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  1. #1
    Hi guys, David Here from Nottingham,

    Great forum ive been lurking around for a while but now im really ready to get stuck in and build my own cnc
    ive been thinking of this for a long time but im the past few months have gotten rather serious and have taken the plunge.
    reading the forums i realised i know very little about what i thought i knew. but why ive got you here ill take the chance to pick your brain.


    So i recently started on a quest to build my own cnc, And now i realised i know next to nothing about electronics.
    I feel like the more i learn the less i actually know and im not sure my project will get finished this year unless i ask for your guys help.

    Now that i have nothing to do but sit at home its a great time to get really stuck in with my cnc build and i could really use some advice.

    I want to build a cnc that has about a meter square working area. mainly to cut foam
    but i will want to cut wood at a later date (possible stepper motor upgrade if needed)

    my design will be based around the root 2 3d printed cnc (machined aluminium parts not 3d prints) and box steel runners (upgraded to liner rail in v2)

    the parts i have acquired so far are ( i will post specifics for each part after )

    1x MACH3 4 Axis 100KHz USB CNC Controller Card Breakout Board

    4x DC20-50V Stepper Motor DM556

    4x Nema23 57BYGH627 3A 270oz (i will upgrade these at a later date in v2)

    plus all the random little bits- limit switches / estop / probe ext

    the bits i am confused with is working out the power supply needed for the system and i want to run my spindle through the mach 3 board but its all a bit confusing and i am struggling figuring it out. Ive looked at lots of different options but im confused i wont post them here as it may just get confusing.

    im looking at purchasing a 500W 52mm ER11 what do i need to connect this to the mach 3 board.

    So i guess my main questions are how do i connect the spindle to the mach 3 board and what do i need for it (pwm speed controller ?) do i need a separate power supply or can i supply it all from one power supply.
    specifications
    MACH3 4 Axis 100KHz USB CNC Smooth Stepper Motion Controller Card Breakout Board

    DC20-50V Stepper Motor DM556 Digital NEMA23 NEMA34 Photoelectric isolation

    * Input Power: 24-50V DC Power, Typical Value: DC36V
    * Output Current: 1.0A-5.6A, 8 Steps Adjustable, Resolution 0.5A
    * Drive mode: Two-level constant current PWM Drive Output
    * Insulation Resistance:> 500MΩ At Normal Temperature And Pressure
    * Insulation Strength: 500V / Min At Room Temperature And Pressure
    * Size: 118 * 75.5 * 34mm / 4.65 * 2.97 * 1.34in(Approx.)
    * Mounting Hole Distance: About 112mm / 4.41in(Approx.)

    Stepper Motor Nema23 57BYGH627 3A 270oz-in 4-Wire Kit

    Part No.: 57BYGH627 single shaft
    Frame Size: NEMA23
    Step Angle: 1.8 degree
    Voltage: 3.0VDC
    Current: 3.0 A/phase
    Resistance: 1.0 Ohm/phase
    Inductance: 3.5 mH/phase
    Holding torque: 19 Kg-cm 270 oz-in
    Rotor inertia: 480 g-cm2
    Detent torque: 0.6 kg-cm
    Number of wire leads: 4
    Weight: 2.20lb (1.0 kg)
    Length: 76mm
    Shaft diamter: 6.35mm (1/4")

    Its probably a bit of an ebay special but atm its only for cutting foam and the fun of actually making something and testing i plan to fully upgrade once i have the basic knowledge and actually know what im doing

    thanks for any help guys

  2. Ignoring everything else but to try to offer some advice on the spindle speed control and the question that you asked. Your controller board will very likely offer a 0-10V output that is intended to control the spindle speed. You can usually configure the controller with either 1 or 2 outputs to control the forward/reverse direction.

    Now, looking at the eBay options that sort of hit your target. There's a number of ER11 collet 500W motors - typically air cooled and some with, some without spindle controllers. There's a much more interesting bundle of a BLDC motor - 500W but ER16 collets with speed controller.

    Firstly - I would look to buy the spindle bundled with a spindle speed controller - it avoids one complication of ensuring that they work together. Spindles look to hit around 40 or 80 with controller.

    Now, there's a number of open-framed spindle controllers on eBay, typically with a potentiometer for the speed control. Normally this would be where the 0-10V control steps in - the controller typically giving a 0V/10V reference and the potentiometer wired between these and a 0-10V speed controller input. But, here's the rub - particularly with DC motor speed controllers and those directly powered from the mains (as some of these are) - the spindle speed control input is not always isolated from the mains - which means that you have to be damned careful how to wire this to the motion-control card (and how you may need to pay care to the wiring to avoid a shock hazard). The problem is - the couple of adverts I've read don't make it clear if the spindle-speed control input is isolated from the mains, or not.

    With that being unclear, what next interests me is the similarly priced BLDC motor and controller with a ER16 collet for around 80 - about the same as the open-cage controllers, but...

    These are designed to take a 50V DC input - which would be the same as your stepper PSU (just means a bigger transformer to drive both). But, the BLDC spindle has a couple of advantages over the traditional DC motor:
    * The controller has a specific 0-10V input voltage range for speed control. This will be compatible with your motion controller board,
    * The BLDC motor, by design, is a synchronous motor (it's actually a 3-phase AC motor) - and that allows a more controllable speed setting (the driver generates the 3-phase supply to the motor that rotates according to the 3 phase frequency, compared with a standard DC motor that rotates as a function of current (ne. voltage) and load.
    * That also improves the low-speed torque.
    * The DLDC controller supports FWD/REV control, unlike the cheap open-frame controllers.
    * The ER16 collet is more flexible that the smaller ER11.
    * BLDC don't have brushes - less audible and electrical noise, and less maintenance.


    You *could* go the full hog and get a 2.2kW water cooled spindle, but that's not what you asked.
    Last edited by Doddy; 5 Days Ago at 08:35 PM.

  3. #3
    Regards the Controller we really need more info or a link to the place you bought it from because there are lots of spurious Chinese controllers around.!

    Regards the power supply then you'll need a separate PSU for the Drives. Ideally, you'll want one around 44Vdc with those 50Vdc max drives. Don't buy one close to the 50Vdc Max rating because you run the risk of blowing them up, as rule leave a 10% safety margin when sizing the PSU for the drives.

    The PSU for the rest of the control box will depend partly on the controller and what Voltage it's Inputs etc will allow and the type of switches your using.
    Ideally, you'd want to run your Control system ie: limits,E-stop etc on 24Vdc. This will give you the best protection from electrical noise issues which can plague a machine, esp if using cheap electronics.
    However, if your controller will only accept 5V on its inputs then you may be forced to use that. This is why we need to know more about the controller to answer more accurately.

    This leads nicely onto the Spindle and Mach3. Same again I Can't really answer without knowing more about the controller board.
    Likewise, need to know more about the spindle its self.? Saying 500W doesn't really help because there are loads of 500W spindles which can run on various voltages using various methods to control them. ie: DC with Speed controller or 3 phase spindles with a VFD right down to mains powered spindles like Dremals with no speed controller.

    In a nutshell, Often a Control box is made up using several PSU of different voltages. The drives are nearly always run on a high voltage PSU and all the bits n bobs like Limits etc on Lower voltage. It's not uncommon for 5v to be needed for signals and 12 or 24V for things like relays etc.

    The Spindle will nearly always be run from Mains voltage, either directly if Dremel type or through some transformer/speed controller/VFD device. Also, some were in the mix often there will a relay used for turning on/off etc hence the other PSU's.

    I know it may seem mind-blowing at first but it's actually not that bad when it's explained better, but to do this we first need a little more detailed Info on what exactly you have or are considering buying.

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