How I feel when as a group effort we fixed something. Y’all take a bow and pat yourself on the back. Casey youdaman for sticking with it.
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When you get a chance, inspect the pins on the connector on the “bad” motor to see if any are burnt.
The screws on all for the motor connectors are really long and will actually back the connector out of the plug when tightened all the way causing a bad connection and actually burning/arcing out the pins.
It’s been a known issue and Langmuir used to include shorter replacement screws but not sure if they still do.
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Alright Joe, since you brought it up, and the answer might help somebody out.
Langmuir doesn’t ship shorter screws anymore. Instead they send you a little packet of washers with instructions to back the motor connector screws out, and install the washers in between, to effectively shorten the screws.
But the washers they send don’t actually fit the connector:
I almost opened a service tag over this, but I test-fit all my connectors and they all seemed to seat fully, and they didn’t look like they were being pushed out as I was tightening the screws.
Of course, now that I’ve had a motor fail, I’ve wondered if I missed something, somehow. Maybe @langmuir-aksel can clear this up for me, and anybody else who might stumble upon this thread later? Please, Aksel? 
FWIW, none of the pins look crispy on my old z-axis connector:
I’d love to see a picture of a connector being pushed out by “too long screws” to know what that looks like.
Anyway, I hope this information can be helpful to someone, at some point.
I think the point of the washer it to shorten the length of the screw thread going into the nut by providing a “stop” when the plastic end of the screw reaches the washer.
I have a first batch Pro so that issues didn’t come up then. Although I don’t use the screws on mine to tighten the connectors. They are just friction fit and have never backed out on their own.
I’m surprised the pins aren’t scorched. I wonder if there’s an internal break in the wires and they are touching somehow.
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Yes, but they don’t fit.
You can see how they’re supposed to be installed in the picture Langmuir sends:
And you can see my “attempt” here:
This makes me wonder if they changed connectors and didn’t update the person who packs the hardware. Maybe the style of connector that I have doesn’t need the washers.
Here’s a pic of the burnt pins.
So after looking at that thread, the OP said the hole in the enclosure needs to be opened up, or the shield on the connector needs to be filed down. My connectors are butted up against the enclosure; if there’s a gap it’s miniscule. They seem snug, but perhaps they are short of making full contact to the female part of the plug.
I can try to find some washers that have a smaller OD to fit the connector, but I don’t think that would get my plugs any closer to the enclosure.
To be honest, I was hoping the spacing people talk about would be more dramatic looking.
Granted, I don’t think this is what went wrong on my table, but it would be good to avoid any future issues.
Interesting read. Did your problem develop over time, or was it like that from the get go? I ask, because I don’t think I have a connection issue, but I haven’t been cutting very long, so I suppose things could still reveal themselves.
Smoked it on the commissioning.
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I appreciate the info. I’ll double check all of my connectors for any signs of scorching, but I haven’t had any issues, beyond, seemingly, a bad Z-axis motor that was back-feeding arc voltage into the electronics enclosure. But it certainly doesn’t hurt to check these things out.
@CrazyCasey those washers do fit, kinda. The trick is to put the washer edge on into that depression as you reinstall the screw. It’s a very tight fit. My first one looked like yours before I figured it out. Langmuir needs to source smaller ones as the washer does push the screw a little bit out of alignment. I also realized those rubber screwdriver slots aren’t up for the task with the additional tension caused by the off-center screw.
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You guys did all the hard work, I just got lucky. I have to admit for a while I was so intimidated by the thread size that I avoided it. But after a while I couldn’t help myself, my curiosity got the best of me!
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Yeah. I figured I could force it, but I wasn’t sure how much of the screw was metal and how much was plastic, so I didn’t want to do that. I could probably just kiss them on the belt sander. I’m not sure how much of an issue it is actually…kinda like my dry air and raw voltage. Probably better just get it done.
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And it’s STILL going! 
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I think we could sell this thread as a reality TV series and recreate it over like 7 seasons. We’d all get rich!
I’m 65 so I guess maybe Richard Gere or Tom Seleck should be cast as me. 
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Let’s go with Tom!
So, in an effort to clear up the whole D-SUB screw length washer debacle, I disassembled all of my D-SUB connectors and found that I had a range of bolt lengths with up to about 1/8” difference between them. So, you may or may not need to add washers on your D-SUB screws. Some of my screws were so short in fact, that with washers on them they would not even engage the threads.
As I stated last night, the Langmuir-supplied washers don’t fit without forcing them, which I never like to do.
So I went down to my local Ace, which has a better hardware selection than most, mind you, and I was able to find some washers that fit perfectly without any forcing. They are a HILLMAN part number 43890-B (though the B seems to be superfluous), and are listed as a M4 “small” washer.
They’re a little thinner than the Langmuir-supplied washers, so you may need to use 2 on the longer bolts, but they fit perfectly without any ham-fisting required.
Yes, really, perhaps these washers may become my Langmuir Legacy. Instead of an ~800 post thread just trying to diagnose a bad Z-axis motor. 
@langmuir-aksel, HILLMAN p/n: 43890-B M4 “Small” Washer UPC: {0 08236 70064 0} fit the connectors much better than the ones you guys currently supply.
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I was cruising the internet and I found a legend that sounds amazingly similar to your story:
There was a saga that began in Nevada one day,
It was suppose to be fun but it was not going that way.
There was a young man set out to tame the Langmuir table,
But instead his efforts were all met with the lore of this fable.
You see, the table had plans of its own to give a head fake,
No one could have predicted the journey he would take.
The torch galloped and jolted with the energy of Thor,
It was enough that most people would have said “No More!”
But it was Crazy Casey who doesn’t give up as is his motto,
He will fight until winning as he knows he’s got to.
Failure is not a word he will say,
But the saga went on for 80* more days.
Many people got involved from the company and the forum,
Everyone and everything was rooting for him.
One cutter, then another and another proved no worth,
Crazy Casey started to feel as helpless as the day of his birth.
Finally there was a light that would appear,
Could this be the answer that he waited to hear?
Scott and BigDaddy and many others were there to push him through,
It was the celebration to end all so lets have a brew.
So is the legend of Crazy Casey from Nevada.
*(80 days…it is a ‘legend’ remember, not meant to be statistically correct!)
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And the offer still stands for Casey his wife and the Crazy two year old for Thanksgiving in Chattanooga.
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