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  1. #25
    *Registered User* DuxEtCapital's Avatar
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    Default Re: DIY CNC Mill - Playing around with the thought

    Quote Originally Posted by dharmic View Post
    A full isolation enclosure with external venting would make it a lot better, also take a lot more room (just how big is your desk!?? ). Not sure I'd bother with a chip conveyor/screw, you have enough on your plate as it is. You'll end up using the blow gun, though, with the cover off, and it's going to end up going everywhere. Still, you're already thinking of all this stuff and are one step ahead of most attempting it, you may be able to make it work.
    Hahaha, I think I am confusing you with my writing here. I am going to build it into my 'computer corner', besides my desk - not upon it :P

    The total space I have I about 2000x1400x2700mm - so as long as I keep within these dimension I should be fine!

    Thank you for the support, friend! I'm going to do my best pulling this of, but the build probably won't commence until a year at least. I have a lot of research and design to do before I can even order materials.



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    Default Re: DIY CNC Mill - Playing around with the thought

    Quote Originally Posted by Stigoe View Post
    Unless you have an old house with old incoming electrical wiring, you have 3-phase coming in to your house, but this is just split up for all the normal circuits.


    If that spindle will pull 7.5Kw, you will need more than a 32 amp circuit just to power the spindle and I can more or less guarantee that you don't have that in your house. Normally you have one 20 amp or 25 amp socket in the house, which is for the oven in the kitchen.

    Whereabouts in Norway are you located?
    I live in Askim, but I'm going to relocate in a year or so. I'll probably stay within Askim though, as it is here I work.

    My problem on the 3-phase question is that I'm not planning on entering the house market any time soon, so I'll probably just keep renting an apartment. Thereby using thousands of dollars to install something that most likely never will be used by other than me would be a waste of money. I have to find a way to stick with 220V single phase - eventually by compromising with the spindle and servos to an acceptable level.



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    Default Re: DIY CNC Mill - Playing around with the thought

    Quote Originally Posted by DuxEtCapital View Post
    I live in Askim, but I'm going to relocate in a year or so. I'll probably stay within Askim though, as it is here I work.
    Not far from me then. I live in Lørenskog. :-)



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    Default Re: DIY CNC Mill - Playing around with the thought

    The common VMCs usually used == 1 kW direct-drive servos for a long time.
    Latest few years, 2-3 kW.

    And they drove a very heavy thick metal milling table.
    And they were very interested in max acceleration and max rapids - for commercial marketing reasons mostly.

    The 40 hp / 25 kW Haas machines with == 2kw axis servos iirc, tended to use 2-3-4 kW of power for cutting steel, mostly.
    Like our demo cuts in our demo room with 7 machines.
    The acceleration on the spindle was 100%, for 1-2 secs, but then the power needed dropped way down.

    I have 750W ac servos, 10.000 counts, on the lathe but use only 20-30% of their peak power and acceleration.
    This cuts down on screw and slide wear, a lot.
    My next-gen lathe saddle will now have 2 toolchangers, front 4 -way (double tooling) and back 7-way servo turret, 70 kg mass.
    Total == 150 kg mass, all-in.
    That mass could be accelerated to 3000 rpm peak servo speed in about 0.05 secs at 750W / 10 Nm == 700 kgf thrust. Or == 4.x G acceleration.

    The VMC mill table == 200 kg mass.
    With 200-300 kg max load on table the 400W servo will still be more than 100% of extra overhead in terms of power and torque and push.

    I previously used a small nema 32 stepper, 48V, on the vmc.
    At 1:3, HTD belts, 5/15 mm.
    It worked fine, at max == 800 rpm speed == 260 rpm at screw.
    (With poor roton ballscrew of 5/8" / 0.2" rise).

    The practical torque from the stepper, 3Nm nominal, is == 50%.
    So about 1.5 Nm, upto 800 rpm, some spare for load on the table.

    The 400W servo, 4Nm peak iirc, is about 2.5 faster and 3-4x more accurate.
    And I don´t need the speed or acceleration, I need the accuracy and rigidity.

    I try to explain my reasons and experiences and spice with some engineering data for credibility.

    - - - Updated - - -

    PS.
    Get the heavy preload if you can !



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    Default Re: DIY CNC Mill - Playing around with the thought

    Mate at 1400x1000x1000 rails will be a substantial machine.
    For instance my machine will be 500x300x350 travel. with x rails being 950, y 600, z 600.
    Frame alone before epoxy is approx 600kg. Completed with stand, motors, spindle & enclosure approx 1T.
    Machine can be broken down into major components so it can be moved by two people without specialized equipment.
    Enclosure size will be approx 1500x1200x2100.
    A Haas Mini Mill by comparison stands at over 1.5T
    With regards to spindle I have only bench tested at this stage. It is an Asynchronous Servo with 2500 line encoder, it can be controlled down to any rpm in speed, torque & pwm mode.
    Regards,
    Michael



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    Default Re: DIY CNC Mill - Playing around with the thought

    No one seems to have mentioned this, so I will........ accuracy = rigidity = mass = weight! I hope you are planning this on the lowest floor of your house! You intimated a move to an apartment later? I would imagine your neighbours wouldn't take kindly to, a) the noise, b) the potential smell, and c) the possibility of them finding your machine in their Living Room if the floor collapsed LOL!
    Your work envelope of 100 x 80 x 80cm would surely require 'table movements of min, 200 x 160 x 100cm + extra to clearance rapids and tool changing? Then add an enclosure? I think your looking at using all the space available (and some) with weight of........loads kg ! A quick comparison of a commercial Haas or Fadal VMC with your quoted work envelope will confirm likely o/all space requirements..... For instance, this one only hits one of your targets - Haas VF-3 | Haas Automation, Inc. | CNC Machine Tools - check out the weight - WOW!



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    Default Re: DIY CNC Mill - Playing around with the thought

    Quote Originally Posted by DuxEtCapital View Post
    I have 220V. I was thinking I could use multiple power supplies - so that each servo, and the spindle, can get their own. Connected to different ports around the house. That way I can distribute the load, and get around the need for all power through one port. I don't have a 3 phase circuit at home, and getting one in my neighborhood would be next to impossible - or at least exceed the the cost of the VMC by itself. I have electrician friends that I hope could help me find a way to make the multiple power-supply idea work.
    The point is not the number of sockets in your house or flat or apartment to distribute the load.
    What is important is the connection to the grid.
    How many phases?
    What amperage rating?
    Look at the fuses on your main board where the grid connection comes in, next to where the electrical meter is that's responsible for you.
    The big ceramic fuses there.
    What is their rating?
    How many of them are there?
    That's what you got.

    I'm in rural Australia and in my little street out in nowhere we got some '2 phase' (180deg), with 32A per phase at 230Vac.
    Back in Germany (single house in city, 10 years ago) we had 3 phase 32A per phase at 230Vac.
    I think the biggest one can get for residential in 230Vac areas is 64A per phase.

    So with everything else OFF on one phase I can run 32A x 230Vac ~ 7kW, total. Anything above that and I blow the fuses on my grid connection.
    And honestly, if I'd have a need for machines bigger than this I'd better get some space in an industrial park and make money with it. ;-)


    Quote Originally Posted by DuxEtCapital View Post
    Hahaha, I think I am confusing you with my writing here. I am going to build it into my 'computer corner', besides my desk - not upon it :P
    The total space I have I about 2000x1400x2700mm - so as long as I keep within these dimension I should be fine!
    Have you checked the load bearing of the floor?
    Anything that isn't on ground level in residential buildings usually tops out at 300kg per square meters..

    Also, are you sure you need those large dimensions for steel capability?
    Building something smaller that can do steel and something larger that can do aluminium should be easier.

    Also, from what I have noticed ATC spindles from China that are affordable and in sizes that hobbyists use (BT30.. maybe even BT40) are usually for aluminium (high rpm, low Nm).
    To get the torque for steel at affordable prices and motor sizes one has to combine a servo motor with a milling head via toothed gear belts.
    This CNC build is using this approach: https://www.cnczone.com/forums/uncat...aluminium.html
    ATC then is a matter of modifying or adapting the rear of the milling head.

    Last edited by JoanTheSpark; 10-23-2018 at 01:20 PM.


  8. #32
    Registered dharmic's Avatar
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    Quote Originally Posted by JoanTheSpark View Post
    The point is not the number of ports in your house to distribute the load.
    What is important is the connection of your house to the grid.
    How many phases?
    What amperage rating?
    Look at the fuses on your main board where the grid connection comes in, next to where the electrical meter is.
    The big ceramic fuses there.
    What is their rating?
    How many of them are there?
    That's what you got.

    I'm in rural Australia and in my little street out in nowhere we got some '2 phase' (180deg), with 32A per phase at 230Vac.
    Back in Germany (single house in city, 10 years ago) we had 3 phase 32A per phase at 230Vac.

    So with everything else OFF on one phase I can run 32A x 230Vac ~ 7kW, total. Anything above that and I blow the fuses on my grid connection.

    The only way out of this for me?
    Solar on the roof and a big battery in the shed, but that's years out and island systems that are able to provide 10kW continuous are no cheap either ;-)
    Strewth! Strike me pink, but I always thought two phase in Oz was a case of “there are three legs, pick any two” ie 120° apart.

    Where in Oz?



  9. #33
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    Default Re: DIY CNC Mill - Playing around with the thought

    North Queensland, Atherton Tablelands, 100km SW of Cairns. A couple houses in a very odd development from like 40-50 years ago that doesn't look like it went by the book (read: farmer cut off some grazing area, put a road in and made some bucks). I think 6 or so houses fed off of a small transformer that is fed 3 phase 19kV and has a total rating of 25kW if I remember correctly. A couple meters (same street oddly enough) there is a real 3 phase transformer for more houses.

    So yeah, we get neutral and 2 phases that are 180 deg apart.



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    Default Re: DIY CNC Mill - Playing around with the thought

    Atherton and surrounds would be exactly the kind of place to have some bizarre power setup of their own. We came visiting from WA a year ago, loved it up there. The “spy museum” in Herbeton(?) was the highlight - guy running it was a vaudeville show on his own, nuttier than Granny’s fruit cake. From there to coffee at the lolly shop, and the lady there made us feel so at home. Crazy, quirky region full of different people all generally getting along and getting on with it. All seemed like such a chilled place to live if you could find a way to make it work. I loved the place.

    I’ll admit it, I’m a little jealous of anyone who’s found a way to live there!



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    Default Re: DIY CNC Mill - Playing around with the thought

    Quote Originally Posted by JoanTheSpark View Post
    North Queensland, Atherton Tablelands, 100km SW of Cairns. A couple houses in a very odd development from like 40-50 years ago that doesn't look like it went by the book (read: farmer cut off some grazing area, put a road in and made some bucks). I think 6 or so houses fed off of a small transformer that is fed 3 phase 19kV and has a total rating of 25kW if I remember correctly. A couple meters (same street oddly enough) there is a real 3 phase transformer for more houses.

    So yeah, we get neutral and 2 phases that are 180 deg apart.
    So you've got 480v line to line? Never heard of that in single phase. (480V 3 phase is common in the US)

    In the US, the standard is 120/240V split phase (is what it's typically called. 180 deg.) Service current ratings are quite a bit higher though. My house is fairly typical with a recent service install and it's 200A (48kVA.)



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    Default Re: DIY CNC Mill - Playing around with the thought

    Quote Originally Posted by skrubol View Post
    So you've got 480v line to line? Never heard of that in single phase. (480V 3 phase is common in the US)

    In the US, the standard is 120/240V split phase (is what it's typically called. 180 deg.) Service current ratings are quite a bit higher though. My house is fairly typical with a recent service install and it's 200A (48kVA.)
    Electricity (Voltage Limits) Amendment Regulation 2017 - Queensland

    The standard voltage for the supply, before 27
    October 2018, of electricity at low voltage from a
    single phase system is ..
    (a) between a phase conductor and a neutral
    conductor ... 240V;
    and
    (b) between the phase conductors ... 480V.




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DIY CNC Mill - Playing around with the thought

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