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Journal of Materials Processing Technology 139 2003 212 218 Computerised price quoting system for injection mould manufacture S F Chana C K Lawb K K Chanc a School of Science and Technology The Open University of Hong Kong Hong Kong PR China b Hasbro Far East Ltd Hong Kong PR China c Department of Manufacturing Engineering Hong Kong Institute of Vocational Education Chai Wan Hong Kong PR China Abstract The budget for making injection moulds is inevitably the major development expense that needs to be well prepared and controlled in the toys industry This is especially important for making hard toys such as Action Figure Toys which accounted for 27 7 growth as in September 1999 in the total toys industry The current major practice in the toys industry for quoting prices for manufacturing an injection mould is either by experience or by comparison with a similar product Owing to the complexity of mould construction and the increasing variety of toys the application of some commercially available computerised package for estimating the cost of manufacturing injection moulds is inaccurate impractical or slow This consequently leads to an underestimated quote which will also become a disaster to the mould manufacturers in terms of manpower planning delivery schedule and profi ts In order to overcome these practical situations and to meet the keen market competition a user friendly more accurate mould cost calculation and quotation system should be introduced This paper focuses on introducing a computerised quotation system for injection mouldmanufacture CQSIM codedinVisualBasic Thiscanbeperformedonapersonalcomputer PC Thesystemistypicallyusefulfor thetoysindustryarea butitcanalsobeappliedinplasticsrelatedindustry Baseduponadatabaseofcostingelements anintegratedsystem isestablishedforthepurposeofstreamliningtheprocessofmouldcostquoting Apartfromimprovingtheaccuracyandeffi ciencyofmould quoting the system is focussed upon robustness such as being easy to learn use and update The system was designed to be expandable and to be integrated with other material planning systems such as engineering resource planning ERP or systems applications and products in data processing SAP 2003 Published by Elsevier Science B V Keywords Mould making processes Injection mould cost Machining time ERP SAP 1 Introduction Toys design and development usually involves expenses on development cost and tooling cost Tooling cost in the industry relates to the mould cost in a specifi c production process such as injection moulding rotational moulding blow moulding and other toys production processes It is widely recognised in the toys industry that the budget for making injection moulds is the largest expense that needs to be well prepared and controlled Hard toys are usually made of engineering plastics such as ABS HIPS PVC or PP as the major parts Investment in injection mould tooling is important in the hard toys cat egory for which they are frequently used Hard toys are playing an important role in the total toys market There are many well known hard toys in the market such as Action Corresponding author E mail address mfgkkc vtc edu hk K K Chan Figure Toys which accounted for 27 7 annual growth as in September 1999 in the total toys industry 1 Mould makers and toys professionals in Hong Kong are showingmoreinterestinadvancedmouldmakingtechniques in the market such as computer aided design and computer aided manufacturing CAD and CAM software develop ment Manufacturers may have some diffi culties in fi nding commercialsoftwareforinjectionmouldcostestimationthat really suits their immediate use Some existing software in the market has many restrictions in data entry For this soft ware machining process selection and mould structure se lection are very limited and good knowledge in the structure ofaninjectionmouldanditsfabricationprocessesisrequired for cost estimators Even if it is easy to use users require a long time to grasp and to modify the values of the diffi culty levels of machining methods for a precise cost estimation They are time consuming for learning not user friendly and the mould cost estimate is not accurate if users do not well understandthemeaningsforindividualinput Owingtothese 0924 0136 03 see front matter 2003 Published by Elsevier Science B V doi 10 1016 S0924 0136 03 00222 X S F Chan et al Journal of Materials Processing Technology 139 2003 212 218213 factors the current major practice in the industry for quoting the price of an injection mould is still for it to be made by ex perience or by making comparison to similar toys products An empirical cost estimation method is generally used which is regarded as a faster and a more user friendly method This cost estimation approach agreed quite closely with Menges and Mohren 2 that the respective mould costs are often not computed at all but estimated based on experience or in comparison with moulds made in the past Moreover the fact that the number of order is only 5 of the number of quotations is also affecting the amount of time allowed for a proper quotation However the empirical cost estimation method requires mould makers to memorise the detailed mould construction steps and tool materials Occasionally when they forget some mould construction details underestimates may oc cur which will affect the mould cost signifi cantly Another problem is the imprecise estimation of material cost which could be a main cost element for mould making in Mainland China because the labour cost will be comparatively lower It is hard to remember all the prices for standard compo nents without reference to handbooks Without calculating the components volume and density it is diffi cult to know the weight of raw materials Finally it is hard to estimate the cost for a certain mould fabrication process Hence the estimated cost by the empirical method is quite inconsistent Theoretically cost estimators who calculate mould cost manually to a very subtle detail may be able to obtain a pre cise and consistent result However it would be extremely time consuming and impractical A software package can quickly compute the material cost and machining time di rectly from its database with known data of the product A good software package can also improve the manufac turer s management By providing machining data time frame and actual fabrication data for reference two things can be improved Firstly the effi ciency of the shop fl oor or designdepartmentcanbeknownandhencecanbeimproved Secondly the accuracy of quotation can be improved when it does not match with the actual production model This paper will discuss upon a prototype system developed to provide a more reliable and consistent method for quotation and better documentation and will discuss the performance of the prototype system 2 Design consideration for computerised quotation system for injection mould manufacture CQSIM User friendly low cost and accuracy are the basic requirement for a good CQSIM Ease of updating for basic cost elements such as labour cost material cost and cutting data should also be considered This is important for main taining the accuracy of the calculated results Further for a complicated mould many data will need to be input for cost estimation Too much data for input will be an obstacle to the users due to time consumption and the complicated procedure It is best that data input can be limited to the ac tual size of inserts machining method required work size quantity special requirement e g subcontract and other necessaryinformation e g nameoftheclient forthemould Suitable sizes of standard raw materials for various given insert sizes should also be considered The fi nal size should be large enough for preparation works such as roughing From the volume and density of the part and the unit price in the predefi ned database its cost can be calculated The choice of machining methods should be as free as possible This is because different mould making processes can achieve the same product shape and fi nish The choice of methods and cutting tools may be constrained by the facility of a manufacturer and the skill of the mould maker All common machining methods such as milling and CNC milling must be provided for the user The machining details set for a chosen process should match with actual machining conditions as far as possible Basic activities can be found as primitives to calculate the lead time for a component in such complex conditions Ac tivities that can be classifi ed as primitives include set up and detaching time drawing study time before machining roughing time semi fi nishing time fi nishing time machine cleaning time to reduce error measuring time deburring time Once the time of these primitives for individual ma chines is defi ned they can be combined to form a synthetic data table 3 In particular the capacity of a cutting tool would vary from different types of cutting and materials For example rough cutting or hard materials yield a shorter depth of cut than do fi nish cutting or a soft material Moreover the depth to be cut for an insert may not be the same as the maximum depth of cut capacity of the cutter That is the needed depth of cut may be shorter than the maximum capacity of the cutter or much deeper than the maximum capacity of the cutter For the same type of machines by adding up these set up times to the machining time to fi nish the task the time to fi nish a component can be found Some machining tools are required for machining pro cesses in mould making For example electrodes for elec trical discharge machining EDM and press tools and or casting models for beryllium copper BeCu moulds The raw material size and cost for each electrode or model should be calculated automatically Of course it would be best for the machining method and quantity to be decided automatically to reduce the amount of data input As regards mould structure some structures should be considered and predefi ned For example a suitable quantity with a suitable size of screws can be assigned to an insert of a certain size Another example a wedge and its fi xing screws angle pins stopping mechanism and springs should be assigned to a slide In this way addition material cost and the machining time for these assumed components can be calculated Generally a mould can be made roughly through the procedures is shown in Fig 1 214S F Chan et al Journal of Materials Processing Technology 139 2003 212 218 Fig 1 The fl ow of a general mould making procedure Combining these mould making procedures and the ma chining method chosen and its machining details as stated above the machining time and the materials for inserts with their tools and associated components can be calculated 3 The prototype CQSIM model A CQSIM is developed to incorporate features that were considered important in Section 2 3 1 Data management of the CQSIM The system is established with Microsoft Access and its programming language is Visual Basic for applications VBA The functional relationship of the components for the CQSIM is shown in Fig 2 The data tables of CQSIM contain data of prices material removal rate MRR 4 5 input data and calculated results for individual purpose The VBA programmes calculate input data with predefi ned data Fig 2 The CQSIM operation diagram from the database and save the calculated data into the cor responding result data table When needed the users can save or retrieve cost estimation fi les and input data into the data fi le product fi les mdb or import template forms for new mould cost estimation 3 2 Users interface The CQSIM software package does not require any mould making experts for data input Moreover there is no need for the users to have on hand mould making experience Instead users are recommended to have a basic knowledge of plastic injection moulds They should know the mould building process from a given product or drawing This is because the user must be able to choose a suitable process and materials for a mould Without correct input accurate results cannot be obtained The terms used in the data input forms like mould base ejector pin cooling line pocket and machining methods are familiartomouldmakers evennewlearners Therefore they are easy to fi ll in by cost estimators who have the basic ideas of injection moulds The main menu of the CQSIM Fig 3 will be shown automatically to users when the programme is selected from the Microsoft Access environment Users can choose a suitable operation from the menu for the desired tasks by pressing a button on it For cost estimation a user only needs about 10 30min a longer time is needed for very com plexity products to fi ll in the blanks of the forms as guided by the programme The results can be obtained within a minute of calculation It is therefore very user friendly 3 3 User input There are six data input form input data for a mould The main data that should be input into the system are a The contents of the products in the mould e g client name part number part name plastic material required and their size Fig 3 The user interface of the CQSIM S F Chan et al Journal of Materials Processing Technology 139 2003 212 218215 Fig 4 A blank data input form for machining details b Mould base details e g width length and height of individual plates c The general structure of a mould e g ejector size and quantity bosses and sleeve ejector if any and ribs and fl at ejectors if any d The part number optional and name of an insert e The machining details of the above insert e g size ma terial cooling line subcontract location of its pocket hole to accommodate the insert machining methods to achieve the shape of the product Fig 4 shows one of the six data input forms Users can switch among these forms by pressing the buttons Previous or Next To start the calculation press the Finish button is pressed Users can also browse among different records in a form by the navigating buttons 3 4 The data tables Four types of data tables are used to store different types of data a Input data i Product details such as name of client product size and polymer required ii Insert names insert dimensions and machining criterion iii General information such as size of mould base gate type and simple structures e g ejectors ribs and bosses Cost is calculated based on these data together with the price and technical data stated below b Resultant data i Materials cost labour cost and machining cost ii Total machining time for individual components and inserts c Price of standard components ii i Price for standard components such as different types of mould bases and ejectors ii Price for different types of materials such as steel and copper The price in these data tables should be updated by the users when their prices are changed d Technical data i Machining data such as MRR and machining sequence ii Standard time for dedicated activities such as the time to compile a CAM programme 3 5 Machining time calculation The CQSIM is developed independent from CAD CAM systems Therefore the shape and volume for machining time calculation are not actual values but factorised values The factors used in the CQSIM include Material Factor and Shape Factor They are used in calculating the actual ma chining time from the standard machining time by means of MRR directly 2 6 Actualmachiningtime standard machiningtime quantity ShapeFactor MaterialFactor preparationtime where preparation time includes set up times tear down times and tool changing time etc 6 The Shape Factor is used to compare the machining diffi culties between in dividual shapes Simple shapes like round rectangular and drilling are assigned a value as standard Other shapes would be more diffi cult for machining lower effi ciency and hence they have higher values Material Factor is designed with reference to the hardness of the material for machining The values for Material Factor can be assigned by referring to data given by manufacturers such as SKF or WIDIA etc 7 8 The factors in the CQSIM can be altered or added to when necessary by the users to suit their needs Since the altered or newly created factors are done by the users themselves they can grasp their meaning more easily to maintain the accuracy of the cost estimation 4 Evaluation of the prototype CQSIM The quotation accuracy of the CQSIM can be divided into four parts These are direct material costs machining time for components overheads and profi t The overheads and profi ts are set by the users before the fi rst time they use the CQSIM by using the Update Database function of the CQSIM Therefore the accuracy of these two types of factors is affected by the set up data from users Thus the accuracy of the CQSIM is based on direct material cost and machining time Fig 5 shows the result after a trial running of the CQSIM for analysis 216S F Chan et al Journal of Materials Processing Technology 139 2003 212 218 Fig 5 The result as an example of running the CQSIM 4 1 Accuracy of estimated direct material cost The cost for materials is simply obtained by searching the database or by calculating the weight of the raw materials for mould components so the accuracy is high up to 98 Standard components are supplied with current market price and counted in quantity required Given the correct quantity and updated price a more accurate cost can be obtained The error for standard components are generated from the predefi ned quantity for angle pins screws etc because the fi nal choice may be slightly different to the programme However these components are generally cheap a few dol lars and of small usage quantity The error is therefore neg ligible when compared with the thousands of dollars total material cost The 2 error comes mainly from the length of raw ma terials cut by suppliers Generally ironmongers will sup ply raw materials 5 10mm longer than the required size Table 1 The trial run result for machining time Insert nameMC time h MillingTurningGrindi