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

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cnc-it:
I see makes sense..maybe it was an option back in the day.

awemawson:
Having got the Spindle Orientation now sorted the next barrier to knock down is getting the powered tooling working, after all that is why I need the Spindle Orientation in the first place.

But first I wanted to investigate a minor irritation in tool changing, where having issued a tool change command the tool disk would come forward unlocking it from its Curvic Coupling, and then pause for what seemed ages before rotating to the next tool position and re-clamping back on the curvic. now the PLC program, the code running in the SMCC turret control card, and of course the mechanics of the turret could all be possible culprits. I feared that the code in the SMCC card had possibly been corrupted. Having 'unclamped', the 'clamped' feedback switch opens and the 'unclamped' switch should close when the tool disk is far enough forwards for the Curvic to have disengaged, which triggers the SMCC card to using it's servo logic to rotate the turret to the next tool. Putting two channels of my 'scope on the 'Clamped' and the 'Unclamped' switches showed that despite the tool disk having travelled forwards it took a few seconds before the 'Unclamped' switch closed where upon the tool disk rotated as it should. This has eliminated the SMCC or PLC code as being an issue and either the switch needs adjustment, or maybe it's sticky.

I wrote a simple diddy to continuously change tools, and as it ran the delay reduced until it vanished, so either a sticky switch has now freed, or maybe warmed up. I'll have to let everything cool over night to see if it is still an issue. I had assumed that the two switches in question were proximity switches, but I don't now think that they are. The Patent Application refers to them as 'precision mechanical switches' - they are two wire, cylindrical and threaded like a proximity switch, but measure zero and infinity when closed and open under no applied power. In the circuit they are just in series with an opto coupler and current limiting resistor across 24 volts.

So on to the powered tooling. There are two issues:

A/ The Baruffaldi Powered tools have a different dog clutch shape than the machine drive spindle

B/ When a Powered tool is mounted, the faces of the two dog clutches are separated by 15 mm so wont drive anyway.

I had expected to have to dismantle the bearing housing for the drive spindle to remove the dog clutch and spindle, and make a complete new assembly, but it turns out that the machine dog clutch is just keyed to it's shaft and retained by a countersunk hex bolt, and I was able to withdraw it though an empty tool position.

Now the new dog clutch needs obviously to engage with the Baruffaldi ones, and be 15 mm longer (plus engagement depth). It would be a nice exercise to make on this lathe if the powered tooling was working, but that's a rather circular argument  :lol:

Have some pictures 

awemawson:
So embryo replacement drive dog drawn up in Fusion 360 and now printing on the Cetus 3D printer. This is just to let me better visualise what I need before I start machining - be nice if a 3D printed part could just be used as is !

awemawson:
So the 3D Printing has finished, and I've been able to use the model to measure how long it needs to be to engage, and yet have clearance when the tool disk rotates.

At the moment the drive dog is installed with it's shaft key but no retaining screw as I need to find a longer one. Amazingly it works. I suspect I could even do a  bit of light milling with it, but probably won't.

Next task is to work out how to make a metal one. The teeth have a 12.5 degree taper when in lies the machining problem.

AdeV:

--- Quote from: awemawson on November 17, 2018, 03:05:03 PM ---Next task is to work out how to make a metal one. The teeth have a 12.5 degree taper when in lies the machining problem.

--- End quote ---

Two options spring to mind:

1) Tapered end-mills.... if you can get one with the right taper.
2) Do it on a manual machine with a rotary table, and have the head tipped over by the correct angle.

3) Mill the bulk of it with straight sides, then use a die eroder to make the tapers (if they can do that sort of thing?)

I'll stop there before someone does a Spanish Inquisition joke...

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