Robot-style handling and positioning performance at a fraction of the cost

08 February 2011

A compact, integrated motion control subsystem for automation applications has been introduced by Festo, to offer machine builders a flexible way of providing programmable rotary and linear movement. Said to be suitable for parts handling and positioning applications, the EHMB module incorporates an interesting decoupled design which enables the rotary and lifting movements to be controlled completely independently, enabling fast and accurate positioning.

The subsystem is capable of performing similar types of loading and unloading movements as many industrial SCARA robots, with comparable performance, but at less than half the cost, says the company.

Users may also tailor the price/performance of the motion subsystem by choosing to use a motor and electrical actuator for the two axes, or a motor and pneumatic cylinder. Festo's modular EHMB design can be configured with a range of the company's positioning cylinders, motors and controllers.

The rotary axis is always actuated electrically using a stepper or servo motor, whereas the lifting axis can employ a Festo DNCE electric or DNC pneumatic cylinder, depending on the user's performance requirements and technology preferences.

A typical low-cost configuration would comprise a stepper-driven rotary axis and a standard DNC pneumatic cylinder to provide simple high accuracy linear movement between two positions. A more demanding application, requiring freely programmable linear positioning, could use suitable Festo servo motors and controllers for both axes - the linear axis being driven by a DNCE electric cylinder. This all-electric approach facilitates implementation of complex rotary/linear movement, with the significant advantage that machine productivity improvement, and even retooling, can be accomplished under software control alone.

Festo offers a choice of two EHMB modules, to simplify application matching. The smaller size 20 model can accommodate payloads of up to 3kg, generate more than 3 Nm of torque and handle moments of inertia as high as 30kg/cm/cm. It is ideal for providing the integral Z movement in portal and Cartesian parts handling systems. The larger size 25 model is more suited to stationary use, such as in loading, unloading and stacking applications. Capable of accommodating payloads as high as 5kg, it can generate 8.8Nm of torque and handle moments of inertia of up to 100 kg/cm/cm. Both modules offer a choice of 100 mm and 200mm stroke lengths, and are capable of generating up to 480 N of lifting force.

Festo's EHMB modules offer fast and accurate lifting and rotating capabilities. Depending on the choice of motors and cylinder, both models are able to handle linear speeds as high as 500mm/sex with ±0.1mm repeatability, and rotational speeds of up to 300 rpm with a repeatability of ±0.05 degrees - a 1kg load, for example, can be rotated through 180 degrees in 250ms.

Several factors make the EHMB easy to install. The lifting shaft is hollow - the size 20 module has an internal shaft diameter of 14mm, while that of the larger module is 21mm - which provides space for routing compressed air tubes and electrical cables up to the platen for controlling attachments such as gripper units. All mounting interfaces are compatible with Festo's existing range of pneumatic grippers. Furthermore, the linear axis can be mounted on any of three sides of the EHMB module, to suit the layout of the machine.

Festo produces several accessories for the EHMB module. These include an adjustable end-stop for the lifting shaft, for use with pneumatic cylinders, a support bush for flexible tubes and cables, and a shaft cover kit. An axial motor mounting kit is also available for modules that employ an electrical linear axis.

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