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Author Topic: Digital Z Axis Control Questions  (Read 2536 times)

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Digital Z Axis Control Questions
« on: January 05, 2010, 05:01:38 PM »
Thanks for all of great topics and answers on VB and control tactics. 

My situation is close to the question posed in http://www.machsupport.com/forum/index.php/topic,3879.0.html

I'm building a machine to drill a particular bolt pattern, repeatedly.  Mach3 R3.042.020, G540 controls.

My X and Y axes are steppers and I'm using a pneumatic cylinder to drive the drill (Z) into the material. 

I have a "home/retracted" position limit switch for the Z and a "hole depth" input limit switch for the bottom of the Z stroke.

My question is how to control it.  I read through the use of 2.5D to control the solenoid valve for the pneumatics.  I would like to use the two inputs I have to know when it is safe to move the drilling head to the next location.  I don't think I can depend on the G4 Px to pause to wait for the drill to retract.

I have limited VB experience but it would seem that writing an Mcode macro is probably the "right" way to get this operation automated.

If you have a suggestion as to how to best approach this, I would appreciate it.  Thank you.

Bill
Re: Digital Z Axis Control Questions
« Reply #1 on: January 07, 2010, 03:39:51 AM »
I don't understand the part with the limit switches. If I get it, I can help you out.
Re: Digital Z Axis Control Questions
« Reply #2 on: January 07, 2010, 09:09:38 AM »

Thanks sunmix for the response.  I'll try to describe it better.

The machine is built around a small drill press head.  I have a limit switch that activates when the quill is in the fully up position.  This is "home", which indicates it is safe to move in the X or Y direction since the drill bit is retracted from the material.

I have another limit switch that activates when the quill is in the bottom position.  This switch activates at the bottom of the drilling cycle.  It indicates the drill has reached the depth that it should in the cycle and that the quill should be retracted.

Let me know if that makes a little more sense.  Cheers!

Bill
Re: Digital Z Axis Control Questions
« Reply #3 on: January 09, 2010, 02:55:00 AM »
In what condition the home limit switch will be activated? when the pneumatic cylinder retracts?

if the bottom limit switch is activated, do you want it to retract instantly?

you see, pneumatic cylinders only have 1 stroke action, and usually the pneumatic cylinders will stroke out the maximum, which is very possible to hit the bottom limit switch. if it happens, you will see the pneumatic cylinders stroking up and down. @@
Re: Digital Z Axis Control Questions
« Reply #4 on: January 09, 2010, 05:06:24 PM »
Hi sunmix,

The home position switch would activate when the quill retracts to the top position.

The "bottom of stroke" limit switch is adjustable to set the right depth of hole (these are blind holes being drilled, not just drilled through).  I would want the pneumatic cylinder to reverse direction once the bottom of the hole has been reached.

The events in the cycle are:

- Move the drilling head into XY position
- Activate the pneumatic cylinder to drive the quill/rotating drill bit into the material
- Once the appropriate depth has been reached, reverse the pneumatic cylinder to lift the quill/rotating drill bit out of the material
- When the quill reaches the top/home position limit switch, move the drilling head into the new XY position.
- Start above cycle all over again
- Once last hole is drilled, move to the safe XY home position

Hopefully, that makes sense.  Cheers!

Bill