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

[seadog]

It would suggest that the socket hadn't been fully located before it was soldered. The pins are hardly likely to have grown, are they? 

[awemawson]

Well yes they could ! It's a semi flexible structure with a heavy cable attached. I can see it happening if an operation happened to hit resonance in the cable / plug / board assembly. The socket is firmly bolted down to the PCB on stand off spacers, and presumably was so when flow soldered, so I don't think that it's a case of it not having been fully inserted as the bolts hold it fully in.

Decades ago (late 1960's) I was involved making multi-element infra-red arrays for use in spy satellites. Everything went though full spectrum vibration testing and you'd be amazed what that can do to apparently rigid structures!

[Will_D]

I remember that ICL (our UK mainframe computer maker in Manchester) tested the large (0.5 x 0.5M) multi layer circuit boards as fitted into the main frame racks. They simulated lorry transport at all the different frequency.  There were some amazing slo. mo./strobe videos of the boards flexing by about 3 times their thickness. These were iirc 13 layer boards and about 6 mm thick fibre glass boards.

And yes they actually recorded the telemetry from a truck driving on roads all over the UK o run on the shaker table.

[awemawson]

Things are definitely looking up on the Renishaw Probe front 

No, still no word about the bits that have "gone walk about" in Australia, but an MP12 brand new probe appeared on eBay that was well out of my price bracket, but the seller had mentioned that he had tested it as working. Now as I had obtained an MP12 in a job lot of bits earlier in the year I fired off a message asking him how he was testing it, as I have no idea if mine works or not.

Turns out that he had a spare OMM (that's the receiver bit that stays fixed to the machine) - mines being kicked about by Kangaroos in the Antipodes 

Discussion ensued and the grand chap let me have it at a very reasonable - far too reasonable - price and not only that let me have an OMI version which is the same as the OMM but includes the electronics of the machine interface.

To cut a long story short, the postman brought me a box this morning with the Renishaw OMM & OMI - I need to curtail my excitement as we have guests for lunch and are out tonight so I wont be able to try things until Thursday.

My MP12 doesn't look too bad, but when I got it, the AA batteries had been left in and had corroded so took some extracting - I hope that the vapours haven't travelled into the electronics. But I do also have an LT02S optical probe in unknown state so quite a bit of experimentation is needed to find what does and what doesn't work.

Renishaw have used several signalling systems for their optical probes, including different IR wavelengths to allow more than one probe system to co-exist in the same machine, so I hope I have a compatible set up - time only will tell !

I am delighted to say that Cliff, the eBay seller has joined us here on the forum as 'Brent Crude' - he is a star and my current hero - thank you Cliff

[tom osselton]

Nice they look like they are in good condition.

[kayzed1]

You meet the nicest people on a Honda I mean at MadModder

[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 

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 

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 


 

[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!
 

[awemawson]

Yes Cliff definitely a good step forwards

Up early to put in yet another call to Australia to chase the original bits, according to a colleague they are still in a tote on PK's desk (who was off picking children up from school). There is now a large entry on his 'white board to do list' asking if I can please have my bits back 

So while I was up I thought that I'd have another go at the MP12. It takes four AA cells, retained by a cover that also does the inter-cell bridging, with the 6 volts being picked up by a pair of spring loaded gold pins. Rigging up the lab power supply with croc clips on the pins, with my trusty Avo 8 in series showed me that when first connected there was an initial surge of perhaps 10 mA, very rapidly falling back to about 1 mA or less. However if I pointed my remote control for my 100 W led flood light at it, and gave it some random IR it would switch into a higher current mode - maybe 5 mA.

Re-installing the four AA batteries and exposing it to the OMM in the lathe there was still no response. Frustratingly like this I couldn't monitor its current draw.

However I conclude that the MP12 is at least partially alive, and can be switched into operating mode by a burst of IR. Still possible that it's signalling specification differs from the OMM.

I may try and make up some sort of replacement battery cover that lets me use a lab supply and monitor current while on the machine exposed to the OMM. This way I can get a better idea if the OMM is actually switching it from standby to the on state.

[Brent Crude]

I have exactly the same MP12 here and was able to start it using the OMI I sent to you. I used the same wiring colours as on the piece of paper I included so it may be you have a bit more wrong with your probe as you suspect. I wonder how easy they are to pop open...

[awemawson]

I 'think' that the body unscrews. With my smaller probe that was sentenced to transportation, PK made a gripper for the body to unscrew it, and I suspect that the construction is similar, using an 'O' ring seal between he two parts.

Do you know what the white LED that emerges downwards through the bit of the top that is not the battery retainer is supposed to indicate ? Perhaps 'probe triggered' status ?


*** later edit, I've found a datasheet implying that it's a switch that changes the probe mode - doesn't look like a switch to me ! ***

[Brent Crude]

I’ve seen that too. I think there were two different versions of the MP12. Mine is the same as yours. Mine isn’t selling. I’m not fussed over mine. Hey, if you were to give me a silly name, you know the score, it might just appear for the cost of postage!! 🤪😃🤪😃

[awemawson]

 

[awemawson]

Here's a picture of the mystery LED

(Cliff I've sent you a PM)

[Brent Crude]

That LED is the one that flashes green when the probe is on and red when it is triggered.

[awemawson]

That LED is the one that flashes green when the probe is on and red when it is triggered.

Or in my case coyly stays off keeping it's own council 

[awemawson]

Spent a bit of time this afternoon writing a little program in the Siemens rather arcane '@ functions' to try the probe under program control. As usual all rather unsettling for first time running as you're expecting the probe to be crushed into oblivion any minute 

All went well I'm pleased to say - phew

(The Z co-ordinate is loaded into register R1)

[tom osselton]

Nice to see it work, is it suppose to just probe the one time? On our mill it contacts twice once initially to find the edge within x distance then measures position.

[awemawson]

Tom, that's just a bit of code I knocked up to try it. In real life action you could probe a few times and take an average of your readings if you wished, but this was just to prove to my own satisfaction that I understood the @720 and @371 functions - their description in the Siemens documents is not exactly flowing with detail!

It doesn't help either that the two probes are numbered 0 & 1  in one function (@371) and 1 & 2 in another (@720) - nothing like having a bit of consistency 

[awemawson]

So at long last I'm in a position to try and make a VDI40 dedicated mounting for my Renishaw MP12 probe.

Apart from the time to do it the hold up has been deciding how to make the actual VDI40 spigot that has the rack teeth that engage with the locking mechanism. I know from when I 3D printed some blanking plugs that the 'phasing' of the teeth is quite critical.

Having worked out a way, an odd shaped VDI tool that looked like it could be a 'doner' cropped up on ebay which I won for the princely sum of £4. I had expected to have to soften it by annealing before I could work on it, but it turns out it is a custom made item using a commercial 'soft blank' where the VDI40 bit is hard, but the rest is still soft(ish). Well that saved digging out the annealing furnace 

So today I found a bit of time to make a start. The blank is far too long so how to lop a bit off - looking at it I reckoned probably at least two parting tool tips were it done on the lathe, so I used the Band saw with a bit of ingenuity in the clamping - went quite well and wasn't all that slow considering it's  85 mm in diameter.

We need a spigot of 44 mm o/d 16 mm long with a projection of 25 mm  4.5 mm long, all bored out to 20 mm for a depth of 36 mm. Renishaw helpfully give an un-dimensioned drawing but I have an SK40 shank to copy - so that's OK

[awemawson]

So reaching for my collet set up on the Colchester Master I was surprised to find they don't go as large as 40 mm OK it looks like a 4 jaw chuck job to get decent concentricity. In point of fact concentricity isn't at all critical as the probe has four screws to adjust it's position - but if you are doing it, it's nice to do it right !

I thought as the three jaw was already mounted I'd pop it in it and see how  perpendicular the band saw cut was. Answer: amazingly good  And even MORE amazing just spinning it by hand the shank LOOKED pretty concentric (I'd wrapped it in brass shim to protect it from the jaws). Putting a DTI on and revolving by hand it was SPOT ON 

So I continued with it in the three jaw and rough turned the two diameters oversize by 2 mm  and drilled the 20 mm bore undersize at 18 mm. I'll let it all cool down before the finish machining while I feed the pigs.

[awemawson]

So, Pigs fed, part cooled in lathe - time to finish the job.

The two outer diameters were taken down to size, and the bore bored out to 20 mm . Then I mounted it in the milling  machine and drilled and tapped the two 8 mm cross threads for the retaining grub screws.

The way it works, is that there are four tiny allen grub screws on the probe body that bear on the smaller outer diameter of the adaptor, and by tweaking them concentricity can (hopefully) be achieved. Then the two 8 mm pointed grub screws in the body of the adaptor bear on a conical washer loosely retained on the rear on the probe body. These screws and conical washers tightly hold the probe body in contact with the adaptor yet allow adjustment.

So that's one more 'round tuit' put to bed 

[Brent Crude]

  Good work, fella!!