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Author Topic: 4th axis question, possibly configuration ?  (Read 9765 times)

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Offline Sage

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Re: 4th axis question, possibly configuration ?
« Reply #20 on: May 15, 2011, 08:35:10 PM »
Don't forget there are two of us experiencing this.
I don't recall which Z moves (+/-) failed but the steppers screatched and the Z-axis was messed up.
I've used my machine for a few years now and never had a problem until I ran the code presented. I would never have such crazy F values in my programs so this issue could have gone un-noticed.

I'll test it thoroughly tomorrow as well.

Sage
« Last Edit: May 15, 2011, 08:37:25 PM by Sage »
Re: 4th axis question, possibly configuration ?
« Reply #21 on: May 15, 2011, 09:57:25 PM »
The machine has never given me any physical problems. I have had some learning curves with Mach 3 and what it will and wont do.

The z goes in the negative. So its stepping down, each pass.

I did try it on my smaller machine, again without the A axis hooked up. And it ran what seemed to be ok with the Z axis. I just quickly did that. I ll research more tomorrow and see what I can come upwith.

Offline Sage

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Re: 4th axis question, possibly configuration ?
« Reply #22 on: May 15, 2011, 10:04:53 PM »
When you say you didn't have the A-axis "Hooked up" do you mean? You had the motor unplugged or what?
Unplugging the motor could damage the drivers. Maybe not Gecko's but a definite don't do for other lesser drivers.

Sage
Re: 4th axis question, possibly configuration ?
« Reply #23 on: May 15, 2011, 10:22:52 PM »
The A axis was unplugged on the smaller machine. It is a Gecko 540 setup on that one.

Also question on the diameter radius correction in the DRO box. From the manual it says you can input the work piece size to make corrections for the co-ordinated axes moves to blend better. Something to that extent.

Can someone explain that a little better to me ?

Thanks
Todd

Offline BR549

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Re: 4th axis question, possibly configuration ?
« Reply #24 on: May 15, 2011, 10:34:12 PM »
When you use Radius correction Mach takes the workpiece diameter and uses that to set a blended feedrate of the A (up to as fast as it can move). You would normally see this with 3D work where all the axis could be moving at the same time. Being that the A normally moves in Deg per min this will speed up the work up to the A  max Vel as set in config.

Without this a move of  X1.000 A40 F20  would be painfully slow as the feedrate is set for both axis at 40.  the slowest moving axis would be A at 40 deg per min (SLOW) and the X could not run any faster as it is linked to the A move as far as feedrate.

This feedrate for A (1357 DPM) is not very fast. it is only about 3 rpm which converts to about 11 ipm surface speed. About right as far as feeds and speeds are concerned.

(;-) TP
« Last Edit: May 15, 2011, 10:38:00 PM by BR549 »

Offline Sage

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Re: 4th axis question, possibly configuration ?
« Reply #25 on: May 15, 2011, 10:52:22 PM »
Ok. I'm really confused now  ???

Can someone run this slightly modified version of the original code listed below.
Put on the SINGLE BLOCK and run it a line at a time.
For me sometimes the A axis moves, sometimes it doesn't.

On my machine (possibly due to config) if the A DRO is sitting at +62.222 and you tell it to go to -62.222 it rotates the A axis counting down from +62.222 to 0 and then continues backwards from 360 till it gets back to +62.222 again. This I expect because I have it configured to wrap around BUT:
On some of the lines it does nothing with the A at all. Sometimes when told to go to +62 or -62 it skips the line doing nothing and I can't see why.

Also note the Feedrate changes as you go along.

I'm really confused. Seems you've created quite the wicked code here.

I don't mean to take this thread off course but until I figure this out I can't get a handle on the feed issue.



N100 G20
N110 G0 G17 G40 G49 G80 G90
N120 T1 M6
N130 G0 G90 G55 X0. Y0. G4 P08 A-62.222 S4000 M3
N140 G43 H1 Z.542
N150 G1 Z.422 F40.
N160 A62.222 F1357.7
N170 G0 Z.542

N180 X-.04 A-62.222

N190 G1 Z.422 F40.
N200 A62.222 F1357.7
N210 G0 Z.542

N220 X-.08 A-62.222

N230 G1 Z.422 F40.
N240 A62.222 F1357.7
N250 G0 Z.542

N260 X-.12 A-62.222

N270 G1 Z.422 F40.
N280 A62.222 F1357.7
N290 G0 Z.542

N300 X-.16 A-62.222

N310 G1 Z.422 F40.
N320 A62.222 F1357.7
N330 G0 Z.542

N340 X-.2 A-62.222

N350 G1 Z.422 F40.
N360 A62.222 F1357.7

M30

Sage

Offline BR549

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Re: 4th axis question, possibly configuration ?
« Reply #26 on: May 15, 2011, 11:11:01 PM »
Runs ok here.    Try turning OFF all the A rotational stuff in Gen config. Rollover,shortest path etc.

Most Cams such as MC treat the a axis as it only has 360 deg rotations so it does not use rollover etc,

Just a thought, (;-) TP

Offline Sage

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Re: 4th axis question, possibly configuration ?
« Reply #27 on: May 16, 2011, 07:58:25 AM »
Ok, I turned off the wrap around and got rid of the odd A moves.
Now it makes more sense and I can get back to the original problem I see with feeds.


I reduced the program down to the minumum required to observe the issue here:

(This code screws up Z moves. Z goes at high feed rate of previous A move instead of G0 rate)
N100 G20
N110 G0 G17 G40 G49 G80 G90
N150 G1 Z.422 F40.
N160 A62.222 F1357.7
N170 G0 Z.542 (Z moves at high feedrate instead of G0 rate here - misses steps)

N190 G1 Z.422 F40.
N200 A-62.222 F1357.7
N210 G0 Z.542 ( again Z moves at high feedrate instead of G0 rate here - misses steps)

M30



If I single block step the above code it works fine.  ???
There is no reason it should. Mach must be missing resetting the feedrate to G0 for some reason.
So I went to the next step and added optional stops M1 before the Z moves and ran it full speed again like this:


(Running at full speed this one works with M1 to pause before G0 Z move)
N100 G20
N110 G0 G17 G40 G49 G80 G90
N150 G1 Z.422 F40.
N160 A62.222 F1357.7
M1
N170 G0 Z.542 (Z moves properly at G0 rate here)

N190 G1 Z.422 F40.
N200 A-62.222 F1357.7
M1
N210 G0 Z.542 (again Z moves properly at G0 rate here)

M30


So this one above runs fine and proves that for some reasom Mach needs some time to process the G0 and re-adjust the feedrate after the previous high feed rate.
So I decided to remove the high feedrates and change the A moves to G0's here:

(This file fixes Z move by setting A moves to G0 instead of high feed rate)
N100 G20
N110 G0 G17 G40 G49 G80 G90
N150 G1 Z.422 F40.
N160 G0 A62.222 (making A move at G0 speed also fixes problem)
N170 G0 Z.542 (Z moves properly here)

N190 G1 Z.422 F40.
N200 G0 A-62.222 (making A move at G0 speed also fixes problem)
N210 G0 Z.542 (Z moves properly here)

M30


 The A axis still moves as fast as it can and it works fine. Presumably this would not be suitable for the application because the feedrate of A might have something to do with the shape of the cut required. But it does prove that the F1357.7 is the culprit.


So my conclusion is that Mach is screwing up.
Why not on all machines - I don't know. Probably some odd combination of the config and hardware employed.
Or others are not noticing the Z missing steps and don't hear anything. The separate DRO on Z shows it for me.


I forgot to try swapping the Z moves for an X or Y to see if something is odd there. I presume the X would screw up on my machine since all the motors are the same. I'll try it later and report back.

So Brian, Hood or anyone else - Got any ideas ????


Sage

« Last Edit: May 16, 2011, 08:00:19 AM by Sage »

Offline Greolt

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Re: 4th axis question, possibly configuration ?
« Reply #28 on: May 16, 2011, 08:04:03 AM »
Did you try it with CV turned off?

Greg
Re: 4th axis question, possibly configuration ?
« Reply #29 on: May 16, 2011, 08:09:10 AM »
Going to try some things this morning.

I had a feeling about trying to lower the feed on the A to a G0 like mentioned here by Sage. I might try that first and just see if that works.

I ll post up later today and let you guys know what I find.

Thanks
Todd