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vfd controlled lathe question

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  • vfd controlled lathe question

    I have finished the rebuild and refinish of my "new" SB16" heavy. I had several years ago fitted a Hitachi vfd to my small mill and was very pleased with the result.

    My lathe has a old massive 3ph 1.5 HP motor. This I had professionally overhauled before I reinstalled it.

    As I have only 220v single phase available A new Hitachi vfd seemed like the way to go. I purchased a Hitachi SJ200 vfd. However reading thru the manual I have been reminded that no disconnect is to be installed between the vfd and the motor. (This was not an issue on my mill.) However on my old faithful Craftsman 12" lathe I seem the use the drum switch frequently and have reinstalled the drum switch on the South Bend.

    Now it would appear I cannot use it?

    Can someone suggest how to set up to be able to start-stop-reverse the lathe?

    The new Hitachi has a nice little removable control module that connects to the main unit with a RJ45 cable.


  • #2
    Read page 4-26 in your deals with the three wire control setup.That will give you start/stop and fwd/rev.
    I just need one more tool,just one!


    • #3
      I have the same setup using Hitachis on my mill and lathe. Definitely use the terminals on the VFD provided for stop/reverse. Three wires are used, they are low current,low voltage control only. On my lathe they are connected to a dinky toggle switch but have no problem controlling my 2hp motor. On the mill, I ran the three control wires from the VFD to the switch on the mill after, of course, isolating the switch from the motor. Works great. I don't have to touch the VFD if I want to adjust the speed, else I use the switch on the mill. I know the Hitachi manual is a bit odd, but it is informative. Mine also came with a smaller, less detailed, but more to the point pamphlet.


      • #4
        You can use the drum switch but you have to configure it to switch the control circuit of the VFD. Don't try to use it in the motor leads.


        • #5
          Swiches to control a Hitachi vfd

          I have my vfd wired up far enough to run the lathe from the vfd unit. Works well. I want to put a small control box on the lathe where the drum switch was mounted. Reviewing some of the neat layouts in past post I have found a nice one to copy.
          Studying the instructions in the Hitachi manual for a 3 wire hook-up the fwd- rev is clear but the stop/start is not (at least to my thick head). Are they talking about 1 momentary contact switch controlling both stop and start? Reading the input states for code 20 and 21. I am not sure how this would work.
          Can someone explain this for me please.
          Thanks much


          • #6
            Is there no pushbutton to control direction?


            • #7
              For the 3 wire - stop and start are separate switches. You wire the Stop switch so it's NC - any break in the circuit will "stop" and it's fail safe for a broken wire. It would help if Hitachi showed this (stop switch "Closed") - what they reflect in their notes.

              I use a toggle switch for forward/reverse.
              Last edited by lakeside53; 02-26-2010, 10:19 PM.


              • #8
                I'm not familiar with the Hitachi, but on the Automation Direct VFD's, you can tell it to recognize either a momentary signal (as in a pushbutton) or a constant signal (as in the drum switch.)

                I almost did the same thing as you; I'd been using my Logan for so long, with a drum switch mounted above the headstock, that I considered leaving the switch in place and using it as the controls for the VFD conversion.

                The two things that convinced me otherwise was first the condition of the contacts in the switch- they'd badly eroded over countless cycles (the machine used to be a factory turret lathe) and while they'd have been fine for the low-voltage VFD signal, it wasn't encouraging. The second was that I wanted to add a speed pot, and there wasn't room inside the drum switch housing.

                I eventually went with an all-new box and controls:

                Top left is speed, lower left is fwd/rev, the other two are appropriately-colored start and stop.

                But the VFD could have supported either one- the momentary buttons I wound up using, or the constant contacts I considered using. You just have to tell it which one, in the settings.

                Doc's Machine. (Probably not what you expect.)


                • #9
                  The Hitachi interface works the same way,


                  • #10
                    I also vote yes on using the drum switch.

                    Here are some pictures of a drum/reversing switch on a machine I have and it has the speed pot inside. YMMV


                    • #11
                      The only thing I like about drum switches is that they are easy to sell

                      I'm sure much of it is just personal preference, but to me tapping a button once is much quicker and easier then twisting a knob/lever. Some VFD will restart after power loss if the drum switch is engaged. it's too late tonight for me to read the Hitachi manual, but you might want to check that and see if there is an override parameter to set.


                      • #12
                        Hmmm??? Not realizing till recently that switching VFD power with the drum switch was an issue, I've been using the drum switch on my mill and lathe for nearly 10 years. I have the mill setup with the low voltage start/stop and speed controls, but use the drum switch for reversing when tapping.
                        The lathe is run from the same VFD using the mill's controls, but still do on/off with the factory drum switch.
                        The VFD is an older Boston Fincor, so far it doesn't seem to mind the switching.


                        • #13
                          Then.. you are just lucky...

                          Pretty much every VFD manual says not too, but some do get away with it.


                          • #14
                            Stop control wiring

                            No problem finding a momentary switch to send a momentary voltage to the selected terminal. ( ie. I can power up.)

                            But: I have not found a momentary contact switch that momentarily breaks the voltage to the other selected terminal. Could the stop function be wired with a SPST toggle switch so that it was "hot" all the time, except when you wanted to stop? Then just switch it off.?
                            Thanks for the help guys.


                            • #15
                              When you say "can't find one do you mean "in your box of stuff".. or you don't know where to to buy one? they are very common. Look for a switch that is a "change -over" type -one side is NO, the other NC. Wire it how you want.

                              yes, you can use a toggle switch NC side if you really want to..