Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: scottybev on February 06, 2006, 11:01:28 PM

Title: Back Lashing??
Post by: scottybev on February 06, 2006, 11:01:28 PM

 ???Any ideas on how to understand why a machine seams to be back lashing but its really not. All part programs run nice and smooth but the overall results are .02 off on all axis. A programed pocket at .5 width ends up being .480. New bits too.
Offsets are all zero. Program design math is all verified and correct. Is it something in Mach3 or maybe the machine??? ???

Anyone have a guess?

 8) 8)Scotty ???

Title: Re: Back Lashing??
Post by: Brian Barker on February 07, 2006, 05:23:34 AM

Scotty did you update to the newest Rev of Mach3? The Backlash should fix your problem...

Title: Re: Back Lashing??
Post by: scottybev on February 08, 2006, 12:03:04 PM

Yes, I reinstalled M3 and saved my xml, test ran a new piece and its still of on all axis. Runs smooth.

Quote from: Barker806 on February 07, 2006, 05:23:34 AM

Scotty did you update to the newest Rev of Mach3? The Backlash should fix your problem...

Title: Re: Back Lashing??
Post by: Art on February 08, 2006, 12:48:50 PM

Hi Scotty:

  Sounds like flex in the machine to me. There is no way the software can always be .2 off. Cant happen in that way. If it returns to zero each time, the axis are flexing or something. If you run it very slow does the DRO read proper ?

Art

Title: Re: Back Lashing??
Post by: scottybev on February 08, 2006, 01:12:29 PM

I ran a 5 inch square with a 1/2" bit reallly slow and the same results. the DRO reads correctly and so does the math on Bobcad. I''m lost

Quote from: Art on February 08, 2006, 12:48:50 PM

Hi Scotty:

 Sounds like flex in the machine to me. There is no way the software can always be .2 off. Cant happen in that way. If it returns to zero each time, the axis are flexing or something. If you run it very slow does the DRO read proper ?

Art

Title: Re: Back Lashing??
Post by: Art on February 08, 2006, 01:22:58 PM

Scott:

  So the 1,000,000 question is, if you do a 8": square, is it still exactly .2 off?

Is it the same as the 5" cut?

Art

Title: Re: Back Lashing??
Post by: scottybev on February 08, 2006, 01:29:51 PM

Yep! If I had a 10" or a 20" or 2" its still off .02

Quote from: Art on February 08, 2006, 01:22:58 PM

Scott:

 So the 1,000,000 question is, if you do a 8": square, is it still exactly .2 off?

Is it the same as the 5" cut?

Art

Title: Re: Back Lashing??
Post by: Brian Barker on February 08, 2006, 02:50:33 PM

1. Put in 1.00 for the backlash amount.
2. Check enable backlash
3. Exit Mach3 to save settings
4. Open Mach3
5. Set the jog to INC .010
6. Jog the axis + and - one press of the key

What do you see happen? You should see the axis move about an inch NOT .01

This will tell us if you have backlash on and working

Title: Re: Back Lashing??
Post by: Graham Waterworth on February 08, 2006, 03:30:16 PM

Hi All,

even if you set the backlash in Mach3 this will not remove the lash it just compensates for it on the movements,  if the cutter is pulling the table you will still get errors.

If you take a shallow cut just deep enough to be able to measure it do you still get the error?

Also

Is the cutter running true?

Is the cutter too far out of the collet and flexing?

Is the Z axis square to the table? if not you need to trapan the table with a clock and set it square.

Graham.

Title: Re: Back Lashing??
Post by: Vmax on February 08, 2006, 08:10:06 PM

Scotty have you tried cutting a square with manual inputs or is it always with a BOBCAD post. It sounds like an offset is being applied incorrectly each time. Try setting up a dial indicator and make a 1" manual MDI move and see what the indicator shows.

Title: Re: Back Lashing??
Post by: Vmax on February 09, 2006, 07:03:46 PM

Scotty have you gotten it figured out yet????  Terry

Title: Re: Back Lashing??
Post by: Aldoseri on February 13, 2006, 01:46:55 PM

Hi Guys,

I have no idea about milling, but i'm assuming so correct me if i'm wrong, Could it be the tool used, maybe it is not straight enough or the diameter setting is not exact? if the Mach thinks that the tip diameter is lets say 6mm but it is actually 6.02 then i would imagine that you'll get an error just as much on all axis. and the same if the tool tip vibrates at that rate.

Title: Re: Back Lashing??
Post by: Brian Barker on February 13, 2006, 02:22:17 PM

I think his cut is undersize :(