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  1. #1
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    Default Help with a new build

    Hello everybody,

    I'm looking for help with choosing the right size motors. I am completely new at this and trying to assemble my first diy cnc. I have finished the frame and now comes the hard part.

    Im building cnc out of mdf and plywood mostly. Work area is approximately 24x48. Z axis is 1605 ball screw 500mm long and 20mm rails. Y axis is 2010 ball screw, it is 1000mm long and 20mm rails. X axis is 2010 ball screw on both sides 1600mm long and 20mm rails.

    The Y axis gantry with Z motor and railing is going to be approximately 100 pounds heavy and will be split between two motors, so about 50 pounds each. Z axis is going to be approximately 30 pounds

    I'm going to be using MACH4 and ESS/MB3 combo

    For my Z axis im considering this motor with a brake
    https://www.omc-stepperonline.com/cl...5BNema%2023%5D
    It is 1.8 inductance and brake is included. From reading online, brake is something i should have so my z does not drop when i turn my machine off. Is this something I should consider or it is not needed? I can get a better motor for less money.


    For my two Y axis motors I am considering these motors
    ?https://www.omc-stepperonline.com/cl...5BNema%2034%5D
    It is 2.8 inductance. I don't anticipate spinning this 2 ball screws (2010-1600MM) more than 1000 rpm for rapids

    For my X axis I am considering same motor that I am using for Y
    I don't anticipate spinning this ballscrew (2010-1000mm) more than 1000 rpm for rapids

    I will be mostly milling hardwoods to start but would like to be able to mill aluminum. I'm not looking to drive this thing 100mph but would not want this thing to be too slow and not have enough torque.

    Do these motors seem ok? and how do i pair MOTOR with DRIVER with POWER SUPPLY?

    Any help greatly appreciated.

    Darko

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    Attached Thumbnails Attached Thumbnails Help with a new build-img_20200510_183332-jpg  


  2. #2

    Default Re: Help with a new build

    Hi,
    with a 1605 ballscrew on the Z axis you will need a stepper capable of high speed due to the fairly fine pitch of the screw. A 1.8mH inductance stepper as you have
    proposed should be capable of 750 rpm with about 50% of rated torque which I think would work well.

    It is possible that the Z axis could slump when the stepper is powered down so a brake would be a good idea. Having said that the vast majority of users do not have
    a brake and get away with it just fine.

    It may be that you have to fit a spring or counterweight so that the Z axis does not slump, many people have used that idea.

    The 34 size steppers you are proposing for your X and Y axes look pretty good. 2.8mH is pretty respectable for 34 size steppers. I think you are being optimistic that they will
    do 1000 rpm. Large motors with comensurately high inductance will not spin fast. I think it more likely that 500rpm is about what you will get.

    I notice that you have selected closed loop stepper and presumably you are happy to pay the extra? The manufacturers claim they are faster, more powerful and never lose steps....
    all pure BS. Closed loop steppers do have some advantages but not all that is claimed by the manufacturers.

    If you use adequately specified open loop steppers and use them within their limits they will never lose steps, after all many people have operated that way
    for many years. So if an open loop stepper never loses steps then why bother with the expense of closed loop?

    I would commend you consider open loop steppers but of EVEN LOWER INDUCTANCE with the highest voltage drivers and power supply you can find.

    For example these 24 size steppers are only 1.18mH:

    Object reference not set to an instance of an object.

    and matched with these drivers:

    Object reference not set to an instance of an object.

    I would use the same steppers throughout your machine. With 1.18mH inductance and 80VDC drives and 80VDC power supply you could expect to get half their rated (3.1Nm) torque at 1000rpm, ie 1.55Nm.
    These steppers will probably out-perform the bigger motors at speed.

    Craig



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    Default Re: Help with a new build

    Hi darko - I agree with Craig on all his points plus you need to check the 1600mm long ballscrew for instability. Hiwin have good formulas for that in their ballscrew manual. Go N24 vs N32 and a brake on the Z is a good idea. Screws can be backdriven by gravity and they do slump and hit your table occasionally if not balanced somehow. The cost of the brake is less or near the cost of balancing and is much easier to implement. Peter



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    Default Re: Help with a new build

    Thanks for your reply and help.

    I was under impression that I would want closed loop steppers so if they lose steps I will know and it will be easier to troubleshoot. I am so new at this I feel like I need any help I can get if something goes wrong!

    I was looking at the same website and this power supply is the biggest one at 60VDC 8.3A. I don't see any 80VDC. Do you have a suggestion on power supply too?

    This might be a stupid question but I'm assuming I need 80VDC power supply for EVERY motor, so 4 in total?

    And you think I should be able to mill aluminum with these components with no problems? I'm planning to buy 220 - 2.2kw water cooled spindle.



    Do I understand this correctly?

    So if I have 2010 ball screw spinning at 500 rpm, that would mean 8.33 rpm a second, so the nut would travel 83.3 mm in one second, so it would take my X gantry approximately 14.64 seconds to move 4 feet (1220mm) in the rapid movement? This is without including speeding up and slowing down.

    Thanks,

    Darko



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    Default Re: Help with a new build

    If steppers lose steps then they are lost no matter if open or closed system. If the steppers are sized correctly then you will not lose steps unless you crash the machine. I'd stay with normal steppers and put the $$$ saved into some other part of the machine. You only need one PS but it has to be able to supply the correct current. So if you have 4x4A motors they don't always pull full current at the same time so usually we say use 75% max so need a PS that has 10-12A capacity. You will get away with less usually ... others can help here with specifics.

    The aluminium holy grail... you have a timber machine and a timber Z axis. It maybe stiff enough but at first glance maybe not. Comes down to many many factors and once your running you will find out.... plus you will need lots of lub that will ruin your machine bed and gantry etc, so many issues.... good luck...

    Rapids your lead is 10mm so at 500rpm the machine will be going 500x10=5000mm/min so 1220/5000*60=14.64 secs your correct....Peter



  6. #6

    Default Re: Help with a new build

    Hi,

    I was under impression that I would want closed loop steppers so if they lose steps I will know and it will be easier to troubleshoot.
    Thats what the manufacturer would have you believe and thereby get your money.

    The only reason a stepper will lose a step is if it is overloaded, and that happens when they are running fast and are therefore running at diminished torque. A closed loop
    driver will insert and extra step to try to 'catch up'....but guess what....the extra step suffers the same fate as all the regular steps.....it gets missed because the stepper
    is overloaded.

    A closed loop stepper that is overloaded is no better than an open loop stepper that is similarly overloaded.

    I agree with Peter, get the lowest inductance 23/24 size open loop steppers you can find and use the dollars you save elsewhere.

    So called 'linear' power supplies, that is supplies with a big transformer/rectifier/ smoothing capacitors, are preferred over cheaper switch mode supplies.
    They have a much better tolerance to overload conditions and absorb reverse braking energy much more gracefully.

    https://www.antekinc.com/ps-10n80-10...-power-supply/

    This is a 1000W 80VDC supply capable of 12.5A and should be enough to power all your steppers. If you wanted a bit more the same company (Antek) do a 1500W 80VDC (16.5A) for
    $227.

    Craig



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    Default Re: Help with a new build

    Quote Originally Posted by peteeng View Post

    The aluminium holy grail... you have a timber machine and a timber Z axis. It maybe stiff enough but at first glance maybe not. Comes down to many many factors and once your running you will find out.... plus you will need lots of lub that will ruin your machine bed and gantry etc, so many issues.... good luck...
    I am still working on the frame and looking to beef up z axis more hopefully to make it more rigid. The reason i want to get motors, drivers and power supply sized properly so i can mill aluminum is because later down the read i want to build frame out of aluminum and make it even more rigid. MDF and plywood is more economic now if i wanted to change something in design and hoping to learn more during this process.



  8. #8
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    Default Re: Help with a new build

    Hi Darko - very good philosophy, I agree with what you say. I expect your hurdle will be the Z axis stiffness. The rest of the machine will cut aluminium with the members being so big. Have a play with aluminium/ply/aluminium laminates/ A laminate of 2mm al/ 15mm ply / 2mm aluminium is the same bending stiffness as 16mm thick aluminium. You can jig saw the aluminium to rough shape, glue it to the plywood then edge trim it flush. Easy to do in your garage. Use epoxy or contact cement to glue the skins on. So I expect your Z axis tool plate to be al/ply/al say 2mm/32mm/2mm and this will be very, very stiff and light.. (equivalent to an aluminium plate 24mm thick )Peter

    Attached Thumbnails Attached Thumbnails Help with a new build-laminate-jpg  
    Last edited by peteeng; 05-16-2020 at 05:50 PM.


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    Default Re: Help with a new build

    Quote Originally Posted by joeavaerage View Post

    So called 'linear' power supplies, that is supplies with a big transformer/rectifier/ smoothing capacitors, are preferred over cheaper switch mode supplies.
    They have a much better tolerance to overload conditions and absorb reverse braking energy much more gracefully.

    https://www.antekinc.com/ps-10n80-10...-power-supply/

    This is a 1000W 80VDC supply capable of 12.5A and should be enough to power all your steppers. If you wanted a bit more the same company (Antek) do a 1500W 80VDC (16.5A) for
    $227.

    Craig


    Thanks for your advice,

    I was looking at that power supply and noticed model PS-10N80N24, I'm assuming this one is giving me 24v also to use on my ESS? Do you think that is ok to do or should i keep them separate and buy 24v power supply?

    I have noticed that stepper motors are louder comparing to hybrid and a lot louder comparing to servos. I guess that is not going to matter when I have my dust control vacuum on, which is super loud.



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    Default Re: Help with a new build

    Quote Originally Posted by peteeng View Post
    Hi Darko - very good philosophy, I agree with what you say. I expect your hurdle will be the Z axis stiffness. The rest of the machine will cut aluminium with the members being so big. Have a play with aluminium/ply/aluminium laminates/ A laminate of 2mm al/ 15mm ply / 2mm aluminium is the same bending stiffness as 16mm thick aluminium. You can jig saw the aluminium to rough shape, glue it to the plywood then edge trim it flush. Easy to do in your garage. Use epoxy or contact cement to glue the skins on. So I expect your Z axis tool plate to be al/ply/al say 2mm/32mm/2mm and this will be very, very stiff and light.. (equivalent to an aluminium plate 24mm thick )Peter
    Thanks Peter,

    I will see if i can incorporate your suggestions.



  11. #11

    Default Re: Help with a new build

    Hi,

    I was looking at that power supply and noticed model PS-10N80N24, I'm assuming this one is giving me 24v also to use on my ESS? Do you think that is ok to do or should i keep them separate and buy 24v power supply?
    Yes you could easily use an auxillary 24VDC supply for other purposes, the ESS for instance. Although an ESS requires 5V, and will not tolerate more than 5V,
    at 5.5V its ready to let smoke out. You would need a regualtor to cut the 24V down to 5V, which would be no problem but a linear regulator will get
    hot so will require adecent heatsink.

    The only potential source of trouble is that the main winding of the transformer will be supplying varying current to your steppers. Any electrical noise
    that generates will be on the auxillary winding as well and could potentially invade the ESS. If you want to use the auxillary supply I would use a linear
    regulator and pay particular attention to capacitive decoupling. I would insist on low ESR tantalum caps in addition to the samller ceramics caps.
    Nothing difficult about it, just you need to dot the i's when using a 7805 reg.

    Craig



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    Default Re: Help with a new build

    Quote Originally Posted by joeavaerage View Post
    Hi,



    Yes you could easily use an auxillary 24VDC supply for other purposes, the ESS for instance. Although an ESS requires 5V, and will not tolerate more than 5V,
    at 5.5V its ready to let smoke out. You would need a regualtor to cut the 24V down to 5V, which would be no problem but a linear regulator will get
    hot so will require adecent heatsink.

    The only potential source of trouble is that the main winding of the transformer will be supplying varying current to your steppers. Any electrical noise
    that generates will be on the auxillary winding as well and could potentially invade the ESS. If you want to use the auxillary supply I would use a linear
    regulator and pay particular attention to capacitive decoupling. I would insist on low ESR tantalum caps in addition to the samller ceramics caps.
    Nothing difficult about it, just you need to dot the i's when using a 7805 reg.

    Craig
    Thanks Craig,

    I just received my ESS and MB3 board and i'm trying to read everything. From looking at stuff online ESS plugs directly in to MB3
    I think i want to build everything on DIN rails.

    https://www.amazon.com/MEAN-WELL-MDR...S8MH9D4NBX0934


    Everything like that look neat and organized.
    All of this is very new to me so i'm learning as i go.

    Thanks for your feedback!



  13. #13

    Default Re: Help with a new build

    Hi,

    Everything like that look neat and organized.
    All of this is very new to me so i'm learning as i go.
    Crikey!!! I always meant to do that but as a temporary measure I nailed the single board PC, the ESS and my two BoBs
    to a piece of plywood....and that was five years ago.

    There's nothing so permanent as a temporary measure
    That little DIN rail power supply will work perfectly. You might find that you want a 24V one as well if you are going to use an MB3.
    The MB3 has 24V tolerant inputs and if I'm not mistaken, 24V outputs, which is the common industrial practice.

    Craig



  14. #14
    Community Moderator ger21's Avatar
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    Default Re: Help with a new build

    The MB3 requires a single 24V PS. You don't need a 5V supply, the MB3 supplies the 5V to the ESS.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Help with a new build

    Quote Originally Posted by ger21 View Post
    The MB3 requires a single 24V PS. You don't need a 5V supply, the MB3 supplies the 5V to the ESS.
    Thanks Gerry,

    I think i had a brain freeze when i mentioned i need 24v PS for ESS, i ment mb3.


    Darko



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    Default Re: Help with a new build

    Just got of the phone with Leadshine customer service and and the guy I spoke to seemed very nice and helpful.

    I was trying to get more info on D57CM31 motors and EM882S drivers. The motors are sold out in the US. You can order from China but shipping is more expensive now. He did have EM882S in stock.

    He mentioned that i don't need EM882S. He suggested EM870S it is a little bit cheaper. While i was talking to him I mentioned how i'm planning to use 1000W 80VDC supply 12.5A, the one Craig suggested, and he mentioned that 80VDC is too much and motor would be overheating on long runs. He suggested 60VDC.

    Help

    Now i'm confused.

    Darko

    Forgot to mention he quoted me $576 for 4 motors and 4 drivers



  17. #17

    Default Re: Help with a new build

    Hi,
    believe as you will.

    Heating is caused by current, remember P=R.I2, called Watts Law....been that way for a couple of centries now.

    The driver on reciept of a new step will apply a full voltage pulse to the windings but only for the duration required for the current
    to rise to its rated (or controlled) maximum. Thereafter the drive supplies very low duty cycle PWM just enough to maintain that
    current. During this phase the 'voltage' is an average of the supply voltage (80V say) for 2% of the time and 0V for 98% of the
    time for an average of 80 x 0.02 + 0 x 0.98=1.6V

    So the only time the full voltage is applied to the winding is that brief instant when a new step is recieved and the voltage 'forces the current'
    into the winding.

    If you want to reduce heating....reduce current not voltage.

    Craig



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    Default Re: Help with a new build

    Thanks Craig,

    I think i'm going to go with power supply you suggested.



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