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report on VFD upgrade for HF 12x36 lathe

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  • report on VFD upgrade for HF 12x36 lathe

    At the risk of insulting your intelligence, I'm going to go into some detail on this upgrade, for the benefit of those who are new to 3-phase motors.

    When the question of "which color chinese lathe should I buy" comes up, one argument for buying the more expensive colors is that they come with a better motor. It's true that HF motors suck. It's also true that all colors use the same basic controls and contactors -- and the contactors are the most failure prone item on the chinese lathes.

    My thinking is that the money you save buying the HF colored lathe will pay for an upgrade to a 3-phase motor and VFD. So I run the HF motors until something breaks and then upgrade to 3-phase.

    The controls on one of my 12x36 lathes conked out recently (the other lathe received a 3-phase upgrade years ago). I spent a day trying to troubleshoot the problem and only succeeded in breaking the drum switch. So I followed my own advice and sprung for a 3-phase upgrade.

    The HF motor has a weird Chinese frame size and weird metric shaft size. But a 145T frame will fit the lathe, more or less. You'll want a TEFC (totally enclosed fan cooled) so it won't be bothered by coolant or chips.

    The HF motor claims to be 2 HP, but we all know that HF HP ratings are a lie. A quality 1.5 HP motor will work fine.

    It is not necessary to use an expensive "inverter duty" motor, however, inverters do make motors run a little hotter, so I favor the industrial grade motors with a cast iron frame and cooling fins.

    I found a new heavy duty Siemens 1.5 HP motor on ebay for $70 delivered. Before ebay went down the toilet, it was common to see 3 phase motors sell for $9.99 plus shipping. Nowdays most motors are "buy it now" so the bargains are harder to find.

    A 145T will not accept the metric HF pulley, so a 7/8" bore pulley must be added to your shopping list (I suppose you could bush the HF pulley, but pulleys are not that expensive). An ebay pulley set me back $19, delivered (the shipping was more than the pulley).

    The cheapest VFD I could find on short notice was a Teco EV from Dealer's Electric, $196 delivered.

    Here's the goodies.

    The 145T frame matches the HF motor mount just fine, however, the metric bolts were too fat for the holes in the 145T frame. 5/16" bolts seem to be called for. I didn't have the appropriate bolts on hand, so I just drilled the holes big enough to accept the metric bolts.

    Flexible metal conduit was used between the motor and the VFD. I had some flex left over from a previous VFD install, so I didn't have to buy more. Special fittings are required to attach the flex to the motor -- you can get the flex and the fittings at Home Depot. The fittings I had on hand were a loose fit in the motor peckerhead, so I JB'd the fitting to the motor.

    Eventually, I'd like to control the VFD through TurboCNC. But that may take a while to set up, and in the meantime, I needed to place the VFD where I could control it while running the lathe. This picture was taken before the wiring bugs were sorted out, so the wiring looks a little different now. This is not a great way to mount the VFD, but it is convenient. Eventually it will be re-mounted in a better enclosure (I hope).

    Most people will want to utilize the lathe's drum switch to turn the VFD on/off and forward/reverse, just like a normal lathe control. My drum switch was broken and who knows when I will find time to fix it, so I used a conventional household switch. I decided to mount the switch on the right hand side. My thinking was that it would be impossible for me to turn on the lathe while my right hand was still busy chucking, something I have been known to do with conventional lathe controls.

    Here is how the switches are connected to the VFD.

    4 o-------o/ o-------o 8 Closing this switch turns the motor on

    5 o-------o/ o-------o 8 Closing this switch enables reverse

    This is what is known as a "Run/Stop-Forward/Reverse" mode. This option must be enabled in the VFD (F06 = 001).

    Remote control must also be enabled (F04=001).

    And NPN must be enabled, which means you turn it on by grounding the terminal. I thought NPN was simpler than PNP for this particular setup.

    As posted in another thread, I had a heckofa time getting the grounding right on this install. And as mentioned in that thread, the manual for this VFD totally sucks. If you have a lot of experience with VFDs and are fluent in electrical symbols and terminology, you won't be bothered by the manual. But if your electrical skills are modest, then you will need assistance.

    I frequently referred to the manual for my other VFD, a Motortronics that I bought from Surplus John. Many of the functions are similar, and the Motortronics manual has good explanations and wiring diagrams. I also had to do some googling and beg for help on this forum. It took too long, but eventually I got it running well.

  • #2
    Today the lathe was run continuously for 8 hours straight. With the grounding fixed, the Gecko stepper drives purred like kittens. The straight cut gears on these lathes are normally quite noisy, but it seemed much quieter after the 3-phase upgrade. The VFD's fan made more noise than the lathe.

    CNCing a stainless alignment bushing.

    This lathe has a spindle tach that interfaces with TurboCNC. There is a bug in TurobCNC that requires you to set up spindle control before the tach will display properly. So I set up a dummy spindle control, just to make TurboCNC happy. Then I added these lines to my programs:

    M03 ; fool TurboCNC by pretending to turn on spindle
    M50 ; read the RPM

    And TurboCNC displayed the RPMs in the status box. It does not refresh automatically, so you have to run M50 each time you want to refresh the RPM.

    My lowest possible speed is 16 RPM, in the lowest gear and at 20 HZ (the VFD can go slower, but I set a 20 HZ minimum).

    My highest possible speed is 2730 RPM, in the highest gear and at 100 HZ (the VFD can go up to 200 HZ, but I set a 100 HZ max).

    In practice, I leave the gears alone and use the VFD to control speed.

    At the moment, I am using the VFD's internal braking resistor, and it works pretty well. I'm interested in adding an external resistor so it can brake even faster, but I haven't figured out how to set that up yet. The manual is no help.

    As time allows, I'd like to set up TurboCNC to control the VFD.

    Even though it was a headache to setup and debug, I'm loving this VFD and motor. It's smoother and quieter than the HF motor. It saves me time because I don't have to monkey with gear changes. How sweet it is !!!!!!
    Last edited by MTNGUN; 10-28-2008, 01:44 AM.


    • #3
      Have you thought about switching to Mach3? Its free up to 200 lines of code or so which is enough for anything short of contouring. It constantly updates the spindle speed and offers closed loop spindle speed control so as the motor slows it kicks up the VFD to compensate. Really nice feature.

      I initially used turbocnc but I got over it.


      • #4
        I have heard good things about Mach III but haven't tried it because of time constraints. My programs do use more than 200 lines, so I'd need to buy the real deal, plus upgrade to better PCs, plus buy or hack a copy of Winblows for each box. Plus it needs a mouse or trackball, a huge drawback in a shop. Mostly it would just take time to switch over and learn to use it.

        I like TurboCNC, but there is no support and no bug fixes, so the day will come when I will be forced to move on.

        I actually prefer DOS and the mouseless interface. Simple is good.


        • #5
          That's the first time I've seen a wall made out of firewood.

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


          • #6
            Aside from your using the CNC, your description of a VFD install very closely matches mine ... with the same amazing end results!! What a magnificent upgrade. I found a 2hp motor in the scrapyard and chose a Hitachi unit. The manual on it was perhaps a bit better than your description but to an un-experienced person, the terminology made it confusing.

            My lathe is also one of the Chinese versions, the Birmingham. I have looked at the HF closely and while not exactly the same, it is very close and I think the crappy electronics run through all the Chinese tools.

            I chose the Chinese route about 3 yrs ago after putting weeks of concentrated effort in finding the proverbial "old American iron" -- it just wasnt happening! After much research, I decided the Chinese route was a practical -- and, economical -- way to go. Since that time, I have continued to follow the comments/experiences of the owners of the several different brands of this size lathe and if had to choose one now, I think I would just take the best deal from them, which would probably be between Enco's version with free frt, or HF's with one of their discounts. The dissatisfaction rate among the owners is very low across the board... with many of these lathes being used in a shop type setting, as yours obviously is.
            If everything seems to be going well, you have obviously overlooked something........


            • #7
              I got around the mouse by using a touchscreen. Now thats the cats meow...


              • #8
                Based on the appearance of your lathe you use it a good bit more than I do mine. I performed much of the same operation on my HF 12 x 36 lathe-- replaced the original motor with a 3phase version. However, I can not claim that the quality of the HF motor was the reason. In fact the original motor had worked just fine for 5 years without a problem. The quality appears to be equal to similar lathes as far as I can tell.

                I purchased a new 2 hp (Chinese made) motor from for $137 and a WEG 10 VFD from dealerselectric (I no longer see them listed) for $120. I made a new pulley which is a nice machining project; I would just buy one if I did it again.

                I did use the drum switch on my lathe and added a switch that bypassed the front panel switches to turn the lathe on and off. I also added a pot to allow for speed changes instead of using the more awkward controls on the VFD. I continue to use the gear box to change speeds in many cases (as per Forrest Addy's advice), although I enjoy the ease of changing speeds to suit especially when doing facing cuts. All in all it was worth the ~$300 investment.


                • #9
                  Originally posted by MTNGUN
                  I frequently referred to the manual for my other VFD, a Motortronics that I bought from Surplus John. Many of the functions are similar, and the Motortronics manual has good explanations and wiring diagrams. I also had to do some googling and beg for help on this forum. It took too long, but eventually I got it running well.
                  Eventho motortronics is not a widely used vfd i agree that they have very good support.

         has lots of pdfs & software downloads.


                  • #10
                    I like your Cordwood shop!

                    And thats a pretty good price on the VFD.


                    • #11
                      The lathe package of Mach3 is limited to about 160 lines. Works great! Got CSS figured out and thats wonderful! (Instead of setting a RPM to cut at you set the SFM you want ro cut at and it controls the spindle speed to keep the SFM at your set point. As you feed the cross slide in it speeds up to a max set point you.