Wednesday, January 22, 2020

Torque vs Speed Characteristics of Steping Motor

The Speed-Torque graph indicates the characteristic relationship between the speed and torque when the stepping motor is driven. The torque vs speed characteristics are the key to selecting the right motor and drive method for a specific application. These characteristics are dependent upon (change with) the motor, excitation mode and type of driver or drive method. On the graph, the horizontal axis is the speed at the motor’s output shaft while the vertical axis is the torque.

Torque vs Speed Characteristics of Steping Motor


1.Maximum Holding Torque

The holding torque is the maximum holding power (torque) the stepping motor has when power (rated current) is being supplied but the motor is not rotating (with consideration given to the permissible strength of the gear when applicable).

2.Pull-in Curve
The pull-in curve defines a area refered to as the start stop region. This is the maximum frequency at which the motor can start/stop instantaneously, with a load applied, without loss of synchronism.

3.Pullout Torque Curve
Pullout torque is the maximum torque that can be output at a given speed. When selecting a motor, be sure the required torque falls within this curve.

4.Maximum Starting Frequency
This is the maximum pulse speed at which the hybrid stepping motor can start or stop instantaneously (without an acceleration or deceleration time) when the frictional load and inertial load of the stepping motor are 0. Driving the motor at greater than this pulse speed requires gradual acceleration or deceleration. This frequency drops when thereis an inertial load on the motor.

5. Maximum Slew Rate

The maximum operating frequency of the motor with no load applied.

Source:https://www.oyostepper.com/article-1110-Torque-vs-Speed-Characteristics-of-Stepper-Motor.html

Saturday, January 4, 2020

A Simple guide to identify the stepper motor you have

You’ve got your stepper motor from Ebay, the manual is in Chinese and you don’t have a clue if the motor is unipolar or bipolar.

Summarizing quickly.
If 8 wires, it will probably be unipolar 8 wires stepper motor, 4 per coil.
If 6 wires, probably unipolar, 3 for one coil and another 3 for the other. This means each coil has its own ground.
If 5 wires, probably also unipolar. 2 for one coil, 2 for the other and a common ground for both coils.
If 4 wires, probably a bipolar 4 wires stepper motor, 2 cables per coil.
I’ve also found this video which can help you differentiate the motor type you’ve got:

A Simple guide to identify the stepper motor you have

Wiring the stepper motors.
This will be a guide to connect the most common stepper motors for 3D printers. They usually mount NEMA17 with 4 wires.

Quick version.
If the motor comes with coloured wires, the typical colours are Red/Blue/Green/Black
Issues: It is not guaranteed to be like this! Who knows where the motors come from, how are they wired, etc. I’ve known many people who were not able to make them work and at the end, they realized the problem was in the wiring.

Longer version
The most common drivers which the 3D printers and home machines use are bipolar. The most known drivers for bipolar motors are pololus a4988 and DRV8825.
The motor will have 4 wires. 2 per coil, therefore what we have to figure out is which ones are the coils.

Figure out the coils
If we are going to wire a stepper motor, we have to figure out which wires belong to which coil.
We can name them coil A and coil B, or coil 1 and coil 2.
Luckily, the drivers designers decided to use both systems (/ironic)
If you read the driver’s label, the DRV8825 specifies A2 A1 B1 B2 and the A4988 specifies 1B 1A 2A 2B.
Just read it several times, and make sure you understand it is exactly the same.

Size and NEMA standard of Stepper Motor You Should Consider

Tuesday, December 31, 2019

Deciding when to use a non-captive linear actuator

Non-captive types of lead screw driven linear motor actuators are different from the more common external versions in that they allow the lead screw to completely pass through the motor. This fundamental difference offers advantages for those that have limited space available or are looking to shrink the overall size of their design package.

With an external actuator, the object being moved is mounted to the nut, and the screw rotates providing the motion along the length of the screw.
By contrast, in a non-captive actuator, the payload or object being moved is attached to the motor, and has screw ends that are typically fixed. In most cases, this setup can allow for a shorter overall screw to be used. It is also ideal for adding the external linear guide bearings that are almost always required for non-captive applications. They provide stiffness and eliminate deflection that causes premature wear on the nut, screw, and internal motor bearings.

A less common situation is where the device or payload is attached to the end of the screw. This is only used for very light loads and requires external linear guidance for stiffness. It is an arrangement that also requires clearance for the screw to extend out the opposite side of the motor.

One feature common to all non-captives is that the nut driving the screw is internal to the motor. Traditionally, this nut has been a standard nut with no mechanism to account for the play between the external threads of the screw and the internal threads of the nut. If, in this scenario, an anti-backlash capability was needed, manufacturers might be able to provide a custom solution, but with significantly higher cost and extended lead times.

To avoid this problem, PBC Linear offers the choice of a standard nut or anti-backlash nut within their non-captive linear actuators. We have the only anti-backlash nut and lead screw assembly available off-the-shelf in a non-captive configuration. This unique combination offers the best positional performance available in a non-captive hybrid actuator by utilizing our patented Constant Force Technology (CFT), which provides greater than two-times the superior backlash compensation as tested against competitors.

This advantage means that the self-lubricating nut will provide lubricant-free, consistent performance and preload over its lifetime. In addition, screws are available either uncoated or with a proprietary PTFE coating. These screws come with standard lead accuracy of 0.003 inches per foot, which is three-times better than typical screws on the market.

Non-captive linear actuators from PBC Linear go beyond the simple definition of motor and lead screw. They excel because they have been designed from the inside out, providing superior performance in linear motion applications.

With an external actuator, the object being moved is mounted to the nut, and the screw rotates providing the motion along the length of the screw.

By contrast, in a non-captive actuator, the payload or object being moved is attached to the motor, and has screw ends that are typically fixed. In most cases, this setup can allow for a shorter overall screw to be used. It is also ideal for adding the external linear guide bearings that are almost always required for non-captive applications. They provide stiffness and eliminate deflection that causes premature wear on the nut, screw, and internal motor bearings.

A less common situation is where the device or payload is attached to the end of the screw. This is only used for very light loads and requires external linear guidance for stiffness. It is an arrangement that also requires clearance for the screw to extend out the opposite side of the motor.

One feature common to all non-captives is that the nut driving the screw is internal to the motor. Traditionally, this nut has been a standard nut with no mechanism to account for the play between the external threads of the screw and the internal threads of the nut. If, in this scenario, an anti-backlash capability was needed, manufacturers might be able to provide a custom solution, but with significantly higher cost and extended lead times.

To avoid this problem, PBC Linear offers the choice of a standard nut or anti-backlash nut within their non-captive linear actuators. We have the only anti-backlash nut and lead screw assembly available off-the-shelf in a non-captive configuration. This unique combination offers the best positional performance available in a non-captive hybrid actuator by utilizing our patented Constant Force Technology (CFT), which provides greater than two-times the superior backlash compensation as tested against competitors.

This advantage means that the self-lubricating nut will provide lubricant-free, consistent performance and preload over its lifetime. In addition, screws are available either uncoated or with a proprietary PTFE coating. These screws come with standard lead accuracy of 0.003 inches per foot, which is three-times better than typical screws on the market.

Non-captive linear motor actuators from PBC Linear go beyond the simple definition of motor and lead screw. They excel because they have been designed from the inside out, providing superior performance in linear motion applications.

Source:https://blog.oyostepper.com/2019/12/31/deciding-when-to-use-a-non-captive-linear-actuator/

Friday, December 27, 2019

Stepper Actuator - Full-Step VS Half-Step

Stepper Actuator - Full-Step
In full step operation, stepper actuator motors step through the normal step angle e.g. 200 step/revolution motors take 1.8 steps stepper motor while in half step operation, 0.9 steps are taken. There are two kinds of full-step modes. Single-phase full-step excitation, where stepper actuator motors are operated with only one phase energized at-a-time. This mode should only be used where torque and speed performance are not important, e.g. where the motor is operated at a fixed speed and load conditions are well defined. Problems with resonance can prohibit operation at some speeds. This type of mode requires the least amount of power from the drive power supply of any of the excitation modes. Dual phase full-step excitation is where the stepper actuator motors are operated with two phases energized at-a-time. This mode provides good torque and speed performance with a minimum of resonance problems. Dual excitation, provides about 30 to 40 percent more torque than single excitation, but does require twice the power from the drive power supply.





Stepper Actuator - Half-Step
Stepper actuator motors have half-step excitation, alternate single and dual-phase operation resulting in steps one half the normal step size. This half-step mode provides twice the resolution. While the motor torque output varies on alternate steps, this is more than offset by the need to step through only half the angle. This mode has become a commonly used mode by Anaheim Automation because it offers almost complete freedom from resonance problems, and is cost-effective. Stepper actuator motors can be operated over a wide range of speeds and used to drive almost any load commonly encountered.


Stepper Actuator - Micro-Step
In Actuator Motors microstep mode, a stepper actuator motor's natural step angle can be divided into much smaller angles. For example, a standard 1.8 degree motor has 200 steps-per-revolution. If the motor is microstepped with a 'divide-by-10', then each microstep would move the motor 0.18 degrees and there would be 2,000 steps-per-revolution. Typically, micro-step modes range from divide-by-2 to divide-by-256 (51,200 steps per revolution for a 1.8 degree motor). The micro-steps are produced by proportioning the current in the two windings according to sine and cosine functions. This mode is only used where smoother motion or more resolution is required. Generally, the greater the divisor, the more costly the microstep driver will be. Also, some microstep drivers have a fixed divisor (least costly) while other have a selectable divisor (most costly).

HOW TO CHOOSE THE RIGHT BUILT-IN TECHNOLOGY
How are Stepper Actuators Controlled?


Saturday, December 21, 2019

What are Brushless DC Motors Used For?

Brushless DC motors typically have an efficiency of 85-90%, while brushed motors are usually only 75-80% efficient. Brushes eventually wear out, sometimes causing dangerous sparking, limiting the lifespan of a brushed motor. Brushless DC motors are quiet, lighter and have much longer lifespans. Because computers control the electrical current, brushless DC motors can achieve much more precise motion control.


Because of all these advantages, brushless DC motors are often used in modern devices where low noise and low heat are required, especially in devices that run continuously. This may include washing machines, air conditioners and other consumer electronics. They may even be the main power source for service robots, which will require very careful control of force for safety reasons.

Brushless DC motors provide several distinct advantages over other types of electric motors, which is why they’ve made their way into so many household items and may be a major factor in the growth of service robots inside and outside of the industrial sector.

If you think your application could benefit from this technology, browse a list of brushless DC motor here:
https://www.oyostepper.com/article-1105-What-are-Brushless-DC-Motors-Used-For.html

https://forum.nutsvolts.com/viewtopic.php?f=45&t=18023
http://blogs.rediff.com/myloveou/2019/12/21/some-useful-tips-of-controlling-a-bldc-motor/

The Most Common Applications of Stepper Motors

The Advantages of Stepper Motors
Not every application will benefit from a stepper motor, but in the right environment stepper motors can be ideal. First, stepper motors have full torque at standstill, and the rotation angle of the motor is proportional to the input pulse. Essentially, stepper motors offer excellent speed control, precise positioning, and repeatability of movement.

Additionally, stepper motors hybrid are highly reliable since there are no contact brushes in the motor. This minimizes mechanical failure and maximizes the operation lifespan of the motor. These motors can be used in a wide range of environments, as many different rotational speeds can be achieved because the speed is proportional to the frequency of pulse inputs.

The Most Common Applications of Stepper Motors


Applications of Stepper Motors
Stepper motors are diverse in their uses, but some of the most common include:

3D printing equipment
Textile machines
Printing presses
Gaming machines
Medical imaging machinery
Small robotics
CNC milling machines
Welding equipment
While these applications are the most common, they’re a fraction of what stepper motors can be used for. Generally speaking, any application that requires highly accurate positioning, speed control, and low speed torque can benefit from the use of stepper motors.

While servo motors have their place in industry as well as numerous advantages of their own, stepper motors are an ideal solution in many applications.

Stepper motors such as (14hs10-0404s, 17hs19-1684s-pg5)are a robust motion control technology and can be found inside of many common machines and equipment.

Brush DC Motor VS Brushless DC Motor

Friday, December 13, 2019

The difference Bettween 0.9 and 1.8 degree Step Size

On my Prusa Mendel RepRap I have Wantai stepper motors. I get them off Ebay, straight from the factory. Like something out of Home Improvement, I went a little over the top and got steppers that are a tad overpowered for 3D printing. But, I love them, they barely break a sweat or heat up even after hours of printing.

Stepper motors are a little different from most electric motors. Rather than just spin, they have the ability to ‘step’ and perform fairly accurate partial rotations. These steps make it very easy to tell your stepper motor to rotate say only 7.2°. This is really important for 3D printing, as a big element of 3D printing is just about making lots of these small, precise movements.



The super power 1.8 degree stepper motors that I run on my RepRap can make 200 steps in a single rotation, this means the smallest rotation they can possible do is 1.8°. I found some other stepper motors that can do a massive 400 steps a rotation, and got me wondering. If I upgraded my stepper motors, will I notice much of an improvement in print accuracy and quality? So I fired off a question to the now defunct Makers Stackexchange. Soon after, the awesome Adam Davis replied with the following answer.

The Answer:
The tradeoff, mechanically, between the two resolutions is typically a small decrease in torque due to the way stepper motors are designed.  You can compensate with higher currents or larger motors if needed.  You also need to double the speed of your driver to maintain the same machine speed if you go with a finer resolution stepper.  Check out and compare the motor specifications to see this effect as you move from one resolution to another in the same size motor package.

Further, current electronics packages and firmware tend to be designed for lower resolution, faster machines.  As such there are reports that you can only go up to 1/8 microstepping on the higher resolution steppers.  If you have 1/8 on the high resolution stepper, and 1/16 on the low resolution stepper, you end up with nearly the same effective resolution.

At this point in time the practical answer to the “will I get better/faster prints from a 0.9 degree stepper motor” is no.  If one costs less than the other, you might choose based on price.  If you are experimenting with high resolution, slow printing and you are writing your own controller firmware, then you might gain some benefit from the 0.9 degree steppers.

http://www.dreevoo.com/forum_post.php?idt=12483

Torque vs Speed Characteristics of Steping Motor

The Speed-Torque graph indicates the characteristic relationship between the speed and torque when the stepping motor is driven. The torq...