MadModder

Um... I'll try to hit the high points!
First, take a file or a directory grinder and grind a higbee on the end of the threads.  Then clean the corners of the higbee.  It's used on firehouses and oilfield iron; you need to google a picture because my explanation isnt going to cut it...
Your lead screw needs to have one end fixed axially to one end of the table.  This can be done with a pair of bearings.  You want to run that end close to the nut, then tighten the screws to the table to produce alignment.  The other end can float axially, but your motor's centerline needs to agree pretty well with the nut.  You can do.the same trick (get close to the nut n tighten) on that end.
Btw, I hate what spell check does to axially and higbee!!

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Thanks for the link Ade, no I don't have that particular manual. It's for the S5-135U  Stand Alone PLC that the PLC embedded in the 820T controller emulates.

Assuming here, but I suppose that Siemens decided rather than have a physically separate PLC they could time slice the CPU in the controller to do the same job logically. The PLC even reports itself as a 135 when I connect to it.

I've yet to get fully to grips with it, but as I understand it the PLC copies it's field of input and output data to the CNC controller and vice versa once every pass of the program and that is how they communicate, setting the flag bits.

. . . It's a whole new world in there ! Bring back COBOL or ALGOL I say or even FORTRAN but I was happy with Z80 assembler 

Oops. Probing about trying to adjust the currents on the steppers. Went and Touched the wrong thing and now the display shows all the pixels on, except briefly returning to normal as it's powering off. Seems it's permanently broken but I wonder what part...

Edit: I can just make out the display at an extreme angle and turn the heater on, but none of the steppers move. I heard these things were fragile but yowch. Glad I didn't buy the stupid £160 board!

Edit again: Gonna go with the MKS Sbase 1.3 for about £50. I can feel the sunk cost fallacy starting to sink in! But it's more that setting the currents with a tiny potentiometer and calculating the whatever with the vref isn't so appealing, especially after finding out the Legends are true and those ramps boards are very fragile.

Trouble is the Sbase uses JST connectors instead of the dupont connectors on the ramps board. So I might need to crimp on new connectors or make adapters. But i've been assured by Some Guy that the dupont connectors fit anyways, but i'm not entirely convinced. Seems you wouldn't get full contact.

3 meters shouldn't be too much Simon, I have well over that on some runs on my CNC Plasma Table. Are the motors 6 wire that you have to interlink, and maybe the linking has gone astray?

Not that boring but does make one scratch their head!
I’m waiting for the lightbulbs to turn on!