Still in the end I did end up with a fairly neat winding and when all was re-assembled and the two halves of the resistor paralleled up it measured exactly and precisely 3.3 ohms - phew what a load of bother for a simple wire wound resistor.
Re-assembling it all on the machine went reasonably well - I thought I'd leave testing to the following day. But in the night I woke up in a sweat thinking 'did I remove that melted dribble of resistance wire on the upper cage frame ?' Of course I had to pull it all apart again to check and sure enough I hadn't - the power of dreams - lucky really.
Anyway testing at least didn't result in the previous glowing fire that I'd had previously - controller came ready but when I pressed 'Reset' to initialise things it went into eStop and dropped the servo crate power displaying:
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Decoding the error message it was implying that the Z position encoder was out of phase, shorted or disconnected. Now the encoder and it's wiring are not the easiest things to access and are far removed from where all the trouble had been. My first suspicion was the servo cards immediately below where that resistance wire had melted and dripped however changing them made not an iota of difference.
OK bite the bullet - open things up - get to the back of the Sinumerik controller by sliding it out of the cabinet onto its shelf so now at least I can see the Z axis encoder cable where it plugs into the Siemens 'measuring card' that takes all four encoders. Nothing looked amiss - suppose it's the measuring card itself? Fortunately I had a spare. A bit of gymnastics - old card out - new card in and lets see:
Whoohay - I can now jog X and Z axis for the first time in months
At that point I decided to quit while I was ahead and reserve more testing for tomorrow - there's only so much excitement I can take these days
