Integrated stepper motors trim accurate metal forming costs

后挡料是冲压制动器上的机动多轴参考边,并使用智能步进,以降低系统复杂性,改善整体设计。

By Yosi Balbul August 5, 2022
Figure 2: STXI Motion is a global designer and supplier of motion control and servo solutions. Recently, the company’s stepIM integrated stepper motors powered by Servotronix closed-loop servo drive were specified into a new series of sheet-metal-bending press brakes from Cincinnati Inc. To reduce design costs and maintain quick and precise positioning of backgauges before each metal-forming cycle, CI chose STXI Motion’s stepIM integrated stepper motors. Courtesy: STXI Motion

Learning Objectives

  • Integrated stepper motors were designed into a series of sheet metal–bending press brakes for Cincinnati Inc.
  • The integrated stepper motors operate closed-loop and communicate via CANopen.
  • These changes led to improved press brake process improvements for Ci.
图1:辛辛那提公司提供激光切割系统、自动化、压下制动器、剪切机、输送系统、粉末金属系统和增材制造系统。在过去的100年里,这家美国公司提供了超过5万台金属制造机器。这款来自辛辛那提公司(CI)的折弯机可以弯曲金属板材。材料的边缘与CI的笛卡尔后挡板的机动边缘相接合。Courtesy: Cincinnati Inc.

图1:辛辛那提公司提供激光切割系统、自动化、压下制动器、剪切机、输送系统、粉末金属系统和增材制造系统。在过去的100年里,这家美国公司提供了超过5万台金属制造机器。这款来自辛辛那提公司(CI)的折弯机可以弯曲金属板材。材料的边缘与CI的笛卡尔后挡板的机动边缘相接合。Courtesy: Cincinnati Inc.

Integrated stepper motors were designed into a series of sheet metal–bending press brakes from Cincinnati Inc. (CI), a machine tool manufacturer.
冲压制动器有一个或多个被称为后挡片的机动边缘,作为尺寸和方向的参考。就像专业级台锯的撕裂围栏一样,工业压弯机上的后挡料可以帮助操作人员准确地将材料定位到模具上。

Material shaped by a press brake is manually or automatically pushed into and held against the backgauges. Then a press mold lowers into the material to crimp, curve or bend it. To reduce design costs and maintain quick and precise positioning of backgauges before each metal-forming cycle, CI chose integrated stepper motors.

The press brakes made by Cincinnati Inc. range from 40-ton-capacity machines for bending 20-gauge material to pairs of 2,000-ton press brakes workingin tandem to bend 4-in. metal plates. The metal pieces shaped on press brakes are found in a vast array of goods and vehicles, including:

  • Aluminum reflecting diffusers on LED light fixtures
  • Computer cases and other metal electronics enclosures
  • Restaurant kitchen equipment, including stainless-steel chicken fryers, warming stations, and work surfaces
  • Refrigerator, washer, and other large appliance bodies
  • Metal light and utility poles
  • Shipping barge bodies, farm equipment sections, and off-highway equipment buckets and grippers.

Press brake backgauges use one to six electric motors (often servomotors) to position workpieces in multiple directions. Those with six motorized reference surfaces provide two reference points in each direction of 3D space for the reliable forming of complicated parts. Most new press brakes come standard with multi-axis motorized backgauges.CIused two “motors for the backgauge vertical axis — called the R-axis on press brakes. Then we use other motors for the X- and Z-axis on the horizontal plane,” said CI electrical engineering manager Bill Molleran.

The motors are integrated stepper models with a NEMA 34 frame size and torque capabilities of 3.5 Nm.

CI switched to these steppers on the vertical axis as a cost-efficiency initiative. Previously, the vertical axis was moved by permanent magnet brush servomotors, a separate controller, and spring-set electric brakes. Getting the functions of all those components from a pair of integrated stepper motors yielded lower costs. The stepper motors include a closed-loop servo drive servo mechanism, following the speed/torque curve, and maximizing motor-drive performances.

This efficient unit is designed优化转矩/机架比,降低标准步进电机的热量和噪音水平。

The stepper motors drive ball screws for up to 8 in. of the R-axis stroke. They are part of the backgauge’s payload as they ride on the horizontal axis. Their lightweight and compact size help the design’s dynamics. In addition, accuracy is comparable to that delivered by the previous motor.

“With the stepper motor’s encoder, we gained higher resolution – though it required us to change the motor-to-screw belt ratio,” Molleran said.

More specifically, servomotors are generally low-torque, high-speed motors, and stepper motors often are high-torque, low-speed motors; thus, they have different rpm sweet spots. That meant Molleran’s team had to scrap their old design’s belt reduction by adding a big sheave on the motor output shaft and a small sheave on the ball screw, which helped increase resolution.

Figure 2: STXI Motion is a global designer and supplier of motion control and servo solutions. Recently, the company’s stepIM integrated stepper motors powered by Servotronix closed-loop servo drive were specified into a new series of sheet-metal-bending press brakes from Cincinnati Inc. To reduce design costs and maintain quick and precise positioning of backgauges before each metal-forming cycle, CI chose STXI Motion’s stepIM integrated stepper motors. Courtesy: STXI Motion

Figure 2: STXI Motion is a global designer and supplier of motion control and servo solutions. Recently, the company’s stepIM integrated stepper motors powered by Servotronix closed-loop servo drive were specified into a new series of sheet-metal-bending press brakes from Cincinnati Inc. To reduce design costs and maintain quick and precise positioning of backgauges before each metal-forming cycle, CI chose STXI Motion’s stepIM integrated stepper motors. Courtesy: STXI Motion

Stepper motor compatibility with CANopen

The integrated stepper motors operate closed-loop and communicate via CANopen. “We need CANopen connectivity for our press brakes and compatibility with the CAN CIA 402 substandard — formerly DSP402 — for motor controllers,” said Matt Garbarino, director of product marketing at CI.

“CANopen motor controller communication is common and established, and something CI has been using for a long time. Things are moving towardEtherCATand other Ethernet-based technologies, which seems to be the way of the future,” Molleran said.

该电机与CI的折弯机canopen控制器集成在一起。与现有CI折弯机控制体系结构的兼容性意味着CI工程师很少需要重新设计。一体化的格式与电子集成到电机使成本效益和紧凑的解决方案。

Integrated stepper motors require fewer parts, less wiring

Since the integrated stepper motors incorporate control electronics, CI was able to replace several different parts with one.

“We previously had to buy a brake from one company, a controller from another, and motors from a third… and then deal with all the integration,” Molleran said.

Figure 3: Traditional approaches require separate wiring for encoder, brake, controller, and motor. Integrated motors simplify power and control wiring. Commissioning software to complement motion controls, ServoStudio developed by Servotronix, satisfied CI’s engineers. Courtesy: STXI Motion

Figure 3: Traditional approaches require separate wiring for encoder, brake, controller, and motor. Integrated motors simplify power and control wiring. Commissioning software to complement motion controls, ServoStudio developed by Servotronix, satisfied CI’s engineers. Courtesy: STXI Motion

集成电机减少了机器布线,在CI的情况下,控制器位于后挡料附近,消除了长时间的电线运行。

“集成电机不需要通过home run电缆将编码器、制动器和电机相位信息来回传输到控制柜中的中央控制器,而只需要电源和CAN现场总线连接。后者适用于长距离,”Molleran说。

Molleran’s team at CI chose stepper motors rated to IP20 because sealing against environmental ingress was unnecessary.

“因为我们已经将电机安装在一个密封良好的系统中,所以我们不需要带有密封连接器的IP65版本。事实上,这种电机的接线端子比密封连接器更容易布线,也更便宜。”

48 Vdc power coming into the drive serves as a keep-alive backup to a 24 V logic supply, which, in turn, keeps the logic circuits powered to avoid any need for rehoming or resets upon any power disconnection. The motor drive includes some input/outputs (I/Os), though CI uses only one home referencing switch for this application, employing the feedback of a proximity sensor. Before using integrated motors, CI employed other I/O modules for separate brake communications and power circuitry. Now, all of that is integrated within the motor itself.

The motor also allowed for the elimination of encoder feedback. “With the previous system, we sourced the encoder separately and built it on the back of the motor,” Molleran said. “To do so required us bolting a brake to the front of the motor and wiring it all together to the controller, but now, the encoder is already in the package with the integrated motor.”

Configuration software eases setup

每个CI折弯机都配备了一个触摸屏PC控制器,运行在微软Windows 10操作系统上,作为人机界面,尽管没有任何机器逻辑在PC控制器的人机界面(HMI)上执行。相反,机器控制采用CI内部构建的电路板上的一个单独的微控制器的形式。微控制器运行实时操作系统和电机、伺服系统和液压控制。CANopenprovides connections to system motors.

Commissioning software to complement these controls was a key factor for CI.“We’ve had various degrees of success integrating different manufacturers’ CAN drivers.” Software used went in seamlessly, Molleran said. “There’s a lot of variation in how well manufacturers support the DS402 standard we employ. Complicating matters is how this standard is also flexible.”

He added, “At times, CI has had to develop custom drivers to make suppliers’ software work. But I didn’t have to make any major software changes to add the stepIM commissioning software to our system. That was another item that dropped in without headaches.”

Molleran继续说道:“除了改变配置值之外,总是会有一些问题迫使我们改变软件。It’s a highly configurable control… but manufacturers who use weird velocity units such as rpm per second for acceleration — mixing minutes and seconds, for example —嗯,这需要一些调整。”这个项目避免了这些调整。

Press brake process improvements

CI sells one to two dozen press brakes per month and has 58,000 machines in the field. The company has supplied brake presses since the 1970s and now sells all-electric machines using roller screws and hybrid servo pumps for 21st-century efficiencies. For future iterations of its press brake backgauges, CI is considering using integrated servomotors primarily to improve backgauge speed.

“Even an over-torqued servomotor only temporarily slows down… and then resumes top performance upon system correction,” Molleran said.

CI still uses separate controllers and brushed servos on its backgauges’ horizontal axis and is keen on changing them to integrated servo motors. However, cost constraints and COVID-related supply chain issues have delayed the design upgrade.

“But we’re due to get integrated servomotor samples any day now and are excited about the possibility of improving our design and trimming more costs,” Molleran said.

In addition to their compact size, integrated drive-motor solutions eliminate the need for a separate drive, minimizing footprint and connecting cables. Particularly when using multi-axis machines, the saving becomes critical in wiring and cabinet costs and size while improving the machine’s overall performance.

Figure 4: STXI Motion and Cincinnati Inc. meeting in Cincinnati, Ohio, on May 20, 2022. From left are Bill Molleran (third from left), Yosi Balbul, Barry Bartos (STXI COO, North America), Adi Kedar (STXI CEO). Courtesy: STXI Motion and Cincinnati Inc.

Figure 4: STXI Motion and Cincinnati Inc. meeting in Cincinnati, Ohio, on May 20, 2022. From left are Bill Molleran (third from left), Yosi Balbul, Barry Bartos (STXI COO, North America), Adi Kedar (STXI CEO). Courtesy: STXI Motion and Cincinnati Inc.

Yosi Balbul,general manager,STXI North America. Edited by Chris Vavra, web content manager,Control Engineering, CFE Media and Technology,

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Keywords: stepper motors, motors and drives

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Yosi Balbul
Author Bio:STXI North America