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IndustryArena Forum > CNC Electronics > Servo Motors / Drives > Servos for old Haas retrofit
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  1. #1

    Servos for old Haas retrofit

    I’ve got a ‘93 VF-1 I’m retrofitting. I’ve been looking at DMM’s DHTA15 servos, which are 1.3kw and Nema 42 frame, for all 3 axis. I think the shaft size and length would let me re-use the old flex couplers and having all 3 the same would make things simpler. I’m pretty sure this vintage machine used the same E728 dc servos for all axis. Do these servos sound reasonable for a machine like this? I’m thinking that if anything, they are a bit larger in capacity than the OEM drives. I haven’t had any luck at all finding the specs on the old servos though..

  2. #2

    Re: Servos for old Haas retrofit

    Sounds like a good choice of servos, I've used DMM servos on a couple of builds an have been happy with them.

    You can find the specs of the 728's here https://www.cnczone.com/forums/servo...tml#post183844 Al_The_Man has uploaded a PDF there.

    The DMM 1.3KW servos have about twice the rated torque of the 728's so no problem there. It's easy to turn the torque down on a servo, but pretty hard to get more torque out of an underpowered servo. Go Big or Go Home

    You may need a brake on the Z axis to keep it from dropping when not powered.

    I'll be interested on your progress on this build.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
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    Re: Servos for old Haas retrofit

    You may need a brake on the Z axis to keep it from dropping when not powered.
    Does that VF-1 have a counterweight or spring setup to help offset the weight of the head? If not; you might consider adding one, if there is room.

    I'll be interested on your progress on this build.
    Me too...


  4. #4

    Re: Servos for old Haas retrofit

    That looks like them. Goofy 3.4” bolt pattern and all. Thank you.

    These old ones have a huge counterweight/chain arrangement that makes the spindle stay put with no motor attached. I only know that because mine has no motor attached. I can raise the spindle by grabbing the end of the flex coupler and twisting, but it doesn’t go anywhere on it’s own. I think the later ones relied on a brake in lieu of the weights or gas pistons (I think).

    I can’t find the A15 motors on the store part of the site so I emailed them. The fatter DST ones could be made to work just fine I’m sure, but the flex couplers are about $300 each so I’d prefer to reuse them (5/8 to 5/8 shaft vs 22mm).

    I’ll start a thread once I really get moving on it. One other small project I promised my wife I’d finish up before I tear into this one. At least I had the foresight to put the thing in her parking spot in the garage (she’ll be begging me to get on it once it’s cold

  5. #5

    Re: Servos for old Haas retrofit

    It might be easier to replace the couplers than try to find the 5/8 shaft motor. I don't think that is a standard motor.

    Here is what I am using for couplers, not cheap, but not $300 either.

    https://www.automationdirect.com/adc...ervo_couplings

    https://www.automationdirect.com/adc.../bore_reducers

    Good luck on your other project. Gotta keep the wife happy.
    Jim Dawson
    Sandy, Oregon, USA

  6. #6

    Re: Servos for old Haas retrofit

    I looked at those couplers the other day and dismissed them not realizing they had a whole slew of bore reducers available. That’s just what I’d need.

    I’ll wait any see if the DHT motors are still available. The largest one shown is a Nema 42 frame with a 5/8 shaft on it that’s just the right length to fit on top of a 1/2” or so thick adapter plate.

    I told her I wouldn’t start working on it but I didn’t say anything about buying parts for it.

    ETA: DMM emailed me back yesterday and said the DHT series servos I’m looking at are new and just haven’t been added to the store yet. I’m going to go with them I think.

  7. #7

    Re: Servos for old Haas retrofit

    Looks like I've hit a bit of a snag with the servo replacement. I took some measurements and the DMM servos aren't even close to fitting on the x-axis. I didn't realize how close the bottom of the table comes to the motor mount, but then the connector dimensions on those motors is the real deal breaker. Over six inches off of the centerline where I've only got room for about 3. I'll keep looking. It would be a bummer to have to put DC servos back on this thing.

  8. #8
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    Re: Servos for old Haas retrofit

    Couldn't hurt to ask DMM if they have a low profile option. Alternatively, I found this (somewhat pricey) Yaskawa 1.3KW servo on eBay that may work as it has the cables exiting the motors axially with the connectors on the cables themselves rather than the motor:

    https://www.ebay.com/itm/121559947732

    Just out of curiosity, did you get the VF-1 from around Rolla?

  9. #9

    Re: Servos for old Haas retrofit

    Quote Originally Posted by seanano View Post

    Just out of curiosity, did you get the VF-1 from around Rolla?
    That's the one.

    I emailed a couple of vendors to see if there are any lower profile options. There isn't much more room around the y-axis mount either.

  10. #10
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    Re: Servos for old Haas retrofit

    I thought that one looked pretty nice for a retrofit. Is it as nice as it looked in the pictures?

    Sorry, I don't have much good input on the servos. I did find these generic chinese 1KW AC servos with a 17bit encoder:

    https://www.ebay.com/itm/113640253066

    It has the low profile cables and based on the drawings looks like it may fit. It has the same continuous torque rating as the DC servos spec'ed above but not as much peak (3X vs 5X). I found some a bit cheaper (< $400 with drive) but they only had 2500 CPR (10000 PPR) encoders which may be on the low side if the motors are direct coupled:

    https://www.ebay.com/itm/122095801157

    I don't know the level of quality these would have and I think you'd have to assume the support would be minimal at best.

  11. #11

    Re: Servos for old Haas retrofit

    It’s in really good shape mechanically. It’s too clean to have ever done any real work. Story I got was that it had a bad spindle drive. The seller scavenged all the controls and sold them to another customer.

    I’ve found a few servos on eBay that look like they’d work but I’m a little nervous buying there.

    The guys at machmotion responded to my email confirming that fitting a proper size ac servo in this machine was going to be a *****. He recommended a 450 watt Yaskawa. I’m not sure about going that small.

    DMM has some 750 watt servos that look like they would fit. Their smaller ones have the wires in lieu of circular connectors which makes a huge difference. They replied to me and asked for dimensions so they could see if they might be able to make something work. I think the newer VF1/2’s have 850 watt motors so 750 might not be too limiting.

    I never thought I’d have any trouble with the mechanical part of this. I haven’t even got to the fun part yet.

  12. #12
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    Re: Servos for old Haas retrofit

    Dumb question - can the connectors that are on the DMM servos be removed and "flying leads" attached instead; and a different in-line connector be fitted instead? Possibly with a custom 3D-printed or machined (if you currently have a working mill) plastic cover for where the wires would exit the motor frame?

    Alternatively... can the table be cut back enough for clearance without doing too much damage to it?

    Or can an extension be fabricated to extend the motor (and thus it's connectors) out from under the table? That's what they did on my Shizouka - the motors that are on it at the moment don't fit the mountings that were machined into the table, so an adapter was made with the bolt hole pattern for the motors on one side, the table bolt pattern on the other side, and a shaft coupler in the middle. The adapter ends up adding about 5 inches to the overall length of the table + adapter + motor assembly.

  13. #13

    Re: Servos for old Haas retrofit

    Yeah those connectors are what's really eating my lunch here. I've attempted to upload a picture of the x-axis situation. If I were to hang the servo out another 6 inches, I think it would allow a much larger motor. I would prefer to do that over using one of the old DC servos, or a really undersized AC servo.

    DMM emailed me late yesterday and proposed the option of building a custom 1kW servo based on their 750W 86mm frame motor (stretching it out ~1.5"). I'm envisioning this thing looking a lot like the old, skinny DC servos that came off of it. Sounds like my best option so far. They aren't charging too much more for it, it's just going to be a 6 week lead time to get them built. DMM has been really great to deal with so far, I'm pretty impressed with their responsiveness and willingness to build a one (or three) off servo.

  14. #14
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    Re: Servos for old Haas retrofit

    Quote Originally Posted by Sam_Beckham View Post
    It’s in really good shape mechanically. It’s too clean to have ever done any real work. Story I got was that it had a bad spindle drive. The seller scavenged all the controls and sold them to another customer.

    I’ve found a few servos on eBay that look like they’d work but I’m a little nervous buying there.

    The guys at machmotion responded to my email confirming that fitting a proper size ac servo in this machine was going to be a *****. He recommended a 450 watt Yaskawa. I’m not sure about going that small.

    DMM has some 750 watt servos that look like they would fit. Their smaller ones have the wires in lieu of circular connectors which makes a huge difference. They replied to me and asked for dimensions so they could see if they might be able to make something work. I think the newer VF1/2’s have 850 watt motors so 750 might not be too limiting.

    I never thought I’d have any trouble with the mechanical part of this. I haven’t even got to the fun part yet.
    You have to be careful what you buy on Ebay even if it is new, you have to know how you can control the servo drives not all are the same there are a lot of control options and you have to know this if you are buying from Ebay or anywhere in general

    Not sure why you would of been thinking of 1.3Kw servo motors they would have way to much power for your machine around 1Kw max 750W may do the X and Y axes but the Z axes I would go bigger

    A 450w Yaskawa would not run your machine, 750W may do it but most machines that size are using 850W so 1Kw if you can fit them would be good , if they are to big in size then get one 750W and try it on the Y axes first if it will work on you Y axes then your X will be Ok as well the Z axes what ever you can fit and you will need a brake on it if it does not have an independent brake
    Mactec54

  15. #15
    Quote Originally Posted by mactec54 View Post
    You have to be careful what you buy on Ebay even if it is new, you have to know how you can control the servo drives not all are the same there are a lot of control options and you have to know this if you are buying from Ebay or anywhere in general

    Not sure why you would of been thinking of 1.3Kw servo motors they would have way to much power for your machine around 1Kw max 750W may do the X and Y axes but the Z axes I would go bigger

    A 450w Yaskawa would not run your machine, 750W may do it but most machines that size are using 850W so 1Kw if you can fit them would be good , if they are to big in size then get one 750W and try it on the Y axes first if it will work on you Y axes then your X will be Ok as well the Z axes what ever you can fit and you will need a brake on it if it does not have an independent brake
    Yes I’m starting to see that 1.3 might have been overkill. I was looking at them because the shaft size/length would have made bolting them up easy. The next size down in the DHT series was a 750watt. I’m going to try putting the custom 1kW motors they are offering on all 3 axis. I think it should be okay as the original motors were all the same and there is a counterweight on this machine to keep the z axis from requiring a brake. I believe the newer models did away with the counterweight and use a 1.3kW motor w/brake instead.

  16. #16
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    Re: Servos for old Haas retrofit

    Hmm.... well, on the one hand, it's always better to have more power available and not need it, than to err in the other direction. On the other hand, you are already doing a significant upgrade to the machine with the new servos, so...

    I’m going to try putting the custom 1kW motors they are offering on all 3 axis.
    Um.... I'm no expert, but it sounds good to me.

    I might think about possibly replacing the counterweight with a spring setup; just for reduced mass (I don't think it's adding to the machine's chatter resistance much).

  17. #17
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    Re: Servos for old Haas retrofit

    Check out the Allen Bradley TLY-A2540P-xJxxx. The J winding versions are 860 watts. You have to hunt them down on ebay, otherwise you will pay a fortune, but they are compact and will run well with the older AB Ultra 100 1398 DDM 009 or 019 drives which are easy to source cheap.
    Halfnutz

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  18. #18
    Quote Originally Posted by Halfnutz View Post
    Check out the Allen Bradley TLY-A2540P-xJxxx. The J winding versions are 860 watts. You have to hunt them down on ebay, otherwise you will pay a fortune, but they are compact and will run well with the older AB Ultra 100 1398 DDM 009 or 019 drives which are easy to source cheap.
    Thank you for the tip. I already went ahead and ordered the servos and drives from DMM.

    I guess I have around six weeks to work on sorting out the rest of the electronics and make some adapter plates for the motors.

    I appreciate all the helpful advice guys.

  19. #19

    Re: Servos for old Haas retrofit

    Quote Originally Posted by Sam_Beckham View Post
    I’ve got a ‘93 VF-1 I’m retrofitting. I’ve been looking at DMM’s DHTA15 servos, which are 1.3kw and Nema 42 frame, for all 3 axis. I think the shaft size and length would let me re-use the old flex couplers and having all 3 the same would make things simpler. I’m pretty sure this vintage machine used the same E728 dc servos for all axis. Do these servos sound reasonable for a machine like this? I’m thinking that if anything, they are a bit larger in capacity than the OEM drives. I haven’t had any luck at all finding the specs on the old servos though..
    If the old servos and CNC are not in good condition, better change to new servo motor and new servo driver and new CNC.
    http://cncmakers.com/cnc/controllers/CNC_Controller_System/CNC_Retrofit_Package.html

  20. #20
    Update:
    The DMM servos showed up in 6 weeks just as they promised. I have them temp mounted now and have moved on to the other electronics.

    Attached is a pic of the x-axis install. They fit with plenty of room to spare.

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