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  1. #1
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    Oct 2006
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    Retrofit for CNCMaster Junior Mill

    I picked up a CNCMaster "CNC Junior" machine from a school auction. Mechanically it is in great shape, I was told it was fired up once a year to show students an example of CNC. It is complete, other than the (proprietary) software to use with their controller. From what I have read their controller/software was the weak link in their system so I am wanting to build a new controller. I have zero cnc experience, am learning as I go.

    Some machine details: The mill is a converted Rong Fu RF-31 (actual, not a clone). It has a 2hp 3 phase motor with a VFD for spindle speed control. It has 3 axis control, with unexpectedly large stepper motors in my limited experience. One of the things I quickly realized is none of the parts have any markings, I assume so that you had to get replacements from them. I did contact them to find out if the software was available, but it was around $4k. I fugured (from the reviews) that I could do better on my own.

    The original controller uses (unmarked) Gecko G201 drives, and I found the current limiting resistor to be 220k (roughly 5.75 amps max). Back-calculating the power supply performance from the transformer shows that it is designed to run at 70v, but has a maximum of 6 amps. It would seem this would work, but it would be limited if you were trying to move more than one axis at a time. So I am concluding that the steppers are at least rated to 70V@5.75amps.


    I have built a stand and have picked up a few parts I thought relevant when I came across good deals. Specifically I have a set of G203V drives, and an Antek PS-8N70C power supply (rated at 70V-11a)



    I am looking for advice on breakout boards/motion controllers and software to use for this mill. What is the first decision given what I have? Do I pick the software and then a BOB? I would prefer to stick with Windows operating systems, as I have quite a few computers with that available.


    Thank you for your consideration.

    -Ted

  2. #2

    Re: Retrofit for CNCMaster Junior Mill

    You've got a good start on understanding what you have.

    If you want to stick with windows that puts you in Mach3/4, UCCNC, Acorn territory.

    There are various merits to each system, but once you decide that will tell you what motion controller you will use. UCCNC for example has a few options, as does Mach3/4 with items like the ESS, Acorn is based on their system, I don't believe there are any options (could be wrong).

    From there, you can look at BOBs.

  3. #3
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    Re: Retrofit for CNCMaster Junior Mill

    Quote Originally Posted by JerryGarcia View Post
    You've got a good start on understanding what you have.

    If you want to stick with windows that puts you in Mach3/4, UCCNC, Acorn territory.

    There are various merits to each system, but once you decide that will tell you what motion controller you will use. UCCNC for example has a few options, as does Mach3/4 with items like the ESS, Acorn is based on their system, I don't believe there are any options (could be wrong).

    From there, you can look at BOBs.


    Outstanding, thanks for your reply... From what I have gathered:

    Ethernet > USB or Parallel
    Mach3 no longer being updated
    Mach4 has some kinks to work out
    Acorn might be the most stable software


    Regarding software, do I need both CAD and CAM software, or does the UCCNC/Mach/Acorn act as the CAM? If not, what are recommendations for CAD and CAM for hobby work?

  4. #4
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    Re: Retrofit for CNCMaster Junior Mill

    I'll throw this into the ring; even though I don't expect you to pick it (my reasons for going with it are... atypical... to say the least).

    Grbl running on an Arduino Mega can drive this kind of machine as well; and it's a fraction of the cost of the other solutions (the software is free; and the complete electronics setup - not including stepper drivers, VFD, or power supply - can be had for under $20). However; it's not as feature-packed as the other options; either. But on the other (third?) hand, many of those features are things that you wouldn't be using on this kind of machine anyway (like lathe threading... well, it's not a lathe).

    Most people using it feed it with a program called Universal G-code Sender (or just UGS for short); which is a Java-based front end for motion controllers like Grbl (also free). Using it like this does impose something of a latency penalty due to the communication delay between the Arduino and the PC; this becomes most apparent when jogging the machine. Mach 3 had an input for a jogging handwheel; I presume that Mach 4 has one; UCCNC appears to have a version of their own that connects via a wireless USB dongle. As far as I know, UGS jogging is keyboard based.

    If you did decide to give Grbl a try, the version I suggest starting with is the Mega version: https://github.com/gnea/grbl-Mega
    The version that runs on an Arduino Uno has literally used up all the flash storage; the last update required shortening the text of the error messages to make it fit. Arduino Mega's have 256K of flash; Uno's only have 32K...

    Mach 3 is getting pretty old; and without an external motion controller (like a SmoothStepper) is rather finicky about the PC it will run on (the issue is that because it's generating the step pulse stream in software, anything that takes over the machine, even for a few milliseconds - remote management firmware in the BIOS is notorious for this, as is battery management firmware on laptops - will cause your motors to "hiccup"). There is no new development to speak of going on with Mach 3; all new development effort is being focused on Mach 4.

    Mach 4 more-or-less requires an external motion control engine; such as a SmoothStepper; and consequentially is relatively immune to the timing issues that plagued parallel-port based Mach 3 setups. Although there is a parallel-port plug-in for Mach 4, it's really not recommended.

    If you get an Ethernet based motion control engine; I would suggest either connecting it with it's own network interface on the PC; or at least have an Ethernet switch dedicated to the CNC setup. It would be unfortunate to scrap a part because someone else in the house started to stream Netflix or Youtube...

    Something I would double-check (if you haven't already) is to make sure that the VFD on the spindle is a regular one; and not customized for CNCMaster. I'd also double check that it is, in fact, equipped with pre-loaded ballscrews - their website says current ones are; but this is an older machine... I suppose they could have kept the acme screws that it came with and used software backlash compensation. If you have acme screws; you will need to either make sure that the control software has backlash compensation (Grbl doesn't, for example); or plan on doing a retrofit of ballscrews to the machine.

    You will need CAD software, CAM software, and a machine controller. Most CAM programs are built on a foundation of CAD software; but the inverse is not true; many CAD programs will not generate tool-paths for your CNC. The machine controller is something else entirely; and (with the odd exception) will not function as CAM software.

    I use Fusion360 from Autodesk for my CAD/CAM solution... not because it's the best, but because it's free to hobby & startup level users (last I checked you don't have to pay unless you are making over $100K/year with it; but double check the license yourself to be sure).

    Otherwise; this seems to be a fairly straightforwards project.


    In case you're curious why I'm going with Grbl, but I'm not necessarily suggesting it for you... it's because I'm a programmer who also dabbles in hardware (prototypes of my own breakout-boards for Grbl should be arriving in a few days); and having the entire source code for the system available is tremendously appealing to me.

    I've got my own version of Grbl under development... if you are curious, it's here: https://github.com/bdurbrow/grbl-Mega/
    It is, however, a work in progress...


  5. #5

    Re: Retrofit for CNCMaster Junior Mill

    Britt's suggestion is a good one, definitely consider it. I think there's an offshoot the Grbl that has backlash comp, but I can't remember the name.

    Fusion360 is the go to software these days. It has CAD and CAM.

    I think ethernet has become the standard Windows setup.

    I'm currently using UC300eth-5lpt with Mach3 and UCCNC. UCCNC is really good, unfortunately i'm very embedded in Mach3 for various reasons, so I use it most of the time.

    Acorn might be the best plug and play option, the price isn't bad.

    I run Windows 10, my PC is on wifi, and I lots of stuff on it beyond just run my mill. That includes CAD/CAM. The ethernet connection is dedicated the UC300eth.

  6. #6
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    Re: Retrofit for CNCMaster Junior Mill

    I have decided to go with the Acorn, I ordered their board and the pendant. I'll need to go with either the PRO software upgrade ($140) or the digitizing bundle ($400) to use the pendant. I am intrigued by digitizing and probing, but have some time to make that decision while I build the controller.

    Generally I have found that CNCMASTERS didn't skimp on hardware, but their controller design is suspect. It does have ballscrews, and the vfd is by Leeson. The controller used G201 drives, and the stepper motors are quite large for this application.

    Common internet wisdom (oxymoron?) seems to be to retrofit a new controller onto this mill and don't look back.

    Quote Originally Posted by Dan Mauch View Post
    One of my customers had a cnc master control unit. He was unhappy with the software and the control unit. He bought one of my control units and is very happy. He decided to give me his CNC masters control unit. I was surprsied to see that it used the G201 in unmarked cans. I was also disappointed to see a few techincal issues that could lead to the problems listed by the orignator of this thread.
    1. The internal filer cap is way to small it was only 1000 UF
    2. The drives use a common buss for power + and power Ground.
    3. The ribbon cable from the power supply to the main board was way to thin a gauge since the drives were set up for 5A per phase.
    4. The transformer did not have enough current to supply three motors running simultaneously.

    While not a problem it does use the serial port through an interface that then sends step and direction signals to the drivers.

    I think the soultion would be to remove the 3/4 drivers form the motherboard and to wire each drive seperately using the star configuration for the power. I would also recommend wiring the step and direction to a parallel port and use Mach3.
    Just my opinion

    Dan Mauch

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