Effect of Blow Moulding on Bottle Weight and Dimensions

Effect of splatter Moulding on feeding bottleful system of weightsing and DimensionsAbstractBlow musical model, which is also called blow forming, is a manufacturing routine for deed of yap-form plastic products. The present report is intended to deal with the effect on bottle weight, bottle dimensions and machine issue of the various process factors. By reference to Rheological properties of plastics, the correlation between the share assess and fuck fixity, flux temperature, die swell, bottle thickness were discussed. Also, the influences of elongational viscousness were suggested.1. IntroductionBlow forge, also known as blow forming, is a process use to produce hollow productions by blowing thermoplastic molten tube into the convention of a mould cavity.Generally, blow moulding can be divided into three main types including stretch blow moulding, injection blow moulding, and lump blow moulding. In this experiment, extrusion blow moulding was studied to attempt the effects of process variables on bottle weight, bottle dimensions and machine take.In extrusion blow moulding, plastic particles are melted into fluid with arouse applied. Then the melt plastic is extruded through a die, forming a hollow tube, which is usually called a parison. After that, the parison is captured by closing it around a mould. Next, air is pumped in to the parison when the ends of the parison keeps sealed at the mould office line during forming. The parison deforms, forming a shape very closed to the mould. The mould is undefended after the component is well cooled. Finally the component is ejected and the procedures are repeated. much and more products are made.In this experiment the plastic particles are full(prenominal)- absorption Polyethylene, the density of which ranges from 0.941 to 0.967 g/cm3. The in spunky spirits-density Polyethylene is preferred for production by blow moulding as it is more rigid and usually has a matt terminus compared with L ow-density Polyethylene.2. ExperimentalEquipmentHayssen extrusion blow moulding machineMaterialsHigh density polyethylene (HDPE), Blow moulding grade, BS2581, Borealis.ProceduresFirstly, HDPE particles were pumped into the hopper though a pipe. After that, the parameters of process variables and the temperatures of different zones were set according to turn off 1 2, respectively. Then the machine was set in automatic mode and continuous bout. Each congregation needs 10 samples, marking 1 to 10. Before the Process Variables were changed, the weight of parison extruded per unit minute was measured. Finally weight of each bottle, was measured along with thickness distribution along the length circumference.3. Results And DiscussionsExperimental ResultsThe original records including weight of bottle, bottle thickness distribution, output regularise and crew speed are shown in attachment I. In addition, the numeration of share step and modified prison length are shown Appendix II and the general results are summarized.Experimental DiscussionsInfluences Of Machine Variables On Bottle Weight And DimensionsGenerally the bottle weight and dimensions is influenced by screw speed, thaw temperature, and vent metre.Screw speed. By comparing grouping A and group C, it is clear shown that output rate increasing with the increasing screw speed due to low viscosity and high school die head pressure. By referring to the rheological properties of plastic, thickness and weight of group A should be high than that of group C, because the higher sagging brings decreasing of weight and thickness. However, the records of the experiment do not accord with the theoretical analysis. The reason is that the machine is too old. thaw temperature. By comparing Group C and Group D, it is found that the bottles of group D are lighter and smallner than those of group C. The higher the melt temperature is, the depress the viscosity of polymer is. Lower viscosity reduces bottle wei ght and dimensions. outlet time. By comparing Group A and Group B, the result is that the bottles of group B are lighter and thinner than those of group A. If the vent time is too all of a sudden, it will cause insufficient cooling and less sagging. divvy up BehavioursAccording to the comparison = (6Q)/ (WH), the results of apparent share rate are stipulation in turn off 4 (all steps in calculation is shown in Appendix II).Experiments runsABCDShear post (s)234.94232.86398.41458.62Table 4 Apparent clip rateGenerally shear rate is related to screw speed, melt temperature, die swell and bottle thickness.Screw speed. The output rate is proportional to the screw speed. According to the equation = (6Q)/ (WH ), as the mean circumference (W) and die gap (H) are immutable in this equation, the shear rate () increases as output rate (Q) increases, in other words, screw speed increases.Melt temperature. The viscosity of polymer becomes lower at higher melt temperature. Lower viscosity r esults in high output rate (Q), which brings out a higher shear rate (). spoil swell. An increase in die swell results in a lower linear output rate. Since extrusion is usually continuous, further adjustments to the process dynamics are sometimes inevitable. Parison length sensors are available, to ease the effects of the conundrum. In consequence, larger die swell results in larger output rate, which brings out larger shear rate. In one word, shear rate is proportional to die swell.Bottle thickness. Bottle thickness is related to the viscosity of polymer. Higher viscosity results in lower shear rate. So, shear rate increase as bottle thickness decrease..Elongational BehavioursAccording to the equation L= (gtL)/ (2), the results of Modified Parison Length are (all steps in calculation is shown in Appendix II).Experiments runsABL(mm)0.5660.944Modified Parison Length (mm)17.56617.944According to Table 5, it can be found that the long-dated the cycle time is, the longer the parison b ecomes. The result can be explained in this way the parison will be elongated if more time is given under the gravity force.The elongational viscosity is influenced by molecular weight and temperature. High molecular weight and high temperature cause a decreasing of the elongational viscosity.4. ConclusionsBlow moulding is a manufacturing process for production of hollow-form plastic products. Process variables have the effects on bottle weight, bottle dimensions and machine output. Specifically, high screw speed, low melt temperature, and short vent time results in the increasing of bottle weight and thickness. High screw speed, high melt temperature, large die swell and thin bottle thickness lead to high shear rate. Longer cycle time results in larger parison length. High molecule weight and high temperature cause a decreasing of the elongational viscosityReferences1 A. W. Birley, B. Haworth and J. Batchelor, Physics of plastic, Hanser, 19912 Edwin G. Fisher, Blow moulding of plas tics, The Plastics Institute, 1971