The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)

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cnc-it:
Nice set of spares for the Beaver machines, I would be interested in the spindle assembly if you ever decide to sell it 👍

awemawson:
I'm very unlikely to need to use the Partsmaster Spindle so you are in with a fighting chance !

Transport might be a challenge - it's ultra heavy and unless in a car boot will need a very stout crate.

Message me to open negotiations :)

awemawson:
Perhaps the summer heat has got to my brain but I've decided to resume testing to try and get this CNC lathe back on it's feet.

A full re-load of known good software still gives me several very odd error reports from the PLC inbuilt to the Sinumerik CNC control so I decided to step back a bit and do some basic hardware testing:

The PLC has 96 inputs (24 v Active 0 V Inactive) and 32 outputs of 0v or 24v. Up until now actually testing these is a physical pain - they are presented at the top of a rack with five cables terminated in 37 pin Sub D connectors - all tightly lashed together.

However a nifty 37 way Sub D break out board turned up on eBay with male and female connectors and a terminal strip allowing me far better access.

awemawson:
So over the last few days I have checked all 96 input lines by temporarily connecting them one by one to 24 volts and using the PLC inbuilt diagnostic tools to display them on the monitor.

Still a bit of a pain, and involves a lot of walking as the terminations are on one side of the machine with the control panel on the other - and yes it's a long way walking round it that gets 'old' very quickly. Still two days spent and I've convinced myself the ALL the input are working fine - now there are several unused inputs but I decided to test them all:

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awemawson:
So now I need to devise a way of testing the outputs. Presented as two cables again terminated in 37 pin D Sub connectors so compatible with the break out board. And again the PLC diagnostic allows me to see what it thinks that it's outputting (it's a Q word) :

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However the way (I think) that the PLC works is that it maintains a table of these bits that is updated by the PLC program and every cycle of the program the table is copied to the Q outputs.

This means that if the PLC program is running anything I write to the outputs will be overwritten in milliseconds and if the PLC program is NOT running I can't access the diagnostic facilities so a bit of a catch 22 situation.

I can do a somewhat less stringent test by reading a particular Q word and checking what is actually set but I'm not convinced that that's good enough?

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Off to scratch my head a bit !

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