Metal bonding is the process of joining two or more metal surfaces using materials like adhesives, superglues, and epoxy adhesives. Regardless of the bonding material, proper surface preparation is essential because it directly impacts the quality and strength of the bond.
Grit blasting and chemical etching are typically used to prepare metals for bonding. However, lasers offer a new, alternative approach that leads to superior bonding quality, increased efficiency, and lower operational costs.
Here is an example of a laser process used before adhesive bonding on aluminum battery casings:
Benefits of Laser Surface Preparation for Metal Bonding
In the following sections, we’ll compare lasers to alternatives when used before metal bonding. More specifically, we will look at the benefits that result in superior metal bonding:
- All Contaminants Are Removed at Once
- Surface Preparation Is Performed in Fewer Steps
- Dust Control Measures Are Simpler
- The Surface Is Not Damaged
- Better Control Over the Surface Roughness
- Beneficial Oxides Can Be Introduced
- Masking Is Not Needed
- Lower Operational Costs
Contaminants and detrimental oxides interfere with the bonding process and need to be removed from metal surfaces. With laser cleaning, all types of contaminants can be removed at once. This simplifies the production cycle and opens the door to increased efficiency.
Grit blasting, on the other hand, cannot remove all contaminants at once. An additional chemical degreasing step is required to remove grease, oil, and other organic contaminants.
To obtain a good bond quality, surface preparation that includes the removal of contaminants and the roughening of the surface is essential. Both operations can be performed in a single operation with a single-mode laser. For other methods, these operations are performed in two separate steps. This makes surface preparation more efficient by reducing the number of steps.
With chemical etching, cleaning and etching require different chemicals regulated at different temperatures, so the two steps need to be performed separately. Rinsing and drying are also needed to remove all residuals.
With grit blasting, chemical degreasing needs to be performed separately (such as with solvents) prior to blasting. Additionally, leftover dust from the blasting operation needs to be removed from the blasted surface.
The dust generated during laser texturing is fully managed by a dust extraction unit. This helps improve quality as dust does not recontaminate the processed surface. This offers a huge advantage compared to grit blasting, which tends to reintroduce dust contaminants that are challenging to completely remove.
Many manufacturers have problems managing dust. Before switching to laser technology, one of our clients used aluminum oxide for grit blasting. Some of the oxide ended up inside the parts, making it complicated for them to prevent quality issues. They no longer have this problem since they switched to laser.
Since laser cleaning is a non-contact and non-abrasive process, the part’s surface is not damaged. This is important for thin or soft metal parts that could otherwise be damaged or deformed by abrasive materials such as sand, aluminum oxide, and steel grits.
Controlling surface roughness is key to improving quality when bonding metal. Laser texturing can generate a specific surface roughness, providing a high level of control over the resulting surface texture. This precision is valuable in applications where consistency is required.
With chemical treatments, roughness depends on the temperature of the chemicals and the exposure time. This can result in variability in the final surface finish, making it less predictable and consistent. Even when chemical processes are perfectly controlled, textures tend to be random rather than in organized patterns (as is the case with laser texturing).
With grit blasting, various factors such as the shape, size, and hardness of the basting media are used to achieve a specific surface roughness. However, the results fall within a range of roughness values and may not be uniform or consistent from one part to another. Additionally, the blasting media wears off after every use, causing inconsistencies over time.
Laser surface treatments can introduce beneficial oxides on the metal surface. While these oxides can be removed, studies show that in the right number, they improve the adhesive strength by generating more surface free energy.
Chemical treatments also introduce beneficial oxides on the surface, but the bonding quality achieved with laser texturing has been shown to be superior than standard Alodine treatments used in metal bonding.
Grit blasting, on the other hand, does not modify the chemical composition of the surface and tends to give lower quality bonding than chemical and laser treatments.
Laser cleaning and texturing can process specific areas with micron precision. This level of precision means that they do not require masking to protect surrounding areas. This simplifies surface preparation for metal bonding by reducing the number of steps and imprecisions caused by masking.
With grit blasting, masking is required to prevent specific areas from being blasted and damaged. The same applies to chemical baths and sprays, where masks are used to prevent specific areas from being treated.
Apart from the initial investment when buying a laser machine, lasers have minimal operational costs. They operate on electricity alone, and their power consumption is extremely low. Maintenance is often limited to replacing dust extraction filters and cleaning the laser’s protective window.
Spare parts may not even be needed during the laser’s lifetime depending on the production environment. But in high-volume production lines, it is still good practice to keep some spare parts available to react quickly and keep the production line running if a problem occurs.
Anyone who’s used grit blasting knows that they generate high maintenance and operating costs due to the abrasive media, pressurized air, PPE, worn equipment, and so on.
Chemicals also generate high operation costs with chemicals, rinsewater disposal, PPE, high power consumption to heat up chemicals, and so on.
Explore the Benefits for Your Metal Bonding Application
Laser technology is a game changer when it comes to surface preparation for metal bonding. The numerous advantages it offers over traditional methods are hard to overlook.
If you want to explore the benefits of laser texturing for your bonding process, Laserax can help you and develop a process for your specific application.