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  1. #76
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    Quote Originally Posted by jack620 View Post
    Good point. I forgot about belt changes. Although I hope they will be far less frequent than they are now.
    Good point. I forgot about belt changes being far less frequent.

    I'd check how long it takes your VSD takes to self check first. If its to long then just run the 24V through the cover switch before going to your fwd/off/rev switch.

    Stuart

  2. #77
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    Hi jack620,
    Stustoys brought up goods points in the control circuit and pointed out that the E/Stop is also the normal stop, a point that I missed.

    I would like to revise my suggestion that you look at as Stustoys suggestion on the the rampdown time of the Altavar and this could be changes via the program to give you a safe stopping time that does not cause any unscrewing of the Chuck.

    The control circuit would be need to be quiet different from the way it is now and would require the addition of some more parts and some of the existing parts would be redundant.

    What you need to look at is if you want a Pushbutton style Start/Stop circuit or a Rotary Switch Start/Stop circuit and the Forward/Reverse can still be done through the existing Rotary Switch.

    As for an Emergency Stop this is where you would need to install a separate unit just as I indicated in my previous post in the Head Stock and wired in series to the Foot Switch.

    Regards,
    Keith_W.

  3. #78
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    Thanks Keith.

    I've hit my first snag. The coil on my contactor is 415V (obviously). I either need to buy a 240V contactor or rethink the wiring.

  4. #79
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    I'm with Stuart on this one. I don't think the best solution on an e-stop is to kill the power. In my experience the potential for an emergency stop is almost always a mechanical problem, and I've never even heard of a VFD "going haywire". In a mechanical problem you want the machine to stop, NOW, not coast to a stop. An isolation switch on the machine would be more than sufficient in case of an electrical problem.

    With all due respect I think you're over-thinking this. Many of us have done this and have a number of these installed in our workshops, even on this identical machine. I also feel you are over-stating the potential for the chuck to unscrew. A motor controller doesn't start and motor with the same violence as a regular motor. By your own admission, the only time you've had a chuck unscrew is when continually starting it in reverse with a regular motor, which was connected to a load (a motor you were running in). A VFD can easily be programmed to slow even a large chuck down relatively quickly and it should not unscrew if the chuck has been installed correctly. I have both a 260 and an older 9", both with VFD, neither have had any issues of the type discussed.

    Pete

  5. #80
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    Quote Originally Posted by Pete F View Post
    With all due respect I think you're over-thinking this.
    Really? I'm getting differing advice (all appreciated) and I'm trying to decide which way to go. Any chance you could post a wiring diagram of your lathe?

    Quote Originally Posted by Pete F View Post
    In my experience the potential for an emergency stop is almost always a mechanical problem,...
    I thought an e-stop was for when you got part of your body or clothing caught in the machine. Whenever I've screwed up and had a mechanical problem the machine has brought itself to a stop pretty quickly- usually well before I can get to the red button. Under such a scenario you just need to kill the power.

    Quote Originally Posted by Pete F View Post
    I have both a 260 and an older 9", both with VFD, neither have had any issues of the type discussed.
    OK, but how often do you use your emergency stop? What's your deceleration time? You say an e-stop should bring a machine to a stop "NOW", but how quickly is "NOW"? I absolutely guarantee that if you brought my 4 jaw to a stop from high speed "NOW", it would unscrew no matter tightly it was installed.

    If getting it right the first time is overthinking then I'm guilty as charged.

  6. #81
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    Quote Originally Posted by jack620 View Post
    Really? I'm getting differing advice (all appreciated) and I'm trying to decide which way to go. Any chance you could post a wiring diagram of your lathe?

    I thought an e-stop was for when you got part of your body or clothing caught in the machine. Whenever I've screwed up and had a mechanical problem the machine has brought itself to a stop pretty quickly- usually well before I can get to the red button. Under such a scenario you just need to kill the power.

    OK, but how often do you use your emergency stop? What's your deceleration time? You say an e-stop should bring a machine to a stop "NOW", but how quickly is "NOW"? I absolutely guarantee that if you brought my 4 jaw to a stop from high speed "NOW", it would unscrew no matter tightly it was installed.

    If getting it right the first time is overthinking then I'm guilty as charged.
    A number of us are saying much the same thing from what I've been reading anyway. The diagram is nothing much to speak of. I've done some machines as 3 wire, but both lathes were wired as with the original switch, just as you mentioned you intended to do. Simply fwd and rev using the existing switching gear in the lathe. I will try to take some photos if that helps. The E-stop is wired to the stop and is in series with the cabinet safety interlocks. I have a 2 second stop cycle. I can guarantee you that it does NOT spin my the chuck! I was referencing the "now" to your alternative you wanted to go with, where power is removed. Not a good idea in my opinion with a VFD as the motor may be back-feeding a now dead motor controller. I have no idea what that would do in the long term, other than that's not how they are intended to be used. I can assure you, that a stop cycle on the VFD will stop the machine much faster than removing the power and letting it coast down. The only issue I have had is when spinning my 4 jaw at high speed and hitting stop is tripping out the VFD's protection. That will shut down the VFD and it coasts to a stop. I could no doubt fiddle with this to prevent it, however I haven't been bothered enough to worry about it at this stage.

    Pete

  7. #82
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    How big is your chuck that does not come off with a 2 second ramp down and from what speed Peter?
    My 5" will not budge, even with dc braking. My 8" chucks and faceplate will do one of 2 things, overload the vfd or if ramp down is slow enough be fine. But if I add dc or have the ramp down time right on the verge of overloading the chuck will unscrew. The faceplate is the worst by far, it will come right off every time. This is on a spindle nose the same size as the hercus, 1.5"x8tpi.

    Cheers,
    Ew
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  8. #83
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    >...........I need to get my head around this 2-wire vs 3-wire control issue...........


    It is actually 3 or 4 wires (not 2 or 3 wires as I mentioned). But let me explain what I mean:

    3-wire start-stop control

    Imagine a VFD that is programmed to run forward, if you apply 24V to input 1. And it runs in reverse if you apply 24V to input 2. And it stops, if both inputs 1 and 2 are open. That is a total of 3 wires (+24V, run FWD, and run REV). If this control cable suffers a short circuit between +24 and any of the other two wires, the motor starts on its own with potentially dire consequences. If say the FWD wire breaks, you may have the operator leaving the main switch in FWD position and walk away, and when someone moves the broken wire it may make contact and the motor starts unexpectedly, with potentially bad consequences.


    4-wire start-stop control

    Imagine a VFD that is programmed to run only forward, if 24V is applied to BOTH input 1 (run FWD) AND input 3 (enable VFD). And it only runs backwards, if 24V is applied to BOTH input 2 (run REV) AND input 3 (enable VFD). Now a simple short between any two wires is not going to start the motor. And a broken fwd, rev or enable wire is going to cause the VFD to trip, so you need to turn it off and on again to restart (the software for 4-wire control regards any fwd or rev signal without enable signal as a potentially broken cable and locks the VFD. It also regards any FWD or REV signal with enable signal both active during power-on of the VFD as a broken wire and locks the VFD).

    Wire shorts usually happen when the control cable gets squashed. Wire breakage happens where control cables are continuously bent, or where cables are not properly finished/protected at the connector ends. Both problems are initially often only intermittant. The 4 wire method uses one extra input, it is still not 100% foolproof, but definitely safer than the 3 wire method. Me personally, I find this reason enough - but I concede that many low cost VFD have limited input lines, and the 4 wire method may mean to sacrifice another feature....

    Chris

    PS: I would personally not recommend to connect the chuck hood to an E-Stop, IF you are the sole user of this lathe. If other people use it too, then yes.

  9. #84
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    Quote Originally Posted by Ueee View Post
    How big is your chuck that does not come off with a 2 second ramp down and from what speed Peter?
    My 5" will not budge, even with dc braking. My 8" chucks and faceplate will do one of 2 things, overload the vfd or if ramp down is slow enough be fine. But if I add dc or have the ramp down time right on the verge of overloading the chuck will unscrew. The faceplate is the worst by far, it will come right off every time. This is on a spindle nose the same size as the hercus, 1.5"x8tpi.

    Cheers,
    Ew
    Mine is a 160 mm 4 jaw, the largest I could fit in without the jaws hitting the bed once it got out around maximum jaw capacity. I must admit I haven't really spun up the face plate to high speed and tried it. I rarely use it, and when I do I use it at low speed due to what's mounted on it.

    I think some are missing the point here. The point is not whether you can get a chuck to spin off if you really try, the point is that you can brake the chuck faster using the VFD that it would brake if you just killed the power. If your own VFD is capable of stopping the chuck faster such that spinning it off may be an issue, simply reduce the braking rate just as Chris has done.

  10. #85
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    The above is a 3 wire installation in a surface grinder



    This is a Hercus 260 using most of the conventional switching. I robbed the "Start" position for the speed control (and still need to turn up a knob for it, I keep forgetting)

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    This is a Hercus Milling machine. The wiring is very similar to the lathes, however I use the "Start" as an e-stop reset.


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    Default VFD switching on a Hercus 260

    Chris,
    Thanks for the explanation. To clarify- does the four-wire method use three logic inputs on my VFD, with the fourth wire being +24VDC?

    Pete,
    Thanks for the photos. They're a big help.
    Chris

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    Quote Originally Posted by Pete F View Post
    If your own VFD is capable of stopping the chuck faster such that spinning it off may be an issue, simply reduce the braking rate just as Chris has done.
    Now why didn't I thinknk of that.........

    You clearly stated earlier in the thread that having a chuck come loose would not be a problem. Several times actually. I am simply reiterating that it can be a problem. You now seem to ha e changed you mind on your earlier comments and are saying it can happen.

    Also it may be helpful to clearly state which Chris you are referring to.
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  14. #89
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    Ewan this is not a competition. I have said that I don't believe it is a problem. It has not been a problem for me, other than the tripping I have mentioned a number of times, and I'm surprised anyone would have a problem with this if they set it up correctly. The standard Hercus 4 jaw chuck is, I believe, 6" and much lighter than the one I'm using. A 260 spindle nose is 1 3/4" x 8 tpi

  15. #90
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    Chris I have no intention of commenting further on this topic. However this is a picture of the wiring to the switch you will find (or similar) in your lathe. I can't recall why I used such heavy wire for the red, it may have been that I was out of thinner stuff, or wanted it self-supporting. Either way, it carries very little current, and could be made quite thin. The first VFD I fitted I used CAT5 data cable in fact. However it should be quite simple to install. You should be able to see from the photo that the control voltage is simply switched to either the white (fwd) or orange (rev) wire. In the centre position, neither white nor orange wire receives a voltage and the lathe is stopped. To answer your earlier question, I do not normally use the e-stop switch to stop the lathe. Since I don't have the reset switch connected on this (260) machine, then an e-stop requires a power off reset IIRC (sorry as I don't use it I can't recall, and I wired it a few months back). It's simply there to kill the motion with a standard e-stop switch at knee height.

    Good luck with it. Just follow the installation instructions and it will be fine.

    Pete


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