Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: raybuilt on December 15, 2010, 09:57:29 PM

Good day,
I'm having an issue with my 4th axis, (running Mach3)
I can't get the rotation feed to speed up as fast as I want. I have radius correct turned on but the only difference it seems to make is, if I set radius to 0.0001 to use Z as radius, the feeds speed up as the radius increases (which seems backwards) Setting it at any radius other then 0.0001, just slows it down all the time.
The part is an eliptical lobe shape, and the feeds speed up as the cutter raises and lowers at the lobe part, but slows back down for the other 180 degs, the constant radius circular arc part.
I can jog the rotary table fast enough to use it as a lathe, but when cutting it's slow.
any idea's?
Thanks,
Ray

What is the 4th axis velocity set at in motor tuning. It typically should be much higher than the other axis, because it's in degrees/minute.

Setting it at any radius other then 0.0001, just slows it down all the time.
Mach3 has a long standing bug in the "Use Radius for Feedrate" feature. That is, setting a value of zero in the "Rotation Radius" DRO will disable the feature.
.......if I set radius to 0.0001 to use Z as radius, the feeds speed up as the radius increases (which seems backwards)
Sounds a bit odd that the rotary axis feedrate speeds up as the Z axis DRO value increases. It does not do that here.
Are you sure you have the Z axis travelling in the conventional direction? Up is positive and down is negative.
Greg

What is the 4th axis velocity set at in motor tuning. It typically should be much higher than the other axis, because it's in degrees/minute.
X is 320 S/P 2200.2 V, 110 acc
Z is 320 S/P 1300.2 V, 65 acc
A is 4.44 S/P 40002 V, 500 acc
Thanks,
Ray

Yes Z is setup correctly, Z feeds down on machine and DRO.
With radius correct turned on, is A feed still deg or is it now inch/min?
I'll try turning radius correct off again and running a feed of 500010,000, now that I have figured out how to change the max feed output in VM from 400.
Thanks again,
Ray

In Config>Toolpath, did you check "Use Radius for feedrate", or whatever it's called?

Yes I did.
I just tried running a cut feed rate of 30000 (VM is setup in metric so programs as mm/min, which converts to 1181.10 inch/min) so G code has a feed of 1181 which should be deg per minute on the A correct?
Doesn't make enough difference to see from 200 /min??
I tried this with and without radius correct, only difference is with R/C it still speeds up over the lobe?
Ray

Did some more testing. When it speeds up as z goes up and back down, while cutting the lobe, it's not the radius correct doing that. It was the slight increase in speed the radius correct was giving. Increasing the feed rate with radius correct off does the same thing.
Had cut feed set at 5511.8 and over riden to 13779.50, but feed rate in Mach DRO only shows 10001750 bouncing around. Cuts the approx 180 deg of circular arc perfectly, takes 1520 sec, then when it gets to the second approx 180 deg, with the raise lobe, it cuts that part in 12 sec. Like it's using angular feed while Z is fixed and lin feed while Z is moving?
I spoke with Visualmill today and they said it's controller problem??
Does this give anyone any other idea's?
Thanks again,
Ray

What does the code look like?

What does the code look like?
It looks like a bunch of letters and numbers, LOL
Seriously, here is a snipet from the code.
Everything is fine while Z is at 0.6917", when Z starts to raise it seems to go to rapid feeds and the A keeps up, once Z goes back to 0.6917" it's back to normal.
X1.8110 Z1.0947 A3600.000 F31.5
X2.0866 Z1.0947 A3600.000
X2.0866 Z0.6917 A3600.000
X2.0866 Z0.6917 A3600.000 F1968.5
X2.0866 Z0.6917 A3600.909
X2.0866 Z0.6917 A3601.818
X2.0866 Z0.6917 A3602.728
X2.0866 Z0.6917 A3603.636
X2.0866 Z0.6917 A3604.545
X2.0866 Z0.6917 A3605.455
X2.0866 Z0.6917 A3607.273
X2.0866 Z0.6917 A3608.182
X2.0866 Z0.6917 A3609.091
X2.0866 Z0.6917 A3610.000
X2.0866 Z0.6917 A3610.909
X2.0866 Z0.6917 A3612.727
X2.0866 Z0.6917 A3613.182
X2.0866 Z0.6917 A3614.091
X2.0866 Z0.6917 A3614.545
X2.0866 Z0.6917 A3615.454
X2.0866 Z0.6917 A3615.909
X2.0866 Z0.6917 A3616.818
X2.0866 Z0.6917 A3617.273
X2.0866 Z0.6917 A3618.182
X2.0866 Z0.6917 A3619.091
X2.0866 Z0.6917 A3620.000
X2.0866 Z0.6917 A3621.818
X2.0866 Z0.6917 A3622.727
X2.0866 Z0.6917 A3623.636
X2.0866 Z0.6917 A3625.455
X2.0866 Z0.6917 A3626.363
X2.0866 Z0.6917 A3627.273
X2.0866 Z0.6917 A3629.091
X2.0866 Z0.6917 A3630.000
X2.0866 Z0.6917 A3630.909
X2.0866 Z0.6917 A3632.727
X2.0866 Z0.6917 A3633.182
X2.0866 Z0.6917 A3634.091
X2.0866 Z0.6917 A3634.545
X2.0866 Z0.6917 A3636.364
X2.0866 Z0.6917 A3636.818
X2.0866 Z0.6917 A3637.727
X2.0866 Z0.6917 A3638.182
X2.0866 Z0.6917 A3640.000
X2.0866 Z0.6917 A3640.909
X2.0866 Z0.6917 A3641.818
X2.0866 Z0.6917 A3643.636
X2.0866 Z0.6917 A3644.545
X2.0866 Z0.6917 A3645.455
X2.0866 Z0.6917 A3647.273
X2.0866 Z0.6917 A3648.182
X2.0866 Z0.6917 A3648.636
X2.0866 Z0.6917 A3649.091
X2.0866 Z0.6917 A3650.909
X2.0866 Z0.6917 A3652.727
X2.0866 Z0.6917 A3653.182
X2.0866 Z0.6917 A3653.637
X2.0866 Z0.6917 A3654.545
X2.0866 Z0.6917 A3656.364
X2.0866 Z0.6917 A3657.273
X2.0866 Z0.6917 A3658.182
X2.0866 Z0.6917 A3658.636
X2.0866 Z0.6917 A3659.091
X2.0866 Z0.6917 A3660.000
X2.0866 Z0.6917 A3661.818
X2.0866 Z0.6917 A3663.636
X2.0866 Z0.6917 A3664.546
X2.0866 Z0.6917 A3665.455
X2.0866 Z0.6917 A3666.591
X2.0866 Z0.6917 A3666.818
X2.0866 Z0.6917 A3667.273
X2.0866 Z0.6917 A3668.182
X2.0866 Z0.6917 A3669.091
X2.0866 Z0.6917 A3670.909
X2.0866 Z0.6917 A3671.818
X2.0866 Z0.6917 A3672.727
X2.0866 Z0.6917 A3674.545
X2.0866 Z0.6917 A3676.136
X2.0866 Z0.6917 A3677.273
X2.0866 Z0.6917 A3678.182
X2.0866 Z0.6917 A3680.000
X2.0866 Z0.6917 A3680.909
X2.0866 Z0.6935 A3680.909
X2.0866 Z0.6987 A3681.818
X2.0866 Z0.7038 A3682.728
X2.0866 Z0.7088 A3683.636
X2.0866 Z0.7137 A3684.545
X2.0866 Z0.7185 A3685.455
X2.0866 Z0.7232 A3686.364
X2.0866 Z0.7278 A3687.273
X2.0866 Z0.7369 A3689.091
X2.0866 Z0.7414 A3690.000
X2.0866 Z0.7458 A3690.909
X2.0866 Z0.7503 A3691.818
X2.0866 Z0.7548 A3692.727
X2.0866 Z0.7594 A3693.637
X2.0866 Z0.7640 A3694.545
X2.0866 Z0.7731 A3696.364
X2.0866 Z0.7777 A3697.273
X2.0866 Z0.7821 A3698.182
X2.0866 Z0.7909 A3700.000
X2.0866 Z0.7994 A3701.818
X2.0866 Z0.8075 A3703.636
X2.0866 Z0.8115 A3704.546
X2.0866 Z0.8153 A3705.455
X2.0866 Z0.8191 A3706.363
X2.0866 Z0.8228 A3707.273
X2.0866 Z0.8264 A3708.182
X2.0866 Z0.8299 A3709.091
X2.0866 Z0.8333 A3710.000
X2.0866 Z0.8367 A3710.909
X2.0866 Z0.8399 A3711.818
X2.0866 Z0.8430 A3712.727
X2.0866 Z0.8461 A3713.636
X2.0866 Z0.8490 A3714.545
X2.0866 Z0.8519 A3715.455
X2.0866 Z0.8547 A3716.364
X2.0866 Z0.8574 A3717.273
X2.0866 Z0.8601 A3718.182
X2.0866 Z0.8626 A3719.091
X2.0866 Z0.8651 A3720.000
X2.0866 Z0.8675 A3720.909
X2.0866 Z0.8698 A3721.818
X2.0866 Z0.8721 A3722.728
X2.0866 Z0.8743 A3723.636
X2.0866 Z0.8764 A3724.545
X2.0866 Z0.8785 A3725.455
X2.0866 Z0.8805 A3726.364
X2.0866 Z0.8824 A3727.273
X2.0866 Z0.8842 A3728.182
X2.0866 Z0.8859 A3729.091
X2.0866 Z0.8876 A3730.000
X2.0866 Z0.8891 A3730.909
X2.0866 Z0.8905 A3731.818
X2.0866 Z0.8918 A3732.727
X2.0866 Z0.8930 A3733.637
X2.0866 Z0.8941 A3734.545
X2.0866 Z0.8950 A3735.454
X2.0866 Z0.8958 A3736.364
X2.0866 Z0.8965 A3737.273
X2.0866 Z0.8971 A3738.182
X2.0866 Z0.8975 A3739.091
X2.0866 Z0.8977 A3740.000
X2.0866 Z0.8979 A3740.909
X2.0866 Z0.8978 A3741.818
X2.0866 Z0.8977 A3742.727
X2.0866 Z0.8974 A3743.636
X2.0866 Z0.8969 A3744.546
X2.0866 Z0.8963 A3745.455
X2.0866 Z0.8956 A3746.363
X2.0866 Z0.8946 A3747.273
X2.0866 Z0.8936 A3748.182
X2.0866 Z0.8924 A3749.091
X2.0866 Z0.8911 A3750.000
X2.0866 Z0.8896 A3750.909
X2.0866 Z0.8879 A3751.818
X2.0866 Z0.8861 A3752.727
X2.0866 Z0.8841 A3753.636
X2.0866 Z0.8820 A3754.545
X2.0866 Z0.8797 A3755.455
X2.0866 Z0.8773 A3756.364
X2.0866 Z0.8746 A3757.272
X2.0866 Z0.8719 A3758.182
X2.0866 Z0.8689 A3759.091
X2.0866 Z0.8658 A3760.000
X2.0866 Z0.8626 A3760.909
X2.0866 Z0.8591 A3761.818
X2.0866 Z0.8555 A3762.727
X2.0866 Z0.8518 A3763.636
X2.0866 Z0.8478 A3764.545
X2.0866 Z0.8437 A3765.455
X2.0866 Z0.8395 A3766.364
X2.0866 Z0.8350 A3767.273
X2.0866 Z0.8305 A3768.182
X2.0866 Z0.8258 A3769.091
X2.0866 Z0.8209 A3770.000
X2.0866 Z0.8159 A3770.909
X2.0866 Z0.8107 A3771.818
X2.0866 Z0.8054 A3772.727
X2.0866 Z0.7999 A3773.637
X2.0866 Z0.7942 A3774.545
X2.0866 Z0.7885 A3775.454
X2.0866 Z0.7826 A3776.364
X2.0866 Z0.7765 A3777.273
X2.0866 Z0.7704 A3778.182
X2.0866 Z0.7640 A3779.091
X2.0866 Z0.7576 A3780.000
X2.0866 Z0.7510 A3780.909
X2.0866 Z0.7443 A3781.818
X2.0866 Z0.7375 A3782.727
X2.0866 Z0.7306 A3783.636
X2.0866 Z0.7236 A3784.546
X2.0866 Z0.7165 A3785.455
X2.0866 Z0.7093 A3786.363
X2.0866 Z0.7020 A3787.273
X2.0866 Z0.6917 A3789.091
X2.0866 Z0.6917 A3790.909
X2.0866 Z0.6917 A3791.818
X2.0866 Z0.6917 A3792.727
X2.0866 Z0.6917 A3793.636
X2.0866 Z0.6917 A3794.545
X2.0866 Z0.6917 A3795.455
X2.0866 Z0.6917 A3796.364
X2.0866 Z0.6917 A3797.273
X2.0866 Z0.6917 A3798.182
X2.0866 Z0.6917 A3799.091
X2.0866 Z0.6917 A3800.000
X2.0866 Z0.6917 A3801.250
X2.0866 Z0.6917 A3801.278
X2.0866 Z0.6917 A3801.818
X2.0866 Z0.6917 A3802.955
X2.0866 Z0.6917 A3803.636
X2.0866 Z0.6917 A3805.455

by the way, the G code is so big because I had to turn coordinate modal off in VM or it caused other issue's with this model.

Looks like fairly poor code but that may be because we are only seeing a small section.
Try some basic code like this and see if you get a better result as far as A axis feedrate is concerned
G21
G1 Z25 F500
A90
Z50
A180
Z75
A270
Z100
A360
A axis feedrate should decrease as Z height increases.
I made this in metric because I think you said that is your native units.
Greg
EDIT: I reread your posts and maybe your native units are medieval english. :)
If that is the case then try this code instead.
G20
G1 Z1 F20
A90
Z2
A180
Z3
A270
Z4
A360

Thanks Greolt, radius correct work fine with basic code like that, Z height, then rotate. Were I'm having trouble is when A axis is rotating while Z is moving at the same time. It should work the same shouldn't it?
Thanks,
Ray

My understanding is that the feedrate correction will update with each line of code.
It's possible that my understanding is not correct.
I have not seen this issue but that might be because I do not machine jobs like cams.
Zip up your code and post, and I will run it here to see if I get the same result as you.
Greg