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limit switches
« on: October 18, 2009, 09:15:33 AM »
Newbee  my next step is to install limit switches on my shopbot . just finished building my controller have not hooked up for testing as yet.
i want to use micro switches as my limit switches.   what i am thinking of doing is just mounting three switches on the y carriage
one for x y and z.
and use operating ramps to trigger switches at both ends or x and y.
have anyone used this system, without a problem?
also what brand of microswitches is recommended and where can they be bought.
a part number would help.
i notice there are some with a long lever and some with the lever in about the centre of the switch.
Is is possible to run mach3 in demo mode and assimilate the limit switches position?
or must the switches be physically struck.
eg can this be done in demo?
With the home switches wired and tested it’s time to home the machine. With the control out
of E-Stop mode, go to the Program Run screen and with one hand on the E-stop button press
the Ref All – Home button. The machine will now start to move Z up until it hits the switch
then it will reverse the axis until it clears it. Then it does the same with the Y-axis and finally
with the X-axis. When each axis is homed the DRO’s should read 0.00 or whatever value you
put in as the Home Off value. If any axis starts to move in the wrong direction press the EStop
button and go to the Home/Limits setup and change the Home Neg setting for that axis.
Thanks paul
 

Offline Hood

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Re: limit switches
« Reply #1 on: October 19, 2009, 02:54:32 AM »
Quote
one for x y and z.
and use operating ramps to trigger switches at both ends or x and y.
have anyone used this system, without a problem?

I use optical switches on my Bridgeport in that way.

Quote
Is is possible to run mach3 in demo mode and assimilate the limit switches position?
or must the switches be physically struck.

You can emulate on the Ports and Pins, Input page, just enable the emulation for the home switches and then assign a keystroke to them. When you home you can press your key on the keyboard and Mach will act like it is a home switch.

Hood
Re: limit switches
« Reply #2 on: October 19, 2009, 07:48:57 AM »
thanks hood   will try that setup later.     another question  where can i get information on setting up a jog home
on my keyboard on my shopbot cnc i just hit JH.
also if i want to pause my cnc when running a file i just hit the spacer bar.  most of the time i hold the keyboard in hand standing in front of the machine.
i could not find any information on the mach3 handbook about setting keystrokes to assimilate these moves.
dont you think using optical limit switches there will be a problem with dust.
thanks woodguy


Offline Hood

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Re: limit switches
« Reply #3 on: October 19, 2009, 08:16:52 AM »
Not sure what you are meaning by a Jog Home.
The customisation manual has the keystroke keycodes in it if I remember correctly(dont like HotKeys so dont use them) To assign a HotKey to a button you need to open the screenset with Screen3 or MachScreen etc and change it or assign it there.

The opticals I have are in housings and a rod extends either side through "O" rings (need to be coolant proof for me), the rod is held central by two springs and attached to the rod is a flag that interrupts the opto. As the machine moves to a stop it contacts a striker which pushes the rod to one side, the flag moves out of the way and the opto is seen.
Re: limit switches
« Reply #4 on: October 19, 2009, 08:34:49 AM »
what i mean by jog home is this  on my shopbot i zero at the right corner of my table  so when i hit jh on my key board
it goes there
did your machine come  with that opto setup, or did you make it yourself.
one day all this will fall into place for me  i hope so.
the link i attached is of a limit switch i found on ebay.  not sure if something like this will work
my other choice is to go with machanical micro switches for now and upgrade later
thanks again

http://cgi.ebay.com/CNC-Proximity-Limit-Detector-for-stepper-or-servo-motor_W0QQitemZ330289837100QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item4ce6cef42c

Offline Hood

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Re: limit switches
« Reply #5 on: October 19, 2009, 09:42:13 AM »
I bought three of them for the first mill I retro fitted but they are no longer sold so I made them for the one I have now. On my lathe and the next mill I  am doing I have high quality industrial limit switches but they are just used to signal my servo drives to look for the index pulse on the encoder, this gives extremely accurate homing. However the optos are also accurate.
 Micro switches also work well, maybe not quite as accurate but should be more than needed on a router (which I presume a ShopBot is? )

The Jog Home button would be easy enough to do with a VB button added to the screen, just have the following in the button.
Code ("G28X0Y0Z0")

That would move all axis together, if you preferred the Z to move first then just have
Code ("G0G53Z0")
While IsMoving()
Wend
Code ("G0G53X0Y0")


Hood