Hello all.  I am a brand spanking newbie to home CNC.  I never thought about it until 3 weeks ago when my fabrication hobby opted for CNC Plasma.  So I have built a controller here using 4 Gecko G214's (y slaved to a), ESS Smooth Stepper, MB2 BOB and THC3T THC up/dwn (installing npn prox sensors when arrive for home/limit).  The cables are Molex SJOOW shielded 18/4c with GX 20 5 pin I/O connectors and 4 Delta 150 cfm fans in a push pull arrangement.  All this in a Hoffman 20x20x8 nema enclosure. Just installed Mach3 a bit ago.  I think I understand.  Just configure I/Os to match my BOB.  Any input appreciated.  Never did this before 3 weeks ago. I'm this far by reading alone.  Thanks

Excellent work - that has the makings of a fine machine.

(Not a criticism just an observation...
I have never used those toggle connectors so don't know for sure but when you have it all up and running perhaps check that you don't get a voltage drop across the ones between the PSU to the Gecko's as it is generally always best to wire each Gecko's power lines direct to the PSU without any terminal blocks).

Tweakie.

Thank you for the encouraging words.  I didn't consider the IR  drop across those toggle terminals.  I never used them before myself.  I will certainly inspect losses under load to see if it is a factor.  They bite hard into the wire though.   I was surprised at how strong they grabbed.

Ok, I am up and running now.  But Houston we have a problem!!!  First I rewired all of my 48V connections straight to PS and eliminated distribution block on my high current outputs.  This did not affect the situation I am about to describe.  

So as stated in my OP I have x slaved to a.  I have 300oz nema 23's 1.8°.  Gear rack and pinion 24DP 15T gear.  Running G214's at 10us.  So my mach3 steps per rev are around 1000.    I verified with dial indicator and running at 1084.312 mspr.  Depending on kernel freq. And ess freq I can get rapids in jog mode over 500 ipm np issue, but only just jogging around.  When I try to run an actual code ladder my slaved drive "a" goes into protect mode at anything over 60ipm.  So I am assuming too much accelerated torque load is being applied to motor.  But why just  "a" and not "x" too?  However in observing "x" I do see status led on gecko flash red momentarily under fast direction change.  Using 12 awg  for power leads on a 2.8A stepper.  

Is it an issue of slaved axis?  If I reduce micro steps I will gain more torque correct?   Could I have too little backlash on pinion gear to rack causing a bind?  (Doesn't seem to bind though).  Any suggestions before I dump these for 600oz/in?  Would i be smart to get a planetary geared stepper instead? Also I think I want to add encoders to my system.  Opinions on encoder brand?

Thanks everyone

Updated pics if they are of any interest

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Excellent. 

Tweakie.