort of conversion from IPM.
A rotary axis is normally speced in 1 degree pieces, ANGULAR and degree
being the key words. AFAIK, if ANGULAR, it never is IPM. I suppose one
might use radians instead of degrees or one of the other names for
rotary stuff.
I only have the 4th Axis version of MECSOFT so I can't generate a fifth axis
program cutting a spiral with the mill using the rotary table.
Why should you need a 5th axis? What are you going to do with it? I
cannot visualize the need.
But I think I agree the best way to do this is probably still by hand or with a
support program that generate the G-code based on parameter input like min/max
SFM.
John
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Cheers, Gene Heskett, CET.
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