Dry ice blasting or laser: which residues suit which process?

Dry ice blasting can be very interesting for grease, soot, dust and certain production residues. Laser-based removal plays to its strengths above all where firmly bonded surface layers such as oxides or coatings are to be processed selectively.

For a sensible selection, the residue should therefore be analysed first – and only then the machine.

Why “dry” is not yet a process decision

Both CO₂-based processes and laser processes are often grouped together under the term dry cleaning.

That merely describes the fact that no conventional aqueous cleaning process is used.

It says little about the actual mechanism of action.

In the field of industrial component cleaning, Fraunhofer IPA lists several established technologies side by side: aqueous and solvent-based cleaning, dry ice, CO₂ snow, plasma and laser.

That in itself shows:

The technologies are not different product names for the same process.

They cover different tasks.

The choice of process should therefore not begin with the question:

“Do we want to clean dry?”

But rather:

“What kind of residue is on which surface?”

Which tasks dry ice blasting handles well

In dry ice blasting, solid CO₂ particles or pellets are carried onto the surface to be processed by a gas stream.

Fraunhofer IPA describes the process for contamination such as grease, soot and dust, for example.

The CO₂ then passes from the solid to the gaseous state.

As a result, no dry ice blasting media remain that would have to be collected afterwards.

That is an important difference from conventional abrasive blasting media.

Dry ice blasting can be particularly interesting where contamination is to be released from a surface but the medium used is not itself to leave any solid residue.

Typical tasks are:

• Grease on production equipment
• Soot
• Dust
• certain release agents
• organic production residues

Which contamination can actually be removed depends in turn on the specific material and its condition.

Where laser-based removal works differently

The laser-based process becomes particularly interesting where the layer to be removed is firmly bonded to the substrate.

These can include, for example:

• Oxides
• Rust
• Paint layers
• Scale
• defined functional layers

The physical principles are covered in the article How does laser ablation work when cleaning metal?.

For this comparison, the practical distinction is enough:

Dry ice is blasted onto the surface as a medium and releases the contamination present through the mechanical and thermal effects this produces.

With the laser, energy is introduced optically and locally into the relevant surface layer.

These are different tools.

Trying to compare the two technologies purely by square metres per hour therefore makes little sense as long as the type of contamination has not been defined.

Loose contamination or firmly bonded layer?

One of the most important questions is:

How strongly is the residue bonded to the base material?

With loose contamination, or contamination merely sitting on the surface, a blast cleaning process can be very efficient.

With a firmly adhering oxide or paint layer, a targeted removal process can make more sense.

There are numerous intermediate stages between these two extremes.

On moulds and tools, for example, a complex build-up of:

• Release agents
• polymer residues
• baked-on residues
• Oxides

can be present.

In such cases, a single technology is not necessarily ideal for all the layers.

For new tasks, a trial processing run should therefore be carried out.

This is particularly important where the surface is valuable or dimensionally critical.

What remains after processing

In dry ice blasting, the CO₂ used sublimates.

That does not mean, however, that no residue at all is present after cleaning.

After all, the original contamination is released from the surface.

Grease, soot or other substances do not physically disappear from the room simply because the blasting medium passes into the gas phase.

Depending on the process, contamination that has been released or distributed therefore still has to be taken into account.

The same basic principle applies with the laser.

The processed layer is removed and should be captured by suitable process extraction as close to the point where it arises as possible.

A technically sound comparison therefore reads:

Dry ice leaves behind no additional solid CO₂ blasting medium.

Not:

Dry ice produces no residues whatsoever.

Material influence and target surface

The choice of process does not depend only on what is to be removed.

How the surface has to look afterwards is just as important.

Is the aim simply to remove contamination?

Or is a metallic layer to be exposed in a targeted way?

Does the topography have to remain unchanged?

Is surface activation necessary for a subsequent joining step?

Fraunhofer IPA, for example, names dry ice blasting as a process for cleaning in the context of joining processes.

Laser-based processes are likewise being investigated by Fraunhofer ILT and IFAM for surface preparation before bonding, welding or coating.

Both technologies can therefore be part of an industrial pre-treatment.

They do not necessarily produce the same surface condition, however.

The decision should therefore not be made on visual cleanliness alone.

Media supply and infrastructure

Dry ice blasting requires a supply of CO₂ or dry ice and typically compressed air or corresponding blasting equipment.

The medium has to be procured, stored and brought to the place of use.

Because dry ice sublimates continuously, the logistics have particular characteristics.

A laser, by contrast, requires electrical energy and, depending on the system, further infrastructure such as cooling and extraction technology.

For mobile applications, the following question can therefore be relevant:

Which supply is more easily available at the place of use?

In a production hall with an existing compressed air supply, dry ice blasting can be easy to integrate.

At another site, the continuous provision of the medium can create a greater logistical share.

With the laser, in turn, the connected electrical load, extraction and the safety area can be decisive.

Operating costs should therefore not be viewed as an energy price alone.

The entire supply logistics belong in the calculation.

Automation

Both processes can be automated.

Fraunhofer IPK, for example, describes a cleaning cell with high-pressure CO₂, snow blasting and dry ice blasting technology that can be used both robot-assisted and manually.

Laser processes can likewise be guided by robots and scanners.

This means that “automatable” is not a clear-cut selection criterion.

What matters instead is this:

How complex is the component geometry?

How precisely does the processing area have to be observed?

How large is the area required?

How quickly can the respective system remove the residue reliably?

For series components, a real cycle time comparison should be carried out.

Moulds and production equipment

Dry ice blasting is often associated with the cleaning of moulds and production equipment.

That is understandable.

Production residues can be released while no solid CO₂ blasting medium remains on the mould.

The DGUV, too, names cryostatic cleaning of moulds with dry ice pellets as an industrial application.

Laser-based processes can likewise be used for moulds.

The advantage there can lie in the precise local energy input.

Which method works better therefore depends heavily on the type of residue.

An easily removable release agent is a different task from a firmly bonded surface layer.

For mould makers, a test series is particularly worthwhile, because the cycle time and the desired condition of the tool surface also play a part.

Sensitive components

With sensitive components, neither dry ice nor laser should be assumed to be “gentle” across the board.

Dry ice blasting brings a medium onto the surface at speed and produces a thermal effect in doing so.

Laser energy likewise acts on the material.

Both processes must therefore be matched to the component and the contamination.

Fraunhofer research on CO₂ snow, for example, deals explicitly with thermal effects on sensitive electronic components.

With the laser, the process window determines how strongly the substrate is affected.

For high-value components, the right method is therefore the one that achieves the required final condition within a safe parameter limit.

Not the one described as “gentle on the material” in a general advertising claim.

Comparing process speed properly

A serious speed measurement has to compare the same task.

Both processes are given:

• the same component
• the same initial condition
• the same target quality
• the same relevant area

Afterwards, it is not only the active processing time that is measured.

Media provision, set-up, post-cleaning and inspection are part of it too.

With dry ice, for example, refilling or providing the medium can be part of operation.

With the laser, setting up the safety area and the filter technology can play a part.

Only the total process time makes a B2B decision possible.

Safety with CO₂ and class 4 lasers

The hazards differ considerably.

DGUV Information 213-115 covers work with dry ice and points out that solid CO₂ continuously produces gaseous carbon dioxide.

In poorly ventilated or unsuitable areas, the CO₂ concentration can therefore become safety-relevant.

The very low temperature of the medium must also be taken into account during handling and storage.

Where high-power lasers are used in the open, by contrast, direct and reflected laser radiation and process emissions are among the central concerns.

DGUV FBHM-139 covers corresponding protective measures for hand-held class 4 lasers.

It would therefore be wrong to present either of the two processes as hazard-free across the board.

Both require an application-specific risk assessment.

Deciding by residue

A simple orientation is this:

For surface-lying or releasable contamination such as grease, soot or certain production residues, dry ice blasting should be examined as a possible technology.

For firmly adhering oxides, rust or defined coatings, laser-based material removal can be particularly interesting.

This is not a universal assignment.

The actual suitability depends on:

• Material
• Residue
• Geometry
• Target surface
• Speed
• Process environment

these factors.

In borderline cases, a direct test is therefore the sensible option.

Conclusion: determine the residue first, then the process

Dry ice blasting or laser: which residues suit which process?

Both technologies work dry, but in different ways.

Dry ice blasting has advantages with numerous surface-lying contaminants and leaves behind no additional solid CO₂ blasting medium.

Laser-based material removal can play to its strengths with firmly bonded surface layers and locally defined processing zones.

For companies, the decision should therefore be made in this order:

1. Determine the residue.
2. Establish the base material.
3. Define the target surface.
4. Check geometry and accessibility.
5. measure the real process time.
6. Take the media or energy supply into account.
7. Compare the safety concept.

Anyone able to choose the process according to the residues actually present turns the general question “dry ice or laser?” into a concrete technical decision.

Sources

• Fraunhofer IPA – Pre- and post-processing of joining processes — practical example of cleaning with dry ice blasting.
• Fraunhofer Business Unit Cleaning – Cleaning Technologies — overview of industrial cleaning processes including dry ice and laser.
• Fraunhofer IPK – Clean Production for Clean Mobility — automated CO₂, snow and dry ice blasting processes.
• DGUV Information 213-115 „Tätigkeiten mit Trockeneis“ — hazards and protective measures when handling solid CO₂.
• DGUV – FBHM-139 — protective measures for hand-held class 4 laser systems.

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