OCCASION This publication has been made available to the public on the occasion of the 50th anniversary of the United Nations Industrial Development Organisation. DISCLAIMER This document has been produced without formal United Nations editing. The designations employed and the presentation of the material in this document do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations Industrial Development Organization (UNIDO) concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries, or its economic system or degree of development. Designations such as “developed”, “industrialized” and “developing” are intended for statistical convenience and do not necessarily express a judgment about the stage reached by a particular country or area in the development process. Mention of firm names or commercial products does not constitute an endorsement by UNIDO. FAIR USE POLICY Any part of this publication may be quoted and referenced for educational and research purposes without additional permission from UNIDO. However, those who make use of quoting and referencing this publication are requested to follow the Fair Use Policy of giving due credit to UNIDO. CONTACT Please contact [email protected] for further information concerning UNIDO publications. For more information about UNIDO, please visit us at www.unido.org UNITED NATIONS INDUSTRIAL DEVELOPMENT ORGANIZATION Vienna International Centre, P.O. Box 300, 1400 Vienna, Austria Tel: (+43-1) 26026-0 · www.unido.org · [email protected] 1.25 1.4 1.6 Ми Mi и i и "г м; ,щ uim N и ,| . млн o UNITED NATIONS INDUSTRIAL DEVELOPMENT ORGANIZATION MANUAL ON JIGS FOR THE FURNITURE INDUSTRY ?.«!*. ?aa.vola. K. N or** UNITED NATIONS {0<S53 ERRATA ID/265 October 1981 New York MANUAL 08 JIGS FOR THE FURNITURE INDUSTRY Brratua Preface, last paragraph The second sentence should read It was compiled by Pekka J. Paavola, Head of the Hood Technology Departaent at the Lahti Institute of Technology, and Eaarlo Ilonen, Lecturer at the School for Seall-Scale Industry and Teachers Training at Lahti, Finland. Printed in Austria ?.81-30086-October 1981-3,200 UNITED NATIONS INDUSTRIAL DCVfcLOHiENi ORGAriiZATSCN Vienna MANUAL ON JIGS FOR THE FURNITURE INDUSTRY UNITED NATIONS New York, 1981 Preface One of the most pressing problems of the furniture industry in developing countries is to increase productivity and profitability in their move from craft to industrial-type operations. Furniture is produced at a craft level in all societies at all stages of development, irrespective of whether or not they are endowed with forest resources. The industrial production of furniture, however, calls for serial production, a rational division of labour in the factory and interchangeable components. The latter in its turn implies accurate machining, which not only requires precise machines, but also jigs. Moreover, simple jigs can greatly increase the productivity of basic woodworking machines, still common in many developing countries, and the accuracy of the components machined on them. The machines, if properly maintained, are sturdy and need not be replaced by more specialized and sophisticated pieces of equipment because of the relatively small markets of developing countries, on the one hand, and the comparatively low cost of labour, on the other. Provided the necessary know-how is available, properly working jigs can be constructed at practically no cost, thus making possible serial production and rising productivity. The object of this manual is to familiarize technical personnel of small furniture plants in developing countries with the basic requirements in the design of Jigs and give some examples of jigs for use on basic woodworking machines. It was compiled by Pekka J. Paavola, Head of the Wood Processing Industries Department at the Lahti Institute of Technology, and Kaarlo Ilonen, a teacher at the Vocational Training School in Lahti, Finland. The views and opinions expressed herein are theirs and do not necessarily reflect those of the secretariat of the United Nations Industrial Development Organization. ili CONTENTS Page INTRODUCTION 1 Chapter I. ECONOMIC ASPECTS OF JIG DESIGN ..................................... 3 Cost of jig ........................................................ 3 Minimum economic batch size .... ................................... 3 Increasing the productive capacity of the equipment installed ..... 4 Quality improvements ............................................... 4 Savings in raw-material consumption ............................... 4 Manpower skills .................................................... 4 Safety considerations .............................................. 5 II. TECHNICAL ASPECTS IN DESIGN OF JIGS ................................ 6 Design according t • a^ k'.jg drawings and prototypes ............... 6 Primary and complsrenta.• measurements ............................ 6 Position and construction of stoppers ............................. 8 Fixing elements .................................................... 9 Single and multi-purpose jigs ...................................... 11 Accuracy of jigs ................................................... 11 Jig materials ...................................................... 13 Quality and price cf jigs .......................................... 13 III. Jl". STORAGE AND IDENTIFICATION ..................................... 14 Planning of storage areas .......................................... 14 Identification of Jigs ............................................. 14 IV , EXAMPLES OF JIGS FOR USE IN MACHINING OF FURNITURE PARTS ........... 15 Jigs for use on band-saws .......................................... 15 Jigs for use on circular saws ..................................... 30 v use on surface planers ............ 33 use on thickness planers .......... 35 use on mortising machines ......... 37 use on single-SDindle boring machines 39 use on spindle moulding machines — 42 U3e on routers ......... ....... 48 OF JIGS USED IK FURNITURE ASSEMBLY . 56 fixing drawer slides .............. 56 boring and fixing hinges .......... 59 frame assembly 60 chair assembly .................... 61 v i Introduction The objective of this manual is to The use of jigs also makes it possible describe the design, construction, and to produce interchangeable parts and use of jigs for machining and assembly avoid manual adaptations in the purposes in the furniture industry. assembly. The jigs introduced in the The term jig usually means a self- following text and illustrations are of constructed appliance which facilitates basic type and therefore easy to modify production, lowers labour cost and and adapt to the particular purposes of improves product quality (figures 1 any furniture factory. and 2 ). ». igure 1 Development from craft level to industry Machining jig for spindle-moulding the edges of chair legs The development of the furniture industry in industrialized countries has beer» very fast during the past two decades. The most advanced factories now operate according to the same production principles as, for example, the metalworking industries. The present level of development has been achieved by a gradual, step-by- step process. The main development stages from the craft level to highly mechanized and automated mass pro­ duction are outlined below. Level 1 : manual or craft level; only Figure 2 hand tools; manufacture according to individual orders; no standard Assembly jig for fixing drawer products. supporting slides on cabinet side panels by nailing or stapling Level 2 : semi-mechanized level; simple machines used for rough cutting of material; finishing stages with hand tools; manufacture principally according to individual orders, eventually small batches of certain standard designs. Level 3 : mechanized level; most working stages done using basic woodworking machinery and equipment; simple jigs used in machining and assembly; manual adaptations necessary in assembly; standard models in small batches but products not system­ atically designed. 1 Level 4: advanced mechanized level; jigs in furniture production, it will nacninery consists of basic and multi­ principally deal with levels three and purpose machines using sophisticated four, which still predominate in jigs and low-cost automation in most furniture factories in both machining and assembly when applicable; developing and developed countries. systematic quality control at decisive ooints of the process makes possible the production of interchangeable Definition and importance of jigs parts; each part or component con­ sidered as a final product and the A characteristic of manual pro­ assembly as a stage where the com­ duction is to work according to pencil ponents are combined; systematic markings when making parts and in process control; no manual adaptations certain assembly fixing operations. in the assembly; standard products in The markings are usually made with large batches designed according to either a tape ruler or a plywood internal standards (standardized template for their correct location. materials, sizes, joints and working The markings are no longer necessary metnods), taking into account machinery when jigs are used, since the guiding and equipment requirements already at elements of the jigs control the the design stage. workpieces in machining and assembly. In general, all production jigs Level 5: automated