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SMART PRODUCTION
53
MAR 2017 FOOD FOCUSTHAILAND
ตารางที่ 1 คุณสมบัติต่างๆของการซีลด้วยอั ลตร้าโซนิ ค
Table 1 Features of ultrasonic seals
Ultrasonic
Technology
Ultrasound is soundwaveswith frequencieshigher than20 kHz
and above that people are unable to hear, but some animals
suchasbats, anddolphinscould.Batsuseultra-sonic frequency
toaccurately identifyposition, shape, anddirectionof theobject
blocking their ways, as well as the maneuvering speed of the
object. Bats use of the reflection of sound waves, the wave is
incident on the surface equals the angle at which it is reflected.
With the same principle, human discover the use of
ultra-sonic wavelength. This kind of wave has a "direction"
to accurately pinpoint to the destination or desired target.
Due towaveproperties, thehigher the frequency theshorter
thewavelength.
The wave is reflected in the travelling directions. The
soundwaves thereforecanbeutilized formanyapplications
including todetermine theunderwaterdepthbyusingsonar,
to reveal the internal structureof abody formedical uses, to
test tube leakage, touse for theultrasonic remotecontroland
ultrasonic cleaner, etc. The frequency of such applications
varies according to the typeof work undertaken.
For the Industry, they utilize the ultra-sonic wavelength
for material testing, sealing or welding. By converting the
electrical signals at high frequency tomechanical vibration
throughPiezoelectriceffectwhichstretchorshrinkaccording
to thedirectionof theelectric field, theheat occurs from the
friction betweenmaterials at themolecular level and takes
place only in the layer wanted to be sealed, unlike external
heat that comes from regular sealing.
In this article, the author will talk about the use of ultra
sonicsealingof films.Theapplicationherewithcanbedone
in twodifferent types:standaloneorequippedwithautomatic
sealingmachine, includingaVertical-Form-Fill-Seal (VFFS),
Horizontal-Form-Fill-Seal (HFFS), Rotary seal, Top seal or
other sealer that is used for the films coherence. These
sealingmachines help support a seal withexcellent quality,
precision bearings, and strength. The frequency of use is
20 kHz - 1GHzby installing thedevice ina sealingposition
of the automatic sealingmachinementioned above.
However, the basic elements are composedof
(1) Ultrasonic generators
(2) Piezoelectric transducer which is a transducer that
converts theelectrical signal into amechanical vibration.
(3) Sonotrode and Horn which are a touching piece or
Seal bar.Working principle of theSeal bar is that when the
seal bar ismovingcloser around20-40 m to theworkpieces,
the Ultrasonic generator will send out a signal to the
Piezoelectric transducer and the Seal bar, respectively.
The vibration, duly occurs at the frequency and amplitude
required. The molecule of the targets here vibrates with a
speedof 20,000 times/sec and fused as one piece.
UltrasonicGenerator
Comparing betweenUltrasonic sealing andHeat
seal, thedifferencehasbeen found thatsealingby
theUltrasonic is not aheatingprocess, but using
the energy as a catalyst to themolecules inside
theobjectsmelted together.Sealingedgesso that
aremore durable and neat. In addition, theHeat
seal requiresdifferent factors; time,pressure,heat,
and theenvironment in light of themoisture in the
product which affects the quality and strength of
the seal.
Conclusion
รูปที่ 2 หลักการทำ�งานของการซีลแบบอัลตร้าโซนิค
Figure 2 Workingprinciples of anultrasonic sealing
ข้ อดี /Advantages ข้อเสีีย / Disadvantages
- สามารถซีลได้ แม้มีสิ่งปลอมปนในรอยซีล
Canbesealedevenbeingcontaminated in the
weldingarea
- ใช้ก�ำลังไฟที่ต�่ำลดค่าใช้ จ่ายในเรื่องการบ�ำรุงรักษา
Lowerpower input,and reducingmaintenance
costs
- ใช้เวลาสั้นในการซีลแต่ละรอบประมาณ0.3วินาที
Fastautomatedwithweld timesofapproximately
0.3 secondsper cycle
- ไม่ครอบคลุมส�ำหรับถุงทุกประเภท
Not all pouchmaterials canbeapplied
- ระบบค่อนข้างแพง
Systems arequiteexpensive
The Ultrasonic seal can increase confidence in the quality of product for its
seal, strength, and quick operation of the sealing process. It is, therefore, an
alternative choice of theproducers in the food industry today.