문병권
(Byung-kwon Moon)
1
추상용
(Sang-yong Choo)
2
방준호
(Jun-ho Bang)
1
유인호
(In-ho Ryu)
1†
-
(Dept. of IT Applied System Engineering, Chonbuk National University, Korea)
-
(PIMACS Co., Ltd)
Copyright © The Korean Institute of Electrical Engineers(KIEE)
Key words
LED fusion lighting, Automated assembly, FR4 type, Defect rate
1. Introduction
In recent years, there has been a growing interest in LED lighting, which has higher
luminous efficacy and lower power consumption than conventional LCD-type lighting,
and can be used for a long time[1]. However, it is difficult to design a fully automated assembly line to replace the
manual process of assembling by hand due to various sizes and designs in the existing
production process of LED lighting[2]. This phenomenon is especially noticeable in the LED fusion lighting market, which
is in the spotlight recently[3].
In response to these market changes, the standardization of general LED lighting and
LED fusion lighting accessories is in progress to enable production with minimal manual
operation in the assembly system. Furthermore, LED fusion lighting is being developed
as a single panel[4]. LED fusion lighting is a so-called emotional lighting, which is a combination of
excellent light emission characteristics of LED lighting and five-sensor technology[5]. Particularly, in the case of LED fusion lighting, since the defect rate occurring
in the existing process is relatively high, the process improvement is urgently required[6]. The LED fusion lighting automation assembly system refers to a system that automatically
assembles various parts by mounting panel type LED fusion lights on the pallet loading
jig and transferring them through the main conveyor[7]. In this process, when assembling the module power supply of the existing LED fusion
lighting, there is a problem caused by the connection through the wire that is not
fixed exactly, which is directly related with the defect rate of complete product[8].
Most of the researches about solving the problem of automation system of LED fusion
lighting are focusing on the problem caused during the transferring of LED panels
through pallet loading jig. There are few studies focusing on the module power supply[9].
Therefore, this study was focusing on complementing these problems and redesigning
the module power supply of LED fusion lighting. Based on this, the final developed
LED fusion lighting was fabricated and the optical characteristics were analyzed to
prove the superiority of performance standard for high-efficiency energy equipment
certification. In addition, by developing a pallet loading jig optimized for the developed
LED fusion lighting, it was ultimately aimed to enhance compatibility with the LED
fusion lighting automatic assembly system, and further to expand compatibility with
various LED auto assembly systems[10].
2. ED fusion lighting design and development method
2.1 Design of power supply structure
In the conventional method, since the position of the wire is not fixed, there is
a problem that the product is not properly connected in the automatic assembly or
the wire is broken due to the bending of the wire. In order to solve this problem,
the first structural improvement was carried out as shown in Fig. 1(b).
Fig. 1. Structural design process of LED fusion lighting
Conventionally, since the space between the connection terminals is narrow, there
are frequent problems in the process of bending the wires. In order to improve this,
a type of wire connector for power supply was adopted by widening the space between
the connection terminals so that the terminals can be connected to each other by a
straight line.
However, in the process test, a wire warping phenomenon could be observed even though
the wire was connected in a straight line by the wire connector, resulting in poor
soldering position.
In order to prevent the warping of the connection part, the structure improvement
was carried out by using the iron type connector as shown in Fig. 1(c).
According to the inherent characteristics of the iron type, it is confirmed that the
warping phenomenon is remarkably lower than that of the wire connector type due to
the excellent electric conductivity and the large area. However, unlike the wire connector
type, frequent breakage could be observed due to the fact that the area where the
electricity is conducted is exposed to the outside and that the rigidity of the iron
connector material are not homogenous. A relatively wide conductive area was designed
to prevent the warping phenomenon. However, this method was found to lower the electric
stability.
Considering these problems, the structure was finally designed as shown in Fig. 2(c) and made by FR4 material. The final product was shown in Fig. 1(d).
Fig. 2. Structural design drawings of LED fusion lighting
Due inherent flexibility of the FR4 material, warpage and disconnection phenomena,
which were the problems of conventional methods, were solved.
In addition, by using FR4, which is the same material as the LED module and the power
connector, the problem of breakage was solved, and high electric stability was maintained
by simplifying the circuit line inside the FR4 connector.
2.2 Design of LED module for automatic assembly machine vision
In the case of LED flat panel type lighting, the accuracy of position of components
is important in the assembly process for automatic assembly of components. Therefore,
black circles were displayed on the surface of the LED module for locating precise
position using the machine vision video system and the motorized stage interface,
thereby to improve the accuracy of work in the assembling process. Fixed bolts, which
automatically adjust position errors during rotation, were used. In the design draft,
six circle lines of LED modules were planned as shown in Fig. 3(a) In order to optimize the positional accuracy during the bolting and soldering, totally
11 circle lines were constructed (Fig. 3(b)).
Fig. 3. LED module design structure of LED fusion lighting
2.3 Design and manufacture of pallet loading jig
Starting from the improvement of the design of the power supply part of the LED fusion
lighting module described above, the design of the LED fusion lighting module was
newly reflected in the existing LED fusion lighting drawing. The improvement and complementary
design of the overall LED fusion lighting structure were then carried out. Finally,
the LED fused lighting pallet loading jig optimized for process automation was developed.
Pallet loading jig is a critical device for automatic assembly system of LED fusion
lighting. It helps to solder and assemble parts in a state where LED fusion lighting
panel is fully fixed during automatic assembly. In order to assemble precisely, it
is important to design the module so that no shaking or clearance occurs in the vertical
and horizontal movements, and the most important thing is to accurately transfer the
LED panel to the auto assembling position.
Considering these characteristics, the pallet loading jig of the LED fusion lighting
is designed as shown in Fig. 4(a), considering the position and size of the redesigned parts.
The combination of the designed pallet loading jig and the LED fusion lighting is
shown in Fig. 4(b), and the pallet loading jig was manufactured based on this.
The pallet loading jig was manufactured to a size of 1400mm×480mm×35mm so that it
could be applied to the existing automation system, and the aluminum material was
processed by the water jet machining method and finished by the final anodizing process
as shown in Fig. 4(c)
Fig. 4. Pallet loading jig
In addition, the block is processed to connect the power to the upper part, that is
used to guarantee the position accuracy of the LED lighting.
The pallet loading jig acts as a support for automatic assembly and is designed to
be assembled in a precise position so that the appropriate parts can be assembled
and it is designed and manufactured to be easily attached and detached from the LED
fusion lighting for automatic assembly. Based on this design, a self-test was conducted
and it was found that the defect rate was reduced by about 17%.
3. LED fusion lighting performance evaluation
3.1 Evaluation of LED optical characteristics
The optical characteristics of the designed LED fusion lighting were analyzed by the
Korea Photonics Technology Institute for the reliability of the results. The characteristics
measured in this study are based on the performance criteria for high efficiency energy
equipment certification (Table 1).
Table 1. Comparison of performance criteria for high efficiency energy equipment certification
and characteristics of developed LED fusion lighting
|
Test list
|
Performance standard for high-efficiency energy equipment certification
|
Characteristic analysis result of developed LED fusion lighting
|
|
Color temperature [K]
|
5700K(±250 K)
|
5862K
|
|
Color rendering
|
80
|
86
|
|
Power Consumption [W]
|
50W
|
50.2W
|
|
frequency content [%]
|
30% below
|
13.4 %
|
|
Power factor
|
0.95
|
0.97
|
|
Light efficiency [lm/W]
|
100 lm/W
|
116.1 lm/W
|
The color temperature and color rendering were measured by Spectroradiometer 2M equipment.
The power consumption, harmonic content and power factor were measured by power analyzer,
and the light efficiency was calculated by equation (1).
The results of the characterization are shown in Table 1. As a result of the analysis, all of the six test items were confirmed to meet the
performance standard for high efficiency energy equipment certification.
Especially, the harmonic content of LED fusion lighting was 13.4% compared to that
of 30% or less for high efficiency energy equipment certification. The characteristic
value decreased by about 55% compared with the standard. In addition, the characteristics
of light efficiency increased by about 16.1% compared to the performance standard
(100lm/W or more), and the LED fusion lighting for automatic assembly developed through
this study satisfied all the performance standards for high efficiency energy equipment
certification. Moreover, it was proved that the LED fusion lighting developed for
auto assembly can be applied directly to LED fusion lighting field.
3.2 Automatic assembly performance evaluation
In order to confirm the automatic assembly performance of LED fusion lighting for
automatic assembly, output per line and defect rate were tested and evaluated. The
equipment used for the test evaluation is the automated inspection and mass production
assembly equipment for LED fusion lighting as shown in Fig. 5 The size of the equipment is 13600 x 5500 x 2400 (H) mm, and consists of assembly
line part, aging part, optical (electrical) characteristic inspection unit, and conveyor
drive unit. The output per line of the automatic assembly equipment was measured during
unit time. Output per line were separated into four assembly processes: LED panel
assembly process, fixing process, soldering process, and diffusion cover assembly
process. The assembly time for each process was tested for three times, and the maximum
assembly time was measured as the assembly time of each process.
Fig. 5. Automatic inspection and Mass assembly production equipment for LED fusion
lighting
The defect rate of the automatic assembly system was determined by the criteria of
acceptance of the inspection units. The defective product was made and moved on the
conveyor and repeatedly measured by the inspection unit.
As a result of assembling performance test, the production time for each process was
31 sec for LED panel assembling process, 32 sec for fixing process, 31 sec for soldering
process, and 30 sec for diffusion cover assembling process. After each line, the final
shipment of the product was recorded for a maximum of 40 seconds.
10 defective products were fabricated and the optical and electrical property were
repeatedly measured by the inspection unit. Defective products may be artificially
reduced in luminance or using color filters, Checking the change in the color temperature
value We checked whether the defective product was recognized as defective products.
In the defect detection standard of illumination(± 10%), color temperature(± 300K)
and color rendering property(± 2), the automatic assembly defect rate of LED fusion
lighting process was 0%.
4. Conclusion
The module power supply of conventional LED fusion lighting was fabricated by wire,
but fixation problems of wire often resulted in defects in the complete product. In
order to solve the problem, two methods of wire connection change and iron wire connector
type were proposed. However, fabrication process problems, such as warping of the
connector, disconnection, and breakage of connector could still be observed. Finally,
the problem of defect rate caused by connecting problem was solved by changing to
FR4 type power supply and high electrical stability was ensured by simplifying internal
circuit lines. It is also confirmed that the output of LED fusion lighting designed
for automatic assembly is 92.3 set/hr per line.
The whole design of LED fusion lighting was carried out according to the newly designed
LED fusion lighting. In order to apply the redesigned LED fusion lighting to the automatic
assembly system, a new pallet loading jig, which can be applied to the existing automatic
assembly system and enable accurate and precise automatic assembly process, was also
developed.
The ultimate goal of the pallet jig development is to accurately assemble the LED
fusion lighting during auto assembly and minimize the defect rate at the same time.
According to the result of the self-test using the developed LED fusion lighting and
the pallet jig, it was confirmed that the defect rate was reduced by about 17% compared
with the existing product.
According to the result of analyzing the optical characteristics of the developed
LED fusion lighting, all 6 conditions of performance criteria for high efficiency
energy equipment certification were satisfied. In particular, it was confirmed that
the optical efficiency was improved by 16.1% compared to the standard. The design
change of the module power supply of LED fusion lighting is supposed to improve the
light efficiency compared to performance standard.
The result of optical characteristics of the developed LED fusion lighting showed
that all six conditions of performance criteria for high efficiency energy equipment
certification were fulfilled. In particular, the light efficiency was confirmed to
be improved by 16.1% compared to the standard. It is supposed that the light efficiency
was better than performance standard due to the design change of module power supply
of LED fusion lighting.
The performance of the LED fusion lighting for automatic assembly system developed
in this study was confirmed. It is expected to become a widely available technology
in the market of direct under panel lights if the universality is verified through
compatibility testing with various automatic assembly systems in the future.
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저자소개
Mr. Moon is currently enrolled in Ph.D program in the dept. of IT Applied System Engineering
at Chonbuk National University.
His research interests include Led Lighting and Low pressure plasma system.
Mr. Choo received Bachelor’s Degree in physics from Soonchunhyang university.
His research interests are Led Lighting measurement.
Dr. Bang is a professor at Major of IT Applied System Engineering of Con-vergence
Technology Engineering Division and smart Grid Research Center, Chonbuk National University.
His research interest include analog circuit and IT convergence system.
Dr. Ryu is a professor at Major of IT Applied System Engineering of Con-vergence Technology
Engineering Division, Chonbuk National University.
His research interest include circuit & control system and IT convergence system.