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More dual axis homing issues
« on: January 09, 2012, 10:38:15 PM »
Hi Everyone,

I have just finished retrofitting my multicam router (big sucker 70"x140") rack and pinion.

Obviously at that size it's dual drive. It has prox switches on both drives to square the gantry when homing. I have everything hooked up via my C32 and my ethernet smooth stepper.

I have my A Axis slaved to X and I have the the direction pin active hi on the A axis and low on everything else. I have the homes set as negative and all the axis normal (ie not reversed). All motors are wired the same. Everything jogs great and the Z and Y axis home just fine BUT.... The XA / XB is a mess.

Here's what happens. Whatever axis hits first does its little bounce off the home switch just fine, the other axis (usually the A) might jump around a little, might not do anything, but it will not move off the axis and the home sensor will remain active on that axis.

If I look at the prox switch locations they are inconsistent, the second switch which hits will always be more "over" the dog where as the first axis will move off the dog so that they are not inline.

What's going on??? I need to get my machine back up and running so I'm desperate.

Thanks!
-Ed
Re: More dual axis homing issues
« Reply #1 on: March 15, 2012, 07:28:12 AM »
I have seen this Question many times.
It seems the problem cant be fixed.
 :o
Re: More dual axis homing issues
« Reply #2 on: August 19, 2013, 08:55:55 AM »
Hello, I have the same problem. Did you get a solution ?
Maybe a custom script has to be made ? Just to drive separately each drive ?

Kind Regards,
Daniel

Offline Jeff_Birt

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Re: More dual axis homing issues
« Reply #3 on: August 20, 2013, 08:54:55 AM »
The 'problem' is that mechanical switches don't switch cleanly. You get bouncing of the contacts and a small area of travel where a bit of wiggling can make/brake the contact. Since the SmoothStepper and other external motion controllers can read there inputs much faster than the parallel port they will 'see' this issue more frequently. To combat this issue you first need to make sure that when your switches re triggered that they are fully triggered, i.e. not just barely triggered. Then you need to make sure that the machine travels fullyonto and off of the switch. Since this 'over-travel' distance can't be set in mach3 we have to fake it. Go into the SmoothStepper configuration and set the noire filtering for the home switches to a high value, like 5000. This will give you a little more travel onto and off of the switch and typically solves the problem.
Happy machining , Jeff Birt
 
Re: More dual axis homing issues
« Reply #4 on: August 20, 2013, 09:10:56 AM »
I found that a NC (Normally Closed) wiring switch choice worked better for me on my large table router(cuts 65 x 110). I am using roller lever action micro switches. Then it is finding the right debounce interval settings, seems like it was between 300 and 450. Watch the Diagnostic page to see the LED in action.

Offline Jeff_Birt

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Re: More dual axis homing issues
« Reply #5 on: August 20, 2013, 09:46:17 AM »
Take a look at the bottom link in the Soigeneris section here: http://www.soigeneris.com/documentation-content.aspx (Mechanical Home / Limit Switch Guide). This is an application note covering some testing I did on different mechanical switches and how contact bounce, etc. can cause you problems.
Happy machining , Jeff Birt