Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: tlbokc on July 24, 2012, 12:09:16 PM

Title: How to make soft limits stay on in Mach3
Post by: tlbokc on July 24, 2012, 12:09:16 PM
I am running a CNC router with Mach 3. To prevent step errors from accumulating, I hit "All Home" after each sheet is cut and the program returns home (program home, not hardware home). But here's the problem, I have to hit "All Home" twice each time because the first time turns soft limits off, the second time turns soft limits back on.  Or, I can manually turn the soft limits back on after "All Home" turns them off.  But why turn them off to begin with? It just costs extra steps. If you forget the step and don't turn soft limits back on, then you can crash the limit switches when jogging for setups, tool changes etc. Crashing the limit switches is big trouble on this machine... and its inevitable when soft limits is always toggling off!

Is there no way to make soft limits stay on until you ask them turn off?

Any suggestions would be greatly appreciated!

Thanks, tlbokc
Title: Re: How to make soft limits stay on in Mach3
Post by: Hood on July 24, 2012, 01:26:53 PM
Do you have home switches?
I am just a bit confused by this bit "I hit "All Home" after each sheet is cut and the program returns home (program home, not hardware home). " If you have Home switches then the axis will move to them and set the machine coords when you press Ref All.

Soft limits never get turned off on any of my machines so not sure whats going on with yours.
If you attach your xml I will have a look and see if I can replicate and find the issue.
Hood
Title: Re: How to make soft limits stay on in Mach3
Post by: tlbokc on July 24, 2012, 02:04:12 PM
This CNC router is running stepper motors without encoders, so when it misses a step, and it does miss steps, then it looses a little position. Each time I run the program, the program goes to "Zero" and rewinds. The program Zero is now flawed because of missed steps. So, before loading and running a new sheet I hit "Ref All Home" to reset the carriage to the machine limit switches.  When I do, the Mach3 refinds the XYZ limit switches as it should BUT turns OFF soft limits. If I hit "Ref All Home" again, it refinds the XYZ limit switches and turns ON soft limits. Every time I hit "Ref All Home" it toggles the soft limits.  (Just like pressing the soft limits button: press on, press off, press on, press off etc.)

Why can't the soft limits remain on until I turn them off?  Is there a preference setting that keeps them from toggleing on and off each time I use "Ref All Home?" 

Besides the extra wear on the machine, there is the constant opportunity to crash the switches when soft limits turns off automatically and the operator fails to notice it.

Thanks, tlbokc
Title: Re: How to make soft limits stay on in Mach3
Post by: Hood on July 24, 2012, 02:06:46 PM
As I said softlimits never turn off for me so it is likely an issue in your config, attach your xml and I will look.
Hood
Title: Re: How to make soft limits stay on in Mach3
Post by: Hood on July 24, 2012, 02:12:04 PM
Also worth mentioning is if your steppers are losing position then they are either under sized for your machine or you have binding axis or you are trying to drive them too fast or possibly even you have a bad pulse.
I have steppers on the coil winder and previously had them on the Bridgeport and never once lost steps unless I crashed an axis or similar.
Hood
Title: Re: How to make soft limits stay on in Mach3
Post by: Overloaded on July 24, 2012, 02:13:20 PM
or maybe a custom screen. ?
be interesting to see what is under that button.
Title: Re: How to make soft limits stay on in Mach3
Post by: BR549 on July 24, 2012, 02:14:41 PM
That would be my question WHAT code is under that button(;-) THis is the stock 1024 button code

DoButton( 24 )
DoButton( 23 )
DoButton( 22 )
DoButton( 25 )

DoOEMButton(133)
DoOEMButton(134)
DoOEMButton(135)
 


(;-) TP
Title: Re: How to make soft limits stay on in Mach3
Post by: tlbokc on July 24, 2012, 03:22:46 PM
Sorry, don't know what an XML file is. How to find it?  I have a text file that is the router program. Is the XML an export from Mach 3?

Thanks,  tlbokc
Title: Re: How to make soft limits stay on in Mach3
Post by: tlbokc on July 24, 2012, 03:35:41 PM
Regarding the stepper motors: the problem is in the drive system. It is rather crude... a rack and pinion with the pinion spring loaded into the rack gear... runs dry.  Even with dry film lube the gears are galling each other and bind. Further, the carriage guide system is dual vee bearings  running on an angle iron track. The carriage long axis is driven by two steppers, one one each side, running in unison.  The carriage guide system runs in slight arcs, binding one motor against the other. When the tension gets too high, one motor must slip a few steps. This usually happens once each direction of travel along the long axis when cutting a 48" x 96" sheet.  I can't fix this problem without buying a better machine.  It's just not a good design.

Thanks, tlbokc
Title: Re: How to make soft limits stay on in Mach3
Post by: BR549 on July 24, 2012, 03:44:58 PM
Sure you can fix it just take the time to realign the angles to run with each other and set the pinion to run with a light preloading.

(;-) TP
Title: Re: How to make soft limits stay on in Mach3
Post by: Hood on July 24, 2012, 03:49:30 PM
Open Mach and lower right you will see the name of the profile you are using. Look in the Mach3 folder for a file with that name and a xml file extension. Copy it to your desktop and rename it to  tlbokc.xml then use the additional options button on the reply page to browse your computer and attach the file to the forum.
Hood
Title: Re: How to make soft limits stay on in Mach3
Post by: tlbokc on July 24, 2012, 04:59:31 PM
I am having trouble posting this. Sorry for the delay (its telling me I have already posted the file, so I renamed it). Attached is the XML file tlbokc.xml

Thanks,  tlbokc
Title: Re: How to make soft limits stay on in Mach3
Post by: tlbokc on July 24, 2012, 05:04:01 PM
I have tried to post this twice. Maybe the third time...
OK, I'll try to realign the angles.  I have been hesitant to try because the angle are 2" x 3" x 3/16" and I don't know if I can get them any straighter (pictures attached).  The problem was made worse by the fact that they used top guide bearing and side guide bearings. As a first measure, I have backed off the side guide bearings. They were actually fighting the stepper motors through the arcs.  The problem is now much improved.  As for realignment, I would need a very accurate 8 ft straight edge, assuming the angles can be flexed into a straight path. Anyway, I will give this challenge further consideration.

Regarding the soft limits, I found the XML file on the drive computer.  It is attached to the previous post. Any suggestions would be appreciated.

Thanks, tlbokc
Title: Re: How to make soft limits stay on in Mach3
Post by: Hood on July 24, 2012, 05:10:21 PM
Ok had a quick look at the xml and you are indeed, as Russ wondered, using a custom screenset. It is likely that the Ref All button contatins the extra code to disable the soft limits.
Can you go to Operator menu then Edit Button Scripts and then the RefAll button should be flashing, click on it then copy the text in it and paste it to the forum.
Hood
Title: Re: How to make soft limits stay on in Mach3
Post by: tlbokc on July 24, 2012, 06:06:57 PM
Here is the text in the "Ref All Home" button script:

DoButton( 24 )
DoButton( 23 )
DoButton( 22 )
While IsMoving
Wend
DoButton( 29 )

Thanks,  tlbokc
Title: Re: How to make soft limits stay on in Mach3
Post by: Hood on July 24, 2012, 06:18:42 PM
Delete from While IsMoving to DoButton(29)
That is what is causing your problem as DoButton(29) is the Softlimits toggle button.
Hood
Title: Re: How to make soft limits stay on in Mach3
Post by: tlbokc on July 25, 2012, 01:42:04 PM
Hood,

Thanks a million! Pulling out the "While IsMoving, Wend, DoButton( 29 )" corrected the problem.  Now the soft limits stay on when I hit "Ref All Home" to reset my XYZ home.  This will save us from hitting the switches when jogging and doing setups. 

Thanks again!

tlbokc
Title: Re: How to make soft limits stay on in Mach3
Post by: Sage on July 26, 2012, 08:57:00 PM
Regarding making your angle iron rails straight. No need for a long straight edge.
Looks as though all you need to do is fasten a taught string from one end to the other along side the rails nearly touching them.
 Keep the two ends fastened down. Loosen the middle bolts and force the middle section  until the rail is evenly spaced along the string.

 As for aligning the rails to each other, equal corner to corner measurements should square it up good enough..

Sage