The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
awemawson:
It's been a bits an bobs day for the last couple of days, chasing up and investigating things. A few positives:
I've managed to find the logical word in the controller that represents the Touch Probes making contact, and for the simpler HPA arm mounted one proved that it works.
For the more complex Optical Probe I have a feeling that it isn't working - the actual contact switch on the probe is working, the Infra Red wake up signal is being issued by the cabinet mounted transmitter / receiver, but the electronics on the probe head isn't waking up and replying. I made a simple IR receiver up using a QSE158/9 IR ic that contains the detector and an amplifier / driver that turns on a visible red LED when IR is found, and proved that the 'OMM' unit that is cabinet based is transmitting OK but being ignored. So far I've not managed to open the unit up for further investigation.
Then the Postman brought a mystery package - contents unknown :scratch: Turns out that a very kind MadModder is my benefactor, and sent me a compatible replacement catch for the one that was damaged. Same hole in the door but slightly more streamlined outer profile. Thank you very much Smiffy. However no further door progress as my 'next day delivery' from RS Components still hasn't arrived two days later.
I've been doing quite a bit of research how this machine is supposed to position it's main spindle rotation-ally for milling using the power tooling. There is an M code 'M19 S<angle>' that should stop the spindle at the specified degrees, but although it stops the spindle, the place is random :scratch: I've managed to find the bit of the controller that monitors the angular spindle position, and sure enough it displays correctly if you manually turn the chuck, or set it slowly turning - but the stopping when there bit doesn't seem to be functioning properly.
The another delivery of Tooling arrived from APT. I thought that I'd ordered a left and a right handed version of tooling for TNMG1604 (triangular) inserts, for SNMG1204 (square) inserts, and for DCMT11T3 (diamond) inserts, but it seems that I cocked the order up and the right handed TNMG one was infact for a 20 mm square shank :bang: Never mind it'll go on the Colchester Master and I've re-ordered the correct item
Oh and another positive - I've braved the 'Gear Change Mechanism' and despite previous reports that it might have a fault, it seems to work OK :thumbup:
awemawson:
I've been having trouble with the tail stock. It is clamped to the bed by spring loaded clamps biased in the 'clamped' direction, and un-clamped by two small hydraulic cylinders. M51 comand clamps it, and M52 unclamps it. In addition there is a pressure switch on the hydraulics that reports the clamped state back to the controller.
The actual tail stock barrel is advanced hydraulically by an M11 command, and retracted with an M12. Despite me issuing an M51 command, the controller got all upset reporting that the tail stock was unclamped, and faulted out if I issued an M11. Fairly obviously something to do with the pressure switch, and eventually traced to intermittent contacts. Almost certainly due to the machine sitting unused for many years
Now it's a sealed unit, so no physical cleaning or squirting contact cleaner was possible. Remembering back to my days with relay logic, most are arranged that the contacts rub a little as they open and close to remove any oxide that forms, and the 'wetting' voltage and current are important to keep the contacts low resistance.
OK maybe I can increase the wetting current - I daren't increase the voltage much as I don't know the contacts ratings. A quick test with the AVO showed me the controller input circuit was passing a mere 15 mA when the contacts decided to close.
Now I had already written a little diddy program that clamped and unclamped the tail stock every second in an attempt to clean the pressure switch contacts, things had improved but about one in 35 closures was unsuccessful.
Time to roll out the big guns - I wired the contacts to my trusty current limited lab power supply, set the volts to 30 and the current limiting to 250 mA and ran the program. Initially still problems but after about 20 seconds - hey we have reliable contacts - this rather off the wall method actually works :ddb:
Lab supply put to bed, contacts returned to the controller to play with, and let the little program run again, which it did faultlessly :clap:
Will_D:
I am so impressed with this thread Andrew. Yout rabnge of skills/knowledge is oustanding.
Guys: When Holywood casts the movie who should play Andrew.
PS: How are the pigs?
Watering and cutting Rugby pitchers is keeping me out of the workshop and is so boring
Joke:
Was talking to a native American friend yesterday.
What is your wifes name is asked.
4 Horses is her name.
What a lovely name for the wife, What does it mean?
Nag, Nag, Nag, Nag!!
awemawson:
Will-D those two Berkshires are off on a one way journey early Monday so don't tell them !
At last today the heavy duty piano hinge arrived for the Tail stock Door, so a suitable length was cut off, I picked up the four tapped M6 holes in he door frame and drilled matching 6 mm ones in one leaf of the hinge. When I'd checked that they aligned OK, I opened the hinge holes to 8.5 mm to get latitude for adjustment when the door is swung.
After a test fitting of hinge and door balanced together in the frame, I then spot welded the un-drilled leaf of the hinge to the door, gave it all a good clean up with IPA, and sprayed the inside RAL9001 to match the machine.
The weather is distinctly cooler and it's raining today, so although the paint was 'touch dry' after an hour I left it a couple of hours more before inverting it to spray the outside.
The Postman brought the replacement lathe tool that I had wrongly ordered as a 20 mm shank rather than the 25 mm that I'd intended - so when I'm brave I can start tooling up.
Today I've spent quite a bit of time investigating how to position the main spindle to a known angle. There seem to be two 'M' codes involved. 'M20' that enables the spindle drive, and 'M19 S<angle>' that orients the spindle to the required angle. I have example programs showing me how it works but it doesn't :bang:
I even called up the chap who used to use this lathe to confirm that the lathe has the capability, which he confirmed, there must be some parameter or setting needed to enable it I reckon :scratch:
modeng200023:
If you go on improving the machine like this your friend will want it back!
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