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  1. #1
    I've recently bought an ex-demo (read as: brand new apart from 2 small chips on paint) Warco WM16 mill/drill for a bargain price of 750. Having weighed up the price of power feed and DRO vs the cost of a CNC conversion, I decided to go CNC.

    This is my first ever build, however I've worked in engineering since starting my apprenticeship 19 years ago.

    I'd like some help and advice for the build, especially for anyone that has previously converted similar machines such as:

    weiss wmd20lv
    champion 20v
    amadeal ama25lv
    warco wm18 (slightly bigger)

    After stripping the machine to get it into my cellar workshop I cleaned off all the packing grease, re-lubricated all slides and screws and set up the gibs to be as tight but smooth as possible. For the time being, because the machine is new and because I don't need micron accuracy, I am going to use the stock lead screws and convert to ball screws if/when I need them. To work out which stepper motors I would need, I ran the Z axis in the up direction (as that is the stiffest to turn by hand) using a dial torque wrench. Worst point was near the top and gave me a reading of 1.6Nm. The X and Y axis were <1Nm with a vice and around 5Kg of weight on them. Based on that, I figured that the commonly available 3.1Nm motors would be more than capable, so I bought a kit from Zapp Automation: http://www.slidesandballscrews.com/d...xis-p-621.html via Gary's eBay listings. He had one kit listed as an auction starting at 180. I won it for 205 so had another joyous moment.

    Sooo, my questions so far:

    1. Have I bought the right kit? I'm pretty sure I've done good as the components in the Hong Kong specials on eBay didn't look very well matched. Plus I wanted separate, easy to replace parts rather than an all in one board.

    2. Are 3.1Nm stepper motors man enough? I thought they were double my needs but have read that "holding torque" is not equal to motor torque.

    3. Should I go for direct drive couplings or use reduction pulleys and timing belts?

    4. The stepper motors are 8-wire. Should I wire them in series or parallel? What's the difference in performance?

    5. I've fabricated a custom stand with a couple of shelves, a stainless steel drip tray and castors (for ease of moving the machine around the workshop!) with intentions of adding pumped coolant/suds at a later date. I'm going to build all the electronics, including the PC components, into a control panel box which will be mounted under the mill, on one of the shelves. Is it "normal" to use 4-core cable and 4-pin plugs and panel mount sockets for the motors or is it better to hard wire them through skin top glands, especially if there's suds in the vicinity? Will there be any problems using this setup?

    6. Software will be 100% Linux based. I've not used any M$ or Windows products for 3+ years, so don't wish to take a step backwards. I'm a complete newby to CAD but have tried FreeCAD, HeeksCAD, Medusa4 and QCAD. Of these, QCAD was by far the most intuitive, and worked well with dfx2gcode which I then ran in EMC2. Bearing in mind that I want to control 3 axis of my mill, will QCAD be sufficient? I know it's only 2D but can 3D gcode be auto-generated by combining standard orthographic views drawn in QCAD?

    Thanks to anyone that can help.

  2. #2
    Nobody can help? :confused:

  3. #3
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 9 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,840. Received thanks 192 times, giving thanks to others 5 times.
    1) Looks like a reasonable kit for starting with, and should be more than up to the job you're asking.

    2 & 3) Certainly on the z-axis, I'd be considering a reduction drive, or an extra counterbalance to reduce the weight the stepper is having to lift.
    You need to allow for the loads being greater when cutting, and also as you're running the normal leadscrews with their reduced effiency compared with ball screws, it may be wise to run reduction on all axis.

    4) Bipolar parallel provides the best match to the drives.

    5) I've seen plenty builds where motors are connected via connectors. Main thing is you use good quality ones, that lock in with a high enough rating, and make sure you never unplug them with the drivers powered on (doing so is likely to lead to the drives becoming an expensive paperweight!)

    6) Probably best to start a thread in the CAD & Cam Software forum, as I have no idea about linux!

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  5. #4
    Thank you for responding.

    Quote Originally Posted by m_c View Post
    ...as you're running the normal leadscrews with their reduced effiency compared with ball screws, it may be wise to run reduction on all axis.
    I was looking at possible ways to mount the motors and using belt drives will make life easier. What ratios should I consider? I was thinking of 2:1 reduction on all axis. Or maybe a bigger ratio on the Z?

    Quote Originally Posted by m_c View Post
    I've seen plenty builds where motors are connected via connectors. Main thing is you use good quality ones, that lock in with a high enough rating, and make sure you never unplug them with the drivers powered on (doing so is likely to lead to the drives becoming an expensive paperweight!)
    Was looking at this today and considering I have to join to the wires on the steppers (probably solder and sleeve with heat shrink), I think it will be better to run the cables through PG16 glands and terminate inside my case. For neatness, it might be worth fitting some 35mm DIN rail and 2.5mm terminals, but will have to decide on a case and play around with the layouts. Regarding motor cables, I've seen mention of 1.5mm shielded 4-core. Is that really necessary? Seems like massive overkill for 4.2A drives/motors? I know it's braided and not shielded cable, but would SY cable be ok? http://www.sycable.co.uk/ It has a bit of extra strength and can more take knocks and bends than most shielded cables. And I can get it from work.

    Quote Originally Posted by m_c View Post
    Probably best to start a thread in the CAD & Cam Software forum, as I have no idea about linux!
    Did that previously but had limited response. I think it's just a case of trying them all until satisfied. Currently trying HeeksCNC and HeeksCAD. They're a bit unorthodox but starting to make sense now.
    Last edited by birchy; 20-03-2011 at 09:47 PM.

  6. #5
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 9 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,840. Received thanks 192 times, giving thanks to others 5 times.
    The benefit of starting with belt drive, is it's fairly easy to swap ratios at a later date with minimal modification.
    2:1 is a typical choice.

    I can't comment about anything to do with linux on a home computer, as my limit with it is the command line on webservers!
    Perhaps asking somewhere like CNCZone may find more linux cad users?

  7. #6
    As you say, it makes sense to go with belt drives as they can be modified easily if I run into problems at a later date. Also, I want to keep the machine as standard as possible and using belt drives should allow me to use existing mounting holes.

    Not too bothered about software at present as I can generate working gcode using either QCAD and dxf2gcode or HeeksCAD/CNC.

    I'd also like to utilise the steppers as power feeds for manual machining. Is that possible or even worth bothering with?

    EDIT: Regarding the cable selection, I can now see why 1.5mm2 is used. I'd forgotten that DC circuits run bigger currents. http://www.solar-wind.co.uk/cable-sizing-DC-cables.html. Still wondering about SY though? We use a lot of multi stranded SY at work in various sizes from 0.5mm2 upto 10mm2. What is the need for screened cables?
    Last edited by birchy; 20-03-2011 at 10:23 PM.

  8. #7
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 9 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,840. Received thanks 192 times, giving thanks to others 5 times.
    It probably is possible, but I'd say learning the required GCode to manually enter moves will be far simpler, or just jog the axis at whatever speed you need.

  9. #8
    The steppers and drivers you have are the same as mine, and they work well on my milling machine which is about the same size as yours. Only difference is I run them on 75v which gets you higher speed. The power supply could be better - I'd advise getting yourself a toroidal transformer for 70v if you want to get the most out of the motors. Nothing to loose by trying the one you've got first though!

    I think belts are a must really. I've not tried direct drive because I think the ability to change the ratio and thus operate the motor in the best torque region is well worth the relatively small amount of money on pulleys. Also I got a heap of pulleys cheap on eBay which always helps!

    When I had 1nm motors on my mill I ran them on 3.2:1 (ish) - not very fast at all. Since then I've had the 3nm motors on 1:1 which is plenty fast enough so I've not bothered testing other ratios. Different story for the router though where I used different pulleys on each axis.

    I quite often manually machine with the steppers and Mach3. Either by typing Gcode or arrow keys/jogging.

    Definitely Bipolar Parallel.

    I used CY 1.5mm cable since SY, though available cheaper, is not as flexible. I think it has an extra layer, or thicker, insulation/shielding which makes it less suitable for constant motion.

  10. #9
    Right, I need to buy some pulleys and belts. What sort of pitch should I be looking at and where's the best place to buy them?

  11. #10
    Hmmmm, they're expensive. Maybe I should buy a dividing head (was gonna get one anyway) and make them myself? Where can I find specifications for such things?

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