Grinding is a great technique for finishing products by smoothing surfaces or other final steps like adding grooves. Given the number of goods that can be produced with flat surfaces, techniques like surface grinding are very common. Other examples of grinding techniques include centerless grinding (typically faster than surface grinding and requires fewer passes) or cylindrical grinding (for specific round product shapes). These different types of grinding have their advantages and use cases, but also have some common challenges. In contrast to most other machining operations, grinding generally does not use an enclosure unless the facility has a customized enclosure for grinding (however these enclosed grinders usually have very high demand oil applications, discussed further below as a case study). Open-air grinding leads to dirtier operations that release lots of byproducts like oil mist. The heat generated by the wearing surface can lead to friction, burning, or swarf accumulation which is why a mist collector for grinders is recommended.
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Oil Mist from Grinding Wheels
The abrasive surface of the wheels used for grinding can come in a variety of materials, usually aluminum oxide, silicon carbide, diamond, or cubic boron nitride. These materials also vary in hardness, which will play a role in determining what the process quality is. However, some materials can cause the previously mentioned issues of heat generation. In some cases, the heat generated can also lead to loose material, lower production quality, and burn marks. Modern machine operations typically address this issue through oils that cool the cutting surface and provide lubrication. The use of oil will improve the process quality and the longevity of the tools but will produce mist and workplace issues that require the use of a mist collector for grinders. This issue is exacerbated by the open-air workspace of grinding.
Typically, the type of oil used will depend on the material of the product. The Manufacturing Product Reference Guide typically recommends light or heavy-duty oils for common materials like aluminum, with the added recommendation of synthetic oils for materials like stainless steel and plastics. Each of these oils will have its considerations such as the particulate formation, current regulatory guidelines (OSHA at a minimum but not a best practice), and viscosity/density (typically, synthetic oils are the cleanest to work).
Causes of Oil Mist During Grinding
A common refrain among oil mist collection for machining is “the faster the process, the finer the particles”. Oil mist is applied to promote speed and reduce heat generation, but this increased speed of machining (in this case grinding) causes subsequent problems. At typical speeds where oil mist becomes a practice, oil mist is producing sprays of droplets mechanically and vapors of oil thermally. As grinding speeds increase, the amount of heat vaporizing the oil will also increase. Vapors are much harder to deal with than droplets because they are significantly smaller in particle size, meaning there are more of them but they are smaller and harder to filter. The size and volume of these vaporized particles mean that an efficient mist collector for grinders is required.
Risks of Oil Mist from Grinding
Oil mist can be contained within the machine enclosure immediately after application but left any longer and accumulation would cause films to develop in your equipment. If exhausted or the hood is lifted, the oil mist will be circulated or released into your shop floor. If you do not have an enclosure, then release is already an issue. Oil mist can create visibility issues from the misty haze, which then lands on your floor and creates slip hazards. While in the air, it can be breathed in by staff or create irritation in body parts like the eyes. If exposure persists, there will be health issues and possibly a workplace that contravenes regulatory requirements for health and safety.
How to Remove Oil Mist from Grinding
The answer to the challenges of a grinding process made efficient with oil coolants that cause dangerous mists? An oil mist collector for grinding that provides an efficient source control solution achieving sub-micron particle removal. The mist collector will need to capture the large droplets mechanically dispersed from the grinding process, as well as the smallest particles vaporized from the heat of faster grinding. It should be efficient, and powerful enough to provide the cycles desired in your shop.
For machining applications like surface grinding, cylindrical grinding, or centerless grinding, Aeroex typically prescribes the use of the Mist-Fit series of oil mist collectors for grinding. Aeroex takes a different approach to open-air grinders than other machine applications and includes configuration options that ensure the source control solution that captures all pollutant particles before they can be released into the shop (at which point elimination by ambient control is much harder to achieve).
The Mist-Fit mist collector for grinding delivers a series of separation processes that remove any oil mist with increasing efficiency in each stage. The primary mechanical and secondary demister capture up to 95% of oil mist, notably the mechanically generated particles that are larger. The next stage in the filtration series is a depth loading fiber bed with high media volume – this MERV 15 rated filter will capture up to 95% of the oil mist particles. This efficiency is often more than sufficient for standard applications, but our products also carry HEPA filters durable enough for long-lasting air purification for machining while providing the highest standards in removal efficiency (99.7% @ 0.3 µm).
Case Studies in Mist Collectors for Grinding
We have seen that grinding as an open-air machining operation poses challenges to workplace safety and quality that can be effectively treated with Aeroex’s Misfit Solution. However, many grinding applications push the limits of current machining practices. Aeroex is at the forefront of these applications and is delivering mist collector solutions.
A customer specializing in biomedical manufacturing was using enclosed grinding centers with high-pressure oil. The demanding nature of the high-pressure oil meant the customer had gone through multiple competitor mist collectors before trying the ARO Series mist collector. The result was the client not seeing any oil leave the machine for the first time. Efficiency was the best they had seen, and they achieved longer filter life than competitor oil mist collectors. As a result, the ARO series deployment was expanded from a pilot station to all the machines in the biomedical manufacturing facility.
Aeroex has seen similar client journeys with other grinding operations. A recent example includes an aerospace parts manufacturing facility. The specialized grinding equipment was enclosed and high-pressure oil was being applied. This aerospace manufacturer went through several competitor mist collectors before ultimately selecting the ARO Series mist collector.
Our mist collectors for grinding are made in Canada, provide the best value and lowest lifecycle cost (achieved through low filter maintenance frequency), and encompass design principles that reflect Aeroex’s leading knowledge of machining processes like grinding. This article provides a brief overview, contact Aeroex today for a specialist who will guide you through the strategy of selecting a solution that provides you your desired outcomes for the best value.
