Semi-Synthetic vs. Synthetic Coolants: Key Differences in Cost, Performance, and Recyclability

Discover the Differences: Semi-Synthetic vs. Synthetic Coolants

Coolants are the unsung heroes of metalworking, reducing heat, preventing tool wear, and ensuring top-notch product quality with smooth surface finishes. However, like any hero, not all coolants possess the same strengths.

Among the most commonly used coolants in CNC shops are semi-synthetic and synthetic coolants. While both are widely adopted, they differ in composition, performance, and recyclability. Understanding these differences, the trade-offs between cost and performance, and the best methods for coolant recycling can help metalworking shops choose the right coolant for their operations.

How Are Semi-Synthetic and Synthetic Coolants Different?

The term “synthetic” may suggest similarities, but semi-synthetic and synthetic coolants have distinct differences.

Semi-Synthetic Coolants:

Semi-synthetic coolants are a blend of synthetic lubricants and 5% to 30% mineral oil. Machine shops often prefer them because they combine the performance benefits of synthetic coolants with the cost-effectiveness of traditional oil-based coolants.

However, recycling semi-synthetic coolants can be challenging due to the presence of mineral oils. These oils degrade over time, which increases maintenance and replacement needs. Fortunately, advances in recycling technology, such as Edje Tech’s Tramp Oil Separator System and C.R.O.S.S. Coolant Recycling System, have simplified the process and extended coolant life by reducing waste.

Synthetic Coolants:

Synthetic coolants, on the other hand, contain no mineral oils and are engineered from chemical compounds. This makes them easier to recycle, and because they lack oils, they tend to last longer without breaking down. The absence of oil also means fewer impurities, leading to reduced contamination during recycling.

Although synthetic coolants have a higher initial cost, their recyclability often results in lower long-term expenses by reducing the need for disposal and replacement. The choice between semi-synthetic and synthetic coolants should take into account not just the upfront cost but also operational efficiency and environmental sustainability.

Cost vs. Performance: Are Synthetic Coolants Worth the Investment?

When comparing semi-synthetic and synthetic coolants, several factors must be considered, such as upfront investment, longevity, and overall performance in machining environments.

Semi-Synthetic Coolants offer a cost-effective solution, providing a balance between affordability and performance for general machining. However, semi-synthetics may require replacement every 6 to 12 months and are more challenging to recycle, leading to 10% to 20% higher long-term maintenance costs due to the need for tramp oil separation.
Synthetic Coolants come with a higher initial investment, but their long-term cost benefits outweigh the upfront price. However, their extended lifespan of 12 to 24 months and 20% to 30% long-term savings through easier recyclability make them more cost-efficient in the long run. Synthetic coolants also reduce downtime due to their stability and ability to extend tool life by 30% to 50%, making them ideal for high-speed machining.

Factor	Semi-Synthetic Coolants	Synthetic Coolants
Peak Performance	Great cooling and lubrication, ideal for general machining	Superior cooling for high-speed and precision operations
Cost	Cost-effective, offering a balance between affordability and performance	Higher initial investment, but long-term savings through extended coolant life and recyclability
Residue and Odor	Low residue, minimal odor	Very low residue, less odor
Foam	Minimal foam during machining	Can produce more foam than semi-synthetic
Compatibility	Suitable for both ferrous and non-ferrous metals	Not always compatible with all metals (e.g., risk of corrosion)
Recyclability	More challenging due to oil content	Easier to recycle due to the absence of oils
Maintenance Needs	Requires monitoring and maintenance to prevent bacterial growth	Requires monitoring, but less prone to contamination
Environmental Impact	Needs proper disposal and recycling to minimize oil-related waste	Chemical composition requires careful recycling to avoid harm
Downtime	5% to 10% more downtime due to maintenance	10% to 20% less downtime due to higher stability

Coolant Recycling: What Every Shop Needs to Know

Recycling coolant is essential for maintaining cost efficiency and environmental responsibility. Proper recycling practices help shop owners extend coolant life and reduce costs. Below are the key steps in effective coolant recycling:

Proper Filtration: Filter coolant to remove contaminants like tramp oil, metal fines, and debris.
Oil Separation: In semi-synthetic coolants, tramp oil must be separated to prevent degradation. Use oil skimmers or tramp oil separators to maintain coolant quality.
Bacterial Control: Regular pH monitoring and biocide treatments help control bacterial growth, particularly in semi-synthetic coolants, prolonging their lifespan. pH monitoring is key, as coolant with a low pH becomes more acidic, making it a breeding ground for bacteria. Adding biocides can prevent this, preserving both semi-synthetic and synthetic coolants.
Recycling Systems: Using coolant recycling systems like Edje Tech’s C.R.O.S.S. can greatly reduce waste, remove impurities, and extend the life of both semi-synthetic and synthetic coolants. The system also mixes coolant for the customer and replenishes essential additives like biocides and lubricity packages, ensuring the coolant remains effective throughout its lifecycle while minimizing waste.

Conclusion

Both semi-synthetic and synthetic coolants play essential roles in metalworking, each offering distinct advantages in terms of performance, cost, and recyclability. By understanding the differences and following proper recycling methods like filtration and tramp oil separation, machine shops can maximize coolant life, reduce costs, and meet environmental standards.

If you’re looking to enhance coolant quality and operational efficiency, contact Edje Tech for expert solutions in coolant recycling and filtration. Whether your shop uses semi-synthetic or synthetic coolants, our team can help you improve performance and sustainability.