1 mold 4 cavity tube bending mold design based on … · 1 mold 4 cavity tube bending mold design...

1 Mold 4 Cavity Tube Bending Mold Design based on Moldflow

Jianmin Han, Dongpo Yang, Junqiang Wang Beijing Jiaotong University, Beijing, China, [email protected]

Abstract In this paper, according to the 1 mold 2 cavity tube bending die without a cooling system, manual

opening and closing mould lead long molding cycle, low production efficiency, and it can't meet the requirements of large-scale production, an automatic opening and closing die of the 1 mold 4 cavity tube bending is designed and development by Moldflow. New design ensures the product quality, saves the cost and improves the production efficiency. Computing with 300000 pieces of production order, relative to the 1 mold 2 cavity die, just to save raw material and save the fill time two computation can save production cost 88235.9 Yuan. In this paper, through the design and development of automatic 1 mold 4 cavity new bending die of the research process, fully verified simulation technology play an important role in modern enterprise production practice. Reasonable simulation technology, expertise and production practice of integration is a new idea about production, study, research development of the modern enterprise technology R & D department.

Keywords: Moldflow, tube bending, mold design, Molding cycle

1. Introduction

In this paper, Tube bending is produced with PP M800E by Zhenxiong V-260 injection molding machine. The mold is a mold two cavity. The four view of tube bending nodel is shown in figure 1. The injection molding cycle operation processes are as follows, as shown in figure 2 and in figure 3. ①Injection, automatic;

Open mode, manual② ; Extract ③ straight core-pulling (A), hydraulic, automatic; ④Rotating wheel (C), extract bending core (B), manual; ⑤Eject the product, semi-automatic; ⑥Half closed type, to press back the thimble, semi automatic; ⑦Back straight core-pulling (A), semi automatic; ⑧open the door of injection molding machine, semi-open, rotating the wheel manually(C), close

bending core (B); ⑨Closed die.

1.1. Existing problems

1. Sixth step: Adopt safety measures involved in the motion of mechanism, it easy to damage the equipment.

2. Sixth step: If closed mold accidentally, perform step eighth automatically, the thimble is damaged inevitable.

3. Seventh step: Manual opened and recovery the rotating wheel (C) lead long molding cycle and low production efficiency. If the recovery is not in place, the waste is produced.

4. Bending core (B) without cooling system, continuous production for a period of time need to spray cooling liquid for cooling, which is easy to cause some scrap.

1.2. Requirement of improvement

1. According to the requirements of large-scale production, and there is limited space to improve the original mold, it need to develop another set of mold.

2. New mold is to be used in a mold four cavity, in order to improve the production efficiency.

1 Mold 4 Cavity Tube Bending Mold Design based on Moldflow Jianmin Han, Dongpo Yang, Junqiang Wang

International Journal of Digital Content Technology and its Applications(JDCTA) Volume7,Number6,March 2013 doi:10.4156/jdcta.vol7.issue6.28

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3. It plans to select the power or hydraulic power device for the operation of Wheel part, in order to improve the efficiency.

4. Design new cooling system to shorten the molding cycle, improve production efficiency.

Figure1 The four view of tube bending model

Figure2 Mold of tube bending Figure3 Mold of tube bending

1.3. Research situation

In recent years, domestic and foreign began to research on forming and production of tube bending by FEA. Dan, W.J and Zhang, W.G searched spring-back angle and plastic elongation prediction of thin-walled tube bending by FEM.[1] Li H, Yang H and Zhan M made a study on plastic wrinkling in thin-walled tube bending via an energy-based wrinkling prediction model.[2] Tang, N.C provides solutions to seven common tube-bending questions. In his paper, some practical formulae are developed to explain the phenomena in tube bending and their magnitudes are also derived.[3] Al-Qureshi and H.A.gives the analytical methods whereby approximate equations are derived to provide a quantitative method for predicting the spring back behavior and residual stress distributions. Comparisons between experimental and theoretical results of spring back have shown remarkable agreement.[4] He Yang, Heng Li and Zhiyong Zhang, etc summary the advances and trends on tube bending forming technologies.[5] Bo Wang and Xianmeng Wang design of the injection mold for the 45ºplastic bend


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tube.[6] Kangfu Wang and Fei Lin design of the injection mold for the 90ºplastic bend tube with a special core- pulling mechanism.[7] Biao Zhou analyzes the plastic injection molding process of the 90° Elbow.[8] Kangfu Wang and Fei Lin design a hydraulic automatic control of 90° plastic pipe injection molding.[9]

2. The numerical simulation analysis of tube bending mold design 2.1. The numerical simulation analysis of 1 mold 2 cavity tube bending mold

Taking Moldflow[10, 11, 12] as a research tool, the grid model and the analysis results of 1 mold 2 cavity tube bending mold is shown in figure 4.

(a)Meshing and Settings (b)Fill time (c)Time to reach ejection temperature

(d)Average temperature, part (e)Volume shrinkage (f)Deflection, all effects

(g)Pressure at injection location (h)Air traps (i)Weld line

Figure 4 Meshing and Settings and analysis results of 1 mold 2 cavity tube bending


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As shown in figure 4, the fill time is 2.069s. Time to reach injection temperature is 49.46s. The position which is finally reached injection temperature appeared in straight core-pulling parts, the highest temperature of products appeared in the vicinity of straight core-pulling, and the biggest volume shrinkage appeared in straight core-pulling position too. So, this part of the cooling should be strengthened in order to shorten the molding cycle, control of deformation, making the volume shrinkage convergence. The highest pressure at injection location is around 60MPa. Air traps appears in the edge of tube bending. Because of the predicted position appeared in the parting plane, the air traps effects can be ignored. Weld line appeared in the position between the two injection gate, the strength of this part will be worse. The maximum deflection is 1.252mm, appeared in the edge of straight core-pulling position. This deformation can be accepted by customers in actual production.

2.2. The numerical simulation analysis of 1 mold 4 cavity tube bending mold

A combination of the above problems and analysis results, 1 mold 4 cavity tube bending mold is designed by Moldflow. The H type of gating system (Idea 1) and X type of gating system (Idea 2) is shown in figure 5. Considering that X type of gating system can realize the shortest filling path, but because this system easy to punch deflection the bending core during filling, the idea 2 design schemes were cancelled. This paper focuses on the study of mold design about H type of gating system of 1 mold 4 cavity tube bending die.

Figure 5 H type of gating system and X type of gating system

Analysis on different ends of size of H type of gating system, Analysis scheme is shown in table 1.

The analysis results are shown in table 2.

Table.1. Analysis scheme of H type of gating system of 1 mold 4 cavity tube bending mold

scheme number

Runner diameter of H type of gating systems(mm)

Relative position and size of

bending core end(mm)

Relative position and size of straight

core-pulling end(mm)

Remarks

A-1 6 29.8 46 Original scheme

A-2 6 32.92 30.5 New scheme

A-3 4.5 32.92 30.5 New scheme


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Table.2. Analysis results of H type of gating system of 1 mold 4 cavity tube bending mold

Scheme number

Fill time (s)

Time to reach ejection

temperature (s)

Maximum clamping force (t)

Maximum deflection (mm)

A-1 1.994 36.94 248.2 0.8774

A-2 2.007 35.90 252.8 0.8558

A-3 2.007 35.90 252.8 0.8558

According to the above analysis result, narrow runner diameter does not influence the final product

quality and gate weight. The packing time of scheme A-2 and A-3 is 30s. At the end of packing, a total weight of products and channel is 102.4551g, which products weight is 88.9188g, a total weight of main runner and runner and gate is 13.5363g. The maximum gate weight value is 14.3359g which appeared in the packing stage of 6.916s. The analysis results scheme A-2 is shown in Figure 6. Compared to the original 1 mold 2 cavity mold, fill time is reduced from 2.069s to 2.007s, time to reach injection temperature decreased from 49.46s to 35.9s, the maximum deflection decreased from 1.252mm to 0.8558mm, the position of air traps and weld lines is similar to the original 1 mold 2 cavity mold, the average temperature of products under 90℃ , the highest temperature appeared in the straight core-pulling. Scheme A-2 added cooling system in straight core-pulling, relatively higher temperature position appeared in the bending core, but its maximum temperature value relative to the original plan of 109.8 ℃ has been reduced. Pressure at injection location of maximum clamping force is 252 tons. If the mold can be installed, it can be used Zhenxiong V260 injection molding machine for production.

(a)Fill time (b) Time to reach ejection temperature (c) Deflection, all effects

(d)Air traps (e)Weld line (f) Average temperature, part


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(g)Maximum temperature position (h)Pressure at injection location Figure6 Analysis results of plan A-2

3. Mold design of 1 mold 4 cavity tube bending

Gear rack has good advantages of big bearing capacity and high transmission precision. In this paper, the bending core is driven by gear-rack automatic opening and closing to realize automatic open-close mould. As shown in figure 7, gear radius is 95mm, the theory of process for cylinder is 1/2Π R=151mm. Mold size is 670mm ×620mm ×440mm. It is equipped with 4 oil pumps, control two straight core-pulling and two bending core. 4 pump distribution in both sides of the die. Die holder and oil pumps and auxiliary device theoretical size is 1200mm ×620mm ×440mm. The position of oil pumps is shown in figure 8. The position of gear and bending core before the mold is opened is shown in figure 9. The position of gear and bending core after the mold is opened is shown in figure 10.

Figure7 Rack and pinion drive schematic diagram Figure8 Oil pump location schematic diagram

Figure9 Key position before the mold is opened


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Figure10 Key position after the mold is opened

The gating system of new mold is shown in figure 11. The inlet diameter of main runner is 4mm, the

outlet diameter of main runner is 6mm, and the length of main runner is 100mm. The diameter of each runner is 5mm, the length of each runner is 170mm. Gate is the rectangular gate, its size is 0.5mm ×3mm, its length is 3.7mm.

Figure11 Gating system schematic diagram

The cooling system of new mold is shown in figure 12. There are 16 cooling channel in female die,

its diameter is 12mm, the two channel interval in the middle is 60mm, outward interval is 70mm, the distance of cooling channel and parting surface is 60mm. The distribution of cooling system is shown in figure 12(b). As shown in figure 12(c), there is a water baffle in the straight core-pulling, its diameter is 12mm, and its length is 110mm through the straight core-pulling, and the distance of center and the interface of straight core-pulling and mold is 90mm, the distance of center and upper surface and is 20mm, the distance of center and lower surface is 20mm, the distance of baffle plate and straight core-pulling edge is 20mm, the distance of two water baffle is 70mm, the diameter of water baffle is 10mm, the thickness of water baffle is 0.2mm, the length of water baffle is 90mm, the length of the channel is 100mm.

(a) (b)


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(c)

Figure12. Cooling system schematic diagram The position of thimble is shown in figure 13. There are 3 thimbles in new mold, one is in the

geometric center, and the other two is in the runner. The distance of the thimble is 130mm. Products to be ejected by thimble under the impetus of column, and back by spring.

Figure13 Thimble location schematic diagram 4. Analysis of cost saving 4.1. Cost saving by raw materials reduced

The gate weight of original 1 mold 2 cavity tube bending mold is 10g, the gate weight of new 1 mold 4 cavity tube bending mold is 13.5g, the price of PP M800E is 10600 Yuan / ton. So each product to save material cost: 10600 × (10×2-13.5) ÷4÷1000000=0.017225 Yuan. The service life of die is the 300000 times. The cost can be saved by raw materials reduced in the die service life for a total of: 0.017225 ×4 ×300000=20670 Yuan. Calculation by 300000 piece product order, it can save cost for: 20670÷4=5167.5 Yuan.

4.2. Cost saving by molding cycle reduced

Only calculation by the molding cycle shorten based on the simulation results, original 1 mold 2 cavity mold loader in EM260-V injection molding machine. Its injection power is 47.7KW. Molding cycle is 49.46 seconds. Pure manual by 70 seconds 1 cycle to calculate. And new 1 mold 4 cavity mold loader in EM400-V injection molding machine. Its injection power is 58.6KW. Molding cycle is 35.90 seconds. Automatic by 40 seconds 1 cycle to calculate. Every degree of electricity is 0.92 Yuan. The service life of die is the 300000 times. Computing with 300000 pieces of production order, the cost saving of electricity is:

[47.7×70×(1/3600)×0.92×300000]/2-[58.6×40×(1/3600)×0.92×300000]/4=83068.4 Yuan. Relative to the 1 mold 2 cavity die, just to save raw material and save the fill time two computation


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can save production cost: 5167.5 +83068.4 =88235.9 Yuan.

5. Physical contrast

New design of the mold has been verified in actual application. In fact, three shifts a day, the production orders of 80000 pieces were completion by only half a month last year. New design of the mold diagram is shown in figure 14.

Male die Female die Cooling system in straight core Cooling system in female die Figure14 The physical mold diagram

6. Conclusion

1. New design of the 1 mold 4 cavity tube bending mold realize the automatic open-close mold. 2. Narrow runner diameter does not influence the final product quality and gate weight, optimized

gating system layout is the main factor of the key of gate weight. 3. New design of the 1 mold 4 cavity tube bending mold has a strong capability of production, it

shorten the molding cycle and improved production efficiency. Computing with 300000 pieces of production order, relative to the 1 mold 2 cavity die, just to save raw material and save the fill time two computation can save production cost 88235.9 Yuan.

4. This study shows that the simulation technology can guide the mold design and process design, improve the design quality and design speed, effective combination of the simulation and analysis can be achieved on control of the plastic products quality and cost, improving production efficiency, and enhance the core competitiveness of enterprises.

7. References [1] Dan, W.J, Zhang, W.G, "Spring-back angle and plastic elongation prediction of thin-walled tube

bending by FEM", Applied Mechanics and Materials, Trans Tech Publications, vol. 152-154, pp.456-461, 2012.

[2] Li H, Yang H, Zhan M, "A study on plastic wrinkling in thin-walled tube bending via an energy-based wrinkling prediction model", Modeling and Simulation in Materials Science and Engineering, Institute of Physics Publishing, vol. 17, no. 3, 2009.

[3] Tang, N.C, "Plastic-deformation analysis in tube bending", International Journal of Pressure Vessels and Piping, Elsevier Ltd, vol. 77, no. 12, pp.751-759, 2000.

[4] Al-Qureshi, H.A, "Elastic-plastic analysis of tube bending", International Journal of Machine Tools and Manufacture, Elsevier Sci Ltd, vol. 39, no. 1, pp.87-104, 1999.

[5] He Yang, Heng Li, Zhiyong Zhang, Mei Zhan, Jing Liu, Guangjun Li, "Advances and Trends on Tube Bending Forming Technologies", Chinese Journal of Aeronautics, vol. 25, no. 1, pp.1-12, 2012.

[6] Bo Wang, Xianmeng Wang, "Injection mold design of 45° plastic pipe", Mold Manufacturing, no. 4, pp. 53-55, 2007.

[7] Yalin Yan, Zhiping Peng, "Injection mold design of core pulling mechanism of 90° plastic pipe joint", Mold technology, vol. 2001, no. 1, pp. 24-26, 2001.


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[8] Biao Zhou, "Plastic Injection Molding Process Optimization of 90° Elbow", Coal Mine Machinery, vol. 29, no.1 pp. 92-94, 2001.

[9] Kangfu Wang, Fei Lin, "Hydraulic automatic control of injection molding of 90° plastic pipe", Mold Industry, vol. 1995, no.1, pp. 46-48, 1995.

[10] Jian Fu, Yongdao Jiang, Guoping Zhao, Moldflow Design Guide, Sichuan University press, China, 2010.

[11] Shaofei Jiang, Hongwei Jiang, Jiquan Li, "Birefringence Analysis of Transparent Plastic Plate Based on Moldflow", JCIT: Journal of Convergence Information Technology, vol. 8, no. 1, pp. 339- 345, 2013.

[12] Xu Yang, Bo Wen, Chao-nan Tong, "Modeling and Fuzzy-PID Control of Hydraulic-Rolls Coupled System in Cold Rolling Mills", AISS: Advances in Information Sciences and Service Sciences, vol. 4,no. 20, pp. 632-639, 2012.


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1 mold 4 cavity tube bending mold design based on … · 1 mold 4 cavity tube bending mold design...

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