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  1. #1
    This is a continuation of this thread. My idea was to build and enclosure for my Chinese 3020 cnc machine, I purchased from Ebay. The top part of the enclosure will house all of the electronics and PC and simply sit over the actual cnc machine. The framework will be made from aluminium profile with perspex side panels and aluminium panels for the top box and back. I have an old 17" touch screen LCD monitor laying about, which will sit on top of the enclosure. For the time being I am going to reuse most of the control electronics, but I have built an opto-isolated addon board, to allow me to connect limit/home switches and a probe, as well as control the spindle from within Mach3. I also plan to have a custom HID controller to allow me to have basic control from the front panel. Lastly I will add some form of led lighting to light up the working area.

    The Frame

    I won’t go into too much detail about building the frame as it’s pretty easy, I'll just give a quick overview.

    First off I made a sketchup model which helped me visualize things and calculate sizes.

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    After pricing everything up I decided to go with the cheapest 4 slot 30mm aluminium profile, as this was my first time of working with aluminium profile, I wasn't sure how easy it would be. To start with I drilled the 8mm clearance holes for the torx tool, this was bigger than the recommend size but it would give me a little extra room to move things to square them up if needed.

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    Although I bought the self-tapping screws, I ended up tapping them anyway and once everything was drilled and tapped, it was simply a case of bolting it all together. That's when I realized my first mistake. In my haste, I had already ordered the Perspex based off the size from the sketchup model. While this was, in a way correct, I had forgotten to allow for the 3.7mm thick end caps, which meant I was 6.4mm out in the height of the panels. I was hoping I would get away with them, but when they arrived I tested them and they were no good. Having learnt from that mistake I checked, checked gain and then checked once more the sizes for the top panels. I managed to find a local company to cut them from 3mm thick aluminium. The cover and reduction profile said it was for panels 4mm to 6mm but in reality a 3mm panel is a nice tight fit, and apart from the cost, thicker aluminium obviously becomes heavier and harder to work with. It would probably have cause problems for things like the front panel switches and buttons too.

    Lastly I got some of the black plastic cover to fill in the slots, and some uniblocks to mount the top panels. Here's some pics of the enclosure assembled.

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    You may notice that I went for a single support for the bottom of the electronics enclosure, as apposed to the 2 in the sketchup model. The 3mm aluminium panel was stiffer than I though it would be and a single support is plenty. As you can see I have ended up with a nice size area, which is plenty big enough to house the electronics and PC, 440mm x 500mm x 100mm.
    Last edited by Pointy; 19-02-2014 at 09:27 AM. Reason: Typos

  2. #2
    Why not consider a removable door to stop chips flying about and also to reduce the noise ? will it need a small vent at the back to let heat escape by convection ? I don't know how hot the stepper motors and spindle get.
    Last edited by EddyCurrent; 18-02-2014 at 12:35 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  3. #3
    Quote Originally Posted by EddyCurrent View Post
    Why not consider a removable door to stop chips flying about and also to reduce the noise ? will it need a small vent at the back to let heat escape by convection ? I don't know how hot the stepper motors and spindle get.

    I did think about a door but decided against it for the time being, but it's something I can look at afterwards. I doubt whether cooling would be needed for the small jobs I do but it would be easy to add a fan or too.



  4. #4
    Electronics Layout

    The next task is to lay everything out in the top enclosure. I have already played about in sketchup and given it lots of thought, so I have a good idea of where to put things. I want to keep the mains as far away from everything else as possible, so this is what I came up with...

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    The 24V PSU, PC PSU and spindle PSU/controller are all located in the bottom left. The mains input will be top left, and the mains switches will be located on the front panel in the bottom left corner of the above picture. The plan is to have an IEC C14 chassis socket for the mains input. This will run down to the main on/off switch and then feed the PSUs and run back to a IEC C13 chassis socket, which I will use to power the monitor. I will also have a separate switch to turn the spindle PSU on and off as an added safety feature. This means a single rocker switch will switch the whole unit on and off, including the PC and monitor. With the locations decided it's time to start fixing things in place.

    I managed to find a PDF template for the motherboard, which is an Intel DG41AN in case you are interested, and then simply printed it off and taped it in place. I drilled some 3.175mm holes, which were perfect for screwing the standoffs in place. I used a 2.5" to 3.5" mounting plate to mount the 2.5" SSD drive using a couple of mb standoffs. I made more paper templates for the PSUs and simply drilled the holes and screwed them in place. Here's the finished layout...

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    The only thing missing is the addon board which you can see top middle in the first picture, I haven't decided where to put it yet, but it will probably go just below the motherboard or just to the left of the SSD.

    Next up I need to work out where to run the wiring, the mains (cyan) and 24V (red) lines in the picture below are pretty much settled. I am not sure which route to take the spindle (yellow) output though, is it better with the 24v lines or running down the left with the mains? I could keep all the mains wires on the bottom and the spindle wires to the top, this would give about 100mm of clearance between them. I think I am going to use the 2nd option, unless anyone has a better suggestion.

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    The last job for today is to make some new connectors to run from the stepper motor driver boards, to the chassis connectors. As the stepper motor drivers are mounted right at the back, I only need about 100mm long wires to connect them. I first had to identify the connectors used so I could order some more. A quick google, proved them to be Molex 2139, which were not too hard to get hold of. While making up the new connectors I couldn't help but notice that all 3 stepper motor connectors are wired differently, with relation to the pinouts on the driver boards an the pin numbers on the 4 pin chassis connectors. I will redo these later, to make more sense, but need to wait until I rewire the connections back to the stepper motors. I also love the way the Chinese just wire things in random colours to match the random order. You need to pay very careful attention to what goes where before you take it all apart, taking pictures and making notes where necessary.

  5. #5
    Good idea to keep the spindle wiring away from the rest, like you said put one cable at the top and the others at the bottom.
    It looks like a good space to house the 'guts'
    Last edited by EddyCurrent; 19-02-2014 at 09:35 AM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  6. #6
    I made some more progress today, I hacked out the back panel and ran the 24v wiring. I also redid the stepper driver connectors as I wasn't happy with them. Lastly I did some of the mains wiring but couldn't finish it because I don't have the right crimp tool for the piggy back spades. I'll try and post some pictures tomorrow.

    I decided to run a quick systems check to test out the new wiring and power supply. All 3 axes worked without a hitch, so far so good. Next I hooked up my IO board to test out the spindle relay. As soon as I turned on the power, the spindle buzzer and relay went off. Everything worked fine once Mach3 was up and running, but we can't have the spindle turning on during start up can we. I was planning to add the charge pump circuit anyway, but now it's a must. I just need to decide the best way to implement it.

    The easiest and most obvious way, is to simply have the charge pump turn on the 24v supply. It does have a remote control feature, which allows it to be turned on or off via 2 pins in the CN100 connector. Without its 24v supply, my IO board will switch off, de-energizing the relay which will turn off the spindle. The only niggle with this setup, is the 24v LED strips I have for lighting up the work area, wont come on until I fire up Mach3 and the charge pump.

    I suppose the best option is to get the charge pump to switch a relay, which will power the motors and IO board, this would still have the same level of safety control, but would allow me to use the LED lights all the time.

  7. #7
    While I was waiting for more parts to arrive, I decided to design the charge pump circuit. base upon the 2nd circuit here, I came up with this...

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    It's using the 12v & 5v from the PC PSU to power the circuit and relay (4 pin 9090-4R connector, top left). I have included a fuse holder and LED indicator (JP1,2). The main 24v supply comes in on the left and will only be fed to the outputs (bottom) when the relay is energized, this should only happen when the PC is on and running Mach3.

    There is a chance I might have the orientation of the 9090-4R connector wrong, so I need to double check this, once my part arrives, and before making the PCB. (This would swap the +12v & +5v lines)

    I have also ordered some new CY cable as I plan to rewire the entire machine now. I will possibly need some new cable chains, so if anyone knows a good supplier, please let me know.



  8. #8
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  9. #9

    Thanks for the links Ed.

    I must have had a real brain fart when I did the charge pump circuit above. Apart from getting the PC power connector the wrong way round, and a couple of other small errors, I made a major mistake with the relay. It's SPDT, so the above circuit makes a direct short across the 24v input, whoops! There's obviously a very good reason for bench testing circuits first, and fortunately I always have the current limiting control on my bench supply turned way down in the milliamp range, so no damage was done. Anyway after a quick couple of tweaks the circuit worked beautifully on the breadboard, I have only tested it connected straight to the BOB, so I just need to make sure it works, through the opto-isolators on the IO board

    Here is the second version of the PCB...

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  10. #10
    Hi Les,

    Nice to see it all coming together nicely for you :)

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