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

[awemawson]

The pump itself is totally immersed in the oil reservoir, so it won't lose it's prime.

There are various joints, again internal to the oil reservoir, that connect the pump to the switch and the outside world. A leak there is possible as it wouldn't show externally.

. . . I'll have to pull it apart and have a look-see over the next few days

[AdeV]

I once half dismantled my entire Bridgeport Interact no less than 3 times before discovering that the automatic oiler had run out.... In my defence, the fault was "24v DC missing" - a complete red herring!

[awemawson]

Ade I remember you having issues

I initialized the machine this morning (no issues) then deliberately disconnected the oil output from the Vogel. It took an amazing time to put on it’s red light to say that there was a fault. Probably about the same time as the dwell between pumping. Good oil flow, and when connected good oil pressure.

So I conclude that it’s probably the pressure switch or more likely the electronics. I’ll pull the orange controller out and go over a few soldered joints when I get a spare hour or so. Last time it seemed to clear when I reseated an ic but quite possibly I had actually disturbed something else!

[awemawson]

I realised last night, that with a new puppy being collected on Saturday after which my time won't be my own, I had a small 'window of opportunity' today and tomorrow to pull the Vogel IG-38 controller and have a close look at it.

Photos taken of connections for reference, listed in my lab day book, wires tagged with 'flag ty-wraps' and I could then pull the unit out of the pump leaving the oily bits behind.

Case opens easily with the usual plastic ramp clips allowing me to pull the electronics from the box. Last time I didn't split the electronics - it consists of two PCBs separated by a third in a sandwich construction with soldered connections on headers holding it together. One main PCB has eight header pins and the other six, so I opted to unsolder the 'six pin side'.

Using my powered solder sucker and some flux the plated through holes seemed quite clean but rather than risk pulling the plated holes though the board I ran some low melting point solder into the joints - this stays fluid long enough just to pull the header pins out all together. A bit of a clean up with the sucker and flux followed by a squirt of brake cleaner and a scrub with a toothbrush and it's good for re-assembly when the time comes.

There is one socketed IC, three transistors, a bridge rectifier, five diodes, a handful of resistors and polyester capacitors and two electrolytic capacitors and two relays all powered by a tiny mains transformer. Also a rotary switch to set repetition time.

I will replace the electrolytic capacitors, try and open the relay cases and clean the contacts, then re-flow every joint on all three PCBs and also the terminal block.

[awemawson]

So checking my stock for the two electrolytics showed that although I could fit something 'that would do' my stock was probably as old (if not older!) than the components fitted so I've placed an order for 47 & 220 uF 63 volt aluminium axial capacitors with RS that should be here tomorrow.

Meanwhile I took the covers off the relays to clean the contacts. Relay 1, is just a single pole change over - no drama, contacts cleaned with a slip of paper and switch cleaner / lubricant. Relay 2 (two pole change over) was a different matter. The armature was stuck in the operated position with no clearance to the magnet At first I thought that the contacts must have welded shut, then I thought that the armature had been deliberately bent, but no, eventually I realised that there were two tiny paxolin 'bridges' - a flat bit of paxolin with a peg sticking out at both ends - deliberately put in the mechanism to force it into the operated position. Obviously a modification to make this module suitable for this particular lubrication pump. Simpler to leave the relay out and link the contacts but Vogel obviously thought differently!

Then I went over EVERY soldered joint re-flowing it with a bit of flux so hopefully any lurking dry joint will have been cured, and equally hopefully I haven't introduced any other faults!

. . . so now just waiting for those capacitors . . I hope that they arrive early . . 'double change over' in cottages tomorrow so times not entirely my own!

(Capacitor photos to make sure I put the replacements in the right way round!)

[awemawson]

The capacitors from RSComponents arrived during lunch, so with no delay they were installed and the orange IG-38 box reassembled.

Then it was just a matter of replacing the wiring, putting my fingers in my ears and switching on.

. . . . what could possibly go wrong ! . . well in this instance nothing thank goodness. It did precisely what it is supposed to. Initially started pumping showing 15 BAR on the gauge, then after a period switched off into idle mode for the prescribed period before starting over again

. . . .PHEW . .  so at least I've not introduced other faults, but whether the long term intermittent fault is cured or not there is no saying 

Still, electrolytics changed, socketed IC removed, pins and sockets treated with switch cleaner and re-inserted. ALL PCB solder pads re-flowed, relay contacts cleaned, and interface terminal posts treated with switch cleaner before re-assembly - what more could I do in the absence of a replacement?

. . . fingers crossed for the NEXT 8 months 

[modeng200023]

The nice thing about older electronics is that the components are of a repectable size 
John

[russ57]

You mean visible...

About to tackle a harman kordon avr2000 amp with dead channel. The circuit diagram (Iove the internet) suggests the pa module is basically direct coupled discrete power transistors. With luck the problem will be a) visible, b) accessible, and c) a component that is either available or at least a substitute.


-russ

[awemawson]

So once again this lubrication fault has reared it's ugly head stopping the lathe in it's tracks . . .


BUT . . I have absolutely positively determined what it is and in essence it is trivial - fixing it might be a different matter.

What is supposed to happen is that on power an, and at pre-set intervals then on, the pump starts up and the electronics 'looks' for the pressure switch to close within a certain time frame. If it does, all very well, it goes to sleep for a bit until the next pumping cycle. However if the oil pressure switch doesn't close for what ever reason the electronics  flags an error to the CNC controller which promptly curls up it's toes and refuses to make any movements.

It turns out the the pressure switch is intermittent high resistance - I've linked it out temporarily and the machine works splendidly.

Now the pressure switch, so VERY conveniently, is immersed in the oil reservoir, so not the easiest thing to get at. System pressure is up to 18 bar so probably a 10 bar switch would be fine, but until I dig in a bit further I have no idea of thread size or terminations or body size, though it looks to be quite compact.

. . . still. . . . sell the positive . . I now know what the fault is that's eluded me for quite a few months.

[WeldingRod]

I hate pressure switches!  It's always a matter of "when" they die, not "if"

Sent from my SM-G892A using Tapatalk

[awemawson]

I seem to remember you saying that once before Rod !

So yet again I pulled the Vogel pump off the machine to investigate the pressure switch further. It has a 24 mm hex body, an M10 x 1.00 mm mounting thread and screw terminals, with apparently an adjuster screw between them.

Now it is just possible that the screw terminals were giving  the high resistance, but they were nice and tight, and it's just possible that tweaking the adjuster a bit might kick it into life, but having got so far now I want to replace it. Sadly it's not really possible to test it without putting it all back together.

A quick web trawl suggests that they may well be available as a spare - I'll make some phone calls on Monday

[awemawson]

Well it seems that pressure switches in this  range of pressures are much more common on an 1/8" stem, so this afternoon I knocked up an M10 x 1.0 mm pitch male to 1/8 BSP female adapter - (there is plenty of axial length to accommodate it ) and ordered an 1/8 BSP switch which is due here mid week

Not sure about 1/4" Lucar connectors immersed in oil - I may do better to solder leads directly on - but comments welcome !

[Pete.]

No harm from immersing electrical contacts in oil far as I know Andrew. The fuel pump on my bike even had un-insulated connections in the fuel cavity.

[mattinker]

No harm from immersing electrical contacts in oil far as I know Andrew. The fuel pump on my bike even had un-insulated connections in the fuel cavity.

I agree with Pete, my K100 has the same sort of connections in the tank! I would have thought that it would be positively advantageous, no corrosion
 risk!

Cheers, Matthew

[WeldingRod]

Oil immersion is commonly used for high voltage work.  Just avoid water in the oil.

Sent from my SM-G892A using Tapatalk

[awemawson]

The oil is ISO68 way oil.

My concern was any sulphur in the oil would possibly promote corrosion, and way oil is sometimes sulphurised.

. . . but I'm no chemist 

[djc]

If you are concerned, is there any way of potting it in epoxy after soldering the leads on?

[awemawson]

On the list at the moment is:

a/ Painting the connections with 'liquid insulation tape'

b/ fitting a pipe extension out and above the oil and putting the switch in the electrical box, but need to check if there is room.

I'm getting very adverse  comments re oil / sulphur & copper on the welding forum - thread here:

https://www.mig-welding.co.uk/forum/threads/any-oil-chemists-on-the-forum-copper-corrosion-in-sulphurised-oil.105672/#post-1673615

[RussellT]

The original connections are presumably brass crimped on to copper.  I suppose they might be the cause of the original fault but it doesn't look as though corrosion has been a problem there.  Solder the wires to the switch and there will be no mating surfaces to corrode.

By the way I wondered if the original numbers on the pressure switch said 12.0 Bar.

Russell

[mattinker]

Hi Andrew,

I would be inclined to inclined to autopsy the switch, turning the end down on the lathe to release the insulation. I'm curious about where the fault actually is? I know it won't fix anything, but interesting to see whether corrosion is the cause of the problem and whether the sulphur in the oil is corroding the brass.

Cheers, Matthew

[RotarySMP]

Hi Andrew,
Sorry I didn't check this thread earlier. I have attached the wiring diagram for the Vögel IG38 I found on line somewhere. Doen't add much to what you already know, but I thought I'd post it for completeness.
Mark

[awemawson]

Russell soldering was my first idea but not yet having seen it i'm not sure if the plastic the spades are embedded in will take soldering heat - many modern electronics bits melt as you solder them - D type connectors being a case in point! I'd also wondered about the numbers - the new one is 5 bar - it's only checking that a reasonable pressure is reached and no  pipe has popped off so 5 should be fine as it's not controlling the pump.

Matthew yes I had that in mind - always like to see causes, but with this one I want to make an adaptor so the I can pump it up and check it out of the pump before destroying it.

Mark, thanks for that - added to my Vogel library 

[David Jupp]

As long as there is no water present, Sulphur can't give corrosion issues.  A lot of the panic comes about when there is potential for H2O from either condensation or combustion products.

[awemawson]

The replacement pressure switch arrived by post this morning, so I've fitted it using the brass adapter that I made.

Interestingly when I came to the electrical connections, one of the original crimped spade lugs had already fallen off and the second fell off when I touched it . The copper cable where it emerged from the crimp had completely corroded through! So I reckon that there is a good chance that the original pressure switch is actually fine. I must make an adapter up to test it under pressure.

Cutting the cable back and crimping on 'female spade lugs' I assembled it and slavered 'liquid electrical tape' all over the crimps externally, hopefully excluding oil ingress in future. Messy runny stuff to use !

Can't put it back in the oil tank until this gunge has set so later this evening probably.

[russ57]

Always good to find the smoking gun...

Seems highly likely that was the issue.



-russ