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Considerations when Switching from Air Cylinders

Air Cylinder and ROBO Cylinder

Air cylinders are devices used to push and grasp objects by means of supplying and releasing compressed air. Air cylinders are used widely in all industries, mainly for transfer equipment, assembly systems, various automation systems, etc.
Air cylinders generally have diameters between 4mm and 320mm, and their lengths (strokes) can also be set in fine steps. There are hundreds of thousands of different air cylinder products, which makes it easy to select optimal models for a variety of applications. However, since product lines are overly complex, many with identical specs, it can be difficult to select the best model for your specifications.

For this reason, there are many cases where air cylinders are selected largely out of past experience and familiarity.
ROBO Cylinders are easy-to-use electric cylinders offering a variety of functions not achievable with air cylinders. The ROBO Cylinder product family makes it easy for you to select the model that best suits the needs of your application. However, the controls and configuration possibilities of ROBO Cylinders are completely different from air cylinders.
This section explains some of the key points to consider when switching from air cylinders to ROBO Cylinders.

Overview of Switching

The following explains the differences in the basic items to be checked when selecting ROBO Cylinders and air cylinders.
Since both are linear motion actuators, there are some common matters that must be taken into consideration. However, the different configurations and controls described below result in different designations for adjustments and mechanical specifications between the two. A comparison of these various items is shown at right.

Installation space

ROBO Cylinders are driven by a motor. Compared with air cylinders, ROBO Cylinders are larger, so it is necessary to pay attention to the installation space.

Home Return

Unlike air cylinders, ROBO Cylinder operation is based on the concept of coordinates. It is necessary to have a set home position at the beginning of operation, because operations are controlled in movement quantities which reference that home position.

In the case of incremental encoders, homing occurs by traveling to the hard stop and needs to be performed when the power is turned ON.

Critical Rotating Speed

The ballscrew will always deflect due to bending and its own weight. In order to run the ROBO Cylinders at high speeds, the ballscrew must rotate at high speeds. As the speed increases, the amount of deflection also increases, which may ultimately cause damage to the rotating axis. These speeds that create a dangerous state in which the rotating axis is damaged are called “critical speeds”, ”whirling speeds”, or “whipping speeds”.
Ballscrew type ROBO Cylinders operate linearly by rotating the ballscrew while the ballscrew end is supported by a bearing. Although the maximum speed for each ROBO Cylinder is set by actuator type, some strokes for certain models have their maximum speed limited by the effect of the critical rotating speed, so please be careful when making a selection.

General Purpose (Type, Mode, Parameter)

There are “air-cylinder type” (or air cylinder mode) ROBO Cylinders that can be used like air cylinders.
When using these, it is possible to operate the actuator by controlling it with ON/OFF external signals, just like air cylinders. This type and mode should be sufficient for simply substituting out an air cylinder. For customers who desire a high value-added usage, various types and parameters have been released. When actually constructing the equipment, we will introduce the functions that meet the needs and usage conditions of customers, so please feel free to contact our customer service.
Please contact IAI for more information.

Maintenance

This section compares the main maintenance points of air cylinders and ROBO Cylinders.
The air cylinders require periodic maintenance depending on the usage frequency and conditions. Although they are flexible since it is possible to temporarily operate cylinders that have minor damages and malfunctions by significantly increasing the air pressure, they cannot be used for very long if maintenance is neglected.
On the other hand, when compared to air cylinders, ROBO Cylinders tend to be seen as requiring troublesome maintenance, due to its structure and number of parts. In actuality, however, they are clearly easier to handle than air cylinders, and they have a long life. Of course, both the ROBO Cylinders and air cylinders require lubrication of the sliding parts.

However, the sliding parts of the ballscrews and guides have lubrication units (AQ seal) equipped on them. This makes it possible to have long-term maintenance free periods of 5,000km travel or 3 years. After traveling 5,000km or 3 years, the product life can be prolonged significantly by greasing it every 6 months to a year as described in the instruction manual.
In addition, regarding the controllers, the absolute types are equipped with a position retention battery. This is a consumable product, so periodic replacements are needed (time varies by product).

Operation

Air cylinders are generally operated with the use of a direction control valve to determine the direction of reciprocating motion, as well as a flow control valve (speed controller) to determine the speed. After their system is started up, many users operate the air cylinder at low speed by restricting the flow control valve.

The same procedure is also recommended for ROBO Cylinders after the system is started up. With ROBO Cylinders, “speed setting” replaces the flow control valve, and it is recommended that operation is performed at a slower speed to ensure safety, and then changing to a desired speed after confirming safety.

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