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Author Topic: BACKLASH PROBLEM MACHV3.042.020  (Read 7436 times)

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Offline RICH

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BACKLASH PROBLEM MACHV3.042.020
« on: March 14, 2009, 09:53:23 AM »
Is there a known problem or has anybody else experienced backlash problems with MACH R3.042.020
current lockdown version?

In trying to help two guys out with their backlash on their lathes and here is the common problem.
All jogging and backlash is working fine, then after some time, and "all of a sudden", The backlash seems not
to be implemented on direction change, during a jog the Z axis will ramp up to speed and then ramp down say over
a long travel distance, say 3" , come to stop, pause, then a short burst ( think it now implements the backlash).
It will do this constantly once it starts this behavior. The only way to stop it is to set the Shuttle Accel to "0"
and all seems to work well. Now if you go out of MACH and come back in and again reset Shuttle Accel to some
more appropriate value  , back comes the problem. In one case thought it was gone and it did this wierd axis
change while durng threading, of course the piece was ruined.
I need to  try and narrow it down more, but anything that i could think just didn't seem to work.


Any experience on this one or thoughts on the matter?
RICH

   
 

Offline Chaoticone

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Re: BACKLASH PROBLEM MACHV3.042.020
« Reply #1 on: March 14, 2009, 11:07:16 AM »
I haven't seen that myself RICH but that doesn't mean it isn't happening. Can you post their XMLs and code they were running with notes when it goes haywire? I don't have the lathe running on Mach yet so I can't do a good test but I will try to emulate.

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!

Offline RICH

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Re: BACKLASH PROBLEM MACHV3.042.020
« Reply #2 on: March 14, 2009, 11:21:38 AM »
Thanks Brett,
Got my other pc hooked up here, so will be using the PP and will try to see if i can duplicate it at my place.
Will first try R.018 since it's still loaded on this PC and never had a problem wiith it. Then go to .020, it could be any number of things.  Even a corrupted
XML or installation. I will fool on my end and also go back over the guys house maybe tomorrow.
I'll repost if i can duplicate it here. 
Save ya some time for now.
RICH
 

Offline Chaoticone

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Re: BACKLASH PROBLEM MACHV3.042.020
« Reply #3 on: March 14, 2009, 11:27:32 AM »
Thanks Rich. If you can get it to repeat you may want to try another version of Mach if you have time. This sounds like a really odd one to me and the more we know about it, the easier it will be for Brian to track down.

Thanks Rich, great group we have here!

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!

Offline RICH

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Re: BACKLASH PROBLEM MACHV3.042.020
« Reply #4 on: March 14, 2009, 12:20:32 PM »
Hey Brett,
See if you can duplicate as this is what seems to cause the problem.

Backlash values / %, motor tuning, CV or exact stop, etc, etc. dosen't seem to be changed or if you change them won't help the problem. Now i was able to duplicate the problem in ver .18 and also .20 as follows:

Simply:
Put in a backlash and enable it / save and do the normal out back in etc.
Just jog the axis's. All should work as expected.

Now for the Shuttle Accel do the following:
Change value to "5" , save the settings, even go out and back in, but just check and see what value it saved.
It saved mine as "5.0073", and if you now jog the axis's back and forth you get the weird movement.

Now change the value to 4, and try, then 3, then 2, then 1  as all are saved for those values but the problem persists. Finaly change the value to "0" and  the problem goes away .

Now change the value back to "5" and see if again you get a value of "5.0037".
Problem comes back.

RICH


Offline RICH

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Re: BACKLASH PROBLEM MACHV3.042.020
« Reply #5 on: March 14, 2009, 12:49:26 PM »
Well here is a liittle more Shuttle Value info:
                        MACH
Shuttle Value     Saved value    Jog Problem
------------------      ----------------    -----------------
.005                 .005              no
.05                   .05                no
.5                     .5                  yes
.6                     .6                  yes
.06                    .06                no
.7                      .7001            yes
.05                    .05                no
5                       5.0073          yes

Obviuosly it's number related and i always thought the number 13 was the unlucky one.  >:D

RICH
 

Offline Chaoticone

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Re: BACKLASH PROBLEM MACHV3.042.020
« Reply #6 on: March 14, 2009, 01:34:03 PM »
Rich, with the larger numbers, I can see where that would be a problem. Can you set the shuttle Accel to .005 and see how that works? If you want, you can leave all other settings the same and have a play with the shuttle accel value and see how it affects the backlash comp. I don't understand it fully yet but most often good results come out of setting the shuttle value to .005. I haven't tried to emulate yet but I'm going to play with the mill and see if I can explain it better in a bit.

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!

Offline RICH

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Re: BACKLASH PROBLEM MACHV3.042.020
« Reply #7 on: March 14, 2009, 02:21:16 PM »
Brett,
I use .005 as the value for my lathe and personaly never had a problem. It was probabaly back a year ago that ya'all mentioned that it affected the speed at which the backlash will be implemented.
This problem came to light when two frends were having problems with the their backlash and described the axis
movement ( of course i said, what?, no way) but once we got playing with the settings the problem surfaced
 then the nature of it was understood to some degree. So still curiuos i duplicated it today at home.

What can happen to the unknowing, is that if they use some random Shuttle Accel value, and gradualy work their way down to a faster speed, like 10 down to one and happen to hit a range of numbers that cause a problem,
then good grief, hours later they don't know what the heck is wrong. Just imagine coupling this with say the curent threading problem yet to be addressed and you would need to have a crystal ball to to even explain what  
what's happening.

I quess until it gets addressed, folks should just make note of what is posted here, and don't use a value like 5, .5,.6, or some range around those  and make sure that they are not skipping steps.

If your using the SS, since it dosen't have backlash implemented yet, all this would be transparent  
/ you wouldn't even be aware of the problem.

Good that your trying on the mill since maybe it's only a problem with MachTurn. Don't know.
RICH

Offline ART

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Re: BACKLASH PROBLEM MACHV3.042.020
« Reply #8 on: March 19, 2009, 09:57:31 AM »
Just to kick in..

>>Well here is a liittle more Shuttle Value info:
                        MACH
Shuttle Value     Saved value    Jog Problem
------------------      ----------------    -----------------
.005                 .005              no
.05                   .05                no
.5                     .5                  yes
.6                     .6                  yes
.06                    .06                no
.7                      .7001            yes
.05                    .05                no
5                       5.0073          yes


  Shuttle Accel is the number of seconds to take to slow to zero to implement BL, so a setting of less than .1 is less than 1/10th of a second, pretty
much instant.. The larger numbers would like 5 is 5 seconds.. which means youd expect the 5 second slowdown. Keep it less than .05 and you shouldnt see
any rampdown..

  So the question is.. if set to .05 does it stay at .05? Does it take several seconds to ramp down ever at that point?

Thx
Art
 

Offline RICH

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Re: BACKLASH PROBLEM MACHV3.042.020
« Reply #9 on: March 19, 2009, 10:43:43 AM »
ART,
"if set to .05 does it stay at .05?"  YES

( BUT IF PRIOR TO INPUTTING .05 , IF YOU HAD INPUT .4, OR SOME RANGE OF VALUES
BL WILL BE BE SCREWED UP..... UNTIL.....  "0" VALUE IS INPUT FOR THE SHUTTLE ACEL)

I remember something like this as a problem in the last year,      
   ------maybe it was a problem in "saving" the setting. -----------
This is a odd one, 2 other Mach users brought it to my attention and it happens
for the mill and lathe.


RICH