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Thread: New lathe electicals and subsequent bench mods, with a hint of restoration.

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    New lathe electicals and subsequent bench mods, with a hint of restoration.

    Hi guys

    I started working through a shortlist of jobs and modifications focused on and around my old Grayson lathe last Sunday.

    She's had a couple of minor niggles and problems in need of attendance for a while now, one of them being the motor which is rather old and nearing the end of it's life and was noticeably struggling, even in backgear.

    Once I had a bit of cash saved up for a replacement, I did some shopping around for one with the same specs as the old one (1/4hp single phase 1450rpm). However, as I work at a factory that makes variable frequency drives, I ended up getting a new/old stock 2hp three phase 2870rpm motor purchased on ebay as it was going for an absolute steal, it also opens up some intersting possibilities (the armoured cable was an awesome score at work and managed to get enough to use it exclusively).


    For now I've set the VFDs parameters to match the specs of the old motor, though I'm going to be playing around with various switches and the manual inputs to find interesting ways of controlling the saddle a little later on.


    After setting up the drive, I made a quick and dirty manual control panel out of a short piece of galvanised right angle, bent it downward a bit to make it more comfortable to use and then installed it next to the MEM starter box that's the safety disconnect between mains power and the drive.




    Once that was done I changed tack and focused on swarf control. For that I used some salvaged polycarbonate sheeting (more discardings salvaged from work) and walled off the bench underneath to prevent chips collecting on the shelf below where the drive and motor are housed.


    The motor is well sealed, bar the air intake round back. The holes are easily big enough to suck chips through, so I took to bending out and flattening the rim of an old perforated aluminium speaker on my vice with a hammer and glued it over the intake. Still plenty of air movement but much reduces the chance of chips getting in.


    With that done I set about mounting the drive as close to the control panel as I could get it. After many iterations on the same theme, the favoured combo was some medium size t slot profile, a heavy duty bracket and a short length of mounting rail.


    During a quick tea break, I orderd a pulley for the new motor as the shaft is a lot bigger than the old one. I did consider boring out the old pulley but it was worn so thin it wouldn't have survived a gear puller.

    I also ordered a new drive pulley for the lathe while I was at it. The original iron pulley casting is out of balance and causes a lot of vibration at certain speeds. It's also damaged, two of the support struts are cracked right through so there was no getting round it.


    With the pulleys ordered, I turned my attention back to the control panel as it looked rather exposed. As luck would have it, the top half of an enclosure from some electronic item or other was in my "doner" materials bin which looked a close enough size to use.

    I first made sure it was oriented so the side with the flange would remain with the parts I wanted to keep so I could add a side panel later, I then marked and cut two slots with my angle grinder and dremel to fit round the switch and trim pots fixings underneath.

    After that, I transferred some measurements from the control panel to the enclosure half, rough cut it a little over size and then filed it to dimention.




    Once that was done, I took the other section and drew the two halves together to make a shorter version of itself and glued them together with superglue.


    It was then black to control panel for marking and drilling four mounting holes for the new panel front, I then lined them both up and used a fine tip marker through the holes to mark their location on the front panel and drilled them out and fixed the two together with some short length course threaded screws.


    I couldn't find any more sheet metal to make a side panel with at that point, so instead, I knocked up door for the front of the bench out of the left over polycarbonate sheet, no point going to all that trouble earlier only to leave that area wide open to swarf.


    I had to cut the top right corner of the cover out to go round MEM box and control panel and used the offcut to make the missing side panel. After which a gave up tinkering as it was very late and I had to go to bed.





    Next morning I remembered I had a door magnet stashed from ages ago, so after my first cup of tea, I went in search of it and eventually dug it out.

    I then fixed the magnet as central as my eyes could deturmin, put a metal plate for the door on the magnet, put superglue on the plate and held the door closed applying pressure directly over them both till the glue set.


    The hinges had to be extended out a bit so the door would lie flat when closed but it left a slight gap running along the top which was of minor concern.


    Luckily we'd got some new curtains for the goods in entrance that were too long and needed trimming, So I grabbed a few and made a skirt to cover the gap in the door.


    I'd made the cutout in the door too deep on purpose as the plan was to use a soft material that would flex around the MEM box a piece of those curtains was just the ticket.



    Which brings us to the end of my adventures for the moment. I have to wait till next week for the pulleys to arrive and other shenanigans as I'm away the weekend, so for now, stay safe, stay happy and keep those chips flyin'
    It's not the destination but the journey you take to get there that matters.

  2. The Following 4 Users Say Thank You to Canobi For This Useful Post:

    rlm98253 (09-30-2017), Seedtick (09-30-2017), Toolmaker51 (09-30-2017), Y-geo (09-30-2017)

  3. #2
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    After much ado trying to sort out some badly machined pulleys, I ended up going for a set of taperlock pulleys, which have made all the difference in eliminating the worst of the vibrations I was getting before with the original drive pulley and as a result I'm getting a much better finish.

    I also now have a brake resistor box that was originally for a 5kw motor that I spotted in the scrap metal bin at work. From the outside (and judging by the amount of things rattling around inside) one could easily discern that the resistors had been fried and partly shattered. After getting it home I opened it up with a view to clearing out the broken resistors to make room for the items I have on my shopping list but to my delight found that both fans worked and one out of the four resistors was still intact and functional. The value was also only 20ohm shy of that recommended in the manual as well and as I'm only driving the new motor at half it's total power rating, it was good enough to bring down my stopping time to 1.3sec. Not the dead nuts I'm aiming for but damn good for free so I'll happily take what I'm given

    I then stripped the box down totally and gave everything a wipe down and then wired things up to suit my setup as I reassembled it. I had to ditch the connector socket that was installed, along with the thermostats that were clamped to the resistors, though I intend to reuse them to control the brake box fans again when my system develops enough, and I get my head around all the wiring involved.

    The scrap bins were full of gems that day as i also found an options control pad/display extention which also tested out as functional. The PCB was somewhat loose inside which could well have been the reason for discarding it but a bit of hot glue sorted that out. I then knocked up a quick mount for it out of some U profile alu and put it somewhere handy enough to use but out of the firing line of flying chips.
    Attached Thumbnails Attached Thumbnails New lathe electicals and subsequent bench mods, with a hint of restoration.-59f32989a7ac0.jpg   New lathe electicals and subsequent bench mods, with a hint of restoration.-59f32989963f5.jpg   New lathe electicals and subsequent bench mods, with a hint of restoration.-59f34b7cd6c99.jpg   New lathe electicals and subsequent bench mods, with a hint of restoration.-59f37bacdc605.jpg  
    Last edited by Canobi; 10-27-2017 at 01:33 PM.
    It's not the destination but the journey you take to get there that matters.

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  5. #3
    Ed.
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    It's a lot of work but it will be very satisfying in the end, great job.

    There is nothing like finding discarded bits and pieces of scrap items and re-purposing them for new projects, and usually they are free which is a bonus!

    Cheers

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    Quote Originally Posted by Ed. View Post
    It's a lot of work but it will be very satisfying in the end, great job.

    There is nothing like finding discarded bits and pieces of scrap items and re-purposing them for new projects, and usually they are free which is a bonus!

    Cheers
    Seeing how clean the finish came out after fitting everything was just as exiting as getting the lathe in the first place, she really is like a new machine, deeper cuts, cleaner finish and no more coasting to a stop.

    I'm taking things a step further and I'm going to be adding some switches and a custom PCB I've designed to take advantage of the VFD manual directions and start/stop to control the carriage. The PCB adds a delay to both directions before they resume so I have time to move the cross slide in and out for thread cutting operations and breaks out the common line to both direction switches that I can use as multiple carriage stops for turning operations.
    New lathe electicals and subsequent bench mods, with a hint of restoration.-59e23ea5dfda4.jpg

    Here's my concept drawing of the switch trigger mechanism for the carriage control system:
    New lathe electicals and subsequent bench mods, with a hint of restoration.-59e64ebab93f0.jpg

    The following diagrams to show how the main control switch is wired to the VFD terminals:
    New lathe electicals and subsequent bench mods, with a hint of restoration.-59dfeed05301c.jpg
    New lathe electicals and subsequent bench mods, with a hint of restoration.-59dfeed0bbd86.jpg
    New lathe electicals and subsequent bench mods, with a hint of restoration.-59dfeecfed18a.jpg

    Placing a button in series with any one of the three lines allows extra control. Using push to break or push to make buttons (latching or momentary) allows one to tailor the system depending on how you want it to work. It's worthy of noting that buttons placed on the common line will effect the both forward and reverse line at the same time, whereas buttons on the forward reverse lines work independently.


    By daisy chaining combinations of both types of switch/button, a complex automated system can be achieve relatively easily without the need for some kind of micro controller or CNC.

    Here are a few diagrams showing single button placement:
    New lathe electicals and subsequent bench mods, with a hint of restoration.-59dfebaa6681c.jpg
    New lathe electicals and subsequent bench mods, with a hint of restoration.-59dfebaabbeb4.jpg


    While I was dreaming up all this I was also trying to figure out if I was actually going to be able to use it due to the way my dog clutch worked. First time I used the brake my chuck unscrewed itself at high speed as it was allowed to spin free until the clutch engaged with its stop which provided just enough rotational forces to overcome the friction holding it in place.

    No manual was ever produced for my lathe and it wasn't until the other day that I discovered I'd been using the dog clutch wrong the whole time, as had the previous two owners. With the chuck now stopping and reversing under control, it shows no sign of coming off on it's own anymore so I'm very relieved, that was about the scariest experience I've had with this lathe to date, I just tapped to have a board in my hand at the time which I was able to use as a shield and the very envious "dink" in it left on one of the ways will help remind me to check the clutch is engaged properly from now on in.

    At least I can move forward with prototyping the PCB now, wiring things up is the easy part.
    It's not the destination but the journey you take to get there that matters.

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  8. #5
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    I bought a new brake resistor of appropriate wattage and value for my motor last month. It arrived in the mail yesterday and was waiting for me when I got home from late shift, which is a good time for a bit of quiate tinkering

    After unhooking the brake box from underneath the bench, I whipped the side off to reveal the current setup:




    I then removed the old resistor and installed the new one. I was able to use the existing mounting holes but the new resistor is a tad longer than the original occupants, so couldn't use oposing pairs to fix it in place. I did consider fixing it on one side only so it could lie parallel to the fans but my bench isn't the most sturdy and would probably cause it to rattle so I made the compromise and used the next hole across:


    It was late and I didn't fancy digging out the soldering iron, so I came up with a bolt together solution for joining the wires using a plastic right angle bracket, three M4 screws and a brass stand off. The essembly was then mounted on the standoff to give clearance for the wires and positioned so the terminals don't come into contact with the housing. Eventual refinements will include making new holes to straighten up the resistor and sleeving the terminals for better protection from short circuits.


    Turns out the resistor doesn't just effect stop times, my lathe can now start scary fast (currently set at 0.8sec), though unfortunately I can't get the lathe to stop quick enough despite the new resistor doing it's thing and the ramp time set to 0.1 sec. As such I'll need to rethink how the carriage control system will work in ordet to comensate but I'm not too bummed, she's already performing so much better than she was not so long ago so I'm happy as Larry right now
    It's not the destination but the journey you take to get there that matters.

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    Seems I had a bit of a brain fart as I needed to enable the brake chopper function which was in the extended parameters. They weren't that easy to get to as they're normally hidden and a code has to be entered to access them but she's now stopping about 1.1/2 turns of the chuck, which is quite good considering the amount of iron being moved at speed and I don't have to rethink my carriage control system now either so it's all good


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