Stepper motors play an essential role in many of today’s computer numerical control (CNC) machines, such as 3D printers, CNC mills, lathes and laser engravers. These motors are responsible for the exacting linear movement that these machines deliver; from the Y-axis to more precise details, the machine’s ability to cut, mill or engrave is entirely contingent on its stepper motor.
If you’ve decided to build your own 3D printer, then you know the importance of choosing and connecting the correct stepper motors. Without these powerful, precision motors, your machine won’t move an inch. Fortunately, we’ve created a guide with all the essential information about stepper motors you need to know.
This article will cover all you need to know about stepper motors, including what they are, how they operate, what they do in 3D printers and CNC machines, a few variations, and installation considerations.
However, let’s begin with the basics first.
Stepper Motors in 3D Printing: A Basic Overview
Stepper motors are an essential component used in a wide array of devices ranging from computer printers to robots. They are an important part of modern machines and can be found almost everywhere today. This type of electric motor stands out since it is powered by electricity, instead of relying on fuels like gasoline.
A typical motor, electric or otherwise, will make a periodic, regular, circular motion – but that is not the limit to their capabilities. Stepper motors take this functionality further by allowing selective turns of specific percentages of a revolution; called steps. These can start and stop whenever required. This enhanced precision makes them perfect for powering machines like 3D printers which need to have precise and intricate movements.
In the image above, you can see a stepper motor disassembled into its individual parts. One of these components is the coils inside; when electricity runs through them, it sets in motion the rest of the parts — thus enabling the machine to operate with a specified precision and accuracy. These electrical pulses control very precisely those coils which ultimately results in a reliable and calculated movement of the motor.
Before we get into the details of how stepper motors work, let’s take a look at what they do in your machine.
The stepper motors attached to the X-, Y-, and Z-axes of any 3D printer or desktop CNC machine are what make it possible for them to move. Generally, one motor each is responsible for the linear movement along the X and Y axes, with those two often making use of belts or screws to transmit rotation. Similarly, a screw is normally used on the Z-axis, which has the added challenge of carrying the weight of the entire tool head. Depending on your machine, you may find one or two motors controlling this axis.
In addition, 3D printers often have an extra stepper motor to control the extrusion of filament, usually in a complex system which includes a spring, pulley, and gear. This intricate setup helps ensure that the filament moves smoothly and consistently throughout the printing process. On CNC machines, however, spindles require more power than one of these motors can deliver in terms of both torque and speed. For this reason, CNC machines use their own integral electric motor instead.
Let’s have a look at the operation of stepper motors now that we have a better understanding of why they are important to the processes of 3D printing and CNC machining.
NEMA Ratings in 3D Printing: Understanding the Basics
The word “NEMA” always comes up when talking about DIY 3D printers, CNC machines and the like. What does it mean though? Many associate NEMA and stepper motors as the same thing, when really they’re not.
In reality, what NEMA stands for is the National Electrical Manufacturers Association, which is a trade association that was formed in 1926 by US-based manufacturers of electrical products. A stepper motor categorized as NEMA will have specific dimensions, capacity, torque, and voltage input that are outlined by the association. This allows for easier interoperability between different stepper motors and other products that utilize them. In short, NEMA’s standards provide a level of certainty and peace of mind for manufacturers and consumers alike.
When discussing stepper motors, it is important to remember that many electric components have the ability to meet NEMA’s specific standards. While these components, such as a traditional AC motor, may be able to be described as “NEMA-rated”, they are not necessarily stepper motors. As such, great caution should be taken when the two terms are mixed together since both refer to different things that each have distinct purposes and roles.
Maximizing 3D Printer Performance: A Discussion on Torque
Torque is an important aspect to consider when looking at stepper motors, as it has a direct relationship with the amount of force used to move the motor. Torque is measured in Newton meters and it is calculated through a simple mathematical formula which multiplies Force and Distance.
To give this idea more clarity, torque can be thought of as the equivalent of force along a straight line but applied to a circular movement; in other words, objects which have higher torque are able to move heavier weights around circularly.
As the formula shows, it uses both force and distance as units, and while two common measurement units include N-cm (Newton x centimetre) and Oz-in (ounce x inch), some stepper motors require more robust measurements like kg-cm (kilogram x centimetre) for their specific applications.
Exploring Different NEMA Ratings for Stepper Motors in 3D Printing
NEMA stepper motors come in two sizes – NEMA 17 and NEMA 23 – which refer to the size of their faceplates. A NEMA 17 has a 1.7″ x 1.7″ faceplate, while a NEMA 23 has a 2.3″ x 2.3″ faceplate. Interestingly, faceplate size is directly related to torque; the larger faceplate implies that there are more powerful transmission components inside like rotors and gear sets, translating into higher torque production capabilities.
Generally, the NEMA 17 can generate up to 50 units of Newton centimetres, while the NEMA 23 can repeat up to 125 units of Newton centimetres of torque. Which should you choose? It depends on what material you’re dealing with. If it’s a lighter material like plastic, the NEMA 17 motor will do the job just fine. However, if you need to cut through heavier materials like aluminium, it’s best to go with a NEMA 23 as it can generate more torque and get the job done faster.
Also, in even more subtle ways the standard can be used to benefit the project. The NEMA 23 and 17 are both high torque motors, but the important thing to realize is that NEMA 23 still has higher max torques than any NEMA 17. This means that if you’re looking for a lower torque than even the lowest available from a NEMA 23, then you must look at a NEMA 17 as it will offer lower torque levels throughout its range of models.
In terms of NEMA 17, there are three primary changes that result in a change in the length of the NEMA. This is due to the fact that the higher the torque is, the larger the rotor needs to be.
The following are the three variants of NEMA 17 stepper motors that are the most common:
- Pancake motors: The amount of torque produced by these is minimal. The 13 N-cm torque shortest measures just 2 cm in length.
- Standard length: The most common one is 4 cm long and has a torque of 50 N-cm.
- High torque: With a length of just 6 centimetres and a torque rating of 65 Newton-centimeters, this is the NEMA 17 component with the highest torque (even if it is still not as high as a NEMA 23 component).
There are further possibilities for NEMA 17, but they might not be as readily available on the business market as the three that were just discussed.
Different Types of Stepper Motors in 3D Printing: Understanding the Variations
There will be occasions when the typical options are not suitable for your requirements. Luckily, there are a few other choices you might consider:
- Geared steppers: Instead of relying on the same old NEMA 17 shape, augmented with gear ratios, you can get customized motors characterized by increased speed or torque. Depending on your objective, this is a great way to optimise your motors: if you need extra torque but don’t have space for a more sizable NEMA 23 motor, then adding a gearbox could be the cost-effective solution. Furthermore, between speed and torque there is an inverse relationship; so if your project requires speed rather than power then you can tap into its full potential while maximising efficiency in size and energy consumption.
- Brushless motors with encoders: They offer a cutting-edge solution to CNC movement, providing increased speed, torque and precision. Despite being more expensive and difficult to set up than traditional steppers, brushless motors are quickly becoming the favoured choice for some applications; the sophisticated system used by these devices can help reduce noise and vibrations by as much as 40%, creating an exceptionally smooth motion that increases their accuracy.
- Servo motors: These are often used as secondary motors due to their torque limitations but they can still create quite powerful results. They are primarily used in small actuating parts such as couplers to help carry out specific tasks. However, it is important to note that servo motors aren’t intended for large intense jobs and unlike stepper motors, have limited abilities when it comes to continuous rotation. Instead, these motors are mostly used for pressing buttons or other simpler tasks because of their precision and accuracy.
Drivers are an important piece of technology that acts as the communication bridge between a computer and a stepper motor. By converting software commands into electric pulses, drivers tell stepper motors exactly how to move so that they faithfully replicate instructions. The driver is connected to the mainboard of your printer while the related stepper motor is then connected to this driver.
Choosing the right drivers for your stepper motor is an important part of the setup process, and not all drivers are compatible with all references. It’s also helpful to note whether or not they are silent, as that shrill sound many machines make could be simply coming from your motors working away. Making sure you have the correct drivers can go a long way in ensuring your system runs smoothly and reliably without excess noise.
Drivers are instrumental to the accuracy of a stepper motor. They manage the precise movement by directing micro-steps, which can evolve from the placement of your printer’s software as well as the drivers being used. A micro-step is derived when a driver sends out a specific quantity of electric pulses for one step to be completed. This series typically adds up in multiples of 8 with the highest being 128. While it may feel sensitive to go for more small steps, approaching this limit can cause communication issues and should be avoided. The suggested range lies between 32 and 64 micro-steps for maximum efficiency.
Steps Per Unit in 3D Printing: Optimizing Your Stepper Motor’s Performance
Your stepper motor moves in a circular motion, whereas the printer runs in a straight path. How do you make sure that the rotation of the motor corresponds to the kind of linear motion that you want?
For instance, if you want your machine to advance a distance of 2 centimetres along the X-axis, the motor will need to rotate a specific amount of degrees. Thus, what are some of the ways in which you may ensure that the machine rotates by the appropriate amount in order to achieve the specified linear distance? This metric is referred to as steps per unit.
Firstly, A stepper motor has a step angle, determined by the manufacturer, that determines how far it rotates in one single step. In the case of NEMA motors, this angle is set at 1.8° and consequently requires 200 steps to make one full turn: 200 x 1.8° = 360°. This means that precision control over the motor’s rotation can be achieved by commanding each individual step.
The number of steps that a motor needs to move to shift one unit of linear motion is referred to as the ‘steps per unit’. This can be influenced by multiple elements including your motor’s specifications and the kind of transmission belt or screw you choose. Math-phones will be pleased to hear that Prusa Printers has designed a calculator which helps calculate the steps per unit upon entering important details like the specifications of all your transmission pieces. If you decide to purchase an already-made 3D printer, this step is usually skipped, however, if you prefer to go the DIY route, then it’s time to take a look at the calculator and figure it out for yourself.
Ensuring Safe Installation of Stepper Motors in Your 3D Printer
Installing stepper motors is surprisingly easy, thanks to the thoughtfully designed connectors and standardized layout used by most manufacturers. With just a few simple steps, anyone can hook up their motor to their control board in no time.
But, there are still a few things that you should keep an eye out for:
- Firstly, It’s important to always remember to power off the printer and unplug it before beginning any sort of work. Failing to do so can have some serious consequences: you risk electric shock, frying components, and in some cases, an electrical fire. Therefore, before you attempt to install something inside the printer, make sure you take all necessary safety precautions beforehand.
- secondly, Unplugging a stepper motor while it is still powered up can be dangerous and can cause irreparable damage. It is important to follow the first step of unplugging the power source before attempting to remove the stepper motor; failing to do so may lead to the frying of your stepper motor driver, or even worse – your control board.
- Third, It is critically important to make sure that stepper motor drivers are providing the correct current for the motors. You can either use the potentiometers on the board of the driver or do it directly through your printer’s software – both methods are simple and provide you with a lot of control. Too little current reduces torque and precision, while too much current can overheat your motor and cause serious damage.
- Many people give up if they encounter difficulty in getting their stepper motor to turn on, leading them to throw it away and buy a new one. But there may be an easy solution to the issue. By using a multimeter to check that the connections correctly match the wire colours, simple mistakes such as inverted or crossed wires can be corrected without much effort. If your wires are inverted, when you press left, it will turn right (and vice versa). And if they’re crossed, it won’t turn on at all as they go to different coils.
Last but not least, It’s important to pay thorough attention to the motor of your printer after installation, as there may be something clearly wrong with its operation. If so, make sure to power off the printer immediately and double-check that your wiring and driver circuit doesn’t have any errors.
Going the extra mile here is highly encouraged since it can help save you from dangerous issues such as fires, damaged components, or worse – explosions. To be completely safe and sure that everything runs smoothly, also ensure that both the driver and software are compatible with the motor. Taking all of these precautions is essential when dealing with electronics.
I am Ganesh Divte. I work as a Quality Assurance Engineer at Dhruvtara WireTech PVT LTD. I have experience in SLS, DMSL, FDM, and SLA additive manufacturing processes. I am very enthusiastic about additive manufacturing and its potential to change the way we manufacture products. I believe that Additive Manufacturing has the potential to revolutionize the manufacturing industry and make it more efficient and sustainable.