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in Vol. 25 - May Issue - Year 2024
Optimizing Metal Parts Cleaning: Asking the Right Questions to Remove Production Contaminants
Understanding the specific contaminants introduced during production processes is crucial for metal finishing companies

Understanding the specific contaminants introduced during production processes is crucial for metal finishing companies

Solvent cleaning inside a vapor degreaser is a fast and efficient way to remove machining oils, coolants, lubricants, and other non-polar contaminants

Solvent cleaning inside a vapor degreaser is a fast and efficient way to remove machining oils, coolants, lubricants, and other non-polar contaminants

Regularly verify and document ongoing cleaning quality, making immediate adjustments as necessary to keep precision

Regularly verify and document ongoing cleaning quality, making immediate adjustments as necessary to keep precision

In the metal finishing sector, meticulous cleaning underpins the success of downstream processes. However, perfecting cleaning protocols requires first in-depth analysis and careful planning to seamlessly align cleaning methods with specific production contaminants. By comprehensively addressing these critical questions at the outset, metal finishers can mitigate costly rework, ensure consistent quality, and prevent process failures.


What Production Contaminants Affect My Parts?

The first consideration is to identify the contaminants introduced during manufacture. Machining processes, including grinding, drilling, milling, and turning, introduce various elements, including metal chips, abrasive dust, spent cutting fluids, and lubricating oils. Forming processes like pressing, stamping, and punching leave residues like drawing compounds, press oils, lubricants, and release agents. Additionally, handling and storage of parts result in substances such as metal oxides, corrosion films, fingerprints, polishing and deburring media, marking inks, dust, and other debris. A comprehensive identification of all potential contaminants is a crucial first step in selecting the best cleaning technique to thoroughly remove each type of soil.

Understanding the specific contaminants introduced during production processes is crucial for metal finishing companies. Metal part contaminants typically fall into three main categories:


- Polar Inorganic Contaminants:

These include heat treatment scale, metal oxides, smuts, salts, corrosion films, and other ionic debris. Addressing the challenge posed by polar inorganic contaminants includes using specific cleaning methods. Aqueous machines, water-based detergents, and surfactants are an effective solution. Aqueous cleaning effectively wets and solubilizes these polar contaminants, allowing for complete rinsing removal. In this process, surfactants play a dual role by aiding in wetting and displacing the soil from the metal surface.

This cleaning method thoroughly removes polar contaminants, leaving metal surfaces clean and ready for later finishing processes. 


- Non-Polar Organic Contaminants:

These includes machining oils, applied during metal cutting for friction reduction; greases and lubricants, vital for smooth machinery operations; drawing compounds, facilitating metal forming; and coolants, used to manage machining heat. All these hydrocarbon-based substances fall under the umbrella of non-polar organic contaminants.

Addressing the challenge posed by these contaminants requires the use of non-polar solvents, which work on the principle of similar polarity interactions, allowing them to dissolve and detach hydrocarbon-based contaminants. This dissolution process ensures comprehensive cleaning, leaving no residues that might compromise the metal part's quality or affect downstream processes.

It is crucial to selecting a suitable non-polar solvent tailored to the specific hydrocarbon contaminants encountered in the manufacturing process.


- Particulate Contaminants:

These are diverse substances inherent in metal manufacturing processes. This category encompasses grinding dust, metal chips, abrasive particles, polishing debris, and other insoluble contaminants. Effectively addressing the challenge posed by particulate contaminants involves employing specific cleaning methods tailored to their nature. Unlike polar or non-polar contaminants, particulate contaminants cannot dissolve and must be physically displaced from the part’s surface. Solutions designed for this purpose loosen and lift away these insoluble contaminants, ensuring a thorough cleaning.

Metal finishing companies need to take the time to thoroughly analyse and document all probable contaminants that could be introduced during their specific production processes, including examining each manufacturing process step, from machining and forming, to material handling procedures, listing every potential substance that may meet parts. For example, understanding the fluids and lubricants used on grinding and milling machines enables matching the best cleaning agents to eliminate them. Or knowing the specific marking inks used for identification tagging ensures choosing cleaning methods to remove the film. Fully detailing every production variable is key for precision cleaning. 

Additionally, metal finishers should inspect sample parts from regular production runs using analytical testing processes to pinpoint contaminants. This aids in selecting the most suitable cleaning technique for reliably removing identified residues from complex part geometries. Continuously testing real-world contaminated parts from ongoing operations confirms the sustained effectiveness of the chosen cleaning method as production evolves.


Which Cleaning Solutions Effectively Remove Specific Contaminants? 

The next important question is: Which cleaning fluid options will most effectively eliminate my identified contaminants without leaving any unwanted residues? 

For industrial metal parts cleaning, common fluid options used within vapor degreasing processes include:

- Mono-Solvent Cleaning: A single, high-boiling, strong fluid able to clean, rinse and dry parts in a two-sump vapor degreaser. It is efficient at removing a wide range of oils, greases, fluxes, organics, and particulates. It may be an azeotrope composed of two or more components that, when combined, forms a stable mixture for enhanced performance.

- Co-Solvent Cleaning: Two different specialty fluids are used - a high-boiling agent dissolves and detaches stubborn soils, while a secondary rinsing solvent cleans at slightly lower temperature. It is ideal for extremely difficult-to-clean contaminants like synthetic greases, grinding media, and polishing compounds.

- Bi-Solvent Cleaning: A two-stage process is used to remove thick, stubborn contaminants. Parts are first submerged in a heated tank with a solvating agent that detaches and dissolves viscous soils. Parts are then transferred to a two-sump vapor degreaser operating at a lower temperature. Here a secondary fluid supplies final cleaning and rinsing to eliminate any remaining contaminants or cleaning solution residues. 

Once all potential contaminants are documented, matching the best cleaning fluid involves careful analysis of each fluid's characteristics, for example, solvency strength, material compatibility, and other properties relative to the identified contaminants.


What Cleaning System Best Matches My Operation? 

Finally, metal finishers should ask: What cleaning technique best matches my production workflow, volumes, testing capabilities, regulations, and other unique operational factors? 

Collaborating with a partner with experience and expertise in effectively cleaning metal parts is crucial. Key considerations in planning cleaning processes should encompass the following steps:

1. Collect contaminated sample parts from production lines and conduct tests to explore potential cleaning fluid and equipment options. This confirms expected cleaning performance under controlled conditions.

2. Create a detailed production audit and needs analysis, matching the process parameters to real-world processes. Consider long-term operating costs, maintenance requirements, waste handling, environmental regulations, and other critical factors when selecting a new cleaning process. This selection criteria prevent unforeseen operating expenses.

4. After installation, perfecting new equipment's settings and documenting ongoing performance through analytical testing methods. Make any necessary adjustments at once to "fine tune" procedures. 

5. Regularly verify and document ongoing cleaning quality using standardized testing procedures, making immediate adjustments as necessary to keep precision.

Although often overlooked, effective cleaning plays a pivotal role in manufacturing, significantly influencing the quality and functions of next surface treatments. By posing key questions and tailoring the cleaning process to meet specific needs, metal parts manufacturers can proactively prevent defects and achieve surfaces free from contamination.


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