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

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kayzed1:
You meet the nicest people on a Honda I mean at MadModder :clap: :dremel:

awemawson:
So testing begins . . .

Connecting the OMI receiver unit to a bench supply and using it to try and trigger the MP12 probe, freshly equipped with new batteries - zilch, the MP12 doesn't 'wake up' so the OMI displays ERROR on time out as it never receives a reply from the MP12.

Getting out the LT02S optical transmitter with it's LT2 sensor module - (both these functions are contained within the MP12) we have lift off :clap:

The two happily talk to each other over quite a range and quite an angle of incidence, and 'probe triggered' status is displayed by the LED on the OMI at the appropriate time.

So in all the months that I've been working on this lathe this is the first time I've had an optical probe doing sensible things and working.

I conclude that the MP12 probe is either doing an excellent impression of a door nail, or is using one of Renishaw's alternative signalling schemes.

Now the original set up was a Renishaw MI12 machine interface sitting between an OMM receiver unit and the Siemens 820T, but as I understand it, the OMI version incorporates the MI12 function within itself thus making the MI12 redundant.

I will initially test the OMM that Cliff sent me and if it talks to the LT02S just install it 'as was' to simplify the wiring, but either way now I know that I have a working system at last.

awemawson:
Now to test the OMM.

The OMM has a different 'start signal' requirement so I can't easily lash it up on the bench. The MI12 generates a one second burst of 125 uSec pulses at 250 mSec intervals, which are passed to the OMM, which transfers them into IR to turn on the probe. So the easiest way to do a test was to lash the OMM from Cliff into the machine on the wires where the original OMM had been.

When I removed the original to send to PK in Australia, I had double bagged and Ty-Wrapped the cable ends to keep out swarf and coolant. Removing the bagging amazingly all was well inside and I was able to connect the replacement OMM, using it's already attached cable and 'chocolate block' connectors leaving the OMM on the 'operators shelf' by the Siemens control.

I'm delighted to report that all was well, and a probe trigger would cause the 'probe status' light on the MI12 to change state and on the Siemens control 'Flag Byte 24 bit #7' also changed state - a result :clap:

This is quite a relief as it's the first time I've been able to definitely prove that the MI12 machine interface is working. Back in the early days when I got the machine, one of the two paralleled up 24 volt power supplies had had a failed 2N3055 transistor dragging the volts up to (iirc) something like 36 volts whereas the absolute maximum spec on the voltage for the MI12 is 33 volts so to find that it IS working is good news.

So altogether a very good day so far. Cliff, there is a pint or two of Harvey's Best Bitter waiting for you when ever you venture down this way - such a relief to at last get close to having an installed work piece probing system set up. Setting G54 off sets with a ruler is far from ideal :lol:

:beer: :beer: :beer: :beer: :beer: :beer:

awemawson:
OK so it works as a lash up but it needs installing.

It's a very awkward location to make off cables - the entry into the OMM body will barely take the sheath of the cable and certainly no room for 'boot lace ferules' which make making off fine wires so much easier. I ended up tinning the bare ends of the individual wires, this isn't good practise as strands can break under vibration where the solder ends, but there wasn't much choice.

All back together I then mounted up the probe in a VDI40 boring bar holder ready for testing. This makes a very long 'tool' so I will probably make a custom holder that can be shorter. The concentricity of the probe with the VDI40 mounting socket is set by adjusting four tiny Allan socket grub screws - I've not attempted that as hopefully soon it will be mounted on a different holder.

A trial test jogging the odd micron at a time showed me that it was working by monitoring the Flagword 24 bit #7 location, so I suppose now I need to get my head around writing some code to handle the probe. I may try and incorporate it in the PLC if there is still room, as that way I can put the brakes on the travel in all cases even when other programs are running as a safety precaution.

Brent Crude:
Yayyy! Glad to see things are progressing in the correct direction!!
Quite a project you have there!
:beer: :headbang:

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