塑料杯蓋注塑模具設計,塑料杯蓋注塑模具設計,塑料,杯蓋,注塑,模具設計 Journal of Materials Processing Technology 182 (2007) 418426 The use of Taguchi method in the design of plastic injection mould for reducing S.H. Tang , Y.J. Tan, S.M. Sapuan, S. , Univer form Abstract mould in with w be machined moulding product. in w are and K 1. Introduction Mould making is an important supporting industry because their ponents design o necks required polymer Approximately using are produce accurac casings and products tend to become lighter, thinner and smaller. Hence, the internal components of products have to be packed into hous- ing, which has smaller volume. One way to increase the space 0924-0136/$ doi: related products represent more than 70% among the com- in consumer products. The high demand for shorter and manufacturing lead times, good dimensionality and verall quality, and rapid design changes has become the bottle- in mould industries 1. It is a complicated process, and skilled and experienced mould maker. Generally, injection moulding is one of the most important processing operations in the plastic industry today. one-third of all plastics are converted into parts injection moulding 2. This is one of the processes that greatly preferred in manufacturing industry because it can complex-shape plastic parts with good dimensional y and very short cycle times 3. Typical examples are and housings of the products such as computer monitor mobile telephone, which have a thin shell feature. These Corresponding author. E-mail address: saihongeng.upm.edu.my (S.H. Tang). of housing parts is to reduce the wall thickness. However, the injection moulding operation becomes more difficult as the wall thickness of plastic parts becomes thinner 4. This is because the significant warpage defect will be appeared. To reduce this significant defect, testing procedure regarding to the effective factors is required. A thin plate with dimension 120 mm 50 mm and 1 mm thickness will be produced. It is use for testing on the effec- tive factors to minimize the warpage defect. Firstly, fabricating the plastic injection mould is needed. After that, the mould is going to be assembled on the injection moulding machine. When the thin plates have been produced, they will be used for test- ing on the effective factors in warpage problem by applying the experimental design of Taguchi method. 2. Preparation In fabricating the mould, some preparations are needed. The capability of the machine that are available in faculty are see front matter 2006 Elsevier B.V. All rights reserved. 10.1016/j.jmatprotec.2006.08.025 Department of Mechanical and Manufacturing Engineering Received 3 September 2004; received in revised Plastic injection moulding is one of the most important polymer processing making and injection moulding machine control will lead to defecti products with thickness less than 1 mm. This project is going to fabricate a mould that produced a thin plate arpage testing. In mould fabrication, the mould base that purchase will machine. The machine setting should be made to produce the warpage problem by applying the experimental design of Taguchi method. From the results, it shows that the most effective factor on the warpage arpage. The optimum parameters that can minimize the warpage defect packing time (0.6 s). 2006 Elsevier B.V. All rights reserved. eywords: Plastic injection mould; Taguchi methods; Experimental design; Warpage warpage Sulaiman, N. Ismail, R. Samin siti Putra Malaysia, 43400 Serdang, Selangor, Malaysia 27 July 2006; accepted 10 August 2006 operations in the plastic industry today. However, lack of skill in ve plastic product. Warpage is one type of defect that usually appears dimension 120 mm 50 mm 1 mm. The thin plate will be used for and assembled. After that, the mould is fixed on the injection Then, the product will be used for testing on the effective factors is melt temperature. The filling time only slightly influenced on the melt temperature (240 C), filling time (0.5 s), packing pressure (90%) S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426 419 investigated. The machines that required in fabricating the mould are drilling machine, milling machine and grinding machine. The plastic injection moulding machine is also needed for producing the product. The machine that has been used is BOY 22D. Besides that, it is also required to search and purchase the mould base, which can fit the injection moulding machine. Carbon steel AISI 1050 had been selected as material for the mould base. Since some components such as ejector pin, locating ring, sprue bush, water junctions and springs are not included in the mould base, these components are purchased independently. The plastic material that has been used is ABS. 3. Mould design There are four design concepts that can be used in this project. The description of these design concepts is as follows: (a) Three-plate mouldHaving two parting lines with single (b) (d) base plate the is during are has moulding mould dimension plate only and T Mould Plate T Ca Core Side Ejector Ejector Bottom Fig. 1. Air vent design. There are relative between the product design and the mould design. Since this project is determined the effective factor that can minimize the warpage defect for a thin shell feature, 120 is core This used damage. the will design is mould. ca Hence, drilling Fig. 2. Configuration of cooling channel for cavity plate. cavity. Two-plate mouldHaving one parting line with single cav- ity without gating system. (c) Two-plate mouldHaving one parting line with double cav- ities with gating system and with ejector pin at the cavities. Two-plate mouldHaving one parting line with double cavities with gating system and without ejector pin at the cavities. Since this project is limited in budget, the type of mould that has been chosen is two plate mould instead of three mould. Among the design concepts for two plate mould, concept d has been chosen. This is because concept b non-productive while concept c may damage the product ejection. Generally, two plate mould consist of eight plates and there their standard dimensions, respectively. The mould base that been chosen must base on the specification of the injection machine that will be used. In this project, the standard base with 250 mm 250 mm has been used and its plates are shown in Table 1. Among these plates that are shown in Table 1, only the cavity and core plate are need to be designed. The other plates are base on the specification of the injection moulding machine the components dimension. able 1 plates dimensions Dimensionwidth height thickness (mm) op clamping plate 1 250 250 25 vity plate 1 200 250 40 plate 1 200 250 40 plate 237 250 70 -retainer plate 1 120 250 15 plate 1 120 250 20 clamping plate 1 250 250 25 the product that has been designed is a plate with mm 50 mm 1 mm in dimension. For the mould base, the cavity that can produce the product designed on the core plate. Since there is enough space at the plate, two cavities with gating system has been designed. design is without ejector pin at the cavity part and only sprue puller to eject the product. This will avoid product Air vent design is important because its function is to release air inside the cavity when the mould is closed. Short shot happen if air is trapped inside the mould. Fig. 1 shows the of air vent in this project. Cooling system is another consideration in design stage. It used to solidify the plastic product before eject out from the Figs. 2 and 3 show the design of cooling channel for vity plate and core plate, respectively, in this project. The product design in this project is only a simple thin plate. the mould can be fabricated by using milling machine, machine and grinding machine. 420 S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426 4. in skilled e 4.1. machine) Step Step Step Step Step T Step Step Step Step Step T (milling Step Step Step Step T and be which time 4.2. machine) Step Step Step Step Step T machine) Step Step Step Step Step Step Step Step Tool, high speed steel; spindle speed, 640 rpm. primeprime Fig. 3. Configuration of cooling channel for core plate. Mould fabrication There are some parts in the mould that need to be machined. It volved high precise and accuracy process. Hence, it is required mould maker. Following is the machining process for very part of the mould. Top clamping plate Part 1: Ream through hole with 16 mm diameter (drilling Operation descriptions Tools 1 Marking the point Height gauge 2 Clamping the plate on the machine table 3 Centering at the marking point Center drill 4 Drilling through hole 15.5 drill 5 Reaming the hole 16 reamer ool, high speed steel; spindle speed, 330 rpm. Part 2: Tap M6 holes (drilling machine) Operation descriptions Tools 1 Marking the point Height gauge 2 Clamping the plate on the machine table 3 Centering at the marking point Center drill 4 Drilling 2 holes with 12 mm depth 5 drill 5 Tapping the holes M6 tapper ool, high speed steel; spindle speed, 1000 rpm. Part 3: Enlarge hole to 40 mm diameter with 14.8 mm depth machine) Operation descriptions Tools 1 Marking 35 and 40 circles Compass 2 Clamping the plate on the machine table 3 Milling the area at 35 circle with 14.8 mm depth 10 endmill 4 Boring until 40 circle with 14.8 mm depth Borebit ool, high speed steel; spindle speed, 820 rpm; depth of cut, 2 mm for roughing 0.8 mm for finishing. Fig. 4 shows the parts of the top clamping plate that need to machined. Note that the first step in Part 1, Part 2 and Part 3 Step Step Step Step Step Step Step T Fig. 4. Parts of the top clamping plate that need to machine. are marking point and marking circle is done at the same before proceed to next step. Cavity plate Part 1: Ream through hole with 16 mm diameter (drilling Operation descriptions Tools 1 Marking the point Height gauge 2 Clamping the plate on the machine table 3 Centering at the marking point Center drill 4 Drilling through hole 15.5 drill 5 Reaming the hole 16 reamer ool, high speed steel; spindle speed, 330 rpm. Part 2: Drill through holes with 8 mm diameter (drilling Operation descriptions Tools 1 Marking the point Height gauge 2 Clamping the plate on the machine table 3 Centering at the marking point Center drill 4 Drilling 2 holes until half width of the plate 8 drill 5 Turn the plate to opposite side 6 Clamping the plate on the machine table 7 Centering at the marking point Center drill 8 Drilling 2 through holes 8 drill Part 3: Tap 1/4 holes (drilling machine) Operation descriptions Tools 1 Clamping the plate on the machine table 2 Drilling 2 holes with 15 mm depth 11 drill 3 Tapping the holes 1/4 primeprime tapper 4 Turn the plate to opposite side 5 Clamping the plate on the machine table 6 Drilling another 2 holes with 15 mm depth 11 drill 7 Tapping the holes 1/4 primeprime tapper ool, high speed steel; spindle speed, 460 rpm. S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426 421 machined. marking step. 4.3. machine) Step Step Step Step Step Step Step Step T Step Step Step Step Step Step Step T Part 3: Enlarge holes to 32 mm diameter with 10 mm depth (milling machine) Operation descriptions Tools Step 1 Marking four 28 and 32 circles Compass Step 2 Clamping the plate on the machine table Step 3 Milling the area at 28 circle with 10 mm depth 10 endmill Step 4 Boring until 32 circle with 10 mm depth Borebit Tool, high speed steel; spindle speed, 820 rpm; depth of cut, 3 mm for roughing and 1 mm for finishing. Part 4: Create the cavity of the product (milling machine) Operation descriptions Tools Step 1 Marking the area of cavity Height gauge Step 2 Clamping the plate on the machine table Step 3 Milling two 120 mm 50 mm 1 mm cavity 3 endmill Step 4 Milling taper at boundary of cavity 8 taper mill Step 5 Milling the runner R3 ball nose mill Tool, high speed steel; spindle speed, 2700 rpm; depth of cut, 0.5 mm per cut. Part 5: Ream through hole with 6 mm diameter (drilling machine) Operation descriptions Tools Step Step Step Step Step T machined. P the used Fig. 5. Parts of the cavity plate that need to machine. Fig. 5 shows the parts of the cavity plate that need to be Note that the first step in Part 1 and Part 2 which is point is done at the same time before proceed to next Core plate Part 1: Drill through holes with 8 mm diameter (drilling Operation descriptions Tools 1 Marking the point Height gauge 2 Clamping the plate on the machine table 3 Centering at the marking point Center drill 4 Drilling 2 holes until half width of the plate 8 drill 5 Turn the plate to opposite side 6 Clamping the plate on the machine table 7 Centering at the marking point Center drill 8 Drilling 2 through holes 8 drill ool, high speed steel; spindle speed, 640 rpm. Part 2: Tap 1/4 primeprime holes (drilling machine) Operation descriptions Tools 1 Clamping the plate on the machine table 2 Drilling 2 holes with 15 mm depth 11 drill 3 Tapping the holes 1/4 primeprime tapper 4 Turn the plate to opposite side 5 Clamping the plate on the machine table 6 Drilling another 2 holes with 15 mm depth 11 drill 7 Tapping the holes 1/4 primeprime tapper ool, high speed steel; spindle speed, 460 rpm. 1 Marking the point Height gauge 2 Clamping the plate on the machine table 3 Centering at the marking point Center drill 4 Drilling through hole 5.8 drill 5 Reaming the hole 6 reamer ool, high speed steel; spindle speed, 880 rpm. Fig. 6 shows the parts of the core plate that need to be Note that the first step in Part 1, Part 3, Part 4 and art 5 which are marking point and marking circle is done at same time before proceed to next step. Grinding machine is for produced air vent. Fig. 6. Parts of the core plate that need to machine. 422 S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426 4.4. terbore Step Step Step Step Step Step T machined. 4.5. machine) Step Step Step Step T to are at plate assembled datum must the machine the from 5. produced reach v ification to is Fig. 7. Parts of the ejector plate that need to machine. Ejector plate Part 1: Ream through hole with 6 mm diameter, drill coun- with 11 mm diameter and 6 mm depth (drilling machine) Operation descriptions Tools 1 Marking the point Height gauge 2 Clamping the plate on the machine table 3 Centering at the marking point Center drill 4 Drilling through hole 5.8 drill 5 Drilling counterbore with 6 mm depth 11 drill 6 Reaming the through hole 6 reamer ool, high speed steel; spindle speed, 880 rpm/460 rpm. Fig. 7 shows the parts of the ejector plate that need to be Bottom clamping plate Part 1: Enlarge through holes to 55 mm diameter (milling Operation descriptions Tools 1 Marking 50 and 55 circles Compass 2 Clamping the plate on the machine table 3 Milling through hole at the area 50 circle 10 endmill 4 Boring until 55 circle Borebit ool, high speed steel; spindle speed, 820 rpm; depth of cut, 3 mm per cut. Fig. 8 shows the parts of the bottom clamping plate that need be machined. After finishing the machining process, all the mould plates assembled together. Each mould plates had its datum plane one corner of the plate, respectively. All the surfaces of the 6. f method will of The product. 6.1. that time, packing mould is Fig. 8. Parts of the bottom clamping plate that need to machine. at datum plane are perpendicular to each other. During the mould, all the plates must be aligned refer to the plane. In other words, all the datum plane of the plates be in the same corner. After the mould has been finished to assemble, the bolt and hook are used to hang up the mould to the injection moulding area. It is installed one by one. The mould is fixed into machine by the bolt tightly to prevent it from sliding down the machine. Mould testing and modification When the mould has been tried run, most of the product that has short shot defect. The plastic material could not the corner of the product. This might cause by insufficient enting and the air trapped in the closed mould. Hence, the mod- has been made on the mould which is added the venting the mould at the corner of the cavity. Finally, this modification produced the product without short shot defect successfully. Process of experiment design To determine the best set of parameter among the effective actors by reducing the number of experiments, the Taguchi has been chosen. Hence, selection of the factors that affect warpage, selection of the factor levels and selection orthogonal array (OA) based on Taguchi method is needed. best set of parameter will be produced a minimum warpage Selection of the factors According to the journal, there are several possible factors can affect warpage defect at the thin plate which are filling mould temperature, gate dimensions, melt temperature, pressure and packing time 4. Since the design of the is different from the journal, so the gate dimension factor eliminated. The mould temperature factor is also eliminated S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426 423 Table 2 The parameter for three levels of selected factors Factors Level 1 Level 2 Level 3 Melt temperature, A ( C) 240 265 290 Filling time, B (s) 0.1 0.3 0.5 Packing pressure, C (%) 60 75 90 P T L9 T 1 2 3 4 5 6 7 8 9 because ent f packing 6.2. T icant lo high f 6.3. pre sen le 7. tion machine done product that places recorded. and measurement Table 4 The combination parameters for the effective factors Trial no. Melt temperature, A( C) Filling time, B (s) Packing pressure, C (%) Packing time, D (s) 1 240 0.1 60 0.6 2 240 0.3 75 0.8 3 4 5 6 7 8 9 (a) (b) (c) (d) (e) w definition is S/N mined. of age f acking time, D (s) 0.6 0.8 1.0 able 3 orthogonal array rial no. Column no. ABCD 1111 222 1333 2123 231 2312 3132 213 3321 the temperature is difficult to control due to the ambi- temperature. Finally, four factors have been selected. These actors are melt temperature, filling time, packing pressure and time. Selection of the factor levels There are three levels of each factors will be conducted using aguchi method. This is because if the selected factor has signif- effect on the product, we may be able to choose among the w, middle and high values instead of just having only low and values to be selected. Each level parameter of the selected actor that suggested according to the journal is shown in Table 2. Selection of orthogonal array (OA) From the number of factors and levels that have been selected viously, the L9 orthogonal array will be used. The L9 is cho- as an OA because it is suitable for four factors with three vels. The L9 orthogonal array is shown in Table 3. Product testing procedure The testing process is started by keying all the combina- parameters for the effective factors into injection moulding as shown in Table 4. There are nine experiments been and each experiment has different combination. After that, the flashing on the product is removed and the is cut out from the runner. The thickness of the product free with flashing and the runner is measured at 10 different by using micrometer. The readings and their average are To measure the warpage of the plate, the dial gauge the granite block have been used. The procedures of warpage are shown below: 8. drilling, cesses the highlight cooling drilling the gear drilling to because 240 0.5 90 1.0 265 0.1 75 1.0 265 0.3 90 0.6 265 0.5 60 0.8 290 0.1 90 0.8 290 0.3 60 1.0 290 0.5 75 0.6 Fig. 9. Definition for symbols h, t a and z. The plate is placed on the flat surface at the granite block. The dial gauge is moved down until its stylus is touched by the flat surface of the granite block and the dial gauge is set to zero. The plate is moved around below the stylus of the dial gauge. The maximum height of the plate is calculated from the scale in dial gauge and the reading is recorded. The procedures are repeated for other plate. After getting all the readings, the deflection, z, which is the arpage of the plate,