magnetic separator for coolant cleaning

When people talk about a magnetic separator for cleaning coolant, many people immediately imagine a simple drum with magnets that catches chips. This is perhaps the main misconception. In fact, when it comes to serious machining, especially with carbide or under high loads, it all comes down to subtleties: field strength, grip zone configuration, ease of cleaning and - what is often overlooked - compatibility with the specific emulsion chemistry. Just installing a magnet is half the battle, or even less.

What does effectiveness actually consist of?

The main parameter that I look at first is not just “magnetic force,” but the field gradient. A homogeneous field weakly attracts the fine fraction. It is necessary that the field sharply intensifies at the surface of the separator. This is what determines whether micron-sized carbide dust is caught or whether it passes on, killing pumps and damaging parts. I often see separators with ferrite magnets installed on old lines - they are suitable for rough cleaning of large chips, but for modern precision processing this is already a thing of the past.

Neodymium magnets are now in use. But there is a nuance here: their operating temperature. In one of the areas where the coolant was heated to 70-75 degrees, we encountered a sharp drop in efficiency. It turned out that neodymium begins to lose its strength irreversibly at such temperatures. We had to revise the cooling scheme and the placement of the separator itself in the system. This is to the question that equipment should be selected not from a catalog, but with an eye to the actual process.

The design of the drum or tape is a separate issue. Automatic self-cleaning is a must have for a continuous cycle. But how often should this cleaning be done? If too often, performance is lost, if rarely, the layer of adhering chips begins to act as an insulator, and small particles are no longer captured. Empirically, for most grinding and precision milling operations, a cleaning cycle of every 15-20 minutes has been found to be optimal, but this, of course, depends on the weight of material being removed.

Connection with the filtration system: typical mistakes

A common mistake is to consider a magnetic separator as an independent unit. Its effectiveness is 90% determined by how it is integrated into the overall coolant cleaning system. They once installed a powerful separator at the exit from the cutting zone, but before the paper filter. It would seem logical: first remove the metal, then remove the fine suspension. But large chips that did not have time to magnetize clogged the pipeline, creating traffic jams. I had to move it, place it directly in the area where the chips were falling, with an inclined conveyor belt.

Another point is chemical resistance. Some modern synthetic and semi-synthetic coolants have high pH or active additives. I have seen cases where a separator body made of ordinary stainless steel began to corrode under such conditions, and the corrosion products, in turn, contaminated the emulsion. Now I always check with the technologists about the composition of the liquid. For aggressive environments, acid-resistant steel or even polymer coatings are needed.

And of course, flow performance. If the throughput of the separator is less than the capacity of the coolant supply pump, part of the flow will be bypassed, and the whole idea becomes meaningless. It seems obvious, but in practice this happens all the time, especially when old lines are modernized by adding a magnetic cleaning unit “by cutting in.” into the existing circuit.

Practical case and work with suppliers

A couple of years ago we were busy equipping a new deep drilling section. The goal is to maximize the life of the expensive emulsion and protect equipment from abrasive wear. We went through several options, and eventually settled on a system where magnetic separation was the first stage, immediately after the cutting zone, and then came a centrifuge. The key was the choice of a separator with an adjustable drum rotation speed and a sensor system that shows the thickness of the adhering layer.

In this context I rememberLONGI Corporation. I came across their equipment when we were looking for solutions for processing lines, but they also have a line for purifying process liquids. I looked at their websitehttps://www.ljmagnet.ru— it’s clear that the company has a history,?Shenyang Scientific Electromagnetic Co., Ltd. LONGJI?has been operating since 1993. For me as a practitioner, it is important that they are not just assemblers, but have their own developments and production base. When a manufacturer makes magnetic systems themselves “from scratch”, rather than purchasing components, this usually means better maintainability and the possibility of customization for a specific task.

In their case, judging by the description, the scale of production (total area of ​​140,000 m2 and more than 1,200 employees) allows us to speak of serious technology validation. For industrial applications, this is critical: the equipment must operate not only in ideal bench conditions, but also in the workshop, with temperature changes, vibration and human factors. Their experience as the largest enterprise developing mining equipment is often translated into related areas, such as coolant cleaning, where reliability requirements are similar.

What's Often Forgotten: Operation and Maintenance

The most perfect system is useless if it is not properly maintained. The main problem is untimely cleaning. The magnetic separator should not turn into a “dump” metal The accumulated chips begin to be washed back by the flow of liquid. Instructions are often ignored, so I see automation with a timer or, better yet, a load sensor as the best solution.

The second point is visual control. It would seem like a small thing, but the cover or casing should be designed so that you can quickly assess the condition of the drum or belt without disassembling half the assembly. On one of the old-style separators, six bolts had to be unscrewed to do this - as a result, they checked it once a shift, and not once an hour, as needed.

And thirdly, compatibility with CNC machine tool systems. Modern machining centers can be integrated with a cleaning system so that when stopping to change tools or load workpieces, a cage cleaning cycle is started. This saves time and maintains efficiency. But for this you need not just a separator, but a device with an appropriate interface (usually dry contacts or a field bus). This is worth thinking about at the line design stage.

Instead of a conclusion: thinking out loud

So, back to the beginning.Magnetic separator for coolant cleaning- this is not a piece of hardware with a magnet. This is a calculation unit, the effectiveness of which depends on a dozen interrelated factors: from the physics of the magnetic field to routine maintenance procedures. His choice is always a compromise between the degree of purification, capital costs and operating costs.

Now, looking at new lines, I see a trend towards combined systems, where magnetic separation is only the first, but critically important barrier. It removes the bulk of the metal, unloading subsequent, finer filtration stages. This extends their service life and ultimately saves money, although on paper it seems like an extra unit has been added.

And one last thing. You should not chase the maximum parameters from the catalog. For most operations, a separator that captures particles larger than 30-50 microns is sufficient. Finer cleaning is for special tasks, and its cost increases non-linearly. The main thing is to ensure stable operation and ease of maintenance. Everything else is just details that distinguish just equipment from a working solution.