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Where is the ref-switch for the rotational A-axis installed?

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Author Topic: Reference/limit switch for A-axis (4th axis)  (Read 12911 times)

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Reference/limit switch for A-axis (4th axis)
« on: March 12, 2009, 06:39:18 AM »
Hi, I am presently familiarizing myself with Mach3 (Demo Version).  I have a home built portal type milling machine.  In order to cut letters I activated the 4th axis (rotational) for a tangential knife.  The setup works fine with one exception:  At the end of cutting a letter the stepper does not return the knife to its original position.  Homing the machine has no result on the 4th Axis.  I can only reset the knife position manually because the axis does not activate a reference switch.  
My question:  is a reference switch required? If yes, where is the switch physically installed? Or is it controlled by software? If yes, where do I find this software?

Best Regards Karl
Re: Reference/limit switch for A-axis (4th axis)
« Reply #1 on: March 12, 2009, 06:57:20 AM »
Hello Karl,
   Here is a similar post.
http://www.machsupport.com/forum/index.php/topic,6134.0.html
I never heard back from him, but I assume the suggestions would have worked fine.
Good luck,
RC
Re: Reference/limit switch for A-axis (4th axis)
« Reply #2 on: March 12, 2009, 07:33:38 AM »
Hi there,

The guys from the forum here have been great.

I have had several issues along the way and at present my machine has been running great.

My A axis stepper is dual shaft, meaning a shaft on either end. I have fitted a round disk to the shaft approximately 50mm dia. To get some kind of good accuracy I have drill a 0.5mm hole in the disk and used cnc4pc optical switch to do the homing. Accuracy is to +1 deg. I'm waiting for the encoder input on the Smooth stepper for real accurate homing.

So to answer your question. Add a optical swicth to your A axis. Set up homing for the A axis and you will be good to go.

I did have a recent problem with my A axis gaining up to +10 deg after a run of cuts. I had purchased gears to gear my A axis so that there was a hole number of steps/deg. However only a few weeks back I installed the latest updates of Mach3 and for the Smooth Stepper. The machine has been running great

If you have any other questions, I would be happy to help out. The moderators/folks on this forum have been great help to me in times of frustration. It is certainly a good learning experience. My machine is now a blessing to use in our workshop and as I have all our patterns created it is just a matter of rolling out the material, loading gcode and hitting cycle start. My next project is a webbing cutter using a hot knife and stepper for cutting webbing/tapes to set lenghts and quantities.
Re: Reference/limit switch for A-axis (4th axis)
« Reply #3 on: March 13, 2009, 01:56:36 PM »
Hi Moderator,
thank you for your email.  One answer to another query was related to a reed switch.  I think that to be the best and least expensive solution.  My stepper has an axis extension on both sides.  I will attach a wheel (clamped to the axis for ease of corrective placement) on the rear axis and glue a magnet near the outside which will pass a normally closed reed contact and open it.  This will zero the reference point of the A-axis when the machine is referenced to zero before starting a new job.
Best regards Karl

Re: Reference/limit switch for A-axis (4th axis)
« Reply #4 on: March 15, 2009, 07:51:59 AM »
Hi XLR84x4
I have followed your suggestion and installed a switch instead of the optical setup you installed.  The reason is that the cnc4pc is very expensive.  They want $27,00 shipping charge for sending it to Germany; that means a total of approx $50,00.
I do get a zero reference.  But every time the actuator passes the switch the machine stops regardless if I mark A++, A-- or Home, or any combination.  Since your setup works, I must a wrong basic setup.  The Mach3 software I use is the latest available. The A-Axis moves the knife up to 900 mm/sec, lifts the axis if the angle is >45 degrees, etc.
Can you help or do you need more info?
Best Regards Karl
Re: Reference/limit switch for A-axis (4th axis)
« Reply #5 on: March 16, 2009, 12:03:29 AM »
Hey Karl,

I'm out of the office until next week. I will check my setup and post my config for you. Off hand I think my homing A- is 0 and A + 360 deg. I do have a speed set to 25%. When I reference A yes it stops once the switch is activated. I have no offset select, meaning it does not go + or - after the limit has been activated.


Re: Reference/limit switch for A-axis (4th axis)
« Reply #6 on: March 18, 2009, 04:37:54 AM »
Hi XLR84x4,
additional comment to my previous query which you posted to comment next week:
the basic set-up of the tangential knife is working fine.  I set the angle to 45 degrees and 1.5 mm for clearance for knife repositioning.  But this works only satisfactory for cutting a square or rectangle. Since the knife is quite expensive I dare not to experiment with other angle values. But I am certain that the angular setting is wrong - but what is the correct value and must Mach3 be set to absolute or incremental value?
Which program is required to produce the dxf (or other) file prior to generating the G-Code, or can any suitable program be used?
Best Regards Karl