Tuesday, December 31, 2019

When to apply external Non-Captive and Captive Step Motor Actuators

When to apply external Non-Captive and Captive Step Motor Actuators

A common way to generate precise linear motion is to use an electric motor (rotary motion) and pair it with a lead screw to generate a linear actuation system. Depending upon what this linear actuator interfaces with it can be constructed in a number of different ways.

Here we will discuss several different ways to combine a lead screw and nut with a stepper motor to create a linear actuator system. The stepper motor is frequently used in motion control as it is a cost effective technology that does not require position feedback to operate correctly.

When to apply external Non-Captive and Captive Step Motor Actuators

3 Different Styles
There are three different styles of linear actuators that are commonly used they are the external nut linear actuator style, non-captive style and captive style. There are many reasons to use a certain style of linear actuator, the three main reasons for selecting one style over another are:

Size 23 stepper motor.
Stroke What is the amount of linear travel required?

Interface Point:
How will the actuator be mounted and how will the load be attached?
Options: What other options might be required from the linear actuator?

External Linear Actuator
The simplest way to envision this combination of parts is to simply affix the lead screw onto the shaft of the motor. The nut that rides on the lead screw must be restrained from rotating so that linear motion will be generated. This type of actuator  is commonly referred to as an external linear style actuator.

Non-Captive (through screw) Linear Actuator
Another option is to locate the nut inside the motor and allow the screw to move linearly through the actuator. In this case the screw must be prevented from rotating to generate the linear motion.This style of actuator is commonly referred to as a through screw or non-captive linear actuator.

Captive Linear Actuator
In instances where the application does not have a mechanism to prevent the rotation of either the nut or the screw a third style exists. This style locates the nut inside the actuator body just like the non-captive actuator above but on the front side a linear spline is attached to the screw, this linear spline engages a front sleeve that is rigidly fixed to the actuator this prevents the rotation of the screw and provides linear output. This style of actuator is referred to as a captive style actuator.


Friday, December 27, 2019

Block Diagram of a Stepper Motor System

A stepper motor actuator is a mechanical device which produces force, as well as motion along a straight path. A stepper actuator uses the core principles of a stepper motor, with some slight modifications. With the stepper actuator, the shaft of a normal stepper motor is replaced with a precision lead screw, and the rotor is tapped to convert it to a precision nut that is adjusted to the lead screw. As the rotor rotates, the lead screw rotates up and down the precision nut, allowing for linear motion. Minimizing outside mechanical systems to convert rotary into linear motion, greatly simplifies rotary to linear applications. The stepper actuator design allows for high resolution and accuracy, while minimizing extra mechanical components.

Block Diagram of a Stepper Motor System
Block Diagram for Stepper Motor System
Figure 1: Stepper Actuator System
Physical Properties of a Stepper Actuator
The physical properties of stepper actuators are made up of the same core properties of a stepper motor, with some modifications. The shaft of a normal stepper motor is replaced with a precision lead screw and the rotor is tapped precision nut that interacts with the lead screw to allow for linear motion. The stator and rotor laminations are comprised of silicon steel which allows for a higher electrical resistivity and lower core loss. There are a variety of magnets used: ferrite plastic, ferrite sintered and Nd-Fe-B (neodymium magnet).
Figure 2: Physical components of a PM stepper actuator with a threaded shaft and a mounting plate.
Figure 2: Physical components of a PM stepper actuator with a threaded shaft and a mounting plate.
Figure 3: Illustration of the threaded shaft with the pitch and lead.

Figure 3: Illustration of the threaded shaft with the pitch and lead.

How do Stepper Actuators Work?
A stepper actuator is driven by a stepper motor driver and/or controller, which provides the instructions to manipulate the stepper actuator to start or stop. The driver and/or controller sends the proper signal pulses to the windings of the stepper actuator, causing the rotor (Economy Linear Stepper or Precision Linear Actuator) to rotate and the lead screw to extend or retract. By the use of instructions, a stepper motor controller designates how far and how fast the stepper actuator should extend or retract. A controller can be pre-programmed or controlled in real time by inputs predefined on the stepper drive or controller.

Monday, December 23, 2019

Some Knowledge on Braking Stepper Motor With Physical Principle

The brake stepping motor is mainly suitable for the vertical movement of the driver. The brake is externally connected to 12~24 VDC. When the stepping motor power and the braking torque start, there is a fixed motor shaft effect, and the stepping motor can still be locked.

There are now 57, 56, 110 series two-phase or three-phase stepping motor brakes available. A brake that electromagnetically forms an air gap is suitable for all areas where heavy objects must be moved to limit deceleration or limitation in a short time and generate braking torque even when power is supplied. Was interrupted. The braking force is generated by a compression spring or permanent magnet, and the DC24V voltage must be connected to all the brakes to form an air gap.

The integrated brake is operated by plug connection under severe environmental conditions (IP54), and the defects of fast, connected, brakeless stepper motors are widely used in semiconductor devices, bookbinding machines, packaging machinery, textile machinery, CNC machine tools, and biological Analyze light detection instruments, various workstations, optical inspection equipment, laser focusing devices, cone conveyors, and vehicle inspection equipment. At the same time, the company provides control cards, stepper motor systems, linear motors, voice coil motors, various reducers, machine vision, ultra-high temperature, low temperature, vacuum, explosion-proof motors, CAN bus controllers and other industrial automation products, to undertake various automation Project development.


Saturday, December 21, 2019

Some Knowledge of Stepper Motor Driven Linear Actuators

Actuators are devices which facilitate motion, and are fitted in components or tools which require movement. Commonly, stepper motor actuators are of the linear type, and hence the name. A stepper motor actuator produces force and motion along a linear or straight path. They share most of the properties with stepper motors, although there are some differences. A stepper motor has a shaft, while a stepper actuator has a precision lead screw and precision nut which together facilitate linear motion. They also have a stator and a rotor just like stepper motors, which in fact have improved resistivity as they are laminated with robust metal coatings such as silicon steel. The driver or controller of the stepper motor controls the movements of stepper motor linear actuators, in terms of switching on or off, speed, and rotation. The controllers translate the signals and clock pulses they receive into phase currents for stepper actuators to interpret and act.

Stepper Motor Driven Linear Actuators

Applications of Stepper Motors:
Stepper motors are used in a wide range of industries from manufacturing and security to medical and electronics. Here are some application areas of stepper motors:

Automated machine tools
Automotive gauges
Surveillance equipment such as cameras
Zooming functions in digital cameras
Medical imagers and samplers
Blood analysis machines
Dental photography equipment
Fluid pumps
Hospital beds
Stretchers and incubators

If you require actuators and stepper motors for your application, ensure you source them from a reliable manufacturer and supplier. Venture Manufacturing Co. makes superior quality and technically perfect linear actuators and more. On certain types of actuators, Venture Mfg. offer stepper motor actuators and brushless DC motors.

How to prevent this problem of extra steps on stepper motor
Application to Speed Control of Brushless DC Motor

Brush DC Motor VS Brushless DC Motor

The motor and motor control markets are thriving in a number of areas, particularly medical and robotic applications. Also, there is a rich demand for small, efficient, high- and low-torque, and high- and low-power motors in the automotive sector.
Brush DC Motors
Around since the late 1800s, dc brush motors are one of the simplest types of motors. Sans the dc supply or battery required for operation, a typical brush dc motor consists of an armature (a.k.a., rotor), a commutator, brushes, an axle, and a field magnet (Fig. 1) (see “Brushed DC Motor Fundamentals”).
Brush DC Motor VS Brushless DC Motor
Brushless DC Motors
In terms of differences, the name is a dead giveaway. BLDC motors lack brushes. But their design differences are bit more sophisticated (see “Brushless DC (BLDC) Motor Fundamentals”). A BLDC motor mounts its permanent magnets, usually four or more, around the perimeter of the rotor in a cross pattern (Fig. 3).
Brush DC Motor VS Brushless DC Motor
To Brush
When it comes to a loosely defined range of basic applications, one could use either a brush or brushless motor. And like any comparable and competing technologies, brush and brushless motors have their pros and cons。
Or Not To Brush
BLDC motors have a number of advantages over their brush brothers. For one, they’re more accurate in positioning apps, relying on Hall effect position sensors for commutation. They also require less and sometimes no maintenance due to the lack of brushes.
The Choice Lies In Our Apps
The bottom lines for making a choice between components of any type are the type of application and the cost cutoff for the end product. For instance, a toy robot targeting the six- to eight-year-old market may require four to nine motors. They can all be brush or brushless dc components or a mixture of both.
The automotive industry also puts higher-power BLDC motors to work in electric and hybrid vehicles. These motors are essentially ac synchronous motors with permanent magnet rotors. Other unique uses include electric bicycles where motors fit in the wheels or hubcaps, industrial positioning and actuation, assembly robots, and linear actuators for valve control.

Friday, December 13, 2019

How to Choose the Right Stepper Linear Actuator

Generally speaking, one of the commonly used methods to achieve precise linear positioning is to make a set of linear positioning system by pairing the motor with the sliding bar. Here we will discuss several different ways to create a linear actuator by using the sliding bar and stepper motor. The stepper motor is the most commonly used selection in the application of motor control because if the operation is correct, it is an economic solution that can achieve accurate positioning without the need of position feedback.

Stepper linear actuator can be divided into three types, external shaft type, non-captive shaft type and captive type.

External shaft stepper linear actuator
The structure directly uses lead screw as the motor shaft. The nut on the screw must limit rotation to achieve linear motion. This type of stepper linear actuator is usually called external shaft type stepper motor linear actuator.

Non-captive shaft stepper linear actuator
The nut is built in the motor, and the lead screw can pass through the motor to have linear motion. The screw rotation should be restricted to produce linear motion in the design. This type of motor is non-captive shaft stepper linear actuator.

Captive stepper linear actuator
The third type of motor can be used in some applications of mechanical devices in which nuts or screws are not available. This type of motor is the same as non-captive shaft actuator which has built-in nut. The screw shaft is connected with the spline shaft, and the spline and the spline housing at the front end of the motor coordinate with each other to prevent the rotation, thus realizing the linear motion of the stepper actuator. This type of motor is called captive stepper linear actuator.

Oyostepepr offers external shaft type and non-captive shaft type two versions of the stepper linear actuators, they come in Nema 11, Nema 14, Nema 17, Nema 23 four size.


Types of Stepper Motor You Should Know About

There are numerous stepper motor types sold, and knowing what each of the different varieties do will help you decide which sort is best suited to the application you have in mind.

Types of Stepper Motor You Should Know About

Bipolar stepper motor
A bipolar stepping motor has an onboard driver that uses an H bridge circuit to reverse the current flow through the phases. By energising the phases while alternating the polarity, all the coils can be put to work turning the motor.

In practical terms, this means that the coil windings are better utilised in a bipolar than a standard unipolar stepping motor (which only uses 50% of the wire coils at any one time), making bipolar stepper motors more powerful and efficient to run. Although bipolar stepper motors are technically more complicated to drive, they tend to come with an inbuilt driver chip that handles the bulk of the necessary instructions and behaviours.

The trade-off is that they’re usually more expensive initially than standard unipolar versions, because unipolar stepper motors don’t require the current flow to be reversed in order to perform stepping functions - this makes their internal electronics much simpler and cheaper to produce.

Hybrid stepper motor
Hybrid stepping motors allow for yet more precision, through techniques such as half-stepping and microstepping. Microstepping is a way of increasing the fixed number of steps within a motor by programming a driver to send an alternating sine/cosine waveform to the coils. Doing this often means that stepper motors can be set up to run smoother and more accurately than in a standard setup.

Hybrid stepper motors usually have poles or teeth that are offset on two different cups around the outside of the magnet rotor. This also means steps and rotations can be more precisely controlled, as well as offering quieter operation, higher torque-to-size ratios and greater output speeds than standard stepper motors.


Saturday, December 7, 2019

Some Question on Stepping Motor, Gear Reduction and Microstep Driver

I'm in the planning stages of building myself a CNC machine, like most people I want it to be accurate and reasonably fast without costing a fortune.

I intend to build most of the structural components with mostly T-Slot Aluminium, the X-A-Y axis's will move using a rack & pinion. What I've learned through Google is that, a rack & pinion setup requires geared reduction of some sort and a microstep driver to achieve a balance of smooth operation and increased torque.
Most of the DIY CNC machines I've seen are using some form of belt/pulley system for the gear reduction along with microstepping. I have my reservations with this type of setup for the following reasons:

Some Question on Stepper Motors, Gear Reduction and Microstep Driver

The belt/pulley system in the link above requires additional space, components and adds complexity to the build.
I have a hard time trusting that the belts won't stretch and miss steps.
I'm cautious off backlash, on-going maintenance and their life expectancy.
Using a microstep driver will be smoother, however less accurate.

I've done a little research on this subject and would like some opinions from more knowledgeable people in this area. Rather than use a belt/pulley system, would using a stepper motor with a planetary gearbox be a viable alternative? Below are links to some NEMA 23 motors, each with vastly different ratios.

4:1 Ratio - Gear Ratio 4:1 Planetary Gearbox High Torque Nema 23 Stepper 23HS30-2804S-PG4|23HS30-2804S-PG4|Geared Stepper Motors
47:1 Ratio - Gear Ratio 47:1 Planetary Gearbox High Torque Nema 23 Stepper 23HS30-2804S-PG47|23hs22-2804s-pg15|Geared Stepper Motors

Below is an excerpt taken from the belt/pulley page which got me thinking.

The R&P system is based on a pinion with a 1" pitch circle.
The total linear distance traveled per revolution of the pinion is thus 3.14159".
With the 3:1 reduction, this means that the distance traveled per motor revolution is 3.14159 / 3, or 1.0472".
If you have a stepper with 200 steps per revolution, this means you have 200 / 1.0472" = 190.9861 steps per inch, or 0.005236" per step.
With 10x microstepping, you would have 1909.861 steps per inch, or 0.0005236" per step.

I've broken down their calculations step-by-step:

Belt/Pulley System with 10x microstepping:

3.14159 / 3 = 1.0472 (distance traveled per motor revolution)
200 / 1.0472 = 190.9861 (steps per inch)
1.0472 / 200 = 0.005236 (per step)
190.9861 * 10 = 1909.861 (steps per inch with 10x microstepping)
0.005236 / 10 = 0.0005236 (per step with 10x microstepping)

Planetary Gearbox Stepper Motor with 4:1 gear ratio and 10x microstepping:

3.14159 / 4 = 0.7853 (distance traveled per motor revolution)
200 / 0.7853 = 254.6797 (steps per inch)
0.7853 / 200 = 0.003926 (per step)
254.6797 * 10 = 2546.797 (steps per inch with 10x microstepping)
0.003926 / 10 = 0.0003926 (per step with 10x microstepping)

Planetary Gearbox Stepper Motor with 47:1 gear ratio that produces similar steps without a microstepper driver:

3.14159 / 47 = 0.0668 (distance traveled per motor revolution)
200 / 0.0668 = 2994.0119 (steps per inch)
0.0668 / 200 = 0.000334 (per step)

Considering the two motors, the 4:1 gearbox would have to be used with a microstep driver. But would it be possible to use the higher ratio 47:1 gearbox and do without the microstep driver? Or am I missing something?


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