Knee mill conversion/ controller advice please


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Thread: Knee mill conversion/ controller advice please

  1. #1
    Member NorthernMachinist's Avatar
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    Default Knee mill conversion/ controller advice please

    Brand new here, Im a journeyman machinist, work with industrial cnc equipment and have done one cnc build on a purpose specific machine using Mach3.

    I’ve bought a new knee mill (microcut pbm-4evs) with the intent of converting it to cnc control.

    I’m sure this had been done a million times but I’ve come up empty trying to lurk... links are welcome!

    Ok so this machine is a manual knee mill, box ways, 50” table, 5ph 3ph motor and nmtb40 spindle.

    I’ll be getting ground ball screws (X,Y) and plan on ~1kw dmm servo motors (X,Y,Z with Z running the lead screw on the table) I also intend to make a 4th rotary axis using a 1.6kw dmm servo and brake.
    I am familiar with mach3 with ess. I’m comfortable using cad/cam and gcode editing so I’m not overly hungry for conversation programming. This is however, a “substantial” , non-hobby, build and I dont want to short change myself where the controller is concerned. I’ve read a fair bit about centroid as well but am looking for suggestions

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    Community Moderator Jim Dawson's Avatar
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    Default Re: Knee mill conversion/ controller advice please

    Looks like a nice mill.

    DMM servos are an excellent choice, I have installed a few of them and have been happy so far. I have 4 of the 1.8KW units on my CNC lathe, been working great for the last 2 years.

    Controllers: I could write a book on this subject. But you are used to Mach3, so sticking with that would not be a horrible idea,not that I'm a fan of Mach3. The one thing I would add is a Galil motion controller, Mach3, and 4 both have a plugin for this. The reason is that it turns Mach3 into a closed loop servo system, well sort of. At least the motors are being controlled and monitored by the Galil controller and the loop is closed there, rather that just being the open loop step & direction Mach3 system. Gives you full control over the motor tuning. Galil DMC-4040 4 axis controllers are available on eBay in the US$500 - 600 range. These are real industrial motion controllers, and very easy to program using any text editor for customization if desired. (Not required when using Mach3).

    Centroid is a reasonable option, as is Dynomotion Kflop/Kanalog for a closed loop system.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Knee mill conversion/ controller advice please

    Quote Originally Posted by Jim Dawson View Post
    Looks like a nice mill.

    DMM servos are an excellent choice, I have installed a few of them and have been happy so far. I have 4 of the 1.8KW units on my CNC lathe, been working great for the last 2 years.

    Controllers: I could write a book on this subject. But you are used to Mach3, so sticking with that would not be a horrible idea,not that I'm a fan of Mach3. The one thing I would add is a Galil motion controller, Mach3, and 4 both have a plugin for this. The reason is that it turns Mach3 into a closed loop servo system, well sort of. At least the motors are being controlled and monitored by the Galil controller and the loop is closed there, rather that just being the open loop step & direction Mach3 system. Gives you full control over the motor tuning. Galil DMC-4040 4 axis controllers are available on eBay in the US$500 - 600 range. These are real industrial motion controllers, and very easy to program using any text editor for customization if desired. (Not required when using Mach3).

    Centroid is a reasonable option, as is Dynomotion Kflop/Kanalog for a closed loop system.
    Mach3 does not work with Galil I have posted this before

    Mactec54


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    Community Moderator Jim Dawson's Avatar
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    Default Re: Knee mill conversion/ controller advice please

    Quote Originally Posted by mactec54 View Post
    Mach3 does not work with Galil I have posted this before
    Mach3 does not work well with Galil. I have done 2 Mach3/Galil setups. In both cases I removed Mach3 and used my own software in the end, but it does work with the plugin. Would not be my first choice, but is not a bad starting point for one already familiar with Mach3.

    Last edited by Jim Dawson; Yesterday at 03:50 PM.
    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Knee mill conversion/ controller advice please

    Quote Originally Posted by Jim Dawson View Post
    Mach3 does not work well with Mach3. I have done 2 Mach3/Galil setups. In both cases I removed Mach3 and used my own software in the end, but it does work with the plugin. Would not be my first choice, but is not a bad starting point for one already familiar with Mach3.
    Not using a Galil it would be a bad starting point, I know the person who did the Galil plugin's for Mach3 and Mach4

    Mactec54


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    Default Re: Knee mill conversion/ controller advice please

    ...more options

    Mesa Electronics

    spaceship

    http://linuxcnc.org/



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    Default Re: Knee mill conversion/ controller advice please

    Quote Originally Posted by machinehop5 View Post
    ...more options

    Mesa Electronics

    spaceship

    http://linuxcnc.org/
    Yes this would be a better choice than any Galil for a first time conversion

    Mactec54


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    Member NorthernMachinist's Avatar
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    Default

    Thanks for the responses!
    Ok just to help me get my head wrapped around this (and I realize this is a hotly debated topic)...
    On my previous build using Mach 3 , Mach 3 isn’t “closed loop” in its self but my system is. (the ac servos+drives provide a closed loop system)
    Mach 3 directs the drives (via ess) of their next move. If Mach goes down(if I disconnect the Ethernet cable mid program, the drive faults and everything stops. If I grab the ball screw and try to turn it, the servo/drive fight to maintain position. However, mach3 isn’t aware of any movement from manually turning the ball screw... to back feed positional info to the computer would allow me to manually use hand wheels and see where I’m at. (Assuming servo motors were Set to “unlocked” to permit this).
    I don’t know that I’ll really WANT to use handwheels, but it’s a thought... am I right in saying that acorn would have that same issue as it’s a “step and direction”? Oak seems a large cost jump, is it worth it for a machine like this?

    Will acorn allow me to run full 4axis or just 3+1?

    I’ll take a closer look at Linux.



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    Community Moderator Jim Dawson's Avatar
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    Default Re: Knee mill conversion/ controller advice please

    I would be lost if I were not able to operate my knee mill manually. It will operate as full manual or 2, 3, or 4 axis CNC, all done with a flip of a switch and a lever to engage/disengage the Z (quill) axis. Encoder feedback to my Galil controller is via 1 micron magnetic linear scales, this is the only encoders used on my machine, I do not use the motor encoders. The loop is closed at the controller as opposed to the drive. The screen displays position data in both CNC and manual mode. Control of the DC servo drives is via a +/- 10V analog signal, with the drives operating in velocity mode. If I were using DMM motors and drives, I would be using torque mode as I do on my lathe.

    Acorn would suffer from the same limitations as Mach3 as far as encoder feedback, it has no provision for encoder feedback. However, I do know that Mach3 when paired with a Galil controller will display the actual position with the data taken from the controller. This works as long as you have an encoder input to the controller. Dynomotion and Mesa may have this available also.

    As I said above, I am not a fan of Mach3, but it will work with Galil, Mesa, and Dynomotion controllers.

    Camsoft is another option, works with Galil controllers, and another brand that I forget the name of.

    Dynomotion also has their own software.

    I don't know if Acorn is 3+1 or full 4 axis.

    Mach3 is full 4 axis. I believe Dynomotion is also.

    I agree, Oak seems a bit expensive.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Knee mill conversion/ controller advice please

    Quote Originally Posted by NorthernMachinist View Post
    Thanks for the responses!
    Ok just to help me get my head wrapped around this (and I realize this is a hotly debated topic)...
    On my previous build using Mach 3 , Mach 3 isn’t “closed loop” in its self but my system is. (the ac servos+drives provide a closed loop system)
    Mach 3 directs the drives (via ess) of their next move. If Mach goes down(if I disconnect the Ethernet cable mid program, the drive faults and everything stops. If I grab the ball screw and try to turn it, the servo/drive fight to maintain position. However, mach3 isn’t aware of any movement from manually turning the ball screw... to back feed positional info to the computer would allow me to manually use hand wheels and see where I’m at. (Assuming servo motors were Set to “unlocked” to permit this).
    I don’t know that I’ll really WANT to use handwheels, but it’s a thought... am I right in saying that acorn would have that same issue as it’s a “step and direction”? Oak seems a large cost jump, is it worth it for a machine like this?

    Will acorn allow me to run full 4axis or just 3+1?

    I’ll take a closer look at Linux.
    Acorn is 4 Axis control plus spindle control and encoder for spindle rigid tapping or threading

    With a servo motor not powered ( unlocked ) you can use your hand wheels, by doing this you won't get a readout unless you have scales or have power to the encoders

    Mactec54


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Knee mill conversion/ controller advice please

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Knee mill conversion/ controller advice please