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  1. #1
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    Nov 2013
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    3

    DM4500M Conversion

    I am hoping there are still some people on here who have successfully completed a conversion from the Meldas3 controls to a modern PC interface. I read the whole thread on the 4400 which has some good info in it but I am hoping to find some more specific info pertinent to my machine and more up to date than 2008 when that thread was active...

    -josh

  2. #2
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    Join Date
    Nov 2012
    Posts
    276

    Re: DM4500M Conversion

    I know you've been in contact with Duke. I would say that you should follow his efforts closely as he is trying to do the same thing as you. More importantly, he is obviously quite creative and ambitious with his project, so it could be very interesting and inspiring for you. The downside is that the project also involves reworking the spindle, and that is just an added complication that could slow down, stall, or sideline the project too. That is always the risk with retrofits (I can personally attest to that!). It is hard when you have a life/wife/family outside of the shop!

    Fundamentally, there is nothing special about the AC servos on an M3 Meldas control. The encoders are also pretty stock except that they have extra tracks to help with the synchronization of the windings. But you don't need to do anything with those tracks, so you can just ignore them if you are using a drive that can take the typical phase quadrature or can use vector feedback to perform the same synchronization function...

    But I think your question is a little broader than that.... I am guessing that you are asking if there is anyone that has cracked the bus structure of the Meldas amplifiers (MR-S11, and MR-S12 for the 4400m). The answer to that is "no, not yet, but there are a few of us that are interested in doing so." it shouldn't be that horrible to do. How beneficial is another matter and, frankly, there are other more pressing questions that some of us have. I think there are two here that are especially interested in the M3 control (myself being one) and extending its capabilities. But, to be honest, I'm not sure I want to *replace* mine, which is where I think you are going. Why am I not? Well, because I'm not convinced that it is a lost cause. I mean, let's face it, the thing is pretty capable. I've already gotten mine so that it can handle a 4th axis, which is something that was important to me. And I've got a Renishaw tool setter working now, and ditto for a Renishaw probe. The only real limitation right now is that I don't have the memory. Well, that isn't quite true.... I've managed to double the memory and I'm working on getting full memory. And, in cooperation, we are trying to see if we can come up with a much more economical way to get full memory on all of these using more modern components.

    Memory, in my mind, is probably the single biggest issue. The reason for this is primarily macro space. The machine will work fine with DNC, but if you want to use a Renishaw setter, it will take up about 28,000 lines of space (everything is lines based, not KB of RAM). We only have 64,000 to start with, so that is a problem. And the Renishaw touch probe is even worse. It takes about 100,000 lines of space, as I recall, for the full suite. I don't have the exact numbers because the more important point, that you don't have enough space even with the 128,000 lines I have now, is a known fact. So, memory expansion is more important to us right now than figuring out the protocol for the amplifiers.

    The biggest issue with the amplifiers is that they are expensive. But, at this point that isn't something that bothers me (personally) all that much. I've managed to fix a few now so I feel better about that. The amps are gigantic, however, and a modern one would do the same thing in literally about 1/20 the space. Yeah, that would be nice, but they are also not repairable. And, the reality is that the amps are stuck in a cabinet... Do I really care that they are big and old? No.... Just change the electrolytic caps and the amps will probably work for another 30 years.

    If there is one area of the control that worries me the most, it is probably the spindle drive. I've not dug into that at all, but it is also basically a servo amplifier on steroids. I'm *guessing* that it isn't too difficult to deal with, assuming you give it time.

    To me, the biggest frustration I have right now is probably (well, beyond finally cracking the memory thing so I can get 1GB) the tool changer. I have a mixture of BT and CAT. You can use either by adjusting the Z height for the change, but you cannot use both at the same time. I'd love to have a carousel that could be configured with a *mechanical* offset so that you could use both at the same time. But there isn't a whole lot of room in there to do this. And, of course, it is a lower priority.... I haven't even *used* my machine for hobby stuff because I'm too busy mucking with it from a control perspective.

    I should also point out that part of my reason for sticking with the control for now is that I've managed to pick up some spare parts. I've had to fix these, but that is OK. It was not only part of the deal but it was also practice and gave me the confidence that I can fix them again in the future. Sure, nothing is guaranteed, but I think the Meldas control actually has some nice features and is probably more nicely integrated than a lot of the home brew stuff we might do. As such, I'm not too eager to replace it just now.... Instead, I'll just hang a DNC off the side of it (make your own, use a PC, or buy one) and I think it will be fine.

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