Why using lasers for cleaning moulds?

If you want to clean a mould, two things are crucial: what type is your contaminant( organic, inorganic, or oxide), and what is the base material? You usually don't want to damage the surface or change the material properties. Laser cleaning is, in fact a balancing act between evaporating the contaminant and not changing the base material of your mold. Many Chinese suppliers don't know the difference and will offer you cutting or marking lasers. These so-called CW (continuous wave) lasers are mass-produced Chinese products with no aim of solving your mould problem. A pulsed laser system is needed to have complete thermal surface control without damage. You don't need 2000 watts to clean a mould. 100 watts can be enough with the right system. It becomes more difficult if you have a unique polished or chrome-coated surface. P- lasers build unique systems with the right laser source and optical components to preserve your mould. Trust our 35-year experience.

Can I use a CO2 laser to clean a surface?

CO2 gas-tube lasers are well known for cutting machines in relation to steel and glass material. There exist also pulsed Co2 laser which are used for surface cleaning. High-speed polygon in combination with Co2 laser are used to strip military aircraft in the US.

But as an industrial cleaning tool it is a no go. Due to the dimensions and the gas medium as a laser beam generator, it is to bulky and complex. This 10x higher wave length number has some advantages in cleaning on the absorption side. This wavelength is absorbed by most organic contaminants at a higher level than the infra-red 1064 nm laser.  This means every Watt unit of laser energy reaching the surface is transferring its light energy at a higher level than one unit of our  1064 nm type infra-red laser. Further, the <Co2 10.000 nm wavelength is not well absorbed by aluminium. So yes in well specific cases in has some advantages, but mainly, it is not used in industrial cleaning applications. Typical due to the high-energy laser beam this kind of light energy is guided over mirrors instead of a flexible fibre. This is the reason in every Co2-based application, the bulky laser source has to be in a very short distance from the surface.

YAG laser and fibre lasers? Are they the same?

The Infrared laser light around 1064 nm or 1 micrometre wave length lasers are conceived in the same material: yttrium-aluminium garnett (YAG) doped with a Neodium element. in the case of a fibre laser, the laser light is generated in the same material as the cristal rod solid-state laser. But then stops the comparison between fibre lasers and solid-state YAG lasers.

The classical YAG laser uses a solid lase cavity to generate the laser light bouncing between two mirrors. Due to the extreme positioning accuracy of the mirrors and the water cooling around the crystal, we get a complex, unstable laser source. Decades of development made this laser the preferred university study object. Industrial applications demand reliable laser sources without needing scientists around to keep the machine running.

With all respect to the enormous developments done in this field, it is not the most preferred laser source in the industrial world. Industrial applications are always demanding continuous improvement quality: cutting/welding thicker steel controlling the surface heat impact. This requires a better laser light quality. In short, the laser quality of your generated light beam is equal to the focability to the most minor laser spot on the surface. This is a problematic point for YAG lasers, seeing the laser cavity restrictions. Instead, the fibre laser can achieve a far higher light quality and stable quality in long production runs. Integrating YAG lasers demands extra controlling sensors to ensure a well-known calibrated laser beam before you start welding. This adds extra costs and process uncertainty in already complex welding processes. I would say a cleaning process is a bit less critical than most welding applications but it is clear the pulsed fibre laser is also, in this field the preferred tool.

What is the real advantage of a fibre laser?

The most significant advantage is they have no maintenance. The light is generated directly in one fibre and connected to the output fibre. You have no moving elements inside. This system is not sensitive to vibrations or temperature variations. Only a cooling is added to the system and will demand some maintenance.

In the case of the traditional YAG laser, you have yearly maintenance to keep the laser on a stable power output level. This demands the intervention of specialized laser technicians.

The nature of the traditional laser-build cavity causes this problem. In short, a laser beam is generated in a cristal rod surrounded by a critical cooling system. The stability of laser output depends on the cooling efficiency. Water cooling systems are never entirely stable and, by nature will influence the laser output. The crystal is fixed on a super stable platform, but every nanometer of material deformation influences the laser performance again. if you get the beam out of the laser cavity, you must direct it into a 200 µ-meter fibre. This is nearly a NASA moon landing operation. Every vibration and thermal material deviation will result in less power output. In welding and cleaning processes, a +/-3%  stable output is crucial for your process. This is the main reason why fibre lasers are used in all automotive high-quality laser processes. They are the preferred tools because of their stability, low maintenance, and low energy use. A further significant difference between a fibre laser and a traditional YAG laser is the pulse duration problem. A fibre laser will generate the same pulse duration for the complete frequency range. The YAG laser will generate its own crystal material- pulse duration and will have a puls-duration variation in function of the frequency you demand. This is an extreme limitation regarding process flexibility. This means you cannot change the frequency without changing the plus duration, which is directly affecting the surface result.

The frequency of the pulses, together with the spot size, will give the maximum cleaning speed. With the puls-overlap plus energy, this is your process's main tuning point. But if the plus duration changes along the frequency, you get different heat effects on your substrate. Your process setting possibilities are limited with the YAG laser. A YAG laser finds its origin as a university development but needs a long way to be industrial reliable.

We find only  YAG solid-state crystal manufacturers like Trump and Cleanlaser. 

Are lasers wall plug efficient?

It will depend on the type of laser used. There are two primary types: the crystal rod laser and the solid-state laser. The latter generates light in an Nd YAG laser cavity. Around an Nd-doped yttrium silica glass crystal, specific LEDs are mounted. These LEDs stimulate the Nd dopant present in the crystal to emit radiation. However, the excess heat energy produced by this process must be cooled down, resulting in an energy deficit. This type of laser has a maximum energy efficiency of 27%, which is relatively low. On the other hand, the fibre laser generates light that stays inside a glass fibre, with no mirrors, outcoupling or fibre coupling. These lasers have energy rates of 40% and are increasing yearly, resulting in highly compact laser systems.

can cleaning lasers be used under water ?

Yes, it is possible to pass transparent materials like water and glass. The laser will lose a bit of the power by absorption losses in the water depending on the water quality.  But yes you can derust under water.

Can laser cut into human flesh?

While it is true that lasers can cut into human tissue, it is essential to note that this refers explicitly to CO2 CW steel cutting/welding lasers. These lasers have been utilized in the medical field to remove tumours due to their ability to stop bleeding after the incision. On the other hand, UV lasers are the preferred choice for eye surgeons as they can cut organic human tissue. The cleaning lasers utilized are primarily Infra Red pulsed lasers, inherently less problematic than their continuous wave (CW) counterparts. This is because infrared laser light can easily be transmitted through a flexible glass fibre rather than relying on mirrors like CO2 lasers.

Additionally, human skin does not absorb this type of radiation well, except for darker-coloured hairs or tattoos on the skin. The inks used in tattoos are usually heavy metal-based, so when exposed to the laser, the chemicals boil and evaporate in the skin tissue and blood vessels. While an infrared pulsed cleaning laser cannot cut through fingers, it can cause significant burning wounds if held in one spot for an extended period.

How to look at a laser as investement in our industrial world?

Lasers are costly tools and are often 2-4 times more expensive than traditional processes like sandblasting dry ice and chemicals. However, the operational costs are only 1/10 of the traditional techniques.

A chemical process is very cheap to start but has high operational costs and unacceptable human risks today when an accident occurs. Blasting processes have a high blasting material, energy - and maintenance cost. The dry ice process is probably the most costly around. First, we need compressed air to produce dry ice with a high carbon footprint. We know dry ice is promoted as a renewable stream from other processes, but finally, it is fake news. It is a waste stream product, creating afterwards more carbon dioxide. So yes, laser cleaning is the ultimate integration process in a brand-new process line. Unfortunately, in 90% of the cases, we want to replace a  multi-functional traditional process. Do we have a chance?    Absolutely, if you need a low-cost production on demand. . Only top efficient production organisations can capitalize massively by investing and adapting their processes. They will take the lead in their segment. Integrating lasers will eliminate unclear quality problems because now you have a controllable process, not adding extra production problems.

If you cut a laser fibre is there a danger for the operator?

Fibre lasers have built-in security devices to avoid this kind of error. After a fibre cut, the laser source will be cut off in micro-seconds. If the light should come out, it will be very fast divergent and lose all density to provoke danger.

Can laser replace sandblasting?

We often encounter this question to replace an existing sandblasting activity. In 80% of the cases, we cannot! Why? A traditional free manual blasting cabinet can handle multi-span-off part dimensions without problems. The mobile laser can also clean many parts but cannot be compared to laser cleaning. The 2,5 m2/hr speed of stripping a paint layer PU 300 µm is too slow compared with a sandblaster at 6-8 m2/hr. The sandblaster is outrunning the laser cleaning system in most cases. If you have dedicated requirements, the laser cleaning can crawl back into the game. You have a single part to be treated in an automated process, and you get everything you want. You can get the same result on every part, you can have an inline quality tracing system, your process can run on start/stop intervals, and you get the smallest carbon footprint on energy level and lowest waste stream.

So yes, laser cleaning will pay itself back numerous times compared to sandblasting in this case. This is the most challenging point for traditional industry to cope with. Integrating laser cleaning demands apparent choices in your process thinking. But in today's industrial world, new big constraints are product quality and slim energy-based processes with low environmental impact.

The mythe off derusting with lasers explained?

Today on YouTube, we see a lot of companies presenting their laser magic by derusting a surface that looks new. Even the most Chinese-offered lasers are non-pulsed low-cost lasers with high power outputs. So what is the catch here? First, you need to know that many different types of rust exist. We have deep and superficial surface rust where the base material is unaffected, also called pitting rust. The Chinese laser companies ignore the differences and sell you a low-cost CW laser. They even have scientific university studies to explain the good derusting possibilities with a continuous laser called CW. The CW laser is the most accessible laser you can produce in the laser world. The Chinese dominate the CW market with cutting and marking lasers of this type and try to sell you this type as a magic cleaning system. Due to the fact the derusting is based on a shrinking or dilatation effect, in short, the breaking of the oxide particle from the surface by the difference of temperature between surface and particle, you need a shock effect to clean it. So, only pulsed lasers are more efficient. The CW laser is a heating device that turns the red rust particles into the black rust-oxide variant. If you need to paint your surface, this is not a good surface preparation. Pitting rust is also tricky for a pulsed laser because the rust particle has adherence on the surface. If you clean it the surface will look dark grey, but below, there is still rust.

What about the difference between fibre and solid state cristal YAG lasers?

In general, we can say the solid state Nd YAG laser source is an older type of laser still used, but it has far more maintenance issues than a modern fibre laser. In contrast to the YAG laser, where the laser light is produced in an Nd crystal rod with two mirrors at each end, the light in a fibre laser is conceived into a fibre directly and guided in one way to the output fibre. Everything stays in the fibre, resulting in a very high wall plug efficiency, unlike the YAG laser, where you have critical cristal cavity cooling. Further, you need to couple the outcoming laser beam into a fibre. You can imagine the sensitivity of injecting a 100-micrometre laser spot into a 400-micrometre diameter fibre. A lot can go wrong with changing environment as those lasers are vibration sensitive. A YAG laser will produce a flatter laser beam, making this laser soft and non-aggressive on most surfaces. The fibre laser produces a more Gaussian type of laser energy distribution beam. This higher beam quality can be tuned down with suitable optics to get a flat beam type. If you consider that pulse duration is always constant with a fibre laser over different frequency settings and not with a YAG laser, your choice must be a fibre laser. Also, the dimensions of a YAG laser are far bigger because of the cooling you need and bulky electronic frequency generators. The future is clearly with the fibre lasers because of the higher efficiency and no maintenance aspects of the source itself.

What about the fibre lenght? Is there a limitation?

Yes, the fibre length is limited by the amount of energy you can guide true a glass fibre. You have high-energy lasers and low energy density lasers. A low-density laser can have up to 100 m fibre. We produced a 2000 watt system with 100m fibre in 2021. You cannot avoid a quality change of your laser light after passing true 100 m of fibre. The power loss is very marginal, but the laser beam has lost a bit of its light quality. This will be seen as you try to focus this light at the end of the fibre.

The low-power systems ( but those are high density) will have 5-8 m as an absolute maximum for the moment. 

Is the puls lenght ( puls duration) something important in the cleaning process?

In most systems, we use fixed pulse length. Depending on the fibre length and light quality we are limited in sending a certain amount of energy through an optical fibre. If we have a pulse of 1mj and 100 nanoseconds long, then we are sending 10 Kw through the fibre. A fibre can withstand a certain amount of energy and can behave non-linear if pushed to the limit. Therefore we could say the pulse duration is an important factor to consider on the engineering side. For the cleaning process, we can conclude: the shorter the puls length or duration the higher the energy shock on the surface and the less the thermal influence. on the surface. Oxides are not so sensitive to shorter pulse lengths but we prefer the non-re-oxidation effect of the shorter duration. For paints or organics, a longer pulslenght is more efficient to overcome the thermal isolation topic.  if to short, the energy is not enough transferred to the paint layer. Only for special applications do we need to consider the pulslenght as an important factor. Seen the fact the pulse duration has some big influence on fibre and optics and there overload risks it is better to have a fixed pulse duration instead of a variable one which could lead to errors. 

What materials can be cleaned?

Mostly we can clean metals and non-metals, also, organic and inorganic ( stones) can be cleaned to a certain degree. To have a good cleaning result, we need an as dark as possible contamination and highly reflective light-coloured substrate to avoid damage. Black smoke deposit on a sandstone is easy to clean. Yellow paint on sandstone is more difficult because this yellow colour is not absorbing well the laser radiation. Laser will remove nearly all oxides in a very big range of metals and non-metals. A shrinking-off effect on the surface removes oxides; the oxide layer has a different energy-heating speed or flux than the substrate. Oxides also absorb more energy than the highly reflective aluminium surface. Example: You can remove ink on a white paper without burning the paper. Lasers are also used to remove hair or tattoos; this is based on the higher absorption of those black hairs and the darker-than-skin tattoo ink. The human skin is not absorbing very well the infrared laser light.

Can a CW laser clean a surface?

Many so-called Chinese CW laser models are on the market, claiming to be a cheap cleaning solution. Yes, the CW laser is a very cheap laser, but it can not be compared with the pulsed laser. Laser cleaning is a surface balance equation between heating and cooling down. The contamination present on the surface must be quickly heated without heating the surface and damaging it. This sensitive balance is only possible with pulsed lasers that will shoot very short ( 100 nanoseconds long) heat-energy- bullets to the surface. In time, the bullet size can be regulated over the software and optical lenses. Although we shoot 100,000 bullets a second (100Khz) with a specific energy value (millijoule), the surface can cool down between the laser bullets. This prevents the surface from overheating and provokes melting on the surface. Every material consists of atoms and electrons circling around, if energy is added to a material, the electrons start to vibrate more. Returning to the normal state is called electron relaxation time, measured in nanoseconds. A pulsed laser can make the electron vibrate but leaves enough relaxation time to bring the electron back in normal relaxation mode. Therefore, you need a pulsed laser to obtain a cleaning result that can be repeated. A continuous wave laser or CW shoots a constant amount of energy to the surface, which you cannot control manually. The bandwidth of useability is 1 against 1000 for a pulsed laser. A CW laser is used for cutting, welding, hardening or cladding. Even in the cutting and welding process, research is developing towards pulsed systems to have more control on the surface. The heat impact is not wanted because it creates oxides in the melt pool. With a CW laser, you create an unwanted overheating effect on your surface; sandblasting will be needed to paint a quality reference surface. CW lasers are mainly a Chinese marketing joke to mislead customers at low prices. They are not on the same quality level as the Western companies about production processes and final customer quality.

In the future, we will see shorter pulse lengths be used for cleaning. Scientific lasers with femto and pico second pulses already exist but are expensive. With a femtosecond pulse duration, the energy transition to the surface is so short that heat impact does not affect the material.

What is the price of P-Lasers?

Prices in the different countries are the responsibility of our distributors. However, in general, P-Laser Low Power machines start from 60.000 euros.

What are the running costs of laser cleaning?

To operate a cleaning laser, you need electricity: 0.4 kW (50W) to 7 kW (1000W).  Furthermore, some cleaning lasers use compressed air. Lastly, there is a yearly fee for the P-Laser software, Cleansweep. The fibre laser is, in fact, maintenance-free. There are no moving parts inside and no micro-positioned mirrors inside the laser source, like a YAG laser. You don't have to shoot your 5 mm laser beam into a 25 µ-meter fibre ( human hair) to transport the laser light to your laser gun. The fibre laser resolves 90% of the problems with traditional YAG lasers sensitive to cooling and exterior temperature changes. No maintenance may be a heavy statement, but you must look at the lasers and optic chiller regularly. A YAG laser requires a minimum of 1 year of a full check by a highly trained specialist. The fibre lasers don't require any maintenance, only chiller filters, and your personnel must check your lens surface.

What maintenance is required with laser cleaning?

Low Power P-Lasers are air-cooled, and don't require a lot of maintenance. However, it is important to keep the lens and filters clean at all time.

Mid and High Power P-Lasers are water cooled, and require a bit more maintenance. Check the filters and chillers every month. Keep the lens clean at all time.

We recommend a yearly check-up of your system by P-Laser staff. We also offer a remote monitoring service, with which P-Laser staff can check alarms, temperatures, humidity etc. as a proactive tool.

Do I need training to operate the cleaning laser?

P-Laser offers one day of training for every customer. The training includes a safety course and training on how to operate the laser and how to use the software.

Do I need a Low, Mid or High Power cleaning laser?

To be able to suggest the right solution, we need some information on the application, such as:

  • What is the application?
  • Which industry are we talking about?
  • Which cleaning method do you use at the moment?
  • What is the contamination you want to remove? 
  • What is the thickness of the layer?
  • What is the type of base material?
  • What is the surface (in m² or in m²/hour) that has to be cleaned?
  • Do you need an in-line application?
  • How often do you need to clean the material?

We always need to test the result of laser cleaning on your material, as every application is different.

What is the speed of laser cleaning?

The speed with which a laser can clean a surface depends on the power of the laser, the software settings, and the variables mentioned above. For example, the removal of wax from a piece of aluminum takes 12m²/hour with a 500W machine; removing blue epoxy paint takes an hour for 2m² with a 100W machine, and removing decolorisation from a weld can be done at a speed of 8.6 m/min.

However, every application has to be tested to determine the best possible cleaning speed.

Generally speaking, automated applications and robots achieve the highest cleaning speed.

Is laser cleaning safe?

Laser cleaning is a safe cleaning method, but the radiation is dangerous for the eyes. Always use appropriate laser goggles when the machine is active. 

What are the power requirements for laser cleaning?

P-Laser Low and Mid Power Machines work with 110-220V, High Power Lasers require 380-440V.

Does the cleaning laser work in all environmental conditions?

The laser works in the following 'normal' conditions: temperatures  between 0 and 38°C, and humidity is between 25 and 55%. If the environment is too hot, cold or humid, P-Laser suggests using climatisation and/or dehumidification. 

Do P-Laser Machines work on a robot?

All systems can be automated or mounted on a robot. 

Can the cleaning laser run 24/7?

Yes, we have some installations that have been running 24/7 for years.

How wide is the laser beam?

The laser beam can go up to 20cm wide (focal length 400mm). However, this is not the most important aspect of the  laser beam. An essential element for our lasers is the CleanSweep software, which allows you to change the frequency, intensity, shape and size of the laser beam. The combination of these variables offers efficient configurations for different applications.

Can I also mark with these lasers?

Yes, our software CleanMark allows marking texts and images with Low Power and High Power Machines.

Can I send parts for testing laser cleaning?

Yes, we can test laser cleaning on your material. After the test, we send you the test results, along with videos of the cleaning process.