Author Topic: It's been one of those days - or rather a few one after the other!  (Read 782 times)

Offline awemawson

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The Beaver CNC lathe developed an odd problem - it wouldn't 'go ready' and allow me to 'reference' the turret.

Much head scratching, examining PLC error codes and even hooking up the laptop to peek inside the PLC  while the problem was there came up with the diagnosis that there was a pressure switch problem with the switches that sense chuck open and chuck closed.

OK simple enough, the switches are in a very inaccessible position but they are after all just adjustable switches rated at 2-40 Bar with a single change over contact. Test them !

Well I went round in circles - nothing was making sense - not easy to test as I have to tell the controller to close or open the chuck, but it's not playing ball due to a switch issue ! I have to disconnect and re-connect wires for the control solenoids to fool it !

At this point I noticed that the 'open' and 'close' hydraulic lines to the chuck were both getting over warm and approaching hot! Now only one should be pressurised but obviously oil was flowing through both. It should briefly flow to operate the chuck then stop, a bit like a double acting hydraulic cylinder.

OK, Blank off the lines to the chuck and resume testing of the switches. I convinced myself that one was faulty. Need to remove them and test them on the bench with a hydraulic hand pump.

Switches removed after some acrobatics, where is my test pump (last used for the pressure switch in the Vogel auto lube system) ? Answer - nowhere to be seen. About 4 hours spent searching - nowhere  :ddb:

What else can I use? The Beaver Partmaster came with an hydraulic vice and pump that I don't use - use that. OK fitting entirely wrong! A brief foray into making a 1/4" to 3/8" BSP taper cone adaptor and we are in business.

One pressure switch was slightly flaky if set to the low end of it's range but OK elsewhere, and the other one was fine. Set them both to operate at 20 BAR and re-fit them - more acrobatics !

Initially things seemed fine but after programming a 'chuck close' we locked up again. More going round the houses in ever decreasing circles and I eventually find that the drive wire for the 'close' solenoid was in the wrong terminal hole. I must have re-installed it wrongly during the diagnosis.

Wire moved back and everything works as it should (except that the chuck can't be operated as it's lines are blanked)

OK attack the chuck - got it removed and on the bench - was able to test that with compressed air applied it passed straight though and didn't build up pressure. Go and change your Tee shirt - yes the oil in the chuck covered me  :doh:

Now it's probably only an O ring gone - dismantle the chuck - well it's certainly got O rings but the main piston element has several double lip seals. All look OK apart from one that has a small nick in it, but it's a secondary seal so I doubt it's the problem.

A fair amount of Googling failed to find the odd sized lip seals - I'm sure they are out there but weren't immediately apparent - so I put it back together replacing 12 O rings that I happened to have to hand - these seal the holes for the mounting bolts so probably irrelevant !

Just as I could I tested it again on air and it worked fine ! Dare I risk it on hydraulic fluid at a much higher pressure - yes of course!

Darn me it worked flawlessly :scratch:

Now I will have to watch it carefully as these thing rarely just go away, but it's working !

Picture of the K53P  pressure switch is the modern RS equivalent
« Last Edit: August 20, 2021, 01:33:36 PM by awemawson »
Andrew Mawson
East Sussex

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Re: It's been one of those days - or rather a few one after the other!
« Reply #1 on: August 19, 2021, 04:41:17 PM »
Glad to know you’ve “solved it for now” Andrew as, like you say , these things develop a life of their own!

Reasonable day today as finally got a package from an american friend but damn me I got st8ng for import duty and a charge from the POmfor collecting it on behalf of HMRC ! :bang:

Still at least it didn’t vapourise over the Atlantic which we were both starting to wonder   :doh:

Offline hermetic

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Re: It's been one of those days - or rather a few one after the other!
« Reply #2 on: August 20, 2021, 09:34:18 AM »
I thought you had gone quiet Andrew, I am also up to my armpits in Hydraulics of the Fordson Major variety! Mine seem to have spent a long time running on a mixture of old engine oil, buts of gasket and straw, no surprise they didn't work!
Phil
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Offline awemawson

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Re: It's been one of those days - or rather a few one after the other!
« Reply #3 on: August 20, 2021, 10:31:13 AM »
Yes Phil, I've been watching your labours on your videos. Messy old business!

Andrew Mawson
East Sussex

Offline Brass_Machine

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Re: It's been one of those days - or rather a few one after the other!
« Reply #4 on: August 20, 2021, 10:42:53 AM »
I have a few of those "solve it for nows" that have been running for a lot longer than it should. Sometimes they turn into just "fixed it"

Here is hoping!

eric
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