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

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awemawson:
At long last the 24v DC solenoid valves have arrived so I've been able to get a better idea of the volume that they take up. The various bits of brass plumbing have been to hand for days.

Dry assembling them and hanging them roughly in the place where I want them is the easy bit. The conundrum is to work out how to actually secure them such that not only are they firm enough to resist the inevitable vibration, but also such that they can be easily removed for maintenance.

All the joints will be sealed with Loctite 542 'pipe seal', which means that their rotational orientation can be set without making them actually tight until the 542 sets.

However there is nothing at all on the valves to fix them with. I've considered various methods - 3D printing a 'cradle' - bending up brackets for the top and bottom 'nozzles' to go through - a bracket with hole that gets interposed between the nozzle thread and the valve - all have their pros and cons.

My current proposal is to braze a lump of brass to the central 'Tee' piece with ears to fix to the machine chassis, and hang everything off that.

seadog:
They would normally be plumbed in to copper pipe which would support them. They're no different to standard zone valves in that respect.

awemawson:
Absolutely so Seadog, but not when on flexible reinforced nylon ! So ...... I got on with making a 'flanged 1/2" BSP Tee Piece :clap:

I found a suitable bit of 4 mm brass plate, marked it out, drilled it, cut it to size (always cut last - more to hold when drilling!) and then brazed it to the Tee piece.

I decided to use Cu-Phos brazing rods for two reasons - a/ I have a bag of it, and b/ it doesn't need any flux when brazing copper or brass - handy stuff but DON'T use it for boiler making. My supply is left over from years back when I was making up custom fittings for the 100 kW induction furnace.

So, wire them together, and have at it with my propane torch. I use MIG welding wire - should be soft iron wire but I don't have any. If you, like me, use MIG wire, anneal it first by flashing the torch over it getting it red hot. In the as supplied state it's too springy and is difficult to handle. Also getting it red hot forms a nice oxide layer which prevents the brazing sticking to it.

Not the neatest item but certainly functional :thumbup:

. . .just need now to mark out the machine frame, drill and tap it, and fit the hoses and wire it up

awemawson:
After lunch I drilled and tapped the machine chassis, and did a test fit of the 'Flanged Tee piece', before screwing all the plumbing together with Loctite 542 onto it, and aligned where they pointed.

While the Loctite was setting to the 'handling' state, I drilled a pair of 20 mm holes in a suitable place for cable glands to bring the digital output wiring to the solenoids.

Once the plumbing assembly had been screwed onto the machine I was able to pull cables through the existing ducting and wire up the coils of the solenoids. Slight delay while I fed the pigs, then a grand tidy up and test. I'm pleased to be able to report that the front panel buttons, via the new PLC rungs, and out via the digital outputs, do precisely what I wanted. At power on, the upper solenoid is driven porting coolant to the turret. When the 'Wash On' button is pressed the upper solenoid is released, and the lower one is driven porting the coolant to the wash down hose. If the 'Wash Off' button is pressed, or the lathe sliding door is closed, the solenoids revert to putting coolant to the turret.

. . . sorted :ddb:

. . . except . . . I've not yet put the hoses on, I'll leave it until tomorrow for the Loctite 542 to fully harden before putting fluid though the assembly to give it it's best chance of not leaking !

awemawson:
This morning I fitted the reinforced nylon hoses to the coolant system, pulling the one for the wash down gun under the machine from the rear to the front.

As the carriage moves both in Z and X it's important that there is enough slack in the hose to the turret for it not to pull itself off, so careful checks and a bit of trundling up and down got me to what seems the optimum length.

So time to test: firstly proving that the feed to the turret still works was successful, with only a minor leak requiring a Jubilee clip to be moved up the barb connector a bit and re-tightened.

Then time to prove the wash down gun. With the gun locked open I pressed the 'Wash On' which gave me a very impressive coolant jet well up to the task :thumbup:

This is when the problem occurred :bugeye:

Releasing the lock on the wash down gun, thus turning off the flow, produced a VERY impressive fountain of coolant from the back of the machine. Rapidly turning off the pump and going round the back it was obvious what the cause was. The high pressure from the pump was easily overcoming the Jubilee clip on the wash down gun hose at the valve end.

Now in hindsight this was predictable. The coolant pump isn't a normal vane pump that can run happily into a shut valve, it's a gear pump, and develops HUGE pressure when blocked - my fault entirely, I should have realised :bang:

I think the solution is either a pressure release valve on the pump output direct to the tank, or possible just a simple mechanical valve allowing some flow even when the gun is closed.

However, having mopped up the flood, now I need to pack up the Racal RA17 communications receiver, as my roll of bubble wrap has been delivered. At least it will give me some thinking time.

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