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Oh Blimey I bought a CNC Lathe !!!!

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vtsteam:
Classic hacking.  :bow:

awemawson:
Whilst it was on the bench I set too with the power supply in the 6 slot. It worked fine except that there was a faulty centre biased toggle switch that latches it on or off, which duplicates a function on the operator control panel. It would stay in the on state, so when youb turned off at the operator control panel, it would immediately turn back on! It's an obsolete micro miniature pcb mounted 90 degree bent 0.1" pin spacing with two extra mechanical pins to secure it and an extended toggle. Closest I could find had the right 90 degree bend 0.1 pin spacing but the two mechanical mounts were in the wrong place and the toggle was short :( . A bit of judicious pin bending got it in the pcb (desoldering with the Weller vacuum sucker worked a treat this time). I reckoned to glue a tube extension to the toggle when re-assembled but in practice it's ok.

Hopefully I can set up a test bed with this 6 slot and the extenders - anyway some pictures:

A/ Old and new switches
B/ New in situ

awemawson:
I spent the day trying to work out why the controller isn't acting on the 'door open and 'door closed' switches. It is quite a complicated system with lots of interlocks. The machines sliding door has a switch for when it is 'open', another for 'closed', and a third for 'locked'. Locking is by an electric shot bolt with switch feedback. Then each rotary axis has a special safety monitoring relay that tells when the spindle is rotating. These three rotary axis monitors are all connected in two series chains of normally open and normally closed contacts, which in combination with the door switches operate 'open', 'closed' and 'locked' relays. Or rather they should but they don't :bugeye:

No complicated controller interaction here - just 'simple' relay & switch logic but I've been chasing my tail all day. I knew that one of the 'zero speed' relays is faulty but I have temporarily linked them all out. Turns out I have lots of relays with bad contacts. Measure a normally closed contact and the chances are it's open! Even after a spray of contact cleaner which de-oxidises contacts there are problems. I suspect that it's quite a bit to do with the fact I'm testing with an Avo meter on ohms that will only bias the contacts with 1.5v whereas the normal operation is 24v. I will set up a battery & bulb tester this evening and see what happens. Machine is quite clean inside so I'm surprised contacts are that  bad.

lordedmond:
Not trying you to suck eggs,but when I first went out on the plant at the end of my apprenticeship I was put with a electricians mate who was abut to retire his two bits of advice to a new wet behind the ears sparks was 1 always test with the voltage that the job uses ( i.e. use a test lamp with on leg on the live side. and two listen to the plant operators when we go to a break down they may just have seen something that is important , brush the off and they will not help you again.

enough of my rambling as you have found out with old equipment most relays do not have much wipe as they close and need a minimum current flow though the contacts to operate correctly, get a 24 v lamp and use that to bell out the contact chain AVO are next to useless in this case as are 1000v megga's on very old VIR cables ( they fail the megga test but are fine on the voltage they used on )

another tip that has held me in good stead was if you have the drawing always start testing from the middle to each rail thus you have halved the amount you need to test, repeat with the remaining section and the fault can be quickly found


note the above does not conform to the current H&S regs of live testing  :Doh: but bear in mind I was was brung up up on open 220vdc open switch gear with only a rubber mat to stand on as well as 550vac barrel type crane controllers

as a comment you have come a long way with this project and I wish you well with this endeavour and I do hope you will have a good end to your journey


Stuart

awemawson:
Stuart,

I totally agree about listening to the operators. After years working on process control computers from biscuit factories to oil refineries through nuclear power stations what you say rings very true.

Before reading your post I'd cobbled up a 24v T5.5 'wedge bulb' on the end of a probe to do precisely what you suggest, and also ordered a Fluke T50 tester! Not convinced the T50 is the total solution as it uses leds, but in this instance better thasn the Avo, which reigns supreme in other uses.

Another extremely useful tool I'm using is a telecoms wire tracer. Hook the oscillator on a wire and you can trace with the receiver where it actually goes rather than where the circuit says!

Andrew

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