Logan Model 200 Servo Threading

Now you got me hooked.

I have zero electronic hardware, so I ordered an Uno starter kit, motor shield and a display. I was trying to get a "mega" card, but couldn't find a true Arduino made unit, and have no idea as to the quality/reliability of the other card builders. If there are any particular brands that you've found to be goods units, can you please advise? Not trying to bad mouth anyone's hardware, but the range of pricing was crazy wide.

As to the infeed shoulder stop / crash stop, I wasn't considering the operating concept properly. I'm guessing it doesn't help much to count motor turns if the half nut isn't connected all the time. Maybe some sort of carriage travel sensor would work? Can the motor controls detect a "crash" into a bed mounted travel limit, and prevent continued infeed movement?
 
Pardon me, I did say that I was using an Arduino Mega. Actually I'm using an Elegoo "Mega" clone that I picked up from Amazon Prime for $14.99. So far I have zero issues, other than blowing out the bootloader with an Atmel ICE and having to figure out how to restore it. It took me a couple of hours to figure out that the hex file existed, buried in the Arduino folder structure (and now I can't remember where!!).

--- Okay, I had to figure that out. The bootloader hex file for the Mega 2560 is buried deep. It's in "Program Files (x86)/Arduino/hardware/arduino/avr/bootloaders/stk500v2/stk500boot_v2_mega2560.hex". Now I'll be able to sleep tonight :).

I've got a DIN rail Mega adapter coming that will give me screw terminals for ALL the pins, unlike the Uno shield that I have plugged in now. Kind of painful to pay more than twice as much for it as I paid for the Mega.

Assuming that I get it written, the "feed to a limit" mode will require that the half nuts be engaged at all times. Anything else will just be too much of a pain. I'll probably put a big button overlay right in the middle that says "Engage Half Nuts NOW!" Hmm, I suppose I could add a Bluetooth sniffer and steal the data stream from the TouchDRO ......
 
Mega it is. I saw the Uno kit with wire, instruction book, etc., and figured that would be a good starting place. The motor shield was pretty cheep, so simply a low cost opportunity to look into the code (but absolutely not a programmer). I thought best to wait for feedback on the various "clones" to see if they were OK. I did notice other small touch screens that mount directly to a shield. Not sure if they have any sort of user interface to help with setup though.

As to the half nut, are you working with a DRO to locate the carriage position?

Sorry about the issue with the lost file. At that point I would have been wondering what was wrong and ordering a new board.
 
This is a brilliant idea! I can't wait to see it in action.
I have a question regarding threading up to a shoulder. If you thread up to a shoulder it seems it would be easy to stop the lead screw to prevent a crash. Is there a way to re-synchronize the spindle and the lead screw after this even if the half nut stays engaged? The thread pitch would play in to this since the ratio of spindle to lead screw turns could be greater or less than 1.0? I suppose the software could do it somehow but I can't get my head around it. Have you figured this out?
I guess this device is actually a single axis CNC on the Z axis.
I'm thinking about putting this on the far end of my lead screw and leaving my gear box intact.
Robert
 
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rwm said:
This is a brilliant idea! I can't wait to see it in action.
I have a question regarding threading up to a shoulder. If you thread up to a shoulder it seems it would be easy to stop the lead screw to prevent a crash. Is there a way to re-synchronize the spindle and the lead screw after this even if the half nut stays engaged? The thread pitch would play in to this since the ratio of spindle to lead screw turns could be greater or less than 1.0? I suppose the software could do it somehow but I can't get my head around it. Have you figured this out?
I guess this device is actually a single axis CNC on the Z axis.
I'm thinking about putting this on the far end of my lead screw and leaving my gear box intact.
Robert
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I'm keeping running totals on the spindle and lead screw, so as long as both are kept engaged it knows where they are relative to one another. Disengage either one and all bets are off. I know how many counts per revolution the spindle encoder puts out, and I know how many steps per revolution the lead screw takes.

Perhaps I should elaborate. The spindle encoder is going to be driven by the stud gear, so it won't see spindle counts unless the feed lever is engaged. It's directly analogous to using the change gears. Engage the feed lever and the lead screw will turn, but of course you don't know where the carriage is unless the half nuts are engaged.

I actually have a drive gear mounted on the tail end of my lead screw that I haven't gotten around to taking back off. I was going to try a simple gear motor drive from that end before I decided to go for full programmability. I figured I would have to pull the screw gear to use it anyway, so why not just replace that gear with a timing pulley and drive from that end? And if I was replacing the screw gear with a timing pulley, why not drive it with a stepper? And if I was driving it with a stepper, why not ...
 
This is rather interesting. Taking old iron and 'computerizing' it, adding functionality and 'ease of use' to it.
I haven't used my ol' Logan for threading at all since I got the Birmingham.
 
Time for a progress report. There is just barely enough room to mount a NEMA23 stepper motor with clearance for the cover. I'm waiting for another timing belt for the encoder. The ones that I have are either too short or too long, and I finally had to go directly to Misumi for a complete selection of sizes. Still have to make the encoder bracket as well. I'm still adding things to the code, the final piece being the ability to set left and right feed limits to allow feeding/threading to a shoulder.

IMG_1633.JPG
 
This is fascinating stuff to me. I have run CNC lathes previously, and currently have a 1947 Logan that I would love to convert to full CNC to cut tapers as well as threads.....this is some cool stuff
 
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Richard White (richardsrelics) said:
This is fascinating stuff to me. I have run CNC lathes previously, and currently have a 1947 Logan that I would love to convert to full CNC to cut tapers as well as threads.....this is some cool stuff
Click to expand...

Well, I'm keeping this simple insofar as I started off just wanting a power feed, and then the feature creep started. I wanted it to be invisible, bolt-on, and reversible. Besides the feed and threading control, I'll have control of feed direction, carriage jogging, and left/right limits. Beyond that the lathe will operate completely normally in the default mode. Once it's up and running I may work on the half nuts to take out some backlash, and maybe build a taper attachment, but it's still going to be the same manual machine -- just a lot easier to use. When I'm gone and it's in the hands of a new owner, if the electronics fail in a few minutes they can still go Old School. I don't see why it can't keep on going for decades yet (even if I can't say the same for myself!).
 
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