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In-situ density measurement for plastic injection molding via ultrasonic technology

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Abstract

Density variation during the injection molding process directly reflects the state of plastic melt and contains valuable information for process monitoring and optimization. Therefore, in-situ density measurement is of great interest and has significant application value. The existing methods, such as pressure—volume—temperature (PVT) method, have the shortages of time-delay and high cost of sensors. This study is the first to propose an in-situ density measurement method using ultrasonic technology. The analyses of the time-domain and frequency-domain signals are combined in the proposed method. The ultrasonic velocity is obtained from the time-domain signals, and the acoustic impedance is computed through a full-spectral analysis of the frequency-domain signals. Experiments with different process conditions are conducted, including different melt temperature, injection speed, material, and mold structure. Results show that the proposed method has good agreement with the PVT method. The proposed method has the advantages of in-situ measurement, non-destructive, high accuracy, low cost, and is of great application value for the injection molding industry.

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Abbreviations

2s + 1:

Filter window size

b :

Intercept of the linear fitting

c :

Ultrasonic velocity

f :

Frequency

f c :

Central frequency of the transducer

h :

Thickness of plastic melt

H(f):

Transfer function of the echo signals

j:

Imaginary unit

k :

Slope of the linear fitting

K :

Proportionality propagation coefficient

m :

Coefficient that convert the unit of damping coefficient from Np/cm to dB/cm

P :

Melt pressure

R 0, R 1 :

Correlation function of u1 and u2

R 0, R 1 :

Reflection coefficients of the Material 1/Material 2 surface and Material 2/Material 3 surface, respectively

Δt :

Time delay between u1(t) and u2(t)

T o, T′0 :

Transmission coefficients of the ultrasonic waves passing forward and backward through the Material 1/Material 2 surface, respectively

T :

Melt temperature

u(t):

Time-domain signals

U o :

Original ultrasonic signal generated ultrasonic transducer

U 1, U 2 :

First and second echo signals reflected from the two surfaces of Material 2, respectively

U(f):

Amplitude spectrum of signals

U 1(f), U 2(f):

Amplitude spectrum of U1 and U2, respectively

V :

Specific volume

Z 0, Z1, Z 2 :

Acoustic impedances of Materials 1, 2, and 3, respectively

α :

Damping coefficient

ρ :

Density

References

  1. Yang C, Su L J, Huang C N, Huang H X, Castro J M, Yi A Y. Effect of packing pressure on refractive index variation in injection molding of precision plastic optical lens. Advances in Polymer Technology, 2011, 30(1): 51–61

    Article  Google Scholar 

  2. Zhao P, Yang W M, Wang X M, Li J G, Yan B, Fu J Z. A novel method for predicting degrees of crystallinity in injection molding during packing stage. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2019, 233(1): 204–214

    Article  Google Scholar 

  3. Hayu R, Sutanto H, Ismail Z. Accurate density measurement of stainless steel weights by hydrostatic weighing system. Measurement, 2019, 131: 120–124

    Article  Google Scholar 

  4. Nemiroski A, Kumar A A, Soh S, Harburg D V, Yu H D, Whitesides G M. High-sensitivity measurement of density by magnetic levitation. Analytical Chemistry, 2016, 88(5): 2666–2674

    Article  Google Scholar 

  5. Davidson S, Perkin M. An investigation of density determination methods for porous materials, small samples and particulates. Measurement, 2013, 46(5): 1766–1770

    Article  Google Scholar 

  6. Zhou X D, Zhang Y, Mao T, Zhou H M. Monitoring and dynamic control of quality stability for injection molding process. Journal of Materials Processing Technology, 2017, 249: 358–366

    Article  Google Scholar 

  7. Xu H, Wu D M, Zhu Q X, Zhang Y J. Research of precision injection control system based on the on-line measurement of polymer melt density. Advanced Materials Research, 2012, 383: 5136–5141

    Google Scholar 

  8. Gao R X, Tang X Y, Gordon G, Kazmer D O. Online product quality monitoring through in-process measurement. CIRP Annals, 2014, 63(1): 493–496

    Article  Google Scholar 

  9. Chen J Y, Yang K J, Huang M S. Online quality monitoring of molten resin in injection molding. International Journal of Heat and Mass Transfer, 2018, 122: 681–693

    Article  Google Scholar 

  10. Wang J, Hopmann C, Kahve C, Hohlweck T, Alms J. Measurement of specific volume of polymers under simulated injection molding processes. Materials & Design, 2020, 196: 109136

    Article  Google Scholar 

  11. Zhao P, Zhang J F, Dong Z Y, Huang J Y, Zhou H W, Fu J Z, Turng L S. Intelligent injection molding on sensing, optimization, and control. Advances in Polymer Technology, 2020, 2020: 7023616

    Article  Google Scholar 

  12. Zhou X W, Zhang Y, Yu W J, Li M Y, Chen Y H, Zhou H M. An imaging performance analysis method correlated with geometrical deviation for the injection molded high-precision aspheric negative plastic lens. Journal of Manufacturing Processes, 2020, 58: 1115–1125

    Article  Google Scholar 

  13. Abeykoon C. A novel soft sensor for real-time monitoring of the die melt temperature profile in polymer extrusion. IEEE Transactions on Industrial Electronics, 2014, 61(12): 7113–7123

    Article  Google Scholar 

  14. Suñol F, Ochoa D A, Garcia J E. High-precision time-of-flight determination algorithm for ultrasonic flow measurement. IEEE Transactions on Instrumentation and Measurement, 2019, 68(8): 2724–2732

    Article  Google Scholar 

  15. Zhao G L, Liu S Z, Zhang C, Jin L, Yang Q X. Quantitative testing of residual deformation in plate with varying thickness based on nonlinear ultrasound. Materials & Design, 2022, 214: 110402

    Article  Google Scholar 

  16. Zheng J Y, Zhang Y, Hou D S, Qin Y K, Guo W C, Zhang C, Shi J F. A review of nondestructive examination technology for polyethylene pipe in nuclear power plant. Frontiers of Mechanical Engineering, 2018, 13(4): 535–545

    Article  Google Scholar 

  17. Kariminejad M, Tormey D, Huq S, Morrison J, McAfee M. Ultrasound sensors for process monitoring in injection moulding. Sensors, 2021, 21(15): 5193

    Article  Google Scholar 

  18. Ageyeva T, Horváth S, Kovács J G. In-mold sensors for injection molding: on the way to Industry 4.0. Sensors, 2019, 19(16): 3551

    Article  Google Scholar 

  19. Zhao P, Zhao Y, Kharbas H, Zhang J F, Wu T, Yang W M, Fu J Z, Turng L S. In-situ ultrasonic characterization of microcellular injection molding. Journal of Materials Processing Technology, 2019, 270: 254–264

    Article  Google Scholar 

  20. Brown E C, Mulvaney-Johnson L, Coates P D. Ultrasonic measurement of residual wall thickness during gas assisted injection molding. Polymer Engineering and Science, 2007, 47(11): 1730–1739

    Article  Google Scholar 

  21. Zhao P, Ji K P, Zhang J F, Chen Y H, Dong Z Y, Zheng J G, Fu J Z. In-situ ultrasonic measurement of molten polymers during injection molding. Journal of Materials Processing Technology, 2021, 293: 117081

    Article  Google Scholar 

  22. Zhao L J, Lai Y, Pei C, Jen C K, Wu K D. Real-time diagnosing polymer processing in injection molding using ultrasound. Journal of Applied Polymer Science, 2012, 126(6): 2059–2066

    Article  Google Scholar 

  23. Shepard C L, Burghard B J, Friesel M A, Hildebrand B P, Moua X, Diaz A A, Enderlin C W. Measurements of density and viscosity of one- and two-phase fluids with torsional waveguides. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 1999, 46(3): 536–548

    Article  Google Scholar 

  24. Abu-Zahra N H. Measuring melt density in polymer extrusion processes using shear ultrasound waves. The International Journal of Advanced Manufacturing Technology, 2004, 24(9): 661–666

    Article  Google Scholar 

  25. van Deventer J, Delsing J. Thermostatic and dynamic performance of an ultrasonic density probe. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2001, 48(3): 675–682

    Article  Google Scholar 

  26. Raišutis R, Kažys R, Mažeika L. Application of the ultrasonic pulse-echo technique for quality control of the multi-layered plastic materials. NDT & E International, 2008, 41(4): 300–311

    Article  Google Scholar 

  27. Knapp C, Carter G. The generalized correlation method for estimation of time delay. IEEE Transactions on Acoustics, Speech, and Signal Processing, 1976, 24(4): 320–327

    Article  Google Scholar 

  28. Yu T M, Jiang F C, Wang J H, Wang Z Q, Chang Y P, Guo C H. Acoustic insulation and absorption mechanism of metallic hollow spheres composites with different polymer matrix. Composite Structures, 2020, 248: 112566

    Article  Google Scholar 

  29. Hayward A T J. Compressibility equations for liquids: a comparative study. British Journal of Applied Physics, 1967, 18(7): 965–977

    Article  Google Scholar 

  30. Wang J, Hopmann C, Schmitz M, Hohlweck T, Wipperfürth J. Modeling of PVT behavior of semi-crystalline polymer based on the two-domain Tait equation of state for injection molding. Materials & Design, 2019, 183: 108149

    Article  Google Scholar 

  31. Ma Z G, Wei W, Zu Y Q, Huang M, Zhou P J, Shi X Z, Liu C T. A novel and simple method to improve thermal imbalance and sink mark of gate region in injection molding. International Communications in Heat and Mass Transfer, 2021, 127: 105498

    Article  Google Scholar 

  32. Michaeli W, Starke C. Ultrasonic investigations of the thermoplastics injection moulding process. Polymer Testing, 2005, 24(2): 205–209

    Article  Google Scholar 

  33. Hoseini M R, Zuo M J, Wang X D. Denoising ultrasonic pulseecho signal using two-dimensional analytic wavelet thresholding. Measurement, 2012, 45(3): 255–267

    Article  Google Scholar 

  34. Smith S. Digital Signal Processing: A Practical Guide for Engineers and Scientists. Amsterdam: Elsevier, 2013

    Google Scholar 

  35. Zhao P, Xia N, Zhang J F, Xie J, Zhang C Q, Fu J Z. Measurement of molecular orientation using longitudinal ultrasound and its first application in in-situ characterization. Polymer, 2020, 187: 122092

    Article  Google Scholar 

Download references

Acknowledgements

This work was supported by the “Pionerr” and “Leading Goose” R&D Program of Zhejiang, China (Grant No. 2022C01069), the National Natural Science Foundation of China (Grant No. 51875519), the Key Project of Science and Technology Innovation 2025 of Ningbo City, China (Grant No. 2021Z044), and the Project of Innovation Enterprises Union of Ningbo City, China (Grant No. 2021H002). The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Authors and Affiliations

  1. State Key Laboratory of Fluid Power and Mechatronic Systems, College of Mechanical Engineering, Zhejiang University, Hangzhou, 310027, China

    Zhengyang Dong, Peng Zhao, Kaipeng Ji & Jianzhong Fu

  2. Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, College of Mechanical Engineering, Zhejiang University, Hangzhou, 310027, China

    Zhengyang Dong, Peng Zhao, Kaipeng Ji & Jianzhong Fu

  3. Beijing Institute of Aeronautical Materials, Beijing, 100095, China

    Yuhong Chen

  4. Haitian Plastics Machinery Group Co., Ltd., Ningbo, 315801, China

    Shiquan Gao

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  1. Zhengyang Dong
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  2. Peng Zhao
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Correspondence to Peng Zhao.

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Dong, Z., Zhao, P., Ji, K. et al. In-situ density measurement for plastic injection molding via ultrasonic technology. Front. Mech. Eng. 17, 58 (2022). https://doi.org/10.1007/s11465-022-0714-2

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