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

[Spurry]

It would be great to see you posting again, Andrew.
Hopefully 2025 brings good health and enthusiasm to all.

Pete

[Muzzerboy]

Oooh that sounds intriguing - I hope you will at least unpack it and show us what you got there!

I know what you mean about lurgies stealing motivation. Between us, my wife and I have been rendered mostly unfit for any serious house / workshop time for the best part of 6 months. Getting sick of sitting around and nothing happening but wife is better now and hopefully I'm not far behind. Obvs that hasn't prevented me from acquiring more tools in the meantime...

Hope you are soon back in the workshop and up to your old tricks again!

[awemawson]

So this is my first opportunity to unpack the pallet of bits, what with the Christmas festivities and various cottage guests coming and going.

First job, with the help of a friend, tug the rather heavy pallet of  bits across the inner yard from the unheated tractor shed into the warmth of the workshop. (My Forklift seems to have lost its foot brake so I don't trust it up and down slopes until fixed!)

First thing off was the servo crate that has all the drivers for all axis's and the turret itself :

 

Then came a spindle assembly for a Beaver Partmaster that he had scraped complete with tool gripper:

 

 

These can sit on the shelf hopefully never to be needed as my Partmaster CNC Mill is ok (another jinx !!)

Then a few interface electronics from the TC20 lathe that one hope I'll not need but better to have them than not:

Turret Logic:

 

Tailstock Logic:

 

Chuck Logic:

 

[awemawson]

Now for the important bit - the SMCC servo logic controller that I THINK is the source of my issues:

 

Also he has returned the Field Coil Drive Card that I let him have as an aid to his diagnosis.

 

Disappointingly the Tool Turret Assembly is missing it's servo motor and is a bit knocked about - I had had ideas to set it up as a test rig but not without the motor

[Sea.dog]

It's good to see you back with motivation, Andrew.

[awemawson]

Slowly cranking up the old engine Graham.

Yesterday I re-read the entire saga to try and refresh my memory of what I’d done and not done, I must say that it left my head spinning 👀

[awemawson]

So having cleared away all the massively heavy bits from that pallet, today I had the oppurtunity to actually make a start.

First objective before changing anything is to check all the internal sensors on the turret are actually working, these are :

A/ Turret Clamped
B/ Turret Unclamped
C/ Index Position
D/ 4 channels of 'Tool Number' in binary

A & B are relatively easy, the massive 'tool disk' is moved forwards hydraulically to unlock and backwards to lock. In the forward direction the 'drive' curvic coupling is engaged and the front locking curvic coupling is disengaged. The two sensors ride on a tapered part of the shaft and measure really small movements of a few thou. The co-axial hydraulic cylinder is driven by a spool valve that has handy DIN43650 electrical connections - as one is driven automatically operated at power up driving to 'locked' it is only a case of swapping the connectors to drive the turret 'unlocked'. Glad to say both sensors test as good as these have given issues before.

The system is servoing onto one position of the drive system, and this 'should' be the Index sensor finding a notch on the drive system, however monitoring the Index sensor and forcibly moving either side of where it is homing (with a spanner on a convenient drive dog) the sensor doesn't  change state. So this definitely needs investigation.

The Tool Disk happens to be set to 'tool #1' and reading the 4 tool number sensors indeed I am getting channel A=24v and channels B,C, & D all at 0v so that seems to be working.

So at least that's 3 of the 4 sensor systems given a god health check but the 4th one with need a bit of rigging up so that I can spin things by hand without fighting the servo but that's for tommorow.

However I did do a tentative MDI command to select tool#2 and amazingly not only did it work but I was able to re-select tool #1 and get back to square one.

Another issue I noticed is that the screen calls for a 'Turret Initialise' (code 6000) but after an initialise the demand remains. Almost certainly this is a program issue in the SMCC card but I don't yet want to risk trying the one I recently aquired as there are no more in the known universe correctly programmed for this lathe.

[awemawson]

Up and at it early today as two sets cottage guests going and arriving.

Having cogitated the best way of isolating the Turret Servo #motor drive it came to me in a flash - the analogue +10-0-1-10 drive signal is on it's own plug with a few associated control signals, so it can just be unplugged - simples

 

This then allowed me to turn the servo motor by hand without fighting the drive, and I was able to detect the 'Index Notch' by monitoring it's proximity sensor, getting a decent signal of 19.1 volts when off the notch and 0v when on it.

As I was monitoring on a terminal strip up behind the turret (gymnastics involved!) I thought it bast to prove it all the way through to the SMCC card as quite a bit of chassis wiring is involved to get it there. The SMCC card is isolated by an adjacent PCB holding opto-isolators and relays - terminal 34 being the Turret Zero Ref signal. Sure enough it's working.


So that's all the internal sensors on the turret proved good so no perhaps I can risk the new (second hand) SMCC card. But that's for later as other duties call.

[awemawson]

Loath to venture outside  this morning as it's  chilly -4 degC but I'd set the heating in the workshop yesterday to 15 so it shouldn't be too bad (?) It had managed to get up to 13C so tolerable.

Now I've long suspected that this problem basically is an erroneous slight offset on the analogue output of the SMCC servo computer card - very difficult to measure anything as it all happens a bit fast but the result (I think!) is a bias on the tool disk so when the front curvic coupling needs to mesh after a tool disk move it cannot lock into position as the fixed and moving teeth clash.

Certainly as a case in point this morning although I can hydraulically drive to tool disk forward to unlock, it would not return to locked until I disabled the servo drive (X111 plug out) and manually gave it a slight turn.

So heart in mouth I decided to install the replacement second hand SMCC card. It was complete with it's mounting bracket which is slightly rusty. If I fix this fault I'll swap the bracket.

The result is that I can move the tool disk to apparently any position and it will return to the locked position (so far!) every time. However the 6000 error message calling for a turret reset still won't clear so more investigations called for.

 

[awemawson]

Well that didn't go to plan.

All sorts of issues emerged reporting :

6006 Spindle Drive Fault
6022 Axis Drive Fault
6030 Lack of Hydraulic Pressure (there isn't!)
6019 Chuck Pressure Switch Fault

Argh !!! I decided that I need to be able to talk to the PLC to monitor the internal ladder logic to see what's going on. But firstly I want to be able to connect the lathe through it's RS232 link to prove communication.

That went well and I was able to dump parameters to my desktop PC and they seem to make sense so the RS232 link is proven.

 

Next I need to steam up Step5 Siemens software to talk to the internal PLC but that's a job for tomorrow.

However I did then try again using the turret (this is after a 24 hour head scratching period) and darn me it's working. So tomorrow a bit more softly softly probing about to see what's going on.

[awemawson]

So this (very cold!) morning I powered the beast up and confirmed that I could still initialise the turret, move all the axis and select tool positions but still with those same errors reported.

But objective today is to power up the old ToughBook lap top with Step5 (Siemens PLC support program) that runs under Windows XT.

A lot of faffing about and trawling through grey matter and eventually I got there - we are CONNECTED to the internal PLC that runs within the Siemens Sinumerik 820T control that controls this lathe.

A few screen shots just to prove it:

It reports the correct PLC type:

 

I can read internal parameters

 

I can see PLC Ladder Logic in real time

 

Now I need to go and warm up and refresh my memory of what is where in the PLC logic that's relevant to the current issue but my brain's a bit numb at the moment

[hermetic]

I am back again and watching with baited breath Andrew!!
Phil

[awemawson]

Glad to have you aboad Phil. As you know I too have been rather remiss in the attendance department.

I  tell you it will be a major fillip physcologically if I can get this beast back on its feet again !