The exploration and practice of the teaching reform of the first part of packaging testing technology [Abstract] aims at cultivating applied talents. This paper first analyzes the basic quality of students majoring in packaging engineering and the characteristics of detection technology course, and then discusses the teaching reform from three aspects: teaching purpose, teaching content, teaching methods and practical links. Through three years of teaching practice, the development direction of teaching reform in the future is put forward.
[Keywords:] testing technology packaging engineering teaching reform
【 China Library Classification Number 】 G 642 【 Document Identification Number 】 A
Packaging Inspection Technology is a compulsory course for four-year students majoring in packaging engineering. With the increasing automation of packaging industry and the improvement of product packaging standardization, it is particularly important to master the knowledge of this course. In order to achieve the teaching effect, we have explored the teaching reform of this course. This paper first analyzes the basic quality of students majoring in packaging engineering and the characteristics of testing technology course, and then introduces the progress and ideas of teaching reform and exploration from three aspects: teaching purpose, teaching content, teaching methods and practical links.
First, the quality of students and curriculum characteristics
The students majoring in packaging engineering are basically middle school students, with weak initiative, understanding and hands-on ability, but active thinking and strong desire to express; In addition, there are more female students than other engineering majors, and the ratio of male to female is close to 1: 1. Girls study harder than boys. Broad foundation and thick specialty are the leading teaching principles of our school, focusing on cultivating students' extensive knowledge and more professional accumulation. Testing Technology is a professional basic course for the majors of machinery, energy and chemical engineering, involving signal analysis and processing, system dynamic characteristics, sensor principle, engineering quantity testing, testing instrument principle and so on. It has a wide range of knowledge, including both theoretical knowledge of spectrum analysis and practical knowledge of sensors and signal processing. Based on the basic quality of students and the teaching policy of the school, the classroom teaching of school-based courses in our school has been reduced to 36 hours, and the experimental and practical links have remained at 18 hours.
Second, the exploration of teaching reform
As a highly open course, testing technology is undergoing the reform of teaching and scientific research. Guo et al. [1] take virtual instrument Labview as the breakthrough of the course, and combine the concept and method of testing to improve teaching; Zhu [2] adjusted the teaching level of the course, emphasizing the combination of learning practicality and production application; Wang Xue [3] adopted an innovative experimental method, that is, students conceived the experiment themselves, designed the experimental scheme, described the experimental data and scored the defense. Want me to learn? For what? I want to learn? . Xu et al. [4] improve students' practical ability by involving them in scientific research; Wu Shixiong and others [5] use applied experiments to improve students' initiative; Hua Chunjian and others [6] stimulate students' enthusiasm for learning by introducing new sensors and new testing methods. It can be seen that all teaching reforms are aimed at improving students' learning initiative and cultivating practical ability. Let's introduce our exploration on the teaching reform of this course.
(A) the reform of teaching objectives
Defining the teaching purpose is the primary task. Packaging engineering majors train talents in packaging electromechanical equipment, packaging materials, printing and packaging design, transportation and logistics. The industry spans a large span, and the learning methods and thinking characteristics of various professional courses are quite different. If the courses corresponding to these potential jobs are evenly distributed with limited class hours, teachers will face the dilemma of uncharacteristic teaching and students will be at a loss. The major of packaging engineering in our school belongs to the College of Mechanical and Electrical Engineering, which has its own characteristics in mechanical design, mechatronics, teachers' equipment, teaching instruments and so on. Combined with the characteristics of students and the social demand for talents, it is gradually clear that the teaching purpose of this major is to cultivate applied R&D talents in packaging electromechanical equipment and packaging material design, which requires students to have the ability to develop packaging equipment, design packaging material inspection scheme and practice.
(B) the reform of teaching content and methods
According to the teaching purpose, the focus of the teaching content is firstly formulated, that is, the application method of sensors in packaging industry is taught, and the concept of error handling, dynamic frequency characteristics, packaging testing methods and standards are introduced as the core. For example, eddy current proximity switch is the most widely used sensor in packaging equipment, and its basic principle and internal modulation circuit involve complex linear amplification and modulation circuits, which are difficult for students to understand. Moreover, as a mature product, it has been completely packaged into the product, and we only introduce its principle, without making understanding requirements; This paper focuses on the acquisition of its output signal. For the NPN open collector output, the principle that the output needs to be connected with a pull resistor is taught and demonstrated in class, and the change of its output level is observed with a multimeter.
Secondly, starting with the authenticity of the classroom content, arouse students' initiative and enthusiasm in learning. Now every student has a mobile phone and wants to play at any time. In addition to emphasizing classroom discipline, teachers mainly rely on classroom content to attract their attention. Teaching should not only emphasize the systematicness and theory of knowledge, but also emphasize the practicality. If it is purely for the integrity of knowledge, it will be boring and the classroom will lack vitality. The application of video, physical objects, experiments and hands-on programming are all aimed at attracting students, changing passive learning into active operation and attracting the attention of the whole class. For example, when teaching the frequency characteristics of the test system, let students recall the knowledge of electrician and electronics, draw the impedance calculation method of capacitance and inductance, deduce the frequency characteristics of the first-order resistance-capacitance series circuit with blackboard writing, and then deform the circuit appropriately so that students can answer on the platform. Then, take out the signal generator and oscilloscope, change the frequency of the input sine signal of the resistance-capacitance circuit, and observe the change of the output signal with the oscilloscope.
In view of the strong desire of students born in 1980s and 1990s, after teaching the engineering application of sensors, students are required to observe things around them, consult literature and write sensor application reports in groups. After reviewing these reports, the teachers set aside a class time for them, so that excellent reports can get the opportunity to speak on the stage and rank them. Linking scores with final grades can promote students' active learning, master the general methods of consulting literature, and cultivate students' ability to express specialized knowledge.
Thirdly, the method of connecting the course content and the theory with software can deepen students' understanding of theoretical knowledge. For example, sensors and filters are related to the frequency characteristics described above; The first, second and third order filters are designed by using FilterLab, a filter design software provided by American chip companies, which makes students feel that the design of filters is not so advanced. Then use signal generator and oscilloscope to observe the frequency characteristics of sensor and test system, and find the purpose of testing frequency characteristics. Then use the transfer function analysis tool of Matlab to observe Bode diagram, and introduce Matlab software by the way, so that students can master a new data analysis software and cultivate their ability to analyze data scientifically.
Finally, combined with the characteristics of the packaging industry, the application-oriented testing methods such as packaging testing, packaging container testing, transportation packaging testing and related national standards are taught to guide students to combine course knowledge with professional applications. In order to avoid the tedious demonstration, we should watch the video and design the packaging test scheme, so as to promote their understanding of the test technology in production and application and lay the foundation for their quick entry in future work. (C) Reform practice
Practice is an important starting point to highlight the curriculum design idea centered on sensor application. Curriculum practice is divided into two levels. The first level is the experimental link. Using CSY-3000 sensor experimental platform, students can feel the characteristics of resistance strain gage, eddy current sensor, photoelectric sensor, bridge and filter circuit, and cultivate their ability to deal with error data. Through the use of corrugated paper testing instruments and sealing testing instruments in packaging testing laboratory, we can understand the testing items and standards of packaging industry. Through this level of practice, theory and practice are initially related. The second level is to set up practical interest groups and carry out project teaching for students with strong learning consciousness and thirst for knowledge. Students report the test items they are interested in, and through the screening of teachers, choose a project that is closely related to the major but can meet the short-term needs to cultivate their knowledge application ability. Instruct students to design the realization scheme of the project, and then start the procurement of sensors and electronic components, welding and debugging of circuits, require data measurement and cultivate data processing ability.
Through all aspects of teaching reform, students initially have the ability to design a testing system for packaging machinery and automatically detect sensor units. In the following courses, such as packaging electromechanical control, hydraulics and pneumatics, they insist on project teaching, and finally achieve the purpose of professional teaching through continuous training and hard work.
Third, the existing problems and the direction of future teaching reform
After three years of practice, the teaching method of Testing Technology has cultivated some students' interest in learning and practical ability. The concept and method of testing have been applied in graduation project, but there are still some problems, such as some students' interest in learning has not been mobilized, and the teaching effect of project teaching is not ideal. There are many reasons. For example, the suppressed exam-oriented education in our primary and secondary schools has dampened the initiative and creativity of many students. We believe that teaching reform is a systematic project, which needs the coordinated promotion of many courses. The future teaching reform direction of this course includes:
1) innovate the teaching material system to adapt to the development of the times;
2) Overall planning, not only to design practical links, but also to improve the allocation of teachers and reward links for teachers and students;
3) Conduct national academic competitions to promote exchanges between different universities.
[References]
[1] Guo, Zheng Shuhua. Research on the course reform of mechanical engineering testing technology in local universities [J]. Journal of Ningbo Institute of Technology, vol. 2 1 2009 (1):118-18.
[2] Zhu,. Mechanical major? Test technology? On Curriculum Teaching Reform [J]. China Electric Power Education, 2009, 139: 89-90.
[3] Wang Xue, Wang Boxiong, Luo Xiuzhi. Teaching Reform and Innovation of Testing and Testing Technology Basis [J]. Research on Higher Science and Technology Education, Vol.28 (04), 2009: 130- 132.
[4] Xu, Cai, Shang Zhendong, Wu Feng, Yang Jianxi. Research and Practice of Experimental Teaching Reform of Testing Technology [J]. china modern educational equipment. 2009,81:107-108.
[5] Wu Shixiong, a native of CHENGYONG WANG. Mechanical engineering testing technology? Exploration of teaching reform [J]. Journal of Guangdong University of Technology (Social Science Edition) .2007,7 (Supplement1):108-109.
[6] Hua Chunjian, You Lihua, Monday. Research on Teaching Reform and Innovation of Testing Technology Course [J]. Journal of Jiangnan University (Education Science Edition), Vol.28 (01), 2008: 69-72
(Author: Ningbo Institute of Technology, Zhejiang University)
Interpretation and Analysis of FedEx Packaging Test Standard Part II: Product packaging plays an important role in product transportation. In order to ensure the reliability of transportation, there are many testing standards for packaging. This paper mainly interprets the FedEx packaging test standard, analyzes the classification of packages in the standard, and the test items and methods of packages exceeding 150 pounds, and compares and analyzes some similarities and differences with ISTA packaging test standard.
Packaging test standard; FedEx
introduce
In the process of product transportation and circulation, product packaging is of vital significance [1], which is convenient for transportation and protects products [2]. If the packaging of the product fails in the transportation environment, the product may be abnormal or even scrapped due to the strong impact during transportation [3]. In order to ensure the reliability of transportation packaging products in the transportation process, it is necessary to carry out transportation packaging tests in advance before transportation [4]. At present, there are many packaging inspection standards. This paper mainly interprets FedEx packaging inspection standards, and compares and analyzes some similarities and differences with ISTA packaging inspection standards.
1 Packaging Classification in FedEx Packaging Test Standard
FedEx packaging testing standards are divided into two parts. The first part is applicable to packages larger than 150 lbs (68kg), and the second part is applicable to packages smaller than 150 lbs. In this standard, this kind of package is divided into three types: flat package, long package and standard package, and the test requirements of different types of packages are different. See table 1 for the specific differences of several packages.
Compared with the package classification in FedEx packaging test standard, ISTA packaging test standard also stipulates the package classification. However, in addition to the above three categories, ISTA also stipulates that one category is small packaging. The specific parameters are: the longest side is less than 35cm( 14in), the volume is less than1310cm3 (800in3), and the mass is not more than 4.5kg (10lbs).
2 Test requirements for packages larger than 150 lbs (68kg) in FedEx packaging test standard.
In the FedEx packaging test standard, for packages larger than 150 lbs, according to Table 2, different types of packages should be tested separately.
The test parameters and process of specific test items in Table 2 are as follows.
(1) side impact test: the slowest impact rate of the inclined plane is 175cm/s(5.75 ft/s), and all sides of the package are tested.
(2) Bottom impact test: Raise the bottom of the sample to 20.3 cm (8 inches) above the impact surface, and then release the sample for falling.
(3)22-degree angle impact test: the bottom surface of the pointed sample is inclined along one edge, so that the bottom surface and the impact surface form an angle of 22? Then release it back to the original angle. Then repeat the above test along the other three sides of the bottom surface.
(4) Bump impact test: The bottom surface of the sample inclines along one edge, so that the opposite side of the bottom surface is 25.4cm( 10in) higher than the impact surface, and then it is released to the initial position. Then repeat the above test along the other three sides of the bottom surface.
(5) Raise the corner impact test: raise the bottom surface of the sample along a corner, so that the sample is supported by the corner of the impact surface, so that the diagonal of the bottom surface of the sample is 25.4cm( 10in) away from the impact surface, and then loosen it to return the sample to the impact surface. Then repeat the above test along the other four corners of the bottom surface.
(6) Compression test: The compression rate is 12.7cm/min(0.5in/min), and the test is finished when one of the following conditions is met: ① Stop load f (lbs) =0.007? ( 108-H)？ l？ W? F, where H, L and W are height, length and width, and F is humidity, time and accumulation factor; ② When the yield detection rate reaches 15%; ③ When the deviation is 2.54cm (1 inch).
(7) Rotational vibration test: ① Place the sample on a vertical vibration table, the vertical direction is not fixed, install an anti-drop device in the horizontal direction, then start to vibrate at the minimum required frequency, keep the vibration displacement at 25.4mm( 1in), then slowly increase the frequency until the sample leaves the vibration table instantly, stop the test and record the frequency; (2) At this frequency, the sinusoidal vibration test is carried out in a certain direction of the sample, with the fixed displacement of 25.4mm and the test time t(min)= 14200/(f? 60); ③ Carry out the same sinusoidal vibration test in the other two directions. For strip packaging, only the longest and shortest sides can be tested for sinusoidal vibration.
(8) Random vibration test: Conduct random vibration test on the sample in a certain direction on the vertical vibration table. The first step is to vibrate according to the truck random vibration program (Grms takes 0.52), the second step is to vibrate according to the aircraft random vibration program (Grms takes 1.06), and finally the truck random vibration program. Two vibration program diagrams are shown in figure 1 and figure 2. Domestic products, each step vibration15min; For internationally transported goods, each step should be vibrated for 30 minutes. Then do the same experiment in the other two directions.
For packages larger than 150 pounds (68kg), there are some similarities and differences between FedEx standard and ISTA standard. The main results are as follows: the tests required by ISTA standard include: ① fixed displacement vibration test; ② Choose one of bottom impact test, inclined impact test and horizontal impact test; (3) If the top surface cannot be impacted, the rotating edge drop test is required, and the test items are not as many as those in the FedEx standard. The fixed displacement vibration test in ISTA standard is the same as the sinusoidal vibration test in FEDEX standard. In the bottom impact test, the sample in ISTA standard is raised to 15.2cm(6in) above the ground, which is different from 20.3cm(8in) in FEDEX standard. The main difference between the rotating edge drop test in ISTA standard and the curl impact test in FEDEX standard is that in the rotating edge drop test, one side of the bottom surface is supported by the pad, while in the curl impact test, one side of the bottom surface is directly supported by the impact surface.
3. The test requirements for packages not exceeding 150 lbs (68kg) in FedEx packaging test standard.
According to FedEx packaging test standard, for packages not exceeding 150 pounds, according to Table 3, different types of packages should be tested separately.
(1) Free-falling test: Free-falling the package onto the steel impact surface in the following order, with the weakest corner touching the ground? Has the shortest edge on this corner landed? Is the next short side on this corner? The longest side of this angle touches the ground? Minimum face landing? The other one falls on the smallest side? Landing in the middle area? Another relatively medium-sized landing? Landing on some maximum surface? The other touches the ground with the biggest face. The drop height is determined by the quality of the package, as follows: 76.2 cm (30 inches) when it does not exceed 75 pounds (34 kilograms), and 6 1 cm (24 inches) when it reaches 100 pounds (45.4 kilograms), and 100 pounds to/kloc. (2) Concentrated impact test: A wooden box with length, width and height of 30.5cm( 12in) is filled with sandbags, so that it weighs 2 1 lb (9.5kg) and the bottom is wrapped with an angle iron. Lay the flat package flat on the steel surface. Mark the center of the package and the center of the angle iron edge of the wooden box. Tilt the wooden box along the edge of the bottom angle iron and raise it to 76.2 cm (30 inches). The box is parallel to the longest side of the package. Then naturally drop the angle iron edge on the package, and the center of the angle iron edge coincides with the center of the package. The specific impact diagram is shown in Figure 3.
(3) Bridge impact test: pad the two ends of the strip-shaped package on two building blocks with the height of 10. 1cm(4in) to find out the center of the package. A wooden box with a length of 30.5cm( 12in) and a width of 30.5cm is filled with sandbags, so that it weighs 2 1 lbs (9.5kg), and an angle iron is wrapped on a bottom edge to find the center of the edge. Tilt the wooden box along the edge of the bottom angle iron and raise it to 76.2 cm (30 inches). The box is perpendicular to the longest side of the package. Then naturally drop the angle iron edge on the package, and the center of the angle iron edge coincides with the center of the package. The specific impact diagram is shown in Figure 4.
(4) Compression test: the same as the compression test of packages exceeding 150 lbs.
(5) Sinusoidal vibration test: It is the same as the sinusoidal vibration test of packages exceeding 150 lbs.
(6) Random vibration test: It is the same as the random vibration test of the package above 150 lbs.
(7) Second free-fall test: For international transport goods, the second free-fall test shall be conducted after the vibration test.
As can be seen, the main difference between the package with no more than 65,438+050 pounds and the package with more than 65,438+050 pounds in FedEx packaging test standard lies in the different types of impact tests. There are obviously more types of impact tests for packages over 65,438+050 pounds than those under 65,438+050 pounds, which just shows the seriousness of impact tests for heavier packages. There are some similarities and differences between FedEx standard and ISTA standard for packages not exceeding 150 pounds. Mainly as follows: in ISTA standard, the types of packages also include small packages; The impact test items in the two standards are different. The impact tests in FEDEX standard and ISTA standard include concentrated impact test of strip package and bridge impact test of flat package, but the impact heights in the two standards are different. The height in FedEx standard is 76.2 cm (30 inches), while the height in ISTA standard is 40.6 cm (16 inches). In addition, the impact test in FEDEX standard includes two corners, two edges and six sides in turn, and the impact test in ISTA standard includes triangle, two corners and two sides in turn, tipping test and rotating drop test. In ISTA standard, there is pretreatment for temperature and humidity testing, but there is no such pretreatment in FEDEX standard. There are also great differences between the two standards in vibration testing, and there is also low-voltage random vibration testing in ISTA standard.
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This paper mainly interprets FedEx packaging test standard and compares it with ISTA packaging test standard. From the above interpretation and analysis, we can see that there are many testing items of packaging, and the testing procedures and parameters of different standards will be different [5]. However, for different standards of packaging, after completing the relevant tests, the reliability of the required transportation environment can be achieved.
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[4] Li Peisheng. Present situation and development trend of transportation and packaging industry in China [J]. Logistics Technology and Application, 2004 (8): 54-58.
[5] Kim. Optimization of transport packaging in logistics chain [J]. Packaging Engineering, 2005,26 (3): 93-95.
Hong Xiang. Engineering basis of packaging design [M]. National University of Defense Technology Press, 2002: 34-38.