Servotecnica Slip Ring Spotlights: Lifetime and Wear with Matteo Bonvicino

Welcome back to Servotecnica Slip Ring Spotlights, our interview series offering a behind-the-scenes look at those driving innovation in slip ring technology here at Servotecnica. In this edition, we sit down with Matteo Bonvicino, from our Assembly & Quality department at Servotecnica, to discuss slip ring lifetime and wear. We’ll explore how Servotecnica ensures its slip rings achieve long operational life through careful material choices, design strategies, and rigorous testing. We’ll also dispel some common misconceptions about wear and maintenance, drawing on Matteo’s experience in developing long-lasting slip ring solutions.

Q: Thanks for joining us, Matteo. To start, could you tell us a bit about your background and your role at Servotecnica?

A: Certainly. I’ve been part of Servotecnica’s engineering team, working on slip ring for over 15 years. Over time, my work has expanded to include evaluating performance trade-offs, analysing wear behaviour, and supporting the development of long-life slip ring solutions. I focus on pushing the performance and reliability of our products – for example, experimenting with different contact materials and refining brush designs to improve lifespan. It’s a fascinating area because even small design improvements can have a big impact on a slip ring’s longevity.

I work closely with both our design engineers and testing labs to ensure that durability is designed into each product from the beginning. A big part of this work is balancing trade-offs: making sure we achieve long life and high reliability without compromising the slip ring’s size or functionality for the customer’s application. It’s especially rewarding to see slip rings operating maintenance-free in the field for extended periods.

Q: The theme of this interview is slip ring lifetime and wear. Why are these considerations so critical for slip rings, and what key factors influence a slip ring’s lifespan?

A: Having a good slip ring lifespan is absolutely critical. A slip ring’s operational life directly impacts the reliability of any system it’s part of. If a slip ring wears out prematurely, it can lead to downtime or maintenance in the customer’s machine, so from an engineering standpoint we need to get it right. Many advanced systems (from industrial machinery to rotating sensors) rely on slip rings as a core component, so ensuring a long, trouble-free life is one of our top priorities.

When it comes to what influences slip ring lifespan, there are several key factors. Materials are a huge one. We use high-quality, wear-resistant materials for both brushes and rings as this means the interface doesn’t degrade as quickly. Manufacturing quality is another big factor: precision manufacturing and tight tolerances help reduce wear over time. We carefully control things like alignment and surface finish inside the slip ring. Even the brush pressure (preload) is finely tuned – it must be just right to maintain constant contact without causing excessive friction. By engineering the brush contact force and alignment precisely, we minimize unnecessary wear while ensuring reliable electrical contact.

Operating conditions also play a major role in lifespan. A slip ring designed for a clean, room-temperature environment might wear very differently than one operating in a hot, dusty factory or exposed to vibration. Harsh environments such as extreme temperatures, high humidity, dust, corrosive chemicals, can accelerate contact degradation if the slip ring isn’t built for them. Likewise, how the slip ring is used whether it be designed for continuous high-speed rotation, frequent start/stop cycles, high electrical load, can introduce mechanical and electrical stresses that shorten its life. That’s why at Servotecnica we look at the specific application conditions and often tailor the slip ring design (materials, seals, lubrication, etc.) to handle those stresses. In short, maximizing slip ring lifespan consists of a number of things: choosing the right materials, building with precision, and matching the design to the operating environment.

Q: What causes slip rings to wear over time? Can you walk us through the wear mechanisms happening at the contact interface?

A: At a basic level, slip ring wear comes from friction and contact stress at the interface of the brushes and rings. Inside a typical electrical slip ring, you have one or more brushes (which can be thin wires or fibers made of a conductive metal) constantly sliding against the surface of a rotating ring. Every time the ring turns, those sliding contacts experience friction. Over many rotations, that friction will gradually remove tiny amounts of material from the brush or the ring surface. So the primary wear mechanism is this slow mechanical abrasion of the contact surfaces. In addition, there can be minor electrical arcing or micro-sparks if the contact momentarily breaks (for instance due to vibration), which can cause very small pitting on the metal surfaces. Fortunately at Servotecnica, we manufacture well-designed slip rings to prevent this by maintaining steady contact.

The good news is that modern slip ring designs greatly mitigate wear. We use multi-wire (multi-fibre) brush technology in many of our slip rings, which means instead of a single large contact, we have many fine filaments sharing the contact load. This spreads out the wear. No single point sees all the friction; it’s distributed across multiple contact points, significantly extending the service life compared to older designs. In fact, our multi-fibre brushes have much lower friction and tend to produce only negligible debris as they wear, especially compared to traditional carbon block brushes. Older slip rings that used carbon-graphite brushes would shed a lot of carbon dust and wear relatively quickly, often requiring frequent cleaning or brush replacement. By contrast, our gold-alloy wire brushes running on gold-plated rings produce extremely little debris and require no lubrication to function smoothly. This means the wear rate is so low that the slip ring can operate for millions of cycles without needing maintenance. Essentially when the wear mechanism is still there, you can’t eliminate friction, but through smart design we’ve minimized its effects. Each individual brush strand might wear down imperceptibly over time, but because there are multiple redundant strands and they’re made of wear-resistant material, the slip ring as a whole keeps working reliably for a very long time.

Q: How do you test or ensure that a slip ring will last as long as it’s supposed to? Are there specific reliability tests you conduct for lifetime and wear?

A: We take validation very seriously. To ensure a slip ring meets its lifetime goals, we perform extensive lifecycle testing in our labs. For example, when we develop a new slip ring model, we’ll run it on a test bench for millions of revolutions continuously. We simulate real-world operating conditions as closely as possible during these tests. That includes the rotation speed, the electrical currents or signals passing through, and environmental factors like temperature or humidity if relevant. We recently upgraded our factory to include high-tech climate test chambers to ensure that our slip rings are suited for every environment.

We also do detailed inspections and measurements after testing. We’ll often take the slip ring apart after a long-duration test to examine how the brushes and rings have worn. We look at the wear patterns, measure how much material is used up, and verify that it matches our predictive models. In many cases, the outcome of a successful test is that the slip ring still meets all specifications at the end of the test (signal quality, temperature, etc.), which tells us it can handle the intended lifespan. To give a concrete example: some of our high-performance slip rings are rated for extremely long service as we have sealed units in the SVTS series that can reach on the order of 100 million rotations at high speed. It’s not unusual for us to log tens of millions of cycles on a prototype to ensure no excessive wear occurs. If a slip ring can survive our torture tests while maintaining performance, we know it’s going to be rock-solid reliable for our customers. In short, rigorous testing for mechanical, electrical, and environmental, is how we ensure that real-world slip ring lifespan aligns with the design expectations.

Q: Are there any common misconceptions about slip ring lifetime or wear that you encounter when talking to customers?

A: Yes, there are a few misconceptions we often hear. One big misconception is that slip rings are inherently high-maintenance or prone to failure. We sometimes find that people have had experience with older slip ring designs and assume that all slip rings need constant upkeep. It’s true that in the past, traditional slip rings did require frequent maintenance.so some engineers automatically think any slip ring is going to be a headache of continual brush replacements and cleaning.

The reality today is much more optimistic. With modern designs like ours, a quality slip ring is often maintenance-free for its entire designed lifespan. As we discussed, using precious metal multi-fiber brushes means there’s very little debris generated and no need for messy lubricants. A well-designed slip ring can literally run for years in a machine without anyone touching it and still provide reliable power/data transmission. We spend a lot of time educating customers that, if you choose the right slip ring for your application, it should not be a frequent point of failure. Another misconception is about lifetime ratings: sometimes people see a number (say, “30 million revolutions”) and assume the slip ring will just fail at that point like clockwork. In truth, that number is usually a conservative estimate under specific test conditions. Actual life can be longer or, if misused, shorter. So we advise customers not to treat lifespan as a fixed number in isolation. Lastly, some think that maximizing slip ring life is just about the contacts, but neglect things like bearings or seals. In our designs, we consider the whole system – the bearings supporting the rotor, for instance, are high-precision and long-lived so that they won’t fail before the contacts do. In summary, the biggest myth is that slip rings are a weak link; in reality, modern slip rings can be extremely robust components if you select and use them properly.

Q: When you’re designing a slip ring for maximum longevity, what trade-offs or challenges do you have to consider? Does focusing on longevity affect other design aspects like size, cost, or performance?

A: That’s a great question. Designing for extreme longevity does involve balancing some trade-offs. One of the first trade-offs is often material and construction choices versus cost and size. If we want a slip ring to last essentially “forever” (or as long as possible), we might choose very high-end materials like thicker gold plating on the rings, or brushes made of specialized wear-resistant alloys. We might also add protective features like better sealing (to keep dust or moisture out of the contacts) or incorporate redundant circuits so the load is shared. All of these things tend to increase the cost or sometimes the size of the slip ring. Using more robust housings (stainless steel instead of plastic, for instance) or larger bearings can make the unit a bit heavier or larger. So we always weigh the benefit of longevity features against the practical limits of the application. If the customer can accommodate a slightly larger unit and a higher price point in exchange for a longer service life, that’s often a worthwhile trade. Our job is to find that balance between delivering the needed lifespan in the given size and budget constraints.

Another challenge is managing friction and contact force. To maximize lifespan, you want to minimize wear, but you also can’t compromise on reliable contact. This means we carefully optimize the brush contact pressure. A higher brush pressure can ensure a very stable electrical connection (even under vibration or shock), but if it’s too high it will create unnecessary friction and wear out the brushes faster. On the flip side, if the pressure is too low, you reduce wear but risk intermittent contact. We address this by precise engineering of the brush system – using spring-loaded brushes and multi-contact designs to maintain just the right pressure. In fact, we have to fine-tune the brush preload to keep continuous, even contact with minimal wear. It’s a delicate equilibrium: enough force for reliability, but not so much that it shortens the life. We also consider the number of brush fibers – adding more can reduce per-contact stress (good for wear) but adds complexity and a bit of friction. So there’s a design sweet spot we aim for.

In the end, designing a long-life slip ring is about holistic optimization. We might accept a small increase in friction or a slight size increase if it dramatically boosts longevity, but we work to mitigate downsides. For example, if additional brush fibers increase friction, we might use a low-friction coating on the ring or a more powerful motor in the system to handle the torque – whatever makes sense for the system as a whole. And while premium materials and intricate designs can raise cost, often the users who need a 20+ year slip ring are willing to invest in that upfront, because it pays off in virtually zero maintenance later.

My advice for engineers is to communicate these priorities early in the design process. If long life and low wear are critical for your project, let’s factor that in from the beginning. We can tailor a slip ring with the right materials, contact configuration, and protective features to meet those goals. It might cost a bit more or require a custom tweak, but you’ll get a solution that runs maintenance-free for years, which in many cases is worth far more than the incremental design cost. In summary, we can absolutely design slip rings to have exceptionally long lifespans – it just involves balancing materials, mechanics, and cost, and those decisions are best made with the end goals in mind. When we strike that balance correctly, the result is a slip ring that you can basically “install and forget,” confident that it will perform reliably for a very long time.