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Author Topic: hickup at 12 and 6 oclock  (Read 6843 times)

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hickup at 12 and 6 oclock
« on: April 18, 2007, 05:04:48 PM »

Hi
We are developing a new machine and part of it is an XY table moving in a circular motion.

Using code listed below.

At 12 and 6 oclock on the graphics we can see a disturbance on the feedrate DRO. This shows in the servo motion as a blip and spoils the smooth motion we need.

I have tried faster PC's = makes no difference
Slowed feed speed down to 100mm/min - still present

It would appear as if at the point of calculating the G03 the pulse output gets disturbed

We are using version .062

Can you provide any ideas as to how to avoid this issue

Regards

Graham


G0 G49 G40  G17 G80 G50 G90
M6 T1 (TOOL DIA. 2)
G21 (mm)
M03 S100
G64

G00G90X0.Y0.
G00G90Z5.
G01G90Z0.F100.
G91G03Y19.Z-0.05R9.5F100.
G03J-19.Z-0.1 F1000
G03J-19.Z-0.1
G03J-19.Z-0.1
G03J-19.Z-0.1
G03J-19.Z-0.1
G03J-19.Z-0.1
G03J-19.Z-0.1
G03J-19.Z-0.1
G03J-19.Z-0.1
G03Y-19.Z-0.05R9.5
G00G91Z.254
G90Y0.
Z5.
M30
%

Offline Chaoticone

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Re: hickup at 12 and 6 oclock
« Reply #1 on: April 18, 2007, 05:09:53 PM »
Hey Graham,
    What do you have your lines look ahead set to? In is in General config. Also, have you checked the backlash on your machine?

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: hickup at 12 and 6 oclock
« Reply #2 on: April 18, 2007, 05:27:05 PM »
Thanks for reply

Backlash and mechanical issues were checked and they are not a factor.

The look ahead was at default val (20 I think)  - I tried 2&5 and 100 as alternatives. No difference

Regards

Graham

Offline Graham Waterworth

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Re: hickup at 12 and 6 oclock
« Reply #3 on: April 19, 2007, 01:58:17 AM »
What is it like if you remove the G64 from the code and replace it with G61.

Graham.


Without engineers the world stops
Re: hickup at 12 and 6 oclock
« Reply #4 on: April 19, 2007, 08:59:06 AM »
Write yor program in G90 mode and see if you have a problem...
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com
Re: hickup at 12 and 6 oclock
« Reply #5 on: April 19, 2007, 04:07:15 PM »
Hi
Thanks for replies,

To Brian, I have tried abs code same behaviour

To Graham, will try G61 later today. Thanks for idea

Regards

Graham
Re: hickup at 12 and 6 oclock
« Reply #6 on: April 19, 2007, 09:00:53 PM »
What are your Accel settings? and what Vel are you looking to use? I Have tested your path and it runs smooth here...
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com
Re: hickup at 12 and 6 oclock
« Reply #7 on: April 19, 2007, 10:13:01 PM »
Hi

I have just got back from the workshop. Its about 8Km away and not always accessible due to production isues.

I have deleted the G64 (having tried G61) G61 was worse, removing the G64 seemed to of made a slight improvement. Not sure what this did as its not in the manual. I had assumed it was a smoothing function or look ahead!!.

F1000 is what we are running, we would like to run up to about 1600 if possible.

In the motor settings I have 1280 pulses per unit, maxed out Velocity, about 1800 (from memory) Acc is set to 150

As a last resort I un ticked the Advanced Compensation Analysis. This seemed to be a further improvement.

However we can still see (and feel) a variation at the 12 and 6 oclock positions.

Ran at 35,000 then tried 45,000 pulse setting.

Task Manager showed a distinct increase in CPU demend. In all cases we have tried to use no more than 80% cpu demand.

I can try scope and Freq Meter. However in the past its been very difficult to follow the pulse output trains as they vary from 0to max in 90deg rotation of the table.

Its getting a bit fustrating. I have had 3 months of wiring, setting up and changing the servo's and drives till we got sets that work. Solving this issue appears to be the last before we can change mode to production of some samples and move to a next phase.

Regards and appreciate all help.

Graham

Offline Chaoticone

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Re: hickup at 12 and 6 oclock
« Reply #8 on: April 19, 2007, 10:34:21 PM »
Graham,

     I have sent you a personal message.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: hickup at 12 and 6 oclock
« Reply #9 on: April 19, 2007, 10:38:51 PM »
As a test please run the program at 500 and tell me if it feels better?

Also You need to know that Vel = Accel * Time (From a stop) and that Mach3 looks at every move from a stop and smooths them from there...

Okay... so if you have a move that you would like to be 1000 Units per sec and Accel of 150..


Vel/Accel = Time
(1000 / 60 )/150 = .11111 sec accel

and will take .5*Accel*Time^2  units to get to velocity
.5*150*.11111^2 = .92592 units to get to vel... if you are over a dis of .92592 you should feel a nice smooth path...

The only way that you will not is if you have played with some of the CV settings... Post your XML from the machine and I will see what I can find

Thanks
Brian
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com