CAT system for body assembly jigs

ELSEVIER

JSAE Review 16 (199.5) 277-282

An integrated CAD/CAM/CAT

system for body assembly jigs

Satoshi Tsutsui a, Masayuki Akaishi a, Masao Goto b, Toshikazu Makino ‘, Ryuichi Ogawa ’ aMechatronics System Division, Toyota Motor Co., Ltd., Teiho 7, Teiho-cho, Toyota-shiAichi, 471 Japan b FA System Division, Toyota Motor Co., Ltd., Teiho 7, Teiho-cho, Toyota-shi Aichi, 471 Japan ’FA Development Division, Toyota Caelum Incorporated, 2-12-12, Sakae, Naka-ku, Nagoya, Aichi, 460 Japan Received S January

1995

Abstract

For manufacturing body assembly jigs, we have developed a system where all the processes, from jig design to accurate jig machining, are performed by continuous operation of CAD/CAM/CAT, and a self-adjusting jig maker which measures and machines jigs in assembled condition by a one-chucking method, and is optimised to accurate machining of jigs. This development has led to improvement in the quality of jigs and in manufacturing efficiency.

1. Introduction

2. Conventional design and manufacturing of pallet jigs

Toyota has employed a Flexible Body Line (FBL) for its vehicle-body production line, to meet the needs for production of various types of vehicles and for model change without shutdowns. The FBL comprises a generalpurpose line, a robot, and body assembly jigs (hereinafter referred to as “pallet jigs”) dedicated to each vehicle type. Figure 1 shows types and configuration of the pallet jigs. Since the FBL is intended to produce various types of vehicles, circulating pallet jigs, the line requires many kinds of pallet jigs in large numbers. Pallet jigs for the FBL must be manufactured accurately and delivered quickly for each model change. In this situation, we have long awaited a revolutionary innovation in the jig manufacturing process capable of reducing cost and lead time and improving quality. This paper describes a new jig manufacturing process using a newly developed integrated CAD/CAM/CAT system, which implements all processes from pallet jig design to accurate jig machining consecutively. We also describe a self-adjusting jig maker developed to realize the CAD/CAM/CAT system, and an application example of the system.

Figure 2 shows the conventional pallet jig design and manufacturing flow. In this flow, the corrective accuratemachining process of pallet jigs requires handwork by skilled workers. The locator surface of the locator block is adjusted manually to the shape of a plastic master model (hereinafter referred to as the “checker”) produced by NC machining in accordance with the original body data, by a process called the precision surface adjusting method. The precision surface adjusting method has the following problems: (1) Special equipment (checker, special jigs etc.) must be manufactured. (2) Handwork by skilled workers is required. With this method, therefore, it is difficult to reduce the manufacturing lead time and man/machine-hours, and to enhance body quality. The checkerless method, another conventional jig manufacturing method (see also Fig. 3), uses a large generalpurpose NC machine. In this method, the locater surface of a pallet jig assembly is NC-machined according to the original body data stored on NC data tape. Upon comple-

0389-4304/95/$09.50 0 1995 Society of Automotive SSDI 0389-4304(95)00016-X

Engineers

of Japan, Inc. and Elsevier Science B.V. All rights reserved JSAE9533532

S. Tsutsui et al. /JSAE Review 16 (1995) 277-282

278 Pallet

)iQ

for

rOOf.~O~l,u~~r

back

t Body data accwisition Pallet

jig

for

lower

back

f Jig

Pallet

iin

for

design

LH -Side

A-+

Special

c

base

Subassembly

Pallet

jig

for

under-body

Fig. 1. Types and configuration

of pallet jigs.

tion of machining, the assembly is transferred onto a large three-dimensional coordinate measuring machine where the machining accuracy of the locator surface is inspected according to the data stored on measuring data tape created separately. Defectively machined areas are corrected manually with reference to the inspection result. However, considering that the locator surface of each pallet jig must be machined lightly to assure rigidity of the jig, and that the required machining accuracy of the locator surface is about f0.2 mm, it is not cost-efficient to use the expensive large general-purpose NC machine and a three-dimensional coordinate measuring machine. Thus, it is necessary to develop a jig manufacturing system which is inexpensive and most suitable for accurate pallet jig machining. Such a system would provide the following features: (1) Data integrated for CAD/CAM and measurement. (2) Single chucking which eliminates the need for a centering operation for each machining or measurement. (3) Five-axis machining which allows optimal machining posture and conditions. (4) Machine-work or automatic correction of defectively machined surfaces.

3. CAD/CAM / CAT-integrated measuring and machining system

+ Wiring and PiPIng 4 Adjustment

Fig. 2. Pallet jig design and manufacturing

flow.

(3) eliminating the need for handwork by skilled workers in the corrective accurate machining process by employing machine-work or automatic correction. 3.2. System configuration and functions Figure 4 shows the configuration of the newly developed system. The CAD/CAM receives original body data-the data indicating the body shape, and the cross section at locator position-online from the Body Design Division, then creates design data, NC data, and three-dimensional measuring data, for pallet jigs. The CAT receives the jig shape data, NC data, and three-dimensional measuring data, online from the CAD/CAM, then gives machining and measuring instructions, analyzes the result of measurement, and gives instruction for correction.

3.1. Purpose of the system To solve the aforementioned problems of conventional pallet jig manufacturing methods, a new CAD/ CAM/CAT-integrated measuring/machining system was developed, with the aim of (1) connecting the CAD/CAM system directly with the CAT system by integrating data required for all processes from body design to pallet jig manufacturing, (2) realizing a checkerless system in which the total setting accuracy of special equipment does not influence the jig machining accuracy, and

CAD/CAM

Measurement

General-purpose General-purpose measuring machine

Manual

Fig. 3. Conventional

checkerless

method.

correction

279

S. Tsutsui et al. /JSAE Review 16 (1995) 277-282 / Body

Design

2. Drilling

l.Cutting

*CAD/CAM ~Transmissionhcept~~ of original body ?? P iia de__ian . allat _.._- ,._ --- _. ,Creation of NC machining data and 3-dimensianal measuring data

data

4. Corrective

The measuring and machining equipment carries out machining and measurement according to the instructions from the CAT, to manufacture a highly accurate pallet jig assembly. 3.2.1. System functions To realize the CAD/CAM/CAT system, we improved an integrated CAD/CAM system so that it can perform jig design, manufacturing, and testing continuously. This system provides the following functions: (1) Five-axis machining data creating function. (2) Self-adjusting machining function to automatically calculate correction data from the result of three-dimensional measurements, add the calculated data to NC data and perform corrective machining where necessary. (3) Three-dimensional measurement function (also called “space net function”) to measure the movable space range of machine, and correct the three-dimensional distortion

soace

machining

*cAI SMachining and measuring Operations =h4easurement result analysis w2onectlve machining operation ~Machine-related correction

Fig. 4. Measuring

Normal

3. Measurement

Division

and machining

5. Measurement

*Self-adjusting jig maker 6-axis machining ?? 3-dimensional measuring

system.

and error according to the master data, thus assuring machining accuracy. Figure 5 shows the concept of the space net function. 3.2.2. Self-adjusting jig maker To construct a measuring and machining system, special equipment capable of machining and measuring a pallet jig assembly by single chucking is necessary. Such special equipment is required to: (1) provide a machining and measuring range equivalent to the vehicle body size, (2) provide NC machining and three-dimensional measurement functions, (3) provide a five-axis machining function to machine pallet jigs under optimum cutting conditions, and (4) be connectable to the CAD/CAM/CAT system.

net

space

Fig. 5. Space net function.

-net

Fig. 6. Self-adjusting

jig maker.

S. Tsutsui et al./JSAE

280

Review 16 (199.5) 277-282

Locater

1. Original body data acquisition

1. Acquisition of jig design data

2. Layout of robot and weld gun

2. Creation of machining and measuring areas

Probe ,-

3. Design of locator block

3. Creation of cutter and probe paths Spindle

jig maker” as the We developed a “self-adjusting equipment satisfying the above requirements. Figure 6 shows the jig maker which is NC-machining a pallet jig.

4. Checking interference head and jig Fig. 8. Machining

and measuring

between spindle

data creation

flow.

281

S. Tsutsui et al. / JSAE Review 16 (1995) 277-282

4.

Example of application

This section gives an example of application system to the design and accurate machining pallet jigs.

of the new process of

4.1. Design of pallet jig (see Fig. 7)

e

To design a pallet jig, the CAD acquires original body data with which to establish the body shape and study locator positions, then determines the installation position and welding posture of the welding robot and designs a locator block by pefforming design and parameter editing. Next, the CAD checks interference between pallet jig and welding robot and creates parts drawings as well as machining and measuring data.

4.2. Creation 8)

of machining

and measuring

data (see Fig.

CAD design data is used as it is to create machining and measuring data. After machining and measuring areas are specified, various parameters, such as machining posture and cutting conditions, are input to automatically calculate machining and measuring data. Next, the CAD checks interference between the locator block and the spindle head of the self-adjusting jig maker operated with the calculated cutter path and probe path. The machining and measuring data are then transferred to the CAT system.

2. NC machining

‘1

-

J

3. Instruction of measuring sequence N=57

Work: Side member

4. 3dimensional

Tolerance

limit

pallet jig

measuring

. I R Color display of measuring data

L.1 -.

1 ffLs3L

5. Measuring data analysis result Fig. 9. Accurate

pallet jig machining

flow.

Dimentional of locater Machining data for

accuracy surface

according to manufacturing

Fig. 10. Transition

Dimentionel of locater master

accuracy surface

After corrective machining

of locater surface cutting accuracy.

282

S. Tsutsui et al. /JSAE

Reuiew 16 (1995) 277-282

4.3. Accurate machining of pallet jigs (see Fig. 9)

5. Conclusion

The CAT system determines the machining and measuring sequence based on the machining and measuring data received. The self-adjusting jig maker performs NC machining according to instructions from the CAT. Upon completion of machining, the jig maker makes a three-dimensional measurement using a probe. The measurement result is displayed graphically. If the measurement result indicates inaccurate machining, correction data is calculated and added to the NC data to perform corrective machining. Figure 10 shows the dimensional accuracy of the locator surface after corrective machining based on the measurement result (right graph), in comparison with that of the locator surface machined according to the master data for manufacturing (left graph).

SHmkssured

The newly developed measuring and machining system performs machining and measurment by continuous operation due to integrated CAD/CAM/CAT data, and by single chucking due to the self-adjusting jig machine, with the following results: (1) Machine-hours have been reduced by a factor of three. (2) Fluctuation of machining accuracy, which determines the jig quality, has been reduced by a factor of three or higher. (3) Lead time from design to manufacturing has been reduced by a factor of two.

products

with

??MAIN

PRODUCTS

Hydraulic Brake Air Brake Automatic Door Operator For Bus

NABCO Ltd. KOKUSAI 9-18,

.

HAMAMATUCHO

KAIGAN

I-CHOME,

PHONE: TOKYO

BLDG. MINATO-KU,

5470-2405--/FAX:

TOKYO, TOKYO

JAPAN

5470-2419