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Oriental Motor
Technical Article

Features of the EZS II Series Motorized Linear Slides

Kenji SATO

1. Introduction
Motorized linear slides are used mainly for carrying loads in industrial manufacturing facilities. As the purpose of the facilities advance, the machinery in them becomes more complicated. Construction time also decreases therefore decreasing the time allowed to prepare the production lines. This makes it necessary for the components used on the production lines to be reduced in size, delivered quickly, and easy to use.

Oriental Motor released the EZS Series motorized linear slides in October, 2001 and the EZHS Series high speed type in November, 2002. Various requests for changes to the products were requested as follows by the sales activities over the last several years.

  • Shortening the total length in relation to the movable stroke
  • Avoidance of interference of motor and load
  • Enhancement of stroke length options, operating speeds, input power supply, higher payloads, etc.
  • Ability to use the actuators of other series with the same controller
  • Compliance with the RoHS Directive

With this paper, we will introduce the features of EZS II Series (Refer to Fig. 1 and Table 1) which was developed in response to the customers’ requests.

Figure 1

Fig. 1 EZS II Series

Model
Slide: (W) x (H)
Lead (mm)
Convey. mass (kg)
Max speed (mm/s)
Horizontal
Vertical
EZS3D
54mm x 50mm
12
~7.5
~3.5
370 ~ 800
EZS3E
6
~15
~7
180 ~ 400
EZS4D
74mm x 50mm
12
~15
~7
400 ~ 800
EZS4E
6
~30
~14
200 ~ 400
EZS6D
74mm x 66.5mm
12
~30
~15
360 ~ 800
EZS6E
6
~60
~30
180 ~ 400

Table 1 - Specifications of EZS II Series

2. Structure

2.1. Structure of the slide
The EZS II Series is a motorized linear slide that combines the Closed Loop stepper motor αSTEP and rolled ball screw. As shown in the component drawing in Fig. 2, the table coupled with the ball screw nut is guided by an LM series guide from THK, and operates as linear motion. The guide rail of the LM guide is built into the frame work and acts as part of the frame base. In addition, a simple dust-proof structure in which a stainless sheet covers the side cover opening for the table to create linear motion.

Figure 2

Fig. 2 Component drawing of EZS II Series

2.2. Shortening total length of structure to movable stroke
To achieve a shorter overall length in relation to the movable stroke, the structure was redesigned; specifically the sheet holder structure on the table, and the installation method for the motor wires in the motor cover.

 2.2.1. Sheet holder structure of the table
The EZS II Series structure is covered by a simple dust proof stainless sheet. The stainless sheet is flexed at the four fulcrums of the sheet holder made of a sliding resin material in the table as shown in Fig. 3. Fulcrum 2 and fulcrum 3 are located in the table to maintain the proper flexing angle. This made the sheet holder more compact, and the total length shorter.

The new sheet holder structure was also analyzed to ensure that table rigidity was not decreased and the stress was not concentrated.

 

Figure 3

Fig. 3 Sheet holder structure of EZS II Series

The sheet holder structure of the earlier EZS Series is the same in basic principle. However, the sheet holder was longer, and the total overall length to the stroke was longer (Refer to Fig. 4) because fulcrums 2 and 3 were located outside of the table to maintain the proper flexing angle.

Figure 4

Fig. 4 Sheet holder structure of EZHS Series

2.2.2. Installation of motor wires
The wire installation of the motor for the EZS II and the EZHS Series under the motor cover is shown in Figs. 5 and 6. The EZS II Series was able to shorten the total length of the slide compared with the structure of the conventional EZHS Series by using the two small connectors, and eliminating the connections through the motor cover to minimize the length as shown Fig. 7.

Figure 5

Fig. 5 Wire installation of motor wires of EZS II Series

Figure 6

Fig. 6 Wire installation of motor wires of EZHS Series

Figure 7

Fig. 7 Structure inside end plate of EZS II Series

In addition, the EZS II Series structure was shortened by allowing the cable to exit the motor cover directly from the cutout part of the end plate while the EZHS Series had a cable exit structure from the rear side of the end plate as shown in Fig. 8.

Figure 8

Fig. 8 Cable exit structures

2.2.3. Total length of slide
The total length was shortened by changing the slide structure. Fig. 9 shows a comparison of the EZS4 without a electromagnetic brake and a stroke of 50mm with the EZHS Series of the same specifications.

Figure 9

Fig. 9 Comparing EZS II and EZHS Series in total length

As a result, for other model numbers and the types with an electromagnetic brake, shortening the total length by the following values could be achieved compared with the EZHS Series of the same model number.

  • EZS3 No electromagnetic brake: Shortened by 81mm
  • EZS3 With electromagnetic brake: Shortened by 76mm
  • EZS4 No electromagnetic brake: Shortened by 134mm
  • EZS4 With electromagnetic brake: Shortened by 129mm
  • EZS6 No electromagnetic brake: Shortened by 121mm
  • EZS6 With electromagnetic brake: Shortened by 115.5mm

2.3. Ensuring that the load on the table does not interfere with the slide
When the motor section is higher than the load table mounting area, a large load may interfere with the motor section. The EZS II Series has decreased the height of motor section by redesigning the motor mounting under the motor cover, and redirecting the lead wires to minimize the height. This has achieved a structure in which no interference with the slide occurs even if a load larger than the table is mounted.

Figure 10

Fig. 10 Comparison of loading condition of EZS II Series and EZHS Series

3. Features

3.1. Features of slide

3.1.1. Extension of maintenance interval
To reduce the maintenance frequency, the EZS II Series has adopted the use of a ball screw with the lubricating device, QZ, and the LM guide from THK Ltd. with a ball retainer for the mechanism.

The lubricating device QZ supplies appropriate doses of the lubricant to the ball rolling contact surface of the ball thread axis. An oil film is always formed between the ball and the ball rolling contact surface, this makes it possible to extend the interval between grease maintenances.

The LM guide with the ball retainer is a structure where the balls circulate while maintaining an equal spacing with a holder called a ball retainer. The ball retainer runs between the balls and that eliminates the mutual friction of the balls. The grease collected in the grease pocket of the ball retainer is applied to the balls evenly, reducing the grease consumed by the LM guide.

3.1.2. Installation and feeding accuracy
The EZS II Series has a structure where the support parts of the ball screw are coupled onto the guide rail of the LM guide, and the guide rail is part of the slide’s frame. This attachment makes best use of the feeding accuracy which the LM guide was designed for. Positioning pin holes have been added to the table for accurately attaching the load, and an attachment datum surface on the guide rail side to attach the slide body has also been added as shown in Fig. 11. By using them, the repeatability of load and slide attachment can be maintained.

Pin hole machining on the load side can be easily done because one of the two pin holes prepared on the slide table is an elongated hole.

Figure 11

Fig. 11 Installation of EZS II Series

3.2. Features of the controller
The newly developed controller for the EZS II Series was designed to be able to also drive other Oriental Motor electric actuators (SPF II, SPV, SPR II, and PWA II Series), shown in Fig. 18.

3.2.1. Input power-supply voltage specification
DC24V, single phase AC100/115V and AC200/230V power supply specifications are available. The interface and the functions are the same for all of the controllers, regardless if they are a DC or AC power supply specification (Refer to Fig. 12).

Figure 12

Fig. 12 Front view of controllers for each power supply voltage specification

3.2.2. Introduction of controller key
For each electric actuator (Refer to Fig. 18) of the EZ II Series, the motor, the lead (amount of linear motion per rotation of motor), and the stroke, etc. are different depending on the model. It is necessary to store these actuator parameters in the controller to operate the actuator. The EZ II Series has adopted a method in which the actuator information is downloaded into the controller by attaching a storage medium (controller key) that has all of the actuator parameters stored on it as shown Fig. 13. This makes it possible to use a common controller (the controllers are different only in input power-supply voltage specification.) among each model.

Figure 13

Fig. 13 Attachment of controller key

3.2.3. Low vibration, low noise, and energy-saving operation
The EZS II Series uses a control method that was developed from the performance of the Closed Loop stepper motor αSTEP, with enhancements for use with actuators.

These enhancements achieve low vibration and low noise operation at low speed by using a patented control method via software. In addition, energy-saving operation can be achieved by the current control in response to the actual load.

3.3. Other features

3.3.1. Motor cable that can pass through flexible conduit
A small connector was used for the motor cable connectors. The actuator is wired by dividing the power line and the signal line into two small connectors, which can pass through a duct like a flexible conduit with an inside diameter of Φ16.5mm, while being able to change the lead length, or adding a cable ground. Wiring through a duct can be realized with one cable between the slide and the controller without cutting the motor cable in the middle (Refer to Figs. 14 and 15).

Figure 14

Fig. 14 Flexible conduit and motor cable

Figure 15

Fig. 15 Connection with controller with one motor cable

3.3.2. Installation of sensor set
Return to home operation of the EZS II Series is based on a sensorless return to home routine that detects the end of travel of the mechanism, reverses a certain amount of travel, and then assumes that point to be the home position.

Though a sensorless return to home operation is the basic function, a sensor set is also available for when it is desired to use a return to home operation that uses a dedicated home sensor, and end of travel limit sensors. As shown in Fig. 16, the sensor can be installed into fixed positions using the slot on the side of the slide, and the flag can be attached directly to the table.

Figure 16

Fig. 16 Installation diagram for sensor set

3.3.3. Combination of 2 axes
As shown in Fig. 17, two single axis slides can be combined in either an "X-Y" or "X-Z" configuration by using the two axis attachment bracket. The "X-Y" configuration is suitable for palletizing and pick-and-place uses, and the "X-Z" is suitable for vertical applications.

Figure 17

Fig. 17 Diagram of two-axis combinations

3.3.4. CE Marking
The CE Marking is applied for the DC24V power supply specification based on the EMC Directive, and single phase AC100/115V and AC200/230V power supply specifications based on Low Voltage Directive and the EMC Directive. As for the EZS II  series, it is not necessary to comply with the Machinery Directive because it is designed and manufactured as a built-in type for the general industrial equipment; however the EZS II series has also been evaluated based on the Machinery Directive as built-in parts.

3.4. Network control
It is possible for each of the EZ II Series actuators to be combined with the standard αSTEP AS Series or network version drivers since the Closed Loop stepping motor αSTEP system is used. When using a network type driver, an AS driver conversion cable is needed in addition to the motor cable. Even if the αSTEP AS Series motor and actuators are used in combination in customer's machine, they can be controlled in similar methods. Network drivers are available for DeviceNet, CC-Link, MECHATROLINK and SSCNET II type networks.

4. Summary
The EZS II Series was developed as the 2nd generation electric slide actuator by taking the customers’ requests as input for its specification. Furthermore, the ease of use and the ease of choice were emphasized, and a framework was laid out that can provide products with a stroke length available in increments of 10mm with a short lead time. The appropriate slide that matches to the customer's needs can be selected.

We intend for the EZ II product group to be useful for the customers that focus on downsizing, short lead time delivery, and ease of use from an electric actuator.

The EZ II product group will continue to be advanced and the variations will continue to expand in the future. Product development that focuses on the ease of use for the electric actuators will also continue.

In Fig. 18, each series of the EZ II product group, including the EZS II Series, are shown.

Figure 18

Fig. 18 EZ II Electric actuator series

Technical reference
(1) Hironobu Otomo: “The features and functions of AZX Series Electric slides”  RENGA No. 166 P16-22 (2006)

Kenji Sato

Kenji Sato
Linear System Company
Technical Division, Development Section

 

 


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