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  1. #1
    Hi All.

    I've had my Sieg X3 languishing for several years, bought with a fried motor control board and recently got started with it, lashed up a 3 phase motor with VFD just to get going but know full well I have to make a proper mounting for it to hold the motor properlystill and provide for tensioning of belt. Started along using https://manualzz.com/doc/23277943/vf...3-mill--part-1 as an example but am open to advice and changing this along the way as having read quite a bit of this forum am now slowing down and hoping for help and advice here before carrying out any more work or spending any more money. I have made pulleys using the example here, it cuts OK although with the motor mount the way it is there is too much vibration to take an real depth of cut

    Locally there is a WM18 for sale that seems to have been looked after, has been CNC converted but had all the motors and electronics removed for another project and left as a manual machine again. I am arranging to inspect the machine this week to try to ascertain exactly what has been done as the current owner is unable to answer my questions regarding whether or not the Z has been converted (I think this unlikely as I see the original Z hand wheel is still on there) and what type of ball screws etc are fitted to the X and Y (maybe Z). I'm looking at this mill as it may be easier for me to have a more stable machine available to work on the X3 conversion. Might it be worth my while to complete the WM18 conversion depending on its status and use the X3 as a nice drilling machine? Or are two CNC mills better than 1?

    Ultimately I want to be able to machine model steam engine parts and do these kind of conversion works. I am at an early stage in my engineering hobby, am computer literate but yet to take the plunge with CAD etc so am really really green and looking for lots of pointers. I have seen Jonathon's thread on here [URL="http://www.mycncuk.com/threads/7656-X3-mill-with-rails-ATC-new-motor/page4"] and am inspired to make something special out of my X3.

    In total I have a Naerok GH lathe, the Sieg X3, a very (very) small bench lathe, a recently purchased LIDL metal bandsaw and a Draper drilling machine at my disposal. I have been making myself tangential tool holders, sharpening jigs etc to give you all some idea of my current level.

    The idea of a CNC mill in the workshop is very appealing, I have studied John Stevenson's conversion in model engineer over the years along with many other conversions. I have made no purchases of conversion equipment bar the 3 phase motor and VFD. Budget is not totally open ended and I'm not in this to make money, this is my hobby and I'm in it for the journey really and to stretch myself.

    I am keen to make the most of what I have and to take this all one step at a time, I have many ideas swirling around in my head having seen the motion rails/bearings in Jonathon's build, wonder if motor speed control is possible with the VFD I have etc etc etc.

    Anyway, enough for now.

    Thanks for looking all!

    Stay safe...

  2. #2
    Hi All,

    I have settled on sticking with the X3 I already have and not to buy anything else. I plan to ditch the pulleys I made for the spindle drive and to use a couple of ratios of pre-made toothed pulleys with belts, I just need to make the plates for mounting and a tensioning system - whether that is spring loaded or moving slots is one decision I hope to make with some advice from the knowledgable people here. I will do this once I have the mill moving under cnc control. With the flexibility of the VFD/3 phase motor I don't envisage having to change the ratios too often so this could have a bearing on this decision.

    Having spent lots of time reading around here I'm conscious of the regular advice not to buy electronics etc. I will be looking to add a 4th axis in the future, so need to have the capacity for this in the electronics I buy so a 4 axis motion controller

    Having said the above, I have just bought some second hand but little used Nema 23 3.1nm steppers + 8mm couplers, originally purchased from cnc4you. They were too good a price to miss. I plan to use these for the X and Y axis motion. I'd like to use UCCNC as it is getting very good reviews and seems well supported with well matched controllers...

    Some questions I have are

    1. What controller card would suit - I have looked at the AXBB-E, the schematic shows it should do everything I need with the X3 now and in the future due to the capacity for the A axis drive
    2. What are the best stepper drivers bearing in mind...
    3. I perceive that Nema 34 is the correct size for the Z but could a higher torque NEMA 23 geared down do the job just as capably?
    4. Is there a suitable power supply option to buy off the shelf or am I better off making my own?
    5. Is anyone who has experience in converting the X3 up for helping out with specifying ball screws, mounts, bearings and maybe doing a bit of machining too? (JAZZCNC I'm wondering if you're interested as I see in Kered's BF28 build you have experience with Sieg...) I'm keen to get this machine cutting things for my hobbies...
    6. Finally for now - does anyone know what happened to John Stevenson's X3 conversion pdfs that used to be on the web? I can't find them any more and didn't save them locally - they were a great resource for me.

    Thanks all and stay safe,


  3. #3
    1. AXBB is fine. I use a UC300ETH on my SX2.7, but only one port (a second port controls, separately, a Starmill).
    2. Go Digital drive!, I've used 2DM860Hs but there's plenty out there. I'm sure someone will express a preference.
    3. I've used a 3.1nm '23 with a 2:1 belt on Z (same on X/Y). I've never encountered a problem with this configuration - noting the X3 is a bit bigger.
    4. Consider your driver options - if you can run AC then it's just a case of bolting a transformer into the control box, it's quite a sensible choice for KISS,.
    5. Not the X3, but the long-bed SX2.7. I just replaced each trapezoidal with a same-length 1605 cheap Chinese ballscrew, appropriating the same mounting holes for each axis (though offsetting and mirroring the motors with 2:1 belts into the space-frame of the machine). YMMV.
    6. Nope, but I gave up trying to find 3rd party designs (mainly because I don't talk Sketch-up and neither did F360 - in the end I realised I was wasting more time chasing these than actually just eyeballing the machine and designing the plates, mounts etc myself.

    Just my experience on a SX2.7L - not the X3, you'll have to take the above with a pinch of salt.

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  5. #4
    Thanks for the reply Doddy - lots of food for thought.

    Hope you don't mind if I follow up your replies with a couple of extra questions?

    4. Could you pass some details of this solution - I have been looking at AndyUK's router build and considering copying what has been done there mainly due to the exceptional schematic he's put up - albeit with some down-speccing in a couple of areas, I don't think I'll be needing anywhere near the amps he's using, although if I'm going to be going 4th axis then I might need it all or close to it, I'll have to finalise my sums.

    5. Did you use the existing bearings at the ends of the table for mounting your ball screws / did you upgrade the bearings to something like opposing taper bearings - the X2.7 might be better as it's a later machine but my X3 has quite horrible bearing races and was expecting to make new plates for mounting BK/BF12 mounts - still to do the CAD model for the XY table, been learning Fusion 360 with Lars... Having said that I could get the ball screw stepper end threaded by the supplier (Fred at BST perhaps) and thread the stepper shaft coupling to suit the end of the ball screw and adjust that way and use better bearings in the existing plates

    6. Coming to the conclusion that you are spot on about this, time to jump in

    Thanks again,


  6. #5
    4. Some drivers will take AC or DC supplies (nothing special - they just have a rectifier to take whatever and make sure its DC internally. Normally there's a smallish cap inside to smooth the rectified supply). With these - just get a suitably rated transformer and present the secondary winding to the driver. If you have only a DC driver, then you need to provide the rectification and smoothing cap yourself. It's slightly more complex, and adds 10-20 to the build, and more space is required, but it's still straightforward. AndyUK provides some excellent documentation of his builds here - by all means follow those, but feel free to ask any questions - particularly PSUs there's not a whole lot of complexity required here, and ask any 5 of us, and you'll get 6 different opinions :)

    5. On each axis I used a BK bearing block at the drive-end (integral AC bearings). On X I used the existing brass bush to support the end of the screw - simply, it was there and it fit perfectly well. On Y, I left the free-end floating (it's only something like 25cm in length, and there wasn't easy space under the bed to mount a block. Similarly on Z, left the end of that floating - plenty of space in this case but there didn't appear to be much need to support the end of the Z screw. Others may have different views on this.

    Click image for larger version. 

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    Example on Y.

    6. Yeah, jump in, what have you to lose?
    Last edited by Doddy; 05-02-2021 at 06:55 PM.

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  8. #6
    Mat's Avatar
    Lives in Near Southampton, United Kingdom. Last Activity: 12-03-2021 Has been a member for 1-2 years. Has a total post count of 4. Received thanks 2 times, giving thanks to others 0 times.

  9. #7
    Hi Mat,

    I tried the link but don't seem to have access...

  10. #8
    Hi All,


    I have measured up and decided on following two people's methods to get to where I want to be.

    I have decided to follow the same approach as Heavy Metal CNC's X3 conversion Z axis solution.

    Doddy - I'm copying some of your work on your X2 conversion, using plates on the end and front of the saddle and will use equal size pulleys initially to get the steppers out of the way a bit but leave myself the option to use a reduction drive if required - any thoughts?

    I will be using 1605 doublenut ball screws for X and Y and a custom machined 2005 on the Z.

    I will machine out the existing Z ballnut aperture to suit the larger 2005 ball nut and use the existing top bearing and lower thrust bearings as they all seem to be in good condition. Just waiting on a quote from Fred so is there anything else I could do with considering while I'm at it? Otherwise relatively confident thus far.

    I have taken delivery of lots of lovely aluminium bar and have my BOXZY mill to do the cutting work for me when I get to the next stage.

  11. #9
    Mat's Avatar
    Lives in Near Southampton, United Kingdom. Last Activity: 12-03-2021 Has been a member for 1-2 years. Has a total post count of 4. Received thanks 2 times, giving thanks to others 0 times.

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  13. #10
    Mat's Avatar
    Lives in Near Southampton, United Kingdom. Last Activity: 12-03-2021 Has been a member for 1-2 years. Has a total post count of 4. Received thanks 2 times, giving thanks to others 0 times.
    Quote Originally Posted by CNCMEBABY View Post

    I will be using 1605 doublenut ball screws for X and Y and a custom machined 2005 on the Z.

    Just bear in mind that you'll need to grind off any flanges, there's about 36mm of space, I've used 1605 ballscrews and the nut flanges were 40mm across. I ended up grinding 2mm off top/bottom on the Y axis and 4mm off the top on the X axis, centre height on X ended up at 21mm (22.5mm originally).

    Also, check the length of your double ballnuts on the y axis: you can probably fit about 23cm of screw in there before it hits the column, so if your nut is 10cm long you'll restrict your travel to 13cm.
    Last edited by Mat; 10-03-2021 at 01:16 AM.

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