If you are building a budget-friendly CNC router, an Arduino is a great option for its controller.
The firmware for CNC control when using Arduino is GRBL. GRBL is free to use and has a large user base.
However, to use GRBL on an Arduino you need a CNC Shield.
In this article, I review the best and most reliable Arduino CNC Shields for CNC machines.
Lastly, I also talk about why using a CNC shield with Arduino is a better idea than connecting a stepper driver directly to your Arduino.
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How to Choose a CNC Shield for your Arduino
I list all the important factors you should consider before moving on to the best CNC shields in the next section.
You will find CNC shields with onboard drivers and without a driver. The former has a stepper driver soldered onto the board and is difficult to repair if you burn the driver.
Furthermore, you'll be stuck with the driver option that the OEM provides, but if it fulfills your requirements you can go for it.
The latter has ports on which you can plug in the stepper drivers of your choice, such drivers are called stepstick drivers. It gives you a lot of flexibility in choosing the right driver based on current and voltage requirements.
If you use CNC shields with stepstick drivers you can swap the driver with a new one easily in case you burn one.
Voltage and Current Rating
You should always choose stepper motors first and then the stepper driver. The CNC shield must be able to supply the voltage and current that the stepper motors you intend to use require.
Check whether the CNC shield supports the driver that you require.
If you have the budget you can go for shields with higher voltage and current ratings as this will be helpful when you want to upgrade your build in the future.
The more the merrier. These ports let you connect limit, E-stop, resume, and hold switches and improve the convenience and safety of using your CNC router.
Additionally, you should also look for PWM (Pulse Width Modulation) support. Arduinos support PWM and if your shield doesn't, it's a waste of Arduino's capability.
You can connect low-powered spindles for engraving directly to the PWM pins and control the spindle.
Some CNC shields also have digital outputs that you can use to turn on and off external appliances.
For example, you can use one to turn on the coolant pump when the cutting starts or wire it up to a relay to turn on a router automatically.
These pins improve the functionality of your build and you must consider the features you need while selecting a CNC shield.
Best Arduino CNC Shields- GRBL Compatible
I have compiled this list after carefully considering each shield for its build quality, reliability, driver support, features it has, and customer support.
Open Source V3.51
This is the most common Arduino CNC Shield design and is a versatile tool.
It is a PCB designed to mount directly on top of an Arduino Uno or other Arduino boards with similar pinouts.
There is no integrated stepper driver on the board and you will have to attach stepper motor driver boards called stepstick drivers.
These are available for most of the popular stepper drivers like A4988 and DRV8825. This also means you get to choose the driver as per your project requirements.
The drivers are not soldered onto the board, instead, they connect using header pins, and hence the drivers can be easily swapped in case one goes bad.
You can attach up to four motor drivers to control up to four axes. It is designed to support A4988, DRV8825, or similar types of stepper motor drivers.
Additionally, it has pins to connect up to six limit switches (two for each axis) and two pins to use any other device like a spindle (spindle control), Z-probe, E-stop, or coolant pump.
It can handle up to 2.6 A of current for each of the stepper motors that it controls and it can drive stepper motors with a voltage rating between 12V and 36V.
You can even select various microstepping levels by changing the jumpers present on specific pins and it supports up to 1/32 microstepping.
For communication, it comes with I2C and UART ports that can connect directly to other circuit boards like Arduino.
It is compatible with GRBL firmware version 0.9 and is quite easy to install and configure.
There are many manufacturers of V3.51 CNC shields but the most popular ones are Elecrow, Protoneer, Ooznest, and Kuman.
Ooznest Arduino CNC Shield
Ooznest is a British CNC and CNC components manufacturing brand and is popular for its WorkBee CNC routers.
This CNC shield from Ooznest uses the V3.51 design but uses premium components that let you use these for long hours of operation.
You can buy it with an Arduino Uno bundled in or without one from their official website. The stepper motor drivers are not included with the board.
If you are in the UK this is a great choice. However, if you are in the US you will have to consider the import duty and shipping.
The Keyestudio V4.0 CNC shield uses a similar design as the V3.0 boards but is designed to work with an Arduino Nano using GRBL firmware.
It can control up to three motors and is suitable for CNC routers and engravers with a small working area.
It is better to use four motors for CNC routers with a large cutting area. This is because you must use a dual drive for the Y-axis to prevent racking of the wide gantry.
You can use A4988 or similar stepstick stepper drivers with this CNC shield and it supports up to 1/16 microstepping.
However, you should only pair it with a 42 step stepper motor.
It requires a 12V DC supply to function, this is for powering the Arduino Nano and the stepper motors.
What it also means is, you cannot use 24 V or 36 V stepper motors with this CNC shield.
There are six header pins to connect up to six limit switches on the 3 axes.
Keyestudio is a Chinese brand and you can get this board shipped to you for under $10.
However, the Arduino or stepper motor drivers are not bundled with your purchase.
- KEYESTUDIO V4.0 board is updated with CP2102 USB serial chip, fully compatible with arduino.
- 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack, an ICSP headers and a reset button.
Synthetos gShield V5
If you need a no-fuss solution to interface your Arduino with your stepper motors, the gShield from Adafruit is a good option.
You can use any Arduino board with this board and it can drive up to 3 four-wire stepper motors.
However, if you are building a CNC router with a wide gantry you’ll need to use two motors for the Y-axis to prevent racking and you’ll need an additional fourth stepper motor driver.
For connecting the motors and power supply, it comes with screw-down terminals that ensure that the wires never disconnect accidentally.
It comes with three TI DRV8818 stepper drivers integrated into the board. This means you don’t have to worry about attaching stepper drivers.
However, it also means, if you burn one of the drivers you cannot swap the driver and you’ll end up with a two-axis shield.
You can drive stepper motors that require a maximum of 2.5 A per phase. Additionally, it also supports up to ⅛ microstepping.
It can support motors with a voltage rating between 12 - 30 V and the shield can work on a 3.3 V or 5 V supply from the controller board (Arduino).
It is priced on the higher end when compared to other shields and therefore for beginners, I would suggest sticking with step stick-type shields.
If you know what you are doing, the gShield is a very good option that is quick to set up and is reliable with several features.
GRBLDuino Uno Shield
This is the only shield on this list that is made for the latest GRBL 1.1 version and can drive up to four motors.
It is available as a kit with through-hole components that you need to solder. Alternatively, you can also buy it assembled.
The assembled version is around $13 costlier than the kit version.
It is compatible with Arduino Uno and it supports DRV8825 or similar types of step stick stepper drivers.
The board can handle up to 45 V supply for the motors, however, the real voltage limitation will depend on the limitation of the stepper driver you use.
It has pins to connect two limit switches for three axes and supports E-stop, hold, coolant pump, probe, and resume connections.
Additionally, it has PWM (Pulse Width Modulation) pins that you can use to connect your spindle and control its speed and direction.
All the connections for the machine components are through screw-down terminals which keeps them from disconnecting accidentally.
The customer support for this CNC shield is the best among all the others mentioned on the list.
It comes with support documents and well-detailed assembly instructions to help you set it up.
Kuman CNC Shield kit
If you haven’t planned out the controller for your build, this is a worthy choice to consider. It comes with all the things you need to control your CNC router.
The kit has an Arduino Uno board(clone), four A4988 stepper motor drivers with heat sinks, and a V3.51 based CNC shield.
You can connect up to four stepper motors but the number of axes you can control also depends on the firmware that you use.
Grbl supports a maximum of three axes, so if you are using Grbl, you can use the fourth driver as a clone of one of the other axes to achieve dual drive.
The driver supports up to 1/16 microstepping and can supply a maximum current of 2 A at a maximum voltage of 36V.
Like the other V3.51 boards, it supports limit switches (3 axes), coolant control, spindle, E-stop, hold, and resume connections.
It is an all-in-one package and easy to set up and you do not have to worry about compatibility issues between Arduino, CNC shield, and motor drivers.
CNC Shield Alternatives
A more efficient but expensive alternative to a CNC shield is a CNC controller.
CNC Controllers are usually much more powerful and require much less DIY to make it work.
Some of the more expensive ones are plug-and-play solutions.
Why do you need a CNC shield?
Do you really need a CNC shied? Can’t you drive the stepper motor directly with an Arduino? After all, Arduinos can do almost anything.
The first problem that pops up when you try to interface a stepper motor directly with an Arduino is the voltage and current rating of the stepper motors.
A stepper motor used for hobby CNC applications will need a supply voltage of at least 12 V for each of its phases.
Arduinos are designed to provide signals at a voltage and current far lower than those required by the stepper motor.
Moreover, a stepper motor will have at least four pins that require individual signals. So if you are making a 3-axis CNC machine you will need at least 12 analog output pins on the Arduino.
This is where a stepper motor driver comes in. A driver IC receives low voltage low current signals from a controller and translates them into signals at the right voltage and current level for the motors.
This makes things easy for the Arduino as you only need two output pins of Arduino to control a stepper motor, be it a 4, 6, or 8-wire stepper motor.
One pin sets the direction of rotation and the next pin provides pulses. The motor moves one step per pulse.
Well, you might be thinking that you can interface a stepper motor and Arduino using a stepper motor driver. It can be done, but it is not so simple.
A typical stepper motor for a hobby CNC application needs a 12V, 24V, or 36V supply. You can connect the power supply to the leads on the driver IC but you will have to connect a filter capacitor between the leads.
Additionally, stepper motor driver ICs will have a microstepping function that needs to be selected by applying the right signal at particular pins.
All these tasks involve soldering components at the right place and making sure the connections are proper and in the right place.
Also, you will have to use up output pins on the Arduino to provide the right signal for microstepping for each motor.
Doing it for three or four motors can be cumbersome and time-consuming with no real benefit.
This is where a CNC shield comes in, a typical CNC shield can mount on top of an Arduino Uno or clone and has ports to plug in stepper motor drivers and stepper motors.
Usually, there is no soldering involved and you can interface four stepper motors with Arduino in under 30 minutes.
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