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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > Converting a CNC boring machine to full 3-axis
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  1. #1
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    Converting a CNC boring machine to full 3-axis

    I recently picked up a Masterwood Speedy 207 for next to nothing, it has 6 hours on the counter. I set it up and for what it's made to do, it works beautifully. But, what it does is boring. As in, it bores holes in cabinet parts and that's all, it does not have a spindle. The "Z-axis" is operated by a pneumatic actuator, so it has no real control besides a mechanical stop for depth.

    The controller is woefully obsolete, it's like using MS DOS. I doubt there's any way to configure it to add the Z-axis.

    I can see the following options:

    -Replace all motion electronics with a typical 3-axis stepper control system like WinCNC or Mach 3. My main question with this approach is how to size the motors, the heavy gantry is run from a single DC servo.

    -Replace the controller and keep the drives and DC servo motors on the X and Y. Add a stepper or servo on the Z. I would use WinCNC for this if it can run the Axor MiniSpeed 140 drives. If not, Centroid Oak has been recommended. Not sure how to determine the compatibility.


  2. #2
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    Re: Converting a CNC boring machine to full 3-axis

    Yeah, looks like another long rebuild project.....could be a winner if the machine is a conventional CNC router design and the outlay for the rebuild is less than a new machine purchase.

    If the expected outlay is 3/4's the cost of an equivalent new machine.....dump it and buy new.
    Ian.

  3. #3
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    Re: Converting a CNC boring machine to full 3-axis

    You have two axis running with servos - do you know what voltage and current rating the servo motors are? I'd take a look at something like the machdrives step and direction drivers like the BRB or BRC (depending on the voltage). You may have to replace the feedback on the motors with a new encoder, but these motors are already sized. Only problem is that they may be undersized since the machine was not designed for an lateral cutting forces. The step and direction drivers would make the servos look pretty much like steppers to whatever software you choose and you should be able to add a stepper to the Z axis. Just one possible way to go. - Dan

  4. #4
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    Re: Converting a CNC boring machine to full 3-axis

    The first thing I'd do is to determine how old the drivers are, and the interface tot the current CNC controller. If the drives are extremely old I'd consider replacing them. The 6 hours of run time is a bit odd so I have to wonder if the run time counter is broken. six hours implies a relatively new machine but I've seen machine sit for years in factories.

    In any event once you know the drives age and interface to the controller, you can make educated decisions on replace, repair or upgrade. In basic terms the drive and the CNC controller have to be capable of using the same interface. That could be step and direction, analog of something else. With DC servos you usually have an encoder feedback device for keeping track of position. You need to know if the encoder closes the loop at the drive or all the way back to the CNC controller (possibly both). This information will help you determine the best fit for a CNC controller.

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    Re: Converting a CNC boring machine to full 3-axis

    Well, I'm definitely in over my head here. I understand what the different parts of the motion controls do, but not how they talk to each other.

    My reasons for wanting to modify the machine are:

    -It is a heavy duty and well built industrial machine. It makes a ShopBot or even my sold $30,000 CAMaster look like an erector set. Weighs 1,600 lbs plus the console!
    -It is set up as a vacuum pod-and-rail which is very convenient for the work I want to do.
    -The envelope is big enough but it fits in my small garage.
    -It really does only have 6 hours, it sat in a dealer's warehouse for 12 years, then the previous owner bought it cheap and couldn't figure it out. It sat in his workshop collecting dust for the last 6. He never even installed any tools.
    -I could probably sell it for $2,000-$3,000, and that kind of cash doesn't get me very far on a different machine

    The case for selling it as-is, and buying something better suited to my application:

    -No re-engineering (AKA guessing) the correct motor size.
    -I wouldn't have to take apart a perfectly good working machine, and someone else could use it for its proper function.
    -I'm guessing it will take the better part of a year to get it working smoothly.

  6. #6
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    Re: Converting a CNC boring machine to full 3-axis

    Here is what I know about the machine:

    X/Y drives: Axor MiniSpeed 140

    The servo motors:


    - - - Updated - - -

    Here is what I know about the machine:

    X/Y drives: Axor MiniSpeed 140

    The servo motors:

  7. #7
    Community Moderator ger21's Avatar
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    Re: Converting a CNC boring machine to full 3-axis

    I'd replace the servos, drives, and control. Go for AC servos with step/dir control.
    Pull the servos to get the physical size, and then determine what size they may be? They don't look to big
    Gerry

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  8. #8
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    Re: Converting a CNC boring machine to full 3-axis

    Quote Originally Posted by kmagyoyo View Post
    Well, I'm definitely in over my head here. I understand what the different parts of the motion controls do, but not how they talk to each other.

    My reasons for wanting to modify the machine are:

    -It is a heavy duty and well built industrial machine. It makes a ShopBot or even my sold $30,000 CAMaster look like an erector set. Weighs 1,600 lbs plus the console!
    -It is set up as a vacuum pod-and-rail which is very convenient for the work I want to do.
    -The envelope is big enough but it fits in my small garage.
    -It really does only have 6 hours, it sat in a dealer's warehouse for 12 years, then the previous owner bought it cheap and couldn't figure it out. It sat in his workshop collecting dust for the last 6. He never even installed any tools.
    -I could probably sell it for $2,000-$3,000, and that kind of cash doesn't get me very far on a different machine

    The case for selling it as-is, and buying something better suited to my application:

    -No re-engineering (AKA guessing) the correct motor size.
    -I wouldn't have to take apart a perfectly good working machine, and someone else could use it for its proper function.
    -I'm guessing it will take the better part of a year to get it working smoothly.
    The system you have there most likely works something like this - To start with, the computer has to know where the X and Y axis are located. It knows where the axis are by a feedback device - most likely some sort of digital encoder and quite possibly a set of homing switches, too (does the machine go through a homing procedure on start up?). The computer has an analog output that is connected to the input of the Servo Amplifiers. This normally sets at 0 volts. When the computer want to make the axis move, it will output either a positive voltage (for one direction) or a negative voltage (for the opposite direction). This voltage usually is between +10 and -10 volts - the higher the voltage the more power the computer wants the amplifier to send to the motor. The amplifier simply takes the voltage and applies the correct amount of dc voltage and the correct polarity, to make the motor spin. There may be a feedback device like a small dc generator in the motor that feeds back to the amplifier to tell the amplifier how fast the motor is spinning. once the motor starts turning, the encoder starts feeding back how far it has moved the axis to the computer. Once it reaches the desired location, the computer drops the dc voltage going to the amplifier back to zero. There is a lot more going on but that should give you a basic idea of how the system works.

    In most current hobby type systems including Mach 3, Centroid Acorn, UCCNC, etc., the servo amplifer is replaced by a drive controller that not only includes the amplifier to drive the motor, but also takes the feedback for the position and speed. It simply uses digital signals from the computer that tell it which direction to move and how many "steps" (encoder counts essentially) to move. It determines the speed to move the drive by the speed of the steps from the computer and reads the speed of the motor from the encoder pulses, The computer simply tells the servo drive how far to move and how fast to move along with the direction to move and the servo drive takes care of the rest. If something keeps it from doing what it is being told to do it simply give an error flag telling the computer that there is a problem with the drive. In both systems, the encoder resolution determines the resolution of the system.

  9. #9
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    Re: Converting a CNC boring machine to full 3-axis

    Thanks SEK22Hornet for the thoughtful explanation. Yes, it does do a homing procedure at startup. I'm not seeing affordable controllers that have the same outputs that these drives seem to need, so I'm slowly coming to the conclusion that I'll need to replace the drives and motors. The question now is what is the most effective and economical way to do that.

    The Centroid Acorn seems like a good value, and paired with the Teknic ClearPath motors seems relatively simple. I wrote an email to Teknic and got a very thorough response from someone who carefully considered my questions...this kind of service impresses me more these days than any other feature of a product.

    As far as sizing the motors, the existing servos have a stall torque of 1.6 Nm = 226 oz-in. It has been mentioned that the original configuration of the machine has very little cutting forces on the X/Y, so the motors are essentially sized only to move the mass of the gantry and/or car. I have no idea how to calculate what those cutting forces might be (e.g. a 3/8" compression cutter moving through 3/4" plywood), but I'm not opposed to grossly oversizing the motors to be sure they will work.

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    Re: Converting a CNC boring machine to full 3-axis

    I ordered the Centroid Acorn. Seemed like a good value as it includes the power supply and software, and it appears to be a robust design.

    Next, I need to source the motors. I'm looking at the Teknic CPM-SDSK-2341S-RLS, narrowed it down to this one based on a frame size similar to the existing servos (NEMA 23 bolt pattern is slightly different by ~1mm??), peak torque 828 oz-in, 1860 RPM.

    The OE servos are rated by "stall torque", I would assume this is the same as "peak torque"? If so these Teknic motors have over 3X the torque. Without an engineering degree I'll just have to hope that is adequate.

  11. #11
    Community Moderator ger21's Avatar
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    Re: Converting a CNC boring machine to full 3-axis

    Is the shaft size the same?
    Gerry

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  12. #12
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    Re: Converting a CNC boring machine to full 3-axis

    Existing motor shaft is 14mm diameter. These drive a timing belt, which drives a ball screw.

    I think there is room to move up to a NEMA 34 frame size, would just require a bit more fabrication work. Is there any wisdom in doing that?

  13. #13
    Community Moderator ger21's Avatar
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    Re: Converting a CNC boring machine to full 3-axis

    AC servos should bolt right into that. Check the size of the 400W DMM servos.

    More powerful than the Clearpaths, and the same or less money.
    Gerry

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  14. #14
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    Re: Converting a CNC boring machine to full 3-axis

    Quote Originally Posted by ger21 View Post
    AC servos should bolt right into that. Check the size of the 400W DMM servos.

    More powerful than the Clearpaths, and the same or less money.
    I couldn't see one from DMM with the same BCD of 65mm and shaft dia. of 14mm.

    I really like the Clearpaths because of their auto-tuning feature, takes all the guesswork out of the setup for a n00b like me. As this is a hobby project I'm always open to suggestions to save money. It's tempting to just dumb it down to a stepper system and save some bucks, but if it takes me an extra 6 months to work out the bugs, it's not worth it.

  15. #15
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    Re: Converting a CNC boring machine to full 3-axis

    I couldn't see one from DMM with the same BCD of 65mm and shaft dia. of 14mm.
    Are you sure it's 65mm and not 70mm? Is there a 50mm boss on the motors?
    Gerry

    UCCNC 2017 Screenset
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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  16. #16
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    Re: Converting a CNC boring machine to full 3-axis

    Quote Originally Posted by SEK22Hornet View Post
    You have two axis running with servos - do you know what voltage and current rating the servo motors are? I'd take a look at something like the machdrives step and direction drivers like the BRB or BRC (depending on the voltage). You may have to replace the feedback on the motors with a new encoder, but these motors are already sized. Only problem is that they may be undersized since the machine was not designed for an lateral cutting forces. The step and direction drivers would make the servos look pretty much like steppers to whatever software you choose and you should be able to add a stepper to the Z axis. Just one possible way to go. - Dan
    This idea is worth revisiting, I think. Would save me a good chunk of cash if it works. And, the motors already fit. The motors seem to be 0-30V DC 10A, would the BRB 20-80V be appropriate?

    Yeah ger21, this machine has some odd and/or antiquated parts.

  17. #17
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    Re: Converting a CNC boring machine to full 3-axis

    A lot of servos use metric sizes which I'm not sure are the same from manufacturer to manufacturer. I've got some 400W 60mm deltas that are very close to a NEMA 23, but not quite. They also have a 14mm shaft and 3000 RPM rated speed, so depending upon where you want to put your effort (or cash,) you might want to look into finding some more traditional AC servos.

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    Re: Converting a CNC boring machine to full 3-axis

    I've decided on the Machdrives running my OE DC Servos. Suppose it will be a little while before they arrive from Australia. Hope they turn motors in the right direction..

    The Acorn should be here any day now, so I'll spend some time mounting the control PC in the console cabinet. Then once I receive the Machdrives and get the X and Y axes moving I will tackle the Z-axis question. That's going to be the biggest challenge as I'll need to machine some parts to mount the spindle, servo motor, and ball screw. Time to butter up my machinist friend, I already owe him way too many favors...

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    Re: Converting a CNC boring machine to full 3-axis

    The Centroid Acorn and Machdrives arrived. Setting up the Centroid control software on the PC was straightforward, I like the clear industrial look of the interface. I'm not running a touch screen but it would be sweet with this software. Got it talking to the Acorn board through Ethernet no problem.

    Next step is to install the drives in the cabinet. The Axor drives were installed in a card rack which included the DC rectifiers and filter caps, I'll have to modify that PS card to pull the DC for the Machdrives. The cabinet has a BIG 3-phase transformer that supplies 38VAC to the drive rack.

    Photos to come.

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    Re: Converting a CNC boring machine to full 3-axis

    I'm really interested in seeing how the combination of the Acorn and Machdrives - I have considered that exact combination to replace the old Linux version of Centroid on my Ajax mill. The operating screen looks like it is very similar to the old Linux software screen.

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