Discover Your Advantage!

Technical Brochure Everything You for Engineers Need to Know About Stepper Motors

Outstanding reliability: The ’s real advantage!

The reliability of stepper motors is sometimes Discover underestimated, and most people are surprised to learn that they are in fact just as reliable as the facts servomotors. This brochure introduces the true strengths and advantages of stepper motors.

CONTENTS

A motor with real benefits Discover Your Advantage! Everything you need to know about stepper motors

What is a stepper motor? Five-minute guide to the basics of stepper motors

Addressing the cost problem A case in point Is there a way to reduce costs? Discover Your Ask the expert Advantage Which offer better stopping accuracy: stepper motors or servomotors?

Pinpoint Stepper Motors Pulse signals are precisely synchronized, and position and speed positioning controlled accurately just by sending pulse signals from controller to driver. Our stepper motors’ low-speed yet high-torque, low- vibration operation makes them ideal for applications that require short-distance, short-time interval positioning.

Free brochure: Please take one Discover Your Advantage Everything You Need to Know About Stepper Motors

There are a lot of people who think servomotors outperform stepper motors – but nothing could be further from the truth. In fact, stepper motors are used in a wide range of devices, from cutting-edge equipment to everyday automatic machinery. So, why should people choose stepper motors? Instead of using technical data, we’ll explain using the perspective of actual users.

Illustrated by Yoriyuki Suzuki

New 5-phase stepper motor and Tell us why you chose a stepper motor: driver package Ease of use 34% A user survey highlighted “ease of use,” RK Series Low cost 17% “simple” structure and system configuration Our newest model combines a high-efficiency Simple 16% and “low cost” as key reasons for choosing a 5-phase stepper motor with a digitally No adjustments needed 12% stepper motor. controlled compact driver. It also has the Other 21% appealing price of 377 Euro, including cables. Based on answers from 258 respondents in a company survey (more than one answer was permitted)

Some readers may have never even seen a stepper be the motor of choice for so many applications and torque and various other characteristics that a motor motor, but they are in fact used in a wide-range of fields? Let’s find out the surprisingly little known needs to perform? Without actually using a stepper applications and fields as the drive force for systems answer to this question. motor, it’s very difficult to grasp the differences that require precise control. These range from compared to servomotors and other control motors. factory applications to semiconductors Ease of use, simple and low cost What’s more, some people may be worried that and flat-panel displays. They are also used in solar there simply isn’t enough information out there to panel manufacturing devices, medical equipment, Actual users will be quick to mention the ease of make an informed decision, and more often than analysis equipment, precision stages, devices used use, simplicity and low cost of stepper motors. This not, when it comes to control motors, “servomotor” in the financial industry, packaging and other food is no surprise considering their simple structure automatically comes to mind – especially for young processing machinery and camera diaphragm and system configuration. However, despite these engineers. adjusters. So, why do stepper motors continue to advantages, do they really possess the precision, If that’s the case for you, we want you to stop and

2 POINT Outstanding stopping POINT Ideal for mid- and 1 accuracy 2 low-speed operation

Stepper motor stopping accuracy is the equivalent of ±0.05° Stepper motors have especially high torque at when measured in the same units as a ball screw mechanism mid- and low-speeds, as the representative Usage requirements characteristic graph (below left) makes clear. For example, a product with 85 mm attachment  RK Series stepper motor dimensions running at 1000 r/min has rated torque  10 mm ball screw lead equivalent to a 400 W servomotor. At low speeds  it can generate up to more than 5 times the torque. Stopping accuracy ±1.4 μm Generating high torque at mid- and low-speed is Typical ground ball screw accuracy is ±10 μm. crucial to short distance positioning. While it is What’s more, since roller ball screw accuracy drops to only a rough guide, a simple conversion of stepper ±20 μm, it’s easy to see that stepper motor stopping accuracy motor torque output looks something like the chart is superior to ball screw mechanisms. on the right below.

How much power does a stepper motor generate equivalent ±0.05° to servomotor watts? Motor output Frame Model Price RK Series/85 mm and 400 W and size (estimate) ± 1. 4 μm RKS543 From 377 Euro 750 W servomotors 50–100 W 42 mm RKS544 From 377 Euro 8 equivalent RKS596AC- RKS545 From 383 Euro RKS599AC- - RKS564 From 415 Euro 6 RKS5913AC 100–200 W 400 W servomotor (rated torque) m] 750 W servomotor (rated torque) RKS566 From 420 Euro equivalent

N- 60 mm

e[ 4 200–400 W

u RKS569 From 424 Euro

rq equivalent

To 2 RKS596 From 465 Euro 400–750 W 85 mm RKS599 From 498 Euro 0 equivalent 0 200400 600 8001000 R KS 5913 From 533 Euro RPM[r/min] *Calculated for the RK Series 42 mm frame sizes generate output equivalent to a 50–100 W servomotor, while 85 mm frame sizes generate 400–700 Rotary table positioning Ball screw positioning W. While this will vary depending on series and model number, this is a handy benchmark when choosing a stepper motor.

When it comes to short-stroke applications, Excellent stopping accuracy, even stepper motors cannot be beat! with open-loop control. And they come at a very affordable price.

think for a moment – because if you understand the Advantages of stepper motors: (without load), and since measurement errors do advantages of using a stepper motor and apply them stopping accuracy, mid- and low- not accumulate between steps, a stepper motor sets to the operating requirements, equipment costs speed operation and adaptability positions with a high degree of accuracy. Moreover, can be significantly reduced. Let’s take a look at an the motor structure does not need an encoder, which easy-to-understand explanation of the surprisingly Coming to the conclusion that stepper motors do not makes stepper motors’ drive system simpler than other motors and helps keep its cost low. little-known advantages and technical information ensure very precise stopping accuracy is something The fact that stepper motors produce high-torque at of stepper motors. We want to completely dispel that may come to cost you. A stepper motor, in fact, mid- and low-speeds is another advantage that must any vague doubts or misconceptions you may have has outstanding stopping accuracy. This advantage is not be overlooked. Servomotors generate flat torque about stepper motors, such as whether you can thanks to an open-loop that enables precise control. from the mid- to high-speed ranges – a feature For example, the RK Series determines rotary really put them to use and how they differ from aimed at multi-rotation tables and other long-stroke servomotors. table position with stopping accuracy within ±0.05º (high-RPM) . Stepper motor torque, on

3 Great for these uses, too! POINT Excellent 3 adaptability!

The synchronized operation of multiple motors is easy to set up

Low-rigidity mechanisms

Substrate conveyor

Frequent starts and stops

Stepper motor AC servomotor RPM RPM

Time Setting time Time Variable loads

Positioning time Positioning time

(Open-loop control) (Closed-loop control) Runs in sync with operation Lags behind operation commands commands

the other hand, is not flat. The mid- and low-speed Excellent adaptability and positioning in vibration-sensitive image inspection torque curve is relatively high, while torque drops at outstanding synchronization processors, cam drives and other mechanical devices higher speeds. Besides providing stable rotation at that servomotors have difficulty controlling, and the very low speeds that servomotors have trouble The third noteworthy feature of stepper motors is mechanisms with changing loads and low rigidity such handling, stepper motors generate high-torque at the none other than its adaptability. The open-loop as belt drives. Of course, stepper motors also make it high-speeds necessary for short-stroke (low-RPM) control transmission of commands to the motor possible to greatly reduce costs by switching from a operation – ideal for angle indexing, inching and unilaterally means that commands have excellent ball screw drive to a belt drive. Most of all, since they other rotary motor tasks. followability. Since a servomotor relies on encoder don’t need to be adjusted when load, inertia or rigidity Given these features, it is interesting to consider feedback, there is a command-response lag. In change, stepper motors are great for anyone busy just where today’s servomotors stand in regard to contrast, stepper motors’ commands are synchronized trying to keep up with the day’s work. delivering high performance at the very highest to a pulse to give them excellent adaptability speeds. Since the actual positioning time for short- with almost no lag at all. For this reason, stepper Use stepper motors to their stroke operation is short, when a servomotor motors are extremely well-suited for uses such as advantages and reduce costs reaches top speed, it soon decelerates and stops. the synchronized operation of multiple motors – for example, attaching motors to two conveyors In other words, these motors don’t actually need Stepper motors have all kinds of advantages, not sandwiching a substrate and producing conveyance. to accommodate high-speed features most of the only on the cost side but on the performance side time. Moreover, when we look at actual use, they as well. For those of you who up to now have never are not usually operated at high-speed, regardless of Ideal for the following applications selected anything but servomotors out of habit, stroke. Thankfully, the recent appearance of the low- isn’t it time to think about a stepper motor? On the cost stepper motor and its superior features means To give you some idea how best to use a stepper following pages, we’ll introduce the structure and that one can expect lower costs if it is used instead motor, we’ll recommend some applications to which system basics of stepper motors and share case of a servomotor. Keeping an open mind and basing they are best suited. studies of them in action for those of you who want decisions on actual usage are important for any Despite the frequent starts and stops related to to know more about these exceptional motors. We engineers looking to get the most out of their setup. inching, stepper motors are ideal for carrying out hope you’ll keep reading.

4 Do you want to learn about stepper motors but have Five-minute guide no time? If you are one of those busy people without time to to the basics of go into the details, here is a short explanation of stepper motors. By reading this, you will become stepper motors familiar with the basics.

followability than servomotors and also produces no shaft vibration, or “hunting.” This Basic 1 Motion and structure makes stepper motors ideal for low-tension belt mechanisms. Utilizes both speed control and positioning control Stepper motor rotation moves in fixed angle units like the second hand on a clock. The motor’s internal mechanical structure enables extremely precise positioning even with Pulses sent from the pulse oscillator to the driver move the step angle according to the open-loop control. number of pulses. The basic step angle for a 5-phase motor is 0.72º and for a 2-phase motor is 1.8º. Rotation speed is determined by pulse frequency (Hz), and motor rotation Pinpoint positioning using only mechanical elements and precision can be easily adjusted simply by changing the pulse number and frequency input to the driver. A stepper motor is not just a positioning control motor – it’s a speed control Even though they effortlessly control rotation volume and speed, stepper motors motor with exceptional synchronization performance. contain no encoder or other electrical parts, giving them a truly simple structure. This also makes them sturdy and very reliable, meaning breakdowns are rare. Stopping  Stepper motor applications accuracy is typically around ±0.05º (no error accumulation) and therefore extremely - Repetitive high-frequency positioning - Variable load, variable tension precise. Positioning with open-loop control is achieved through attraction generated by of a predetermined angle - Segmenting and positioning in a loop an excited and a with a fine-toothed . This ensures better command - Positioning for long stop times aligned - Systems that require synchronized with width or other criteria operation, such as conveyance shafts

A-phase Shaft Does not use Stator Positioning accuracy B-phase 0.72˚ sensors or other Rotor ±0.05° electrical parts C-phase

0.72° 1. 4 4° D-phase ±0.05°

E-phase

precision control operations such as interpolation. This reduces the number of controllers Basic 2 Operation system (pulse oscillator, PLC positioning unit and so on) needed for operation and reduces cost.

No need for sensors or feedback makes control simple Closed-loop control incorporating a sensor is also an option

Since the system synchronizes command pulse number and speed to move and stop Open-loop systems can also position highly accurately, but they are prone to certain accurately, no sensors are required for positioning. This makes the overall system simple. problems. These problems however, can be dealt with by using an encoder or a motor A motor with the controller function installed in the driver is recommended for non- unit incorporating a sensor that performs closed-loop control( ).

Rotation volume is proportional to 5-phase 2-phase pulse number (0.72°/step) (1.8°/step) 1 pulse 0.72° 1.8°

10 pulse 7.2° 18°

Pulse signal provides simple 125 pulse 90° 225° rotation volume and speed control.

Positioning Power Power Power Driver CPU supply Pulse signal Motor Rotor position PLC unit AZ Series detection sensor

5 A case Is there a way to in point reduce costs? Every manufacturer is concerned with reducing costs, so for this project, we attempted to push this to limit. We sought to set up a ball screw mechanism with improved specifications and reduced costs. Although this is just one example, we hope it gives you an idea of our approach to solving problems and pursuit of cost reduction.

Aims For a linear motion mechanism: Increase speed and reduce cost!

1. Increase speed Servomotor 50 W 7 kg 2. Achieve real cost reductions Lead: 12 mm Original conditions for the subject device Mechanism: ball screw + servomotor with load, speed, lead, etc. criteria as shown on the right. · Maximum speed: 600 mm/sec · Stroke: 1000 mm Using a ball screw in servomotors is standard.

Proposal Change to a belt and pulley mechanism • An effective way to increase speed is to change from a ball screw to a belt mechanism A belt mechanism is capable of 1000–1500 mm/sec. If there are no positioning accuracy issues, change to a belt mechanism. • If changing to a belt mechanism is straightforward, costs will be considerably reduced Belts are cheap; however, they lack rigidity which could be an issue for servomotors’ auto-tuning function.

1. Difference between screw and belt stopping accuracy: How precise does stopping accuracy need to be? Concerns 2. Effects of low-rigidity: Negatively affects settling time, potential tuning issues.

1. Ball screw mechanism provides better stopping accuracy. Would switching to a belt mechanism be problematic? After double-checking, the intended usage does not require the ±0.05–0.1 mm precision stopping accuracy provided by a ball screw mechanism, so switching to a belt mechanism is okay. 2. Switching to belt lowers rigidity on the mechanism side, which makes the servomotor’s motion less stable. Although they are also positioning motors, stepper motors do not have an encoder, meaning they do not require adjustments – a major plus for low-rigidity mechanisms. Variable loads are not a factor, so operation is stable. If there is another option capable of the same output, research into it further.

Estimate Mechanism: belt and pulley + motor – trial using a stepper motor

Typical servomotor (50 W) + ball screw 5-phase stepper motor and driver package. RK Series + belt and pulley (1/2 deceleration) RK Series Typical servomotor €895 €424* Motor and driver package: RKS569AC-3 €30 (2 belts) Price Ball screw, guide, €150 (C10 grade screw) Price Belt, pulley, guide, etc. €100 (3 pulleys + 1 idler) €120 (guide) etc. €120 (guide) Total €1,165 Total €674

 Load capacity: permits up to 7 kg  Speed: improved to 800 mm/sec  Belt lead: 50 mm *Oriental Motor direct sale price Motor: switching from a servomotor to a stepper motor results in a 53% cost reduction! Total Mechanism: switching from ball screw to belt results in a 7% cost reduction! 42% cost reduction!

Results Potential for cost reductions Reevaluating the mechanism from the ground up and selecting a motor based on its capabilities resulted in increased motor capacity, as well as helping to achieve enhanced performance with lower costs. While ease of use and appearance were also factored into the selection, upon reflection it is better to focus on the differences between servomotor and stepper motor motion. Furthermore, in terms of price, the fact that the stepper shaft cost less than expected was a surprise. Given the result, we have to investigate if there is yet more room for cost reductions in other devices as well. This experience reminded us of the importance of taking advantage of motor characteristics and of motor selection that balances performance and cost. We will apply what we learned when selecting motors in the future.

6 Ask the expert

Which offer better stopping accuracy:

Oriental Motor stepper motors or servomotors? Customer Support Oriental Motor Sales Center employee Division employee To learn more, we spoke to Ms. Tell – a customer support center employee Ten-year Rising star with company popular for her contributions to our company info magazine “New Motion.” three years’ veteran, During our visit, she gave a lecture about stepper motors to Mr. Lerner – a young experience, Mary Tell sales division employee. Paul Lerner

Ms. Tell: What’s the matter Paul? You look troubled. fact, we have data for stepper motor and AC servomotor per rotation Mr. Lerner: A customer is looking for a motor with good stopping stopping accuracy. Let’s take a look. [See graphs at bottom of page] accuracy and he wants me to tell him the difference between a stepper Mr. Lerner: Wait a minute! Both stepper motor and AC servomotor motor and a servomotor… starting accuracy is around ±0.02º–0.03º. They’re almost the same! Ms. Tell: And what do you think, Paul? Ms. Tell: That’s right. They have the same stopping accuracy Mr. Lerner: Well, since our NX Series AC servomotors have a 20-bit performance. What’s more, since stepper motor accuracy is determined encoder, they have very fine resolution and good stopping accuracy. by the precision of the motor’s mechanical parts, if the stopping position Ms. Tell: I think we need to up on the difference between is 7.2º steps, then the motor’s structure can perform positioning with resolution and stopping accuracy. Resolution is the number of divisions the same small rotor teeth every time, which also increases stopping per revolution. For a stepper motor we call this the “step angle.” accuracy. Stopping accuracy is the difference between theoretical and actual Mr. Lerner: Looks like I was a little mistaken. A stepper motor also stopping position, so it’s completely different. has good positioning accuracy. Ms. Tell: But a stepper motor generates displacement angle with Stepper AC load torque value, while for an AC servomotor we have to pay attention Motor servomotor to increased hunting due to gain-control response under certain mechanism conditions. Max. 200,000 steps Max. 100,000 steps Mr. Lerner: I see. Resolution (Smallest Oriental Motor (Smallest Oriental Motor step angle is 0.0018º) servomotor resolution is Ms. Tell: RK 0.0036º) One more thing. Don’t forget to introduce the new Series of 5-phase stepper motor and driver package. Stopping ±0.05° Within ±1 pulse Accuracy (static angle error) (encoder resolution) Mr. Lerner: Of course. This new lineup is causing quite a stir because compared to the old RK Series, they combine high-efficiency motors Mr. Lerner: I get it! You need to know the resolution when looking that reduce power consumption costs and improve performance with a into how fine the positioning needs to be, while stopping accuracy is compact drive size and an even lower price! the stopping position error for the target position. And that means an Ms. Tell: You’ve got it! I’d say you have the potential to eventually AC servomotor with a precision encoder is the one with better stopping become an authority yourself! accuracy. Mr. Lerner: Wow! You’re usually angry with me, so this sudden Ms. Tell: Well, not exactly. The idea that servomotor accuracy equals burst of praise has really made my day! I know our customers will encoder resolution within ±1 pulse was no problem in the past, but be delighted to know that using the RK Series will bring them the servomotors these days have 20-bit (1,048,576 step) encoders and superior performance and lower cost that make stepper motors a extremely fine resolution, so encoder assembly accuracy error has a big perfect choice. I’m going to start telling our customers about this right effect. So now we think about stopping accuracy a bit differently. In away!

Stepper motor and AC servomotor stopping accuracy comparison

 Stepper motor stopping accuracy  AC servomotor stopping accuracy  Stepper motor stopping accuracy when (measured value) (measured value) positioning every 7.2º (measured value) 0.06 0.06 0.06 Actual value Actual value Actual value 0.04 within ±0.02º 0.04 within ±0.03º 0.04 within ±0.006º

0.02 0.02 0.02

0 0 0

−0.02 −0.02 −0.02 Static angle error [º] Static angle error [º] Static angle error [º]

−0.04 −0.04 −0.04

−0.06 −0.06 −0.06 0 60 120180 240300 360 0 60 120180 240300 360 0 60 120180 240300 360 Rotation angle [º] Rotation angle [º] Rotation angle [º]

7 Discover Your Advantage: Everything You Need to Know About Stepper Motors Stepper About You Know to Need Everything YourDiscover Advantage:

The New 5-Phase High performance that will change the way you think about stepper motors. What’s more, this is high performance starting at an affordable 377 Euro.

New 5-Phase Stepper Motor and Driver Package RK Series June 2016 Schiessstr. 74, 40549 Düsseldorf, Germany Published by Oriental Motor (Europa) GmbH Oriental Motor is the only choice when it comes to stepper motors

Closed-loop 2-Phase Stepper Motors 5-Phase Stepper Motors Stepper Motors with Electric Actuators Stepper Motors

Value-added pre-assembly and a wide range of standard products Easy selection and next day delivery Stepper motors make minute and precise positioning easy. Oriental Motor’s diverse Use our selection service via our website. Alternatively, stepper motor lineup includes 2-phase and 5-phase models, as well as models such you can send a fax or email to inquire and select your as using our exclusively developed closed-loop control. We also have a ideal stepper motor in as little as two hours. complete lineup of product variations, including a geared type for each model and Receive quick delivery of one or more stepper motors motors equipped with electromagnetic brakes. What’s more, we have a wide variety configured exactly to your needs. of electric actuators, including slide and cylinder stepper motors and hollow rotary actuators.

Germany Tel: 0211-52067-00 www.orientalmotor.de Customer Center (Support in German & English) Oriental Motor (Europa) GmbH UK Tel: 01256-347090 www.oriental-motor.co.uk Free Hotline 00800 22 55 66 22 [email protected] France Tel: 01 47 86 97 50 www.orientalmotor.fr www.orientalmotor.eu Italy Tel: 02-93906346 www.orientalmotor.it UK/062016/VERS01