-
Abstract: Effect of material change of plastic product is investigated in this research paper. The parameter observed are waste recycle, impact property of product, aesthetic look, cycle time, production rate and cost of product. In this study it was found that by changing the material of product from thermoset plastic to thermoplast plastic and production process from compression molding to injection molding, the product becomes eco friendly because thermoplast material is recyclable. It was also found that impact strength and production rate/hour was also improved due to reduction in cycle time. The aesthetic look : smoothness of surface and glossy look of the product was become better and long lasting. And finally the cost of product was reduced tremendously. The research was carried out in a small scale industry with a case study of ball knob of machine tool handle lever. Key words – Ball Knob, Bakelite, Nylon-6, Compression Molding, Injection Molding I. Introduction Today plastic is used in our life, from home appliances to industrial goods. Plastic product manufacturing industries are suffering tremendous pressure for improving quality of product as well as reducing the cost of the product. Recycling of plastic waste is also big problem for the environment. Government policies become stricter day by day. In such condition plastic industry has to change the material of the product and manufacturing process according to it. So many plastic products are unnecessary made from thermoset plastic which is non recyclable. The plastic product which has not to work under application of heat can be converted into thermoplast plastic which is recyclable. 48117
- 上一篇：塑料成型生产过程中形成的凹陷英文文献和中文翻译
- 下一篇：塑料注射模具设计U型铣槽英文文献和中文翻译
Compression molding – In this method the Bakelite, in the form of powder, converted into disc, is dried by heating and then further heated to near the curing temperature; this heated disc is loaded directly into the mold cavity. The temperature of the mold cavity is held at 250°C–300 °C, depending on the material. The mold is then partially closed, and the plastic, which is liquefied by the heat and the exerted pressure, flows into the recess of the mold. At this stage the mold is fully closed, and the flow and cure of the plastic are complete. Finally, the mold is opened, and the completely cured molded part is ejected. This method generally used for themoset plastic material. The process is shown in fig-1 [i][ii]. Fig.1 compression molding[ii] Injection molding – It is based on the ability of nylon-6 materials to be softened and melt by heating and to harden when cooled. The process thus consists essentially of softening the nylon-6 material in a heated cylinder and injecting it under pressure into the mold cavity, where it hardens by cooling. Each step is carried out in a separate zone of the same apparatus in the cyclic operation. A diagram of a typical injection-molding machine is shown in Fig. 2[ii]. Granular material (the plastic resin) falls from the hopper into the barrel when the plunger is withdrawn. The plunger then pushes the material into the heating zone, where it is heated and softened (plasticized or plasticated). Rapid heating takes place due to spreading of the polymer into a thin film around a torpedo. The already molten polymer displaced by this new material is pushed forward through the nozzle, which is in intimate contact with the mold. The molten polymer flows through the sprue opening in the die, down the runner, past the gate, and into the mold cavity. The mold is held tightly closed by the clamping action of the press platen. The molten polymer is thus forced into all parts of the mold cavities, giving a perfect reproduction of the mold. The material in the mold must be cooled under pressure below melting point temperature before the mold is opened and the molded part is ejected. The plunger is then withdrawn, a fresh charge of material drops down, the mold is closed under a locking force, and the entire cycle is repeated.[i][ii]. Fig-2 Injection molding process[ii] Productivity – as per ILO productivity can be defined as ratio of aggregate output to aggregate input. According to Peter Drucker, “Productivity means a balance between all factors of production that will give the maximum output with the smallest effort”.[iv][v] [vi] II. Literature Review A. George Staniulis, AGS Technology, Inc. & Schaumburg, III has focused on automobile companies to lower their costs. He suggested that productivity improvement and reuse of scrap after conditioning and modification of process are only the solution. He found that the raw material saving is possible upto 50% [vii]. James Henderson, Aaron K. Ball, James Z. Zhang have focused on optimizing the parameter of injection molding process. They optimized the process parameter like cooling time, back pressure and cycle time for each part. In this paper it was proved that only significant parameter was cooling time and it was only parameter that had major effect overall cycle time. By manipulating the four temperatures in the heating bands could decrease the cooling time which would decrease the overall cycle time. [viii]. Adekunle A. Fagade and David O. Kazmer have focused on early cost estimation of by using CAD design. [ix]. Mika Hunnula and Petri Suomala have focused on finding out which are the most important obstacles to productivity improvement in small and medium size manufacturing companies in Pirkanma, a province in southern Finland.[x]. M.E. Sheriver, K.A.Beiter and K.Ishii in which they have focused on change in properties of recycled thermoplastics [xi]. They found that 1. Mw – molecular weight decreases slightly over ten generations of processing. Blending the tenth generation regrind with virgin material does not significantly alter the Mw of the regrind. 2. The melt index for polycarbonate is directly proportional to the number of regrind generations, i.e. viscosity decreases as the material degrades. Blending virgin material with tenth generation regrind decreases the MI i.e. viscosity increases. 3. Polycarbonate mechanical performance did not significantly degrade over the ten generations of processing. Izod impact strength increases with increasing virgin material percentage. 4. Yellowness and darkness increase as generation number increases. III. Materials & Methodology Product – Machine tool lever ball knob shown in Fig.-3(A) Volume – 22.12 cm3 Bakelite ball knob manufacturing by compression molding in industry was observed and different parameters noted in the observation table-2. Then for manufacturing same product by injection molding, die was designed shown in FIG.-3(B). The knob of same dimension and volume was made by manual injection molding and different parameters were recorded in observation table-2. Material used for both knobs were compared in table-1[iii]. The cycle time is calculated by application of time study method of actual cycle time recorded of different workers[iv][v] [vi]. All dimensions are in mm Fig-3 (A) Knob sketch (B) Injection molding die Table -1 MATERIAL COMPARISION [3] Sr. No. Property Bakelite Nylon-6 1 Molding Qualities Good Excellent 2 Relative Density (gm / cm3) 1.25-1.30 1.13-1.15 3 Tensile Strength, Mpa