Precision Position Feedback DetectorーGeneral

Precision Position Feedback DetectorーGeneral

MP SCALE

PRECISION SCALE

Ultra Precision Position Feedback Detector

• Contact
• General
• Application
• Principle
• Features

MP SCALE is a non-physical contact, ultra-precision position detector used for detecting linear or angular position utilizing the inductive coupling principle.
The manufacture and sale of MP Scale has been started under the technical cooperation with INDUCTOSYN Co. in U.S. since 1970.

MP Scale detects the amount of movement of a machine and outputs an analog signal. This signal is converted into a digital signal by an A/D converter and fed back to the NC system.
Thus the machine can be controlled accurately by the fully closed-loop NC system based on the position feedback data from MP SCALE.

Note) Full closed-loop NC system ：The control method which detects the last position (or angle) of the machine by Scale, and return detected data to NC equipment in order to move the machine to the target position (or angle).

Linear Feedback Detector

Slider of Linear MP Scale is mounted on the movable part, and Scale is mounted on the fixed part. The position of the linear axis is detected with high precision by Linear MP Scale.

Rotary Feedback Detector

Rotor of Rotary MP Scale is mounted on the rotation shaft of the rotating axis like the rotary table or the angle head, and Stator is mounted at the fixed part. The rotation angle is detected with high precision by Rotary MP Scale.

Highly precise 5-axis machining is attained by mounting Rotary MP Scale on the rotary table of 5-axis machine.

Each axis of the machine is equipped with the MP scale.

Rotary MP Scale are mounted on B axis and C axis of 5-axis angle head, and highly precise 5-axis machining is possible.

Rotary MP Scale is used for the large-sized precision positioning table of the manufacture equipment for LCD and PDP.

The highly precise curve machining is possible by mounting Rotary MP Scale for the control of spindle speed and C axis positioning, and mounting Rotary MP Scale also for B axis positioning for the tool tilt.

Mounting Linear MP Scale in X-axis and Y-axis with few spaces is possible. This mounting is effective for the heat expansion of the ball screw.

1. 1.The induction pattern, in the rectangular form, is printed on both Slider and Scale in the Linear type and Stator and Rotor in the Rotary type MP Scale.
2. 2.When the alternating current is fed to the Slider(Stator) patter, the voltage is energized to the Scale(Rotor) pattern due to the inductive coupling action.
3. 3.The energized voltage will vary as the relative position of Scale (Rotor) and Slider (Stator) changes. The position of the machine is detected based on the variation of this voltage.

1. 1.At position A, the degree of the inductive coupling is the maximum in the positive direction as the patterns of both Slider and Scale coincide with each other.
2. 2.At position B, where Slider is shifted by 1/4 of a pitch relative to the Scale pattern, the current that that flows in the both directions of Slider cancels out the flow in Scale, thus nullifying the degree of the inductive coupling.
3. 3.At position C, where Slider is shifted by 1/2 of a pitch to the Scale pattern, the situation becomes reversed to that of position A, thus degree of the induction coupling becomes maximum in the negative direction.
4. 4.At position D, where Slider is shifted by 3/4 of a pitch relative to the Scale pattern, the situation becomes similar to that of position B, thus nullifying the degree of inductive coupling.
5. 5.At position E, where Slider is shifted by 1 pitch relative to the Scale pattern, the situation becomes same as that of position A.

Slider comprises two patterns set at 1/4 a pitch apart. This enables generation of the sine and cosine curve inductive coupling.
The extremely precise position detection is made possible without any effect of in the difference of the gap between Scale and Slider as Slider moves along the applied axis.

The guarantee accuracy of Linear MP Scale MPS-25CSC is 2 μm and the guarantee accuracy of Rotary MP Scale MPI-1272B is 2 seconds.

Note) The description of all accuracy is shown as the width of the error.

There is no effect of the ball screw expansion as Scale is mounted to the final moving element of the machine.

Due to the adoption of electromagnetic inductive detection method, the position can be detected without influence from oil contamination , dust, and condensation in the gap between Slider and Scale. Air purge is unnecessary.

Thin: Only 14-20 mm thick

Since Rotary MP Scale has the center hollow, the wiring and piping can be passed in this hollow in the case of 5-axis head.

MP SCALE will last for years without any deterioration in accuracy because of its non-physical contact design that eliminates any bearing or spring.

By combining the absolute battery-back-up encoder mounted on the feed motor, the NC system provides the method in which the encoder detects the rough absolute position and the MP Scale detects the fine position.
(Offset absolute system)

Absolute system combined motor encoder

MPRZ series detects the absolute value using an independent Scale. Highly suitable for detector of DD motor.

A/D converter can be connected to NC system built by MITSUBISHI CNC, FANUC, SIEMENS, and AC servo BY MITSUBISHI, and YASKAWA ΣV & Σ7. SSI communication is applicable as general code for serial interface.

Eccentricity often occurs according to the shaft movement by the difference in the rotation direction or the eccentric work road. With MP SCALE, eccentricity does not cause big detecting error and high repeatability is acquired.

Since conventional other scale has one detecting head, the detecting error is in proportion to the quantity of eccentricity, and the repeatability is bad.
As conventional countermeasure to this eccentricity on scale, two detecting heads are mounted into he opposite position and the detecting error is canceled by two heads.
On MP Scale, by arranging many detecting patterns all over the circumference, the error by the eccentricity is canceled and the high repeatability is acquired.

Example) Even if machined at 17℃, directed dimension is realizable at 20℃.