chemistry

Laser welding of polymers

Laser welding of polymers is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Laser welding of polymers rather than just read about it. In short: Laser welding of polymers is a set of methods used to join polymeric components through the use of a laser. It can be performed using CO2 lasers, Nd:YAG lasers, Diode lasers and Fiber lasers.

Key takeaways

Laser welding of polymers belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Laser welding of polymers to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Laser welding of polymers from memory before moving on to harder problems.

Reference excerpt

Laser welding of polymers is a set of methods used to join polymeric components through the use of a laser. It can be performed using CO2 lasers, Nd:YAG lasers, Diode lasers and Fiber lasers. When a laser encounters the surface of plastics, it can be reflected, absorbed or penetrate through the thickness of a component. Laser welding of plastics is based on the energy absorption of laser radiation, which can be reinforced by additives and fillers. Laser welding techniques include:

Direct laser welding Laser surface heating, Through transmission laser welding Intermediate film welding. Because of high joining speeds, low residual stresses and excellent weld appearances, laser welding processes have been widely used for automotive and medical applications.

Laser sources The types of lasers used in the welding of polymers include CO2 lasers, Nd:YAG lasers, Diode lasers and fiber lasers. CO2 lasers are mostly applied to weld thin films and thin plastics due to the high energy absorption coefficients of most plastics. Nd:YAG lasers and Diode lasers produce short wavelength radiation, which transmit through several millimeters of unpigmented polymer. They are used in the transmission laser welding techniques.

Carbon dioxide lasers Carbon dioxide lasers have a wavelength of 10.6 μm which is rapidly absorbed by most polymers. Because of the high-energy absorption coefficients, processing of plastics using CO2 can be done rapidly with low laser powers. This type of laser can be used in direct welding of polymers or cutting. However, the penetration of CO2 lasers is less than 0.5 mm and is mostly applicable for the welding of thin film and surface heating. Because the beam cannot be transmitted by silicon fiber, the beam is commonly delivered by mirrors.

Nd:YAG lasers Nd:YAG lasers have a wavelength in the range of 0.9 - 1.1 μm, with 1064 nm being the most common. These lasers provide a high beam quality allowing for small spot sizes. This type of beam can be delivered via fiber optic cable.

Diode lasers The wavelength of diode lasers is typically in the 780 - 980 nm wavelength range. Compared with Nd:YAG laser and CO2 laser, diode laser has supreme advantage in energy efficiency. The high-energy light wave can penetrate a thickness of a few millimeters in semicrystalline plastics and further in unpigmented amorphous plastics. Diode lasers can be either fiber delivered or local to the weld location. The relatively small size makes assembling arrays for larger foot prints possible.

Fiber laser Fiber lasers typically exhibit wavelengths ranging from 1000 to 3500 nm. The expanded range of wavelengths has allowed for the development of through transmission welding without additional absorbing additives.

Equipment The equipment settings may vary greatly in design and complexity. However, there are five components included in most of the machines:

generator/power supply control interface actuator lower fixture upper fixture.

Generator/Power supply This component transforms the received voltage and frequency to the corresponding voltage, current and frequency to the laser source. Diode laser and fiber laser are the two most commonly used system for laser welding.

Control interface The control interface is an interface between operator and machine to monitor operations of the system. It is constructed by logic circuits to send operators the information of machine status and welding parameters. Depending on different laser modes, the control interface will vary the parameters allowable to change.

Actuator This component is a press activated by pneumatical and electrical power. It compresses the part in the upper fixture to touch the components in the lower fixture and apply pre-determined loads during welding processes. Displacement controls are added to actuators to monitor precisely the movements.

Lower fixture Lower fixture is a jig structure that locates the lower part of a joint. It provides locations and alignments that ensure the welding of components with tight tolerances.

Upper fixture The upper fixture is the most complicated and important component in the whole system. Laser beam is generated in this component to heat up the welding parts. The design of upper fixture often varies from laser sources and heating modes. For example, when a YAG laser or a diode laser is used as the heat source, optical fibers are often employed to provide mobility. However, the welding part cannot move.

Laser interaction with polymers There are three types of interactions that can occur between laser radiation and plastics:

reflection, absorption transmission The extent of individual interaction is dependent upon materials properties, laser wavelength, laser intensity and beam speed.

Reflection

Reflection of incident laser radiation is typically on the order of 5 to 10% in most polymers, which is low compared with absorption and transmission. The fraction of reflection (R) can be determined by the following equation,

R = ( n − m ) 2 ( n + m ) 2 {\displaystyle R={\frac {(n-m)^{2}}{(n+m)^{2}}}}

where n {\displaystyle n} is the index of refraction of the plastics and m {\displaystyle m} is the index of refraction of air (~1).

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Laser welding of polymers

Start with the simplest possible case. Write down what Laser welding of polymers claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Laser welding of polymers before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Laser welding of polymers ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Laser welding of polymers

In research: Laser welding of polymers appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Laser welding of polymers in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Laser welding of polymers is common in secondary-school and first-year university syllabi. It links to neighbouring topics Laser applications, Polymers, Welding, so understanding it makes those chapters shorter.
In everyday life: Look for Laser welding of polymers outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Laser welding of polymers in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Laser welding of polymers means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Laser welding of polymers out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Laser welding of polymers in simple terms?

Laser welding of polymers is a set of methods used to join polymeric components through the use of a laser. It can be performed using CO2 lasers, Nd:YAG lasers, Diode lasers and Fiber lasers.

Why does Laser welding of polymers matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Laser welding of polymers?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Laser welding of polymers.