development of super processing center -basic concept...

Click here to load reader

Post on 18-Apr-2021

0 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • Development of Super Processing Center

    -Basic Concept and Possibility of Turn-Grinding Method-

    Daisuke Yoshii1, a *, Takeshi Nakano1, Yuki Tsukuda1

    Minoru Ota1,b, Kai Egashira1, and Keishi Yamaguchi1 1Kyoto Institute of technology, Matsugasaki, Sakyo-ku, Kyoto, Japan

    a yoshii.kit@gmail.com, b m-ota@mech.kit.ac.jp

    Keywords: processing center, prototyping, multi-functional unit, process integration, turn grinding

    Abstract. Ultra‒Agile Advanced Manufacturing System (U‒AMS) has been proposed for an agile

    prototyping system of research and development, and Super Processing Center (SPC) has been

    developing as a core machine tool of U‒AMS. In this report, basic concept and development status of SPC is described. SPC has a high accuracy, a high rigidity, various functions and

    process‒integration performance. SPC base machine has a double column structure based on a

    vertical precision machining center. Hydrostatic oil guides and hydro static/dynamic hybrid oil

    bearing were used in the base machine. A linear motor drive having 0.01 μm resolution was used for

    positioning system. Moreover, SPC has various processing functions by mounting various processing

    units such as a laser processing unit, an electrical discharge machining unit, a micro forming unit and

    a high speed spindle unit to spindle head. On the other hand, the authors devised turn‒grinding

    method to expand the versatility of SPC. In this method, a grinding wheel is set on the main spindle

    and a cylindrical workpiece is held on a horizontal rotary table. Therefore, cylindrical grinding using

    SPC will be carried out, and it is expected to integrate the processing steps of prototyping requiring

    cylindrical grinding by employing the turn‒grinding method.

    Introduction

    The Ultra-Agile Advanced Manufacturing System (U-AMS) has been proposed as an agile

    prototyping system for research and development, and a Super Processing Center (SPC) is being

    developed as a core machine tool of the U-AMS. In this report, the basic concept and development

    status of the SPC are described. In addition, a turn-grinding method which realize cylindrical grinding

    by a vertical machine tool and extends the versatility of the SPC is described. SPC realizes a

    process-integration performance of prototype requiring cylindrical grinding and has a diversity of

    processing by employing the turn-grinding method.

    Basic concept of SPC

    The base machine of the SPC is based on a precision microfabrication machine (Zµ3500, Komatsu

    NTC Co, hereinafter referred to as Zµ3500) to provide high rigidity and accuracy. The SPC has

    various functions and realizes process-integration performance by a multifunctional processing unit.

    As shown in Fig. 1, even parts such as pulleys, requiring multiple steps in their fabrication and

    machining with many different machine tools in the conventional are expected to be realized by

    ultrarapid processing by using the SPC to consolidate processes. The concept of the SPC is shown in

    Fig. 2. The basic specifications of the SPC base machine are as follows. The machine has a double

    column structure hiving a high rigidity based on a vertical precision machining center. It has control

    axes of X, Y, Z, C, which are controlled by an NC rotary table (simultaneous control of four axes) and

    an another axis. The amounts of movement along the X, Y, and Z axes are 500×700×300 mm for small parts. Hydrostatic oil guides are used in the guide surfaces. Hydrostatic/dynamic hybrid oil

    bearings, are used in the main spindle, which can perform milling, turning, and grinding. A linear

    motor drive having 0.01 µm resolution is used for the positioning system. In addition, by mounting

    multifunctional processing units that are mounted on the SPC base machine, it can realize a

    471

    Proceedings of the 20th International Symposium on Advances in Abrasive Technology 3-6 December, Okinawa, Japan

    mailto:a%20yoshii.kit@gmail.com

  • process-integration performance, a multifunctional processing, versatility, flexibility, high accuracy,

    and high rigidity. As shown in Fig. 2, the processing functional units include, for example, the small

    electric discharge machining function units, the laser machining function unit, the micro forming unit,

    and so on. The small electric discharge machining function unit is shown in Fig.3(a) and has been

    developed for processing high hardness materials, narrow holes which are 0.3 to 3 mm in diameter,

    deep holes with 500 aspect ratios. The laser machining function unit is shown in Fig.3(b) and has been

    developed for expanding uses (which are cuttings, welds, heat-treatments, and so on.) by increasing

    variations of laser oscillators. The Micro forming unit is shown in Fig.3(c) and has been developed for

    plastic processing of free form surfaces [1][2]. Furthermore, the SPC makes it possible to perform more,

    varied and high-accuracy processing by installing a high-speed truing device and a tool /

    workpiece-measuring device.

    P r o

    d u

    c t

    R a

    w M

    a te

    r ia

    l

    Ultra-Agile Manufacturing Process

    Super Processing Center

    Conventional Process

    NC Turning

    Vertical Milling

    Spline Machining

    Groove Milling

    Hard Milling

    Hard Turning

    Cylindrical Grinding

    Angular Grinding

    Ball Groove Grinding

    Heat- Treatment

    Fig. 1 Ultra-Agile Advanced Manufacturing System

    ④Ultra High-speed Spindle

    ⑤Small Electrical Discharge Machining Unit

    ⑥Laser Machining Unit

    ⑦Micro Forming Unit

    ⑧Fixed-Abrasive Finishing Unit

    ⑨Small Honing Unit

    ⑩Ultra-sonic Vibration Spindle

    High-speed Truing Equipment

    Tool and Workpiece

    Measuring Device

    ①Milling

    ②Turning

    ③Grinding

    Super Processing Center

    Scale FB Linear

    Motor Drive

    Hybrid Oil Bearing

    Main Spindle

    Universal

    Rotary Table

    Completely Oil

    Static Pressure Guide

    Multifunctional Processing UnitUltra Precision and High Rigidity Base Machine

    Fig. 2 Basic concept of Super Processing Center

    (a) Small electrical discharge

    machining unit

    (c)Micro forming unit(b) Laser machinig unit

    Fig. 3 Multifunctional processing units

    472

    Advances in Abrasive Technology XX

  • Processing experiment using Zµ3500

    A fine-cutting experiment on turning by

    Zµ3500 was performed to determine the

    microfabrication performance by the SPC base

    machine. The condition of the experiment is

    shown in the Fig. 4(a). The turning experiment

    was performed by using a monocrystal diamond

    turning tool to process V-shaped grooves on the

    outer circumferential surface of the cemented

    carbide rollers plated with electroless

    nickel-plating with a groove depth of 1 µm and a

    pitch of 4 µm. After the experiment, the groove

    shape was measured using a laser microscope

    (VK-X200, KEYENCE Co., Ltd.), the result of

    which is shown in Fig. 4(b). It can be seen that

    V-shaped grooves were formed at interval of 4

    µm. The groove depth has a submicron

    inclination, which was caused by thermal

    displacement.

    Dressing experiment for turn-grinding method

    A turn-grinding experiment was performed

    using a grinding cBN wheel (BN200L125VE4A,

    A.L.M.T. Corp.) with Zµ3500. The shape and

    dimensions of the grinding wheel are shown in

    Fig. 5. First, as shown in Fig. 6, the dressing

    experiment was performed to adjust the initial

    shape of the grinding wheel and to dress the grains of its by rotary dresser (SD#100-C125-M64,

    A.L.M.T. Corp.) with a diameter of 50 mm referring papers [3][4] about truing of small-diameter CBN

    grinding wheel. The rotary dresser was set on a table and positioned at an angle of about 45° via a jig.

    The end face of the grinding wheel was dressed the top of the rotary dresser. As shown in Fig. 6, the

    dressing was performed from an outer to an inner peripheral edge of the grinding wheel along the

    normal. Here, a single cut of 2 µm was made, the grinding wheel speed was 8,333 rpm, the dresser

    speed was 5,000 rpm, and the dressing lead was 0.015 mm/rev. Also, the shape of the grinding wheel

    became inclined as a result of one-way dressing. Then, as shown in Fig. 6, after the dressing reached

    the inner peripheral edge of the grinding wheel, the dressing was performed with reversing the feed

    direction and 2 µm cutting. By repeating this processing, the dressing was continued up to a total

    dressing amount of 32 µm which is approximately the average grain diameter of the grinding wheel.

    Micro form roller

    Roller holder

    Diamond bite

    NC rotary table Digital microscope

    Bite holder

    (a) Photograph of processing situation

    H ei

    g h t

    [µ m

    ]

    Scan length [µm]

    A A’

    (b) Laser microscope view and cross-sectional

    profile

    Fig. 4 Micro grooving with turning

View more