Limit/home Switch Repeat Ability In Home Cnc

Metal said:
Thanks for the info!
for my research what breakout board are you using ? since parallel voltage is 5.5v at best and these take 10v at minimum I'm assuming either you're using something more advanced than I used previously or there's another board inline with the switches.
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Both machines have PMDX-126 breakout boards with PMDX-107 spindle control add-on boards. The PMDX-126 is powered by 110vac or 220vac and has 12 vdc on the board to power the proximity sensors. Otherwise you could use a separate power supply for the sensors.

Not sure what your looking at for motion control. My mill uses an Ethernet Smooth Stepper motion controller which mounts directly to the PMDX-126 and the router uses a UC100 USB motion controller. The UC100 works okay but will occasionally loose connection which is really frustrating. Eventually I will replace the UC100 with another Smooth Stepper.
 
I've been looking at copley servo amplifiers, since I already have two beefy servos and encoders, and they are surprisingly cheap: http://www.copleycontrols.com/Motion/pdf/412.pdf

I'm not sure if I am going to have the Z axis be the quill, or the knee (I'm leaning towards knee since quill runout looks like a thing, but ive seen people suggest both) and will eventually build a 4th axis.
 
The Copley amps look like a good choice. You just need a motion controller that is compatible with the inputs, outputs, and your choice of CNC controller software.
 
Yep, I'll shop around tonight but i'd like to get this nailed down soon, steppers were easy in comparison and I have no way of testing the encoders on these servos so I want to keep this as cheap as possible, if I have to upgrade to more accurate/featured electronics later I'm fine with that, but going all in on expensive controllers and then get stuck buying new servos may put me way over budget.

Or I could sell these things and just go steppers again...
 
Many motion controllers will run both steppers and servos.

The encoders can be tested with a scope, it is also possible to test them with a Fluke 87 multimeter in Hz/% mode. Normal input voltage to the encoder is 5VDC.

A 12 volt battery will run the servo motors just to confirm that they work.

This is just my opinion, but I would (did) put the Z on the quill.
 
RJSakowski said:
I was concerned about poor repeatability with the Tormach mechanical limit switches. I installed an optical homing system and can routinely get +/- .ooo1".
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Yes, the only way to get that level of repeatability is via optical sensors. Some DRO scales are actually optical and you know what the repeatability is them. Trick is if you are going to do a DIY setup you need the Stops to be almost centered on the machine and have a sliding bar with holes that are very small that the detectors are reading through. The setup would need to block the light unless you were at the stop as opposed to allowing the light all the time its' not at the stop.
 
JimDawson said:
Many motion controllers will run both steppers and servos.
The encoders can be tested with a scope, it is also possible to test them with a Fluke 87 multimeter in Hz/% mode. Normal input voltage to the encoder is 5VDC.
A 12 volt battery will run the servo motors just to confirm that they work.
This is just my opinion, but I would (did) put the Z on the quill.
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Yeah i can confirm the servos spin, one seems a little rougher so I may replace the bearings in it
For the controller I'm eying this guy, which comes highly recommended and appears to have all the features I could want http://www.pmdx.com/pmdx-126
 
Hey one more question: would putting LED's inline with limit/home switches so that I would know which one is tripped cause any sort of issues you can think of?
 
That could be done, but normally you can visually see which switch is tripped. The exception to this might be in the case of a switch failure or a broken wire and the switches are wired in series. Would aid in troubleshooting, but not really needed in normal operation. It might take a little electronic logic to get the LEDs to come on properly without tripping the input.

Depending on which controller or breakout you are using, it may have individual inputs for all of the switches so the state could be monitored via the computer screen.
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