KAYABA TECHNICAL REVIEW No. 66 APR. 2023

aryslosGFMS
Refer to “Incorporation of Processing of Base Plates for Piston Motors into FMS Lines” (page 13)

HANAEDA Ken
Production Engineering Sect., Production Engineering Dept., Sagami Plant, HC Operations

1

What is FMS?

FMS is the acronym for “Flexible Manufacturing System” and refers to a highly flexible production systemthat can efficiently produce batches of many different
parts. The main features of FMS include systematic interfacing among parallel processing equipment and variousdevices including stockers, and efficient production of avariety of products by leveraging unattended operation.

2

used as guided vehicles.
[5] Set-up station
An area used to attach or detach workpieces. Work, after being attached or detached, is automatically transferred to equipment units for processing with a commandfrom the system PC. Unattended operation is enabled bysupplying work waiting for processing to the stocker.

Examples of Configuration

Based on an example of configuration of FMS systems(Fig. 1) manufactured by Makino Milling Machine Co.,
Ltd., the following introduces the functions:[1] System PC
A personal computer (PC) for controlling the FMSsystem. The PC is linked to individual equipment units
via communication lines. The system PC issues production commands, based on which instructions are sent toequipment units. The operator can view the operating
status of equipment units and work instructions to theset-up station, etc., on the PC screen (Fig. 2).
[2] Stocker
Several types of jig can be stored in a stocker so as toproduce many different parts that cannot share the same
jig. For a set-up change, the system PC can call the relevant jig to complete the set-up. The stocker capacity isdecided by the types of parts, the number of lots, the timezones of unattended operation, and other factors. Thestocker can house jigs with their work installed.
[3] Machining center (MC)In many cases, parallel type machining centers are introduced. The number of machining centers is decided by
the work processing time and production volume.
[4] Guided vehicle
A vehicle used to automatically transfer materials toequipment units. Stacker cranes, loaders, and robots areFig. 1 Example of FMS configuration

Fig. 2 System PC screen
Reference
1) Pallet Transfer System, MODULE MMC 2https://www.makino.co.jp/ja-jp/machine-technology/automation/pallet-system― 51 ―

Counterbalance ValvearyslosG

Counterbalance Valve
Refer to “Development of Anti-cavitation Vane for Travel Motor of 7-ton Hydraulics Excavator” (page 28)

SAITO Keiji
Editor of KAYABA Technical Review

12What are Counterbalance Valves?

Counterbalance valves are used to prevent hydraulicactuators installed in construction machinery or machine
tools from dropping with their own weight or to maintainthe descending speed of such actuators. The counterbalance valve limits the flow rate in one direction and lets
fluid flow freely in the other direction. Actuator controls
speed by generating back pressure so that is does not exceed the control speed.
Fig. 1 shows a structural drawing of a counterbalance
valve. When the inlet pressure in the valve is not morethan the pressure setting of the spring, the spool is keptpressed down. When the inlet pressure is higher than thepressure setting, the spool is pushed up to open the outlet
port, releasing oil. If it is necessary to let pressured oilflow from the outlet port side to the inlet port side, acheck valve should be installed in the circuit.
For example, the counterbalance valve can be used toprevent a vertical press machine from dropping with its
own weight. Another example of an application is a drilling machine using a cylinder where the counterbalance
valve is installed in a hydraulic circuit designed to prevent the piston rod from abruptly sticking out when theload resistance suddenly decreases upon completion of adrilling process.

Counterbalance Valves for Travel Motors

Travel motors for hydraulic excavators or other opencircuit applications are equipped with counterbalance
valves. Fig. 2 shows a circuit diagram of a travel motor.
The counterbalance valve for travel motors has the following two functions:[1] Motor braking
The counterbalance valve is combined with a relief
valve or an anti-cavitation valve to constitute a braking
circuit that can apply a braking force to the piston motor
so as to bring the motor gradually down to a stop.
[2] Overrun prevention
Where a piston motor is forced by an external load to
be rotated at a speed higher than the rpm decided by thesupply flow rate (pumping effect), the counterbalance
valve is used to control the motor speed to a level suitable for the supply flow rate.

カウンタ
Counterbalancevalve
バランスバルブP1 P2Dr

Fig. 2 H ydraulic circuit diagram ofcounterbalance valve for travel motor(relief valve type)Fig. 1 Counterbalance valve― 52 ―