Maximizing Efficiency in Metal Fabrication with Dry Ice Blasting
Few industries use more precision and cleanliness than the metal fabrication sector. Clean room applications in an electronics or pharmaceutical production setting might need more manufacturing fidelity, but it is close.
Fabrication environments rely on contaminant-free processing and clean and pure workpieces. Metal fabrication also requires exact measurements and tight tolerances, where the smallest error can result in a costly mistake.
If a fabrication shop is serious about its non-abrasive parts cleaning routine, it must examine dry ice blasting closely.
Why incorporate a prep stage?
Pure metals and alloys rarely come to the factory floor in pure form. Rust or paint, store-marked inventories, and film-oxidized layers are all too common. The former two issues are easily spotted, and the marker or sticky label problem is also predictable. Then there’s the film-forming problem.
Unless the metal is stored in a vacuum (unlikely), alloy parts are exposed to the air. A filmy, weld-interfering oxide layer is chemically introduced due to some reactive element in the alloy. It dulls the metal and impacts everything from cutting efficiency to drilling speed. While this oxide layer can be beneficial after a metal part is sent to the client, seeing as how it becomes corrosion-resistant, that layer is not desirable when it’s being subjected to tooling work or welding.
To resolve this issue, a cleaning process is introduced. First and before the fabrication, the workpiece can be chemically cleaned or sandblasted.
Why is dry ice blasting being discussed when existing cleaning solutions are already available?
Explaining the benefits of dry ice blasting
A chemical bath works, but these chemical solutions can be expensive and they’re harmful to the environment. There are also bound to be issues when disposing of chemicals. Over with the sandblasting station, the abrasive quartz-based particles clean the rust and oxide coating. Then, the sand blunt, sharp edges, and intricate geometries can alter the texture of the metal.
With dry ice, the tiny pellets can be utilized on complex metal geometries. They won’t alter the texture of an alloy, even if it’s a soft aluminum-based amalgam, nor will it create a bad byproduct when the job is finished. In fact, the dry, icy pellets are extracted as a gas after the job is done.
Shortlisting the benefits:
- First and best: Dry ice pellets are non-abrasive, perfect for a soft cleaning action that won’t impact the base metal or its geometry.
- The gas sublimation effect: Due to the change of state, from solid pellet to gas, as the blast hits a surface, more energy is released, thus imparting an additional cleansing boost.
- Reduced post-process downtime: Dry ice is, by definition, made of CO₂ pellets. At room temperature and above, the solid form of the cooled and compressed substance becomes a gas again, leaving little trace matter behind.
The blast-cleaning technique is directable, not as uniformly applied as a chemical bath, and it’s safer for workers to be around as long as the area is well-ventilated. Additionally, as cooling is involved, cryogenic burns are possible. Operators on this prep station must therefore wear PPE gear to prevent cold burns to exposed skin.
Maximizing efficiency at the dry ice blasting stage
It’s suggested that the compressor be maintained at regular intervals. Otherwise, the “dry” nature of this work could be compromised. It’s a well-known fact that air compressors collect suspended beads of moisture. This undesirable element is typically absorbed and filtered before it reaches the collector cylinder, but filters can age. Planned maintenance is the solution.
Likewise, a uniform discharge from the ice blast nozzles is desirable, and that’s not going to happen if the apertures on the discharge nozzle are clogged. Expect this to happen if there’s moisture in the air or ice crystals are forming inside the multi-apertured component due to the pick-up of airborne contaminants.
Other than those process preparation and maintenance caveats, optimizing the dry ice blast operation isn’t too challenging. It’s important to maintain the correct distance between the pellet discharge applicator and the metal part to be blasted. Too close, the pellets impart more force, but finite material removal control is reduced. If the distance between the metal part to be blasted and the jet nozzle is too far, though, reduced cleaning efficiency is likely.
Conclusion
Because air compressors are major energy consumers, and the cost of these pellets can fluctuate, it’s a best operational practice to encourage efficient running. Source the pellets from a known byproduct process, one that’s as green as possible. Next, maintain the equipment. The compressor will need regular care, namely filter and water separator inspections. The same can be said for the hose and nozzles exiting the compressor.
Last of all, and perhaps most importantly, the operating conditions in and around the processing station need an optimizing overhaul. PPE equipment should be issued, as the cold cleaning action can cause cryogenic burns to exposed skin. Ventilation is another tradeoff, acting as a preventative mechanism when icy buildups occur.
By prepping the main gear linkages and fine-tuning all ancillary parts in this manner, expect abrasion-free cleaning. The equipment can deliver that feature to fixed nozzles or portably maneuvered cleaning guns. Moisture and dry ice don’t mix, so the ventilation system must run smoothly with planned maintenance care.
To learn more about Red-D-Arc’s line of dry ice blasting equipment, visit our website.