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Design and Analysis of Shutter in Injection Molding Machine
Ajay P Shevale
PG student of mechanical department Kalol institute of technology and research center
ajay.shevale007@gmail.com
Ronak Shah
Assistant professor and head of department Kalol institute of technology and research center
ronak.r2626@gmail.com
Abstract: Injection molding machines uses the process, in which hot molten plastic is injected under high pressure into a thin cold mould. There are many types of injection molding machines available in plastic processing industries according to its clamping unit. In hydraulic ram type clamping machine a component called shutter often get breakdown due to high compression force generated on it. So design and analysis of Shutter in ram type injection molding machines is used to increase the strength of shutter so it helps to reduce the failure of shutter. The aim of research is to reduce the breakdown of shutter in hydraulic ram type clamping injection molding machine.
Key Words: Design and analysis, injection molding machine, shutter.
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I. INTRODUCTION
Injection molding is the process of shaping of plastics by injecting molten material into the closed mould and removes it after it has solidified. This is very widely used, since this is the only process by which one can form plastics parts with complicated geometry ranging from small ball pen parts to large bumpers used in cars.
The injection molding is machines that melt plasticize the molding material inside the heating barrel and inject this into the mold cavity to create the molded product by solidifying inside it. The injection machine is constructed of a mold clamping device that opens and closes the mold tool, and device that plasticize and inject the molding material.
There are several types in the injection machine, and the difference is made by how these two devices are arranged.
In order to meet demands of modern day’s injection molding technology is continuously updated. Various models are available in market with different clamping mechanisms. Toggle type clamping machine called mechanical locking machine, and ram type clamping machine is called hydraulic clamping injection molding machine. Clamping mechanism is used to clamp two parts of mold or die together with high clamping force. Injection molding machines works on Pascal’s law of pressure.
This paper shows the design modification and analysis of shutter used in injection molding machine. Here we will study about ram type locking of injection molding machine. The design and analysis of shutter in ram type injection molding machines is used to increase the strength
of shutter so it helps to reduce the failure of shutter. This paper is also shows the forces acting on shutter during generating the clamping force. The aim of this design and analysis is to increase the strength of shutter.
A. Shutter in injection molding machine.
Generally shutter used only in ram type hydraulic clamping mechanism in injection molding machine.
Function of shutter is to support the mould height adjusting Screw mounted in Ram, to create clamping force. During the production process in machine shutter often get broken due to uneven load acting on it. To create clamping force in machine, there is a hollow clamp cylinder located behind the shutter, who helps the shutter to press the ram by using hydraulic, high pressurized oil.
Fig.1 clamping mechanism of ram type hydraulic machine
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40 B. Function of shutter :
Fig.2 Force acting area of shutter
The main function of shutter is to support the clamping cylinder with ram. The shutter is used as supporting component between both mechanical components. Ram assembly is a bulky and long component assembly. In this assembly the threaded component called mould height adjusting screw, rotates in ram. According to the size of mould the adjusting screw takes position in ram assembly by rotation forward and reward direction. To measure the position of the adjusting screw in ram proximity sensor or LVDT (linear variable displacement transformer) is used. If the production mould changes in machine at that time only the position for adjusting screw in ram assembly need to be change. There is a facility provided in machine program called “Auto mould height adjustment” by software. After 200 to 250 cycles continuous production of machine we need to correction of position of adjusting screw in ram assembly. Here auto mould height program will support for position correction.
Fig.3 Shutter and mold height arrangement II. PROBLEM IN EXISTING DESIGN:
From many practical experiments found that the clearance of ram assembly should be 0.3±0.05mm for proper rotation of adjusting screw in ram. If this clearance is reduce than after the adjusting screw not rotate in ram
assembly, because here whole assembly is bulky weighted made from harden casting process.
In this ram and screw assembly the higher clearance and weight causes cantilever effect created. Due to cantilever effect whole assembly get 6 to 9mm deflection at the end of adjusting screw head.
The face of shutter and ram should be parallel to each other if the gravitational force and cantilever effect should not be considered. But in piratical matter we have to consider both the effect in calculation so we can get actual result and it may be needful to solve the existing design.
Fig.4 Error in design assembly
In actual practice, observation of following error in both parallel faces is done and 10 same machine measurement by using slip gauge or filler gauge taken. Here observed 10 same machine results of both parallel faces between shutter and ram face at top & bottom position.
TABLE.1
DEFLECTION DUE TO CANTILEVER EFFECT Machine
SR. No.
Idle gap (mm)
Top side gap (mm)
Bottom side gap (mm)
Deflection due to Cantilever
effect at end of ram
assembly (mm)
6500815 3 1.5 4.5 6.8
6500816 3 2.0 4.0 6.0
6500817 3 1.2 4.8 7.2
6500818 3 1.6 4.4 6.5
6500819 3 1.3 4.7 7.0
6500820 3 1.5 4.5 6.8
6500821 3 1.9 4.1 6.2
6500822 3 1.3 4.7 7.0
6500823 3 1.7 4.3 6.3
6500824 3 2.0 4.0 6.0
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6500825 3 1.4 4.6 7.0
So hereby concluded that the cantilever effect should not be controlled because the both assembly components are very bulky weighted. If this clearance will be changed, than it is not possible to rotate the adjusting screw in ram. So there is not chance to control the cantilever effect. The clearance should be precise by 0.3±0.05mm. So here we will focus on the gap that is not parallel to each other.
The average difference for all studied 10 machines, got the average value of the gap is 1.5 to 2.0 mm at the top side and 4.0 to 4.5mm at bottom side of both parallel face (Shutter face and ram face). So to neglect this difference value a tapper platen is decided to add in assembly that can used to reduce this uneven gap between both surface the unequal force is generated on platen, so here point load is introduced in assembly instead on uniform distributed force.
III. MODIFICATION IN EXISTING DESIGN:
In real practice, because of the previous disused error, point load is created, if this kind of error of cantilever and gravity force is considered. So by using solid work software, we can found that the area indicated with red colored is the high force and stress is generated. Here there is a chance for breakdown from that highly tension area so shutter. So the following parameters should be considered to prevent this breakdown of shutter.
Fig.5 Failure of shutter
FV
Fig.6 Tapper angle calculation
Fig.7 Tapper plate
As shown in figure the old shutter had 130mm thickness.
Here in modified model we reduced the shutter thickness by 30mm (15mm from front side and 15mm from rear side).
The front side plate was kept tapered by 0.86’ according to calculation. Thos both plates were assembled with nut and bolt. This plate should harder than the shutter material. So here the plate material selected was mild steel.
Due to reduction of thickness of shutter the weight of shutter is reduced. The material used for platen is hardened than casting of shutter material, so compressive strength of shutter is increased. Front and rear side mild steel plate provided to attend parallisam between shutter face and ram assembly face. The front side mild steel plate kept 0.86’
tapper angle, hence the rear side platen is flat face.
A. Comparison of both shutter design:
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42 TABLE.2
COMPARISON OF BOTH DESIGNS Parameters Old shutter Modified
shutter
Material Grey cast iron Grey cast iron + Mild steel
Thickness 130 mm 100 mm
Force 650 ton 650 ton
Weight 1940 N 1653 N
Density 7200 kg/m³ 8005 kg/m³ Poisson’s Ratio 0.27 0.26 Elastic Modulus 2.0 × 10 ̂ 5
N/mm²
66178.1 N/mm²
IV. SOLID MODELING OF DESIGN:
Solid modeling for the Shutter in injection molding machine are following major components need to be geometric modeling.
Modified Shutter
Front side M.S. plate
Rear side M.S. plate
Nut & Bolts
All Component Assembly
A. Finite element analysis:
The finite element analysis is a numerical procedure for analyzing structure of complex shapes, otherwise would be difficult to solve by classical analysis methods. Mainly FEA method transforms physical model into small finite elements. FEA tool is not solving the problem for the entire body in one operation. The process of selecting only certain numbers of discrete points in the body is termed as discretization and each part of discredited body is called element. For every element has one more node, that is lie along the boundary. The finite element analysis is a computational technique used to obtain approximate solution of boundary value problems in engineering.
Fig.8 Solid modeling and assembly of shutter B. Finite elements analysis steps:
a. Import Geometry in design software.
b. Apply connections and fix geometry for components.
Fig.9 Apply fix geometry
c. Apply Force 650Ton at force acting area and give
Fig.10 Apply force d. Apply Meshing
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Fig.11 Apply mesh
e. Run mesh program and find the result of solution
Fig.13 Deflection of shutter
Fig.14 Strain result
V. RESULT COMPARISON BETWEEN EXISTING DESIGN AND NEW DESIGN
TABLE 3
COMPARISON OF RESULT Properties Old Design
Shutter
Modified Shutter
Material Grey Cast
Iron
Grey Cast iron + M.S Plates
Mass Density 7200 8005
Properties Old Design Shutter
Modified Shutter (kg/m3)
Weight (N) 1940 1653
Elastic Modulus (N/m²)
6.61 × 10 ̂ 4 2.0 × 10 ̂ 5
Poisson’s Ratio 0.27 0.26 Compressive
Strength (N/m²)
5.17 × 10 ̂ 8 7.32 × 10 ̂ 8
Stress (N/m²) 1.635 × 10 ̂ 5 1.065 × 10 ̂ 6
Strain 4.0799 1.45168
Deformation (mm)
0.325 0.915
Nodes 14484 14480
Conclusion: From the software analysis data we can say that, the stress caring capacity of shutter is increased. So strength of shutter is increased.
Reference:
[1] International Journal of Scientific and Research Publications, Volume 4, Issue 4, AISSN 2250-3153 [2] Neeraj Singh Chauhan et al. / International Journal
of Engineering Science and Technology
[3] www.elsevier.com/locate/matdes Application of Taguchi optimization technique in determining plastic injection molding process parameters for a thin-shell part
[4] Impact forces in injection molding by Graham Poulter Applied Mathematics honors project, prepared for Prof. Tim Myers, Dept. Mathematics University of Cape Town
[5] Bown, J.: Injection Molding of Plastic Components. London, McGraw-Hill, 1979.
Buchanan. B. and Feigenbaum,
[6] Seaman,C.M., “Multi-objective optimization of a plastic injection molding process”. IEEE Transactions on Control System Technology,1994.
[7] D.V. Rosato, M.G. Rosato, Injection molding handbook” Massachusetts: Kluwer Academic Publishers, 2000. 3. M.C. Huang and C.C. Tai [8] https://en.wikipedia.org/wiki/injection-molding
