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Soft Limits Help
« on: September 22, 2013, 10:52:11 AM »
Soft limit switch
First time on this Forum and it wont be my last, What I have been reading has been a lot of help, But now I am stuck.
I need help in setting up my soft limits This is my first CNC router That I have built it has a cutting table size of 850mm X 500mm it also has limit switch's on all axis.
The computer is an old windows XP that I got from a friend that hadn't been used since 2005.  
When I start Mach 3 and get it to run a G code, all is well and it will home  when asked. Then I will jog the X Y and Z to a new position that will be fine also,  Now when I press the soft limit button and I jog back to the end of the table near the home position it will crash into the ends bending the limit switch. I do a manual check  and find the limit switches are not working, I can move the axis away from the end and press the limit switch with my finger and none of the limit switches are working, when I switch off the soft limit and reset Mach 3 the limit switches are back working.
I have set the size on the Motor home / soft limit  to 5mm smaller that the cutting area hoping that it would not bang into the stops, but I have already had to replace three switches as it hit them hard.
What am I doing wrong? I have attached a picture of the setting I have on the Motor home / soft limit screen.
Or could it be the computer does not have enough RAM to keep up with Mach 3 program.

Mike.
« Last Edit: September 22, 2013, 10:58:59 AM by Bush Flyer »

Offline Hood

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Re: Soft Limits Help
« Reply #1 on: September 23, 2013, 01:59:06 PM »
Can you attach your xml please, that way I can see all of your relevant settings for limits/home switches and it will stop me having to guess :)
Hood
Re: Soft Limits Help
« Reply #2 on: September 24, 2013, 07:04:18 AM »
Thank you for replying Hood I appreciate the time you are taking to help me sort out my CNC Gantry router
I found this in the Mach 3 folder and I hope this is what you need.

Mike.
« Last Edit: September 24, 2013, 07:07:16 AM by Bush Flyer »

Offline Hood

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Re: Soft Limits Help
« Reply #3 on: September 24, 2013, 03:04:06 PM »
I cant see anything wrong with your setup so assuming the values you have entered in the homing and limits page are correct I am at a loss as to what could be wrong.
Can you do a wee test, home the machine and move away from the switches and then press them manually. Do the limits trigger? Both with softlimits enabled and disabled (although it should not make any difference)


Hood

Offline Fastest1

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« Reply #4 on: September 24, 2013, 09:06:39 PM »
Is your motor tuning calibrated accurately? Does it actually go the correct distance even upon reversal (backlash 0 or compensated for?)
Are your limits and home switches both enabled? Or just 1 of those? Do you have any debounce? If so how much? If the number is too high then the machine would keep traveling until that time period after the switch was triggered.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)
Re: Soft Limits Help
« Reply #5 on: September 25, 2013, 08:44:31 AM »
Hi Hood and Fastest1,
Well I have spent the morning checking my CNC router. I traced it down to the fault that after I home all axis then jog away from home the limit switches would not work till after I pressed the Reset button on then off after I done this the limit switches would work as would the soft limits, also I found that after I homed all axis and then jogged away from home that it would not home till once again I pressed the rest button on and off.
But I fixed it, I went through all my setting once again and I found in the engine configuration ports & pins on the input signals, that I had the A axis enabled with the same port 1 pin 10 that is the same as my X axis. Now I have two stepper motors on my X axis and I have them slaved X and A axis together but I only have limits switches on one side and I wrongly thought that by enabling the A axis with the same ports and pins it would just copy  the signal that it received from the X axis limit switch. I was Wrong, I disabled the input signal from the Axis and now it works great I am so chuffed.  ;D
Many thanks for your help.

Mike.

Offline Hood

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Re: Soft Limits Help
« Reply #6 on: September 25, 2013, 05:54:04 PM »
Thats good that you found the problem, it is also a good bit of info that  will try to retain in case someone else has a similar issue, thanks for posting :)
I have never used a slaved axis with Mach and although I did see in your xml that you had the same inputs for the switches I had just presumed you had the swithches in series on both sides of the machine.

Hood
Re: Soft Limits Help
« Reply #7 on: September 26, 2013, 04:29:08 AM »
I always try to do a build review on the appropriate forum, and I always try to be helpful as I can. The help I got here has been some of the best.
I will keep coming back here to this forum it is a great and friendly  place to learn about Mach 3 and I hope some day that I can help some one else.  :)
My thanks again Mike.

Offline Hood

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Re: Soft Limits Help
« Reply #8 on: September 26, 2013, 04:43:50 AM »
You already have helped Mike :) By posting you resolution you have done that and also for people in the future that have that issue it is now down in words so can be searched :)

Hood