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Problem with Backlash...
« on: November 07, 2010, 09:51:25 PM »
Hello.
I'm new on this forom and on CNC world.Also I,m a french Canadian and sorry for my bad English !!!

I modify a metal lathe to turn wooden piece with step motor...good.All run great but I have a .008 inch of backlash on Y axis and I have a problem when I use the backlash fonction on Mach3. I expland...The backlash function operate well separately but when run a program the function didn't run because stop and start X axis with not slope programed...???

If anything have an idea for resolve my problem I appreciate.

Thanks
Claude Turcotte

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Re: Problem with Backlash...
« Reply #1 on: November 07, 2010, 10:08:44 PM »
Claude,
Do you mean the X axis has backlash?
Lathe is usualy X and Z axis ( no Y axis ).

RICH
Re: Problem with Backlash...
« Reply #2 on: November 07, 2010, 10:46:05 PM »
Hello Rich,
Thanks for your response,effectively lathe use X and Z but I use Machmill for this machine because with Machturn the drawing is not translate correct.

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Re: Problem with Backlash...
« Reply #3 on: November 08, 2010, 05:31:05 AM »
Claude,

My 50-50-50 rule for backlash setting which you may want to consider.

50% - The max velocity is 50% of where your steppers will start to skip ( in Motor tuning )
50% - Set the shuttle Wheel setting in configuration to .0050  to .050 ( .5 too slow ) ( in Config )
50% - Backlash speed % of max ( in config>backlash )
This is a good starting point and refine upward.

RICH
Re: Problem with Backlash...
« Reply #4 on: November 08, 2010, 03:35:58 PM »
Hello Rich,
The problem is not with axis with backlash but the other...I try to explain with my bad english...;-)))
When X axis get back the backlash, stop for a fraction of time the Y axis and when restart the motor go skip even if the backlash speed is 5%...???

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Re: Problem with Backlash...
« Reply #5 on: November 08, 2010, 07:01:35 PM »
Understand the language problem, we'll just work through the problem very slowly......
Smile   :) ......you French ......me Lithuanian.....here we go..... ;)

Do you mean the following movement:

X and Y are moving
X changes direction, X backlash is implemented, and then the Y axis stops for a short time.
When the Y axis tries to move, it skips.

Please correct motion described above,

RICH
Re: Problem with Backlash...
« Reply #6 on: November 08, 2010, 07:06:06 PM »
Yes it's my problem

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Re: Problem with Backlash...
« Reply #7 on: November 10, 2010, 04:55:40 PM »
What is your velocity settings in motor tuning for the X and Y axis?
Post your xml file.

RICH
Re: Problem with Backlash...
« Reply #8 on: November 10, 2010, 05:42:33 PM »
Hello Rich,
The lathe is not here but the velocity is approx X=22 IPM  and Y is is 30 IPM
Because it's an older metal lathe the carriage is very heavy (approx 200lbs) and it's hard to move also the slope for start and stop is approx 1.2sec
thanks
Claude

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Re: Problem with Backlash...
« Reply #9 on: November 10, 2010, 10:07:48 PM »
Here is what i am thinking, could be wrong. I think the Y axis is trying to adjust for the backlash. ie; With a heavy load like that the Y can't stop or accel instantly. Have you tried running at even slower speeds like 5 ipm just to see what happens. I thought you may have been running at 100 at 150 ipm. Try the slower speed and see what happens.

I get a chance, will play with the lathe here and refresh my backlash memory.....
The trouble is the whole lathe is little more than your carriage weighs.

RICH