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Thread: MultiCAM MG101 Gutted & Reborn

  1. #1
    Member highvoltagefeathers's Avatar
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    Default MultiCAM MG101 Gutted & Reborn

    Hi everyone!

    I'm an electrical engineer by training, mechanical engineer by trade, our company's additive manufacturing subject matter expert by default, and a machinist by the absolute seat of my pants.

    My base of experience in machinist work extends to manual mill & lathe work, tig welding, and CNC programming and machining using DIY routers, a bridgeport torq-cut 22, and a Tormach 770.

    With a big-boy job and some reliable income, I wanted to land myself a large, capable machine able to perform (to some degree) a combination of the work I've been doing on both routers and VMCs for my projects at home, and in pursuit of a business involving carbon composite tool production.

    I was looking, rather unsatisfied, through 6040 router builds and applying for financing options to get my hands on a proper garage VMC (ideally a Syil X7, backup being tormach 1100 MX), when this 20-year-old Multicam MG101 caught my eye on craigslist for $3600:

    IMG_20190810_222652

    I've clearly already started pulling parts off and cleaning this up. My thought is that with modern controls, servos, and motion hardware upgrades, this could be a serious machine for all my needs right up to (and in a very limited capacity including) mild steel.

    I bought it from a sign shop who had used it for 20 years and (bless this guy) "greased it every 2 weeks". Certainly can't say you didn't. Never bothered to wipe any off either:

    IMG_20190810_222906

    They were using a high quality Mobil moly grease, and they really did seem to keep up with it. The machine was very tight when I went to take a look, no measurable slop other than a few tenths of deflection in X and Y, the Z is another story. 20 years of travel over the same 2" on this poor, poor leadscrew:

    IMG_20190810_222831

    All their work was entirely 2D, so they didn't care or even notice. Obviously since I'm doing surfacing work, this needs to be replaced with a ballscrew.

    The X-axis runs on a 1" OD X 64" multi-start leadscrew, and the thing is still tight. Moves freely with no measurable lash. That said, the pitch is very high and is going to leave a lot desired in terms of positioning accuracy. I'm looking to replace this with a rolled ballscrew:

    IMG_20190810_222807

    I was delighted to hear (and see paper evidence) that the spindle had been rebuilt in the last year. Feels great, no runout, noise, or visible damage to speak of:

    IMG_20190810_222841


    In total, my wishlist is as follows (for now):

    - Centroid Acorn CNC Controller
    - 4X DMM DYN4 & 86M-DHT-A6MK1 servo kits
    - Z-axis ballscrew retrofit
    - X-axis ballscrew retrofit

    Future work including:

    - 2.2kW ATC spindle & tool rack
    - Y-axis ballscrew conversion (if the rack & pinion is as terrible as I'm reading)


    I'm super excited to get to work on this thing, and am about to pull the trigger on a lot of the controls. I chose the DMM DYN4 & 86M-DHT-A6MK1 as (as far as I can tell) a more powerful and more economical alternative to the similar Teknic offerings NEMA-34 frame. Let me know if I've misread the existing options.

    Additionally I'm definitely going with chinese rolled ballscrews to make this a practical DIY build. Does the community have a preferred brand/supplier for motion hardware like this? I know there's a lot of garbage out there...

    Cheers,

    - Feathers

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  2. #2
    Community Moderator ger21's Avatar
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    Default Re: MultiCAM MG101 Gutted & Reborn

    Looks like a great deal you got there.

    Gerry

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    JointCAM - CNC Dovetails & Box Joints
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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  3. #3
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    Default Re: MultiCAM MG101 Gutted & Reborn

    Great buy!

    I wouldn't rush into replacing the X leadscrew. What is the pitch/lead?

    A high count servo encoder should provide plenty of resolution.

    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)


  4. #4
    Member Jim Dawson's Avatar
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    Default Re: MultiCAM MG101 Gutted & Reborn

    Looks like you did well and your choice of hardware is very good. I have DMM servos on my lathe and they work very well. I don't think you need to worry about the high lead screws, my old router had 25mm and 40mm lead respectively on the X and Y and I was easily able to position to 0.0005 inch with steppers, and with the DMM servos you won't have a problem hitting 0.0001 inch consistently. The servos will have much better resolution than your leadscrew error. (all ball and lead screws have some linear error).

    For the Z ball screw, go to EBay and find a NOS Thomson or THK ground ball screw w/nut that is the right length.

    Jim Dawson
    Sandy, Oregon, USA


  5. #5
    Member highvoltagefeathers's Avatar
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    Default Re: MultiCAM MG101 Gutted & Reborn

    Thanks for the advice!

    The X screw is a 1" diameter, 10-start and whopping 1" pitch. It's super tight so if you guys say you can run sub 0.001" on 25+mm pitch then I believe you! I'll give it a shot. I'll look for a larger timing pulley & belt to give the servo an advantage in this regard. Probably a 50-tooth instead of 30, giving 0.001" per 0.9° servo input.

    I found this NSK W1603FA-1P-C3Z+472L ballscrew on Ebay for the Z axis:

    z ballscrew

    Ballscrew closeup

    ballscrew fixed support

    Seller says these are well used and "can feel slightly backlash". I'm gonna take my chances and enjoy the C3 pitch accuracy in any case if lash is anything better than horrible. The 16mm screw and AK12 fixed support are larger than the 12mm screw and BK8 support this came with. I'll probably have to do some machining to get everything fitting back together properly, including machining the free end of the screw to length (it's a little long for my application), but I'm confident it won't be too difficult. I've got carbide to spare if things are hardened well (as they should be).

    The DMM servos are equipped with 16 bit encoders, so they will certainly not be the sloppy end of things :P

    Thanks for the tips!

    Cheers,

    - Feathers

    EDIT/P.S.: I'm reading through the Centroid manual on master/slave homing and squaring for the Y-axis. This seems like a very handy feature, but this machine is extremely rigid. With one side locked, I can put nearly all my weight into the other end of the gantry and it deflects ~0.005", returning right back to zero. It seems like I may be able to get this machine very square mechanically, and it's on servo control so I'm not anticipating any substantial discrepancies between executed positioning across either side of the gantry (deviation from electronically geared servo positioning that would cause the axis to lose square).

    Is there a good reason I'm not thinking of to retain auto squaring? I'd love to keep the extra axis open on the AcornCNC board if possible, and mechanical squaring would simplify my wiring. Open to any considerations.

    Last edited by highvoltagefeathers; Today at 02:18 AM.


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