maximize slip ring lifecycle and performance

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5245-3 Old Dowd Road, Charlotte NC, 28208 | T: +1 704 705 4711 | F: +1 704 733 9170 WHITE PAPER https://www.kuebler.com Maximize Slip Ring Lifecycle and Performance Do your slip rings run trouble free for their expected lifecycle? If you answered “no,” you’re not alone. Many engineers who work with rotating machines experience slip ring problems or downtime at some point. The good news is you can easily keep your slip rings running smoothly for the long haul by following just three simple steps. All you need to do is configure, install and maintain the slip rings properly. Unfortunately, even experienced engineers sometimes configure slip rings without paying enough attention to how the device will be installed on the machine. It turns out that different mounting orientations call for different slip ring configurations. And if you get the configuration wrong, the slip ring may suffer from recurring signal loss problems and a shortened working life. Maintenance isn’t always straightforward either. It’s easy to lay the blame for poor maintenance on end-users, but the truth is some slip ring designs are inherently difficult to maintain. What’s more, engineers do not always consider the actual operating conditions when setting maintenance expectations, causing them to overstate or understate service intervals. Bottom line is that slip ring maintenance starts on the drawing board, not on the factory floor. In this article, we’ll go over some simple design strategies that will help you ensure the longest possible life and lowest possible maintenance for the slip rings used on packaging and other industrial machines. Eliminate Configuration Errors To maximize design flexibility and minimize size, modern slip rings typically have a modular design. Modularity allows users to freely combine power and signal channels to meet their exact application requirements. Our SR085 slip ring, to take one example of the modular approach, allows you to configure up to 20 channels, divided between load and signal any way the application requires. Each additional module adds just 10 mm to the slip ring’s base axial length of 64.5 mm. A few simple design tips will help you get the most out of your slip rings Modular Slip Ring Applications Packaging machines Bottling lines Textile machines Robotics and automation systems Cranes Rotary tables

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5245-3 Old Dowd Road, Charlotte NC, 28208 | T: +1 704 705 4711 | F: +1 704 733 9170

WHITE PAPER

https://www.kuebler.com

Maximize Slip Ring Lifecycle and Performance

Do your slip rings run trouble free for their expected lifecycle? If you answered “no,” you’re not alone. Many engineers who work with rotating machines experience slip ring problems or downtime at some point. The good news is you can easily keep your slip rings running smoothly for the long haul by following just three simple steps.

All you need to do is configure, install and maintain the slip rings properly.

Unfortunately, even experienced engineers sometimes configure slip rings without paying enough attention to how the device will be installed on the machine. It turns out that different mounting orientations call for different slip ring configurations. And if you get the configuration wrong, the slip ring may suffer from recurring signal loss problems and a shortened working life.

Maintenance isn’t always straightforward either. It’s easy to lay the blame for poor maintenance on end-users, but the truth is some slip ring designs are inherently difficult to maintain. What’s more, engineers do not always consider the actual operating conditions when setting maintenance

expectations, causing them to overstate or understate service intervals. Bottom line is that slip ring maintenance starts on the drawing board, not on the factory floor.

In this article, we’ll go over some simple design strategies that will help you ensure the longest possible life and lowest possible maintenance for the slip rings used on packaging and other industrial machines. Eliminate Configuration ErrorsTo maximize design flexibility and minimize size, modern slip rings typically have a modular design. Modularity allows users to freely combine power and signal channels to meet their exact application requirements.

Our SR085 slip ring, to take one example of the modular approach, allows you to configure up to 20 channels, divided between load and signal any way the application requires. Each additional module adds just 10 mm to the slip ring’s base axial length of 64.5 mm.

A few simple design tips will help you get the most out of your slip rings

Modular Slip Ring Applications• Packaging machines• Bottling lines• Textile machines• Robotics and automation systems• Cranes• Rotary tables

5245-3 Old Dowd Road, Charlotte NC, 28208 | T: +1 704 705 4711 | F: +1 704 733 9170

WHITE PAPER

https://www.kuebler.com

For all the design flexibility of modular slip rings, they can lead to a common configuration mistake. Oftentimes, engineers will configure a slip ring without regard for its mounting orientation.

The reason orientation matters is that the signal channels are more susceptible to contamination from dust or other particulate than the load channels. Accumulated dust can degrade the signal integrity, ultimately shorting the maintenance intervals and lifecycle of the slip ring.

So it’s important to configure slip rings with the signal channels above other modules—such as those for power and labyrinth seals. As long as the signal channels are on top of the slip ring, gravity will work in your favor and minimize the amount of dust that falls onto signal channels.

Inductive Data TransmissionMany slip ring performance issues come down to dust on the contacts, especially the more sensitive signal contacts. And configuring the slip ring with the signal channel above the load channels can only minimize, not prevent, the inevitable buildup of dust. There is a new technology, however, that makes dust irrelevant, at least on the signal channel.

Our newest slip ring, SRI085 uses a contact-less inductive coupling to transfer signal and data. Developed for use on high-speed packaging machines, this new slip ring ensures signal integrity without any worry about dusty contacts.

Other than its inductive coupling, which does add some cost, the SRI085 is drop-in replacement for our SR085 slip ring, which uses oil-free contacts for both the signal and power channels.

Caption.

Figure 1

Vertical Mounting Position Standing

Vertical Mounting Position Hanging

5245-3 Old Dowd Road, Charlotte NC, 28208 | T: +1 704 705 4711 | F: +1 704 733 9170

WHITE PAPER

https://www.kuebler.com

Keeping the signal channels on top requires an awareness of the mounting orientation. Vertical hanging and standing orientations in particular will need different configurations to ensure that the signal channels remain above the labyrinth seals (see Figure 1).

With horizontally mounted slip rings, gravity doesn’t help or hurt the dust situation much. You can locate the signal and load channels in any order that makes sense for your application (see Figure 2).

Follow Maintenance InstructionsAnother threat to smooth slip ring operations is a disregard for recommended maintenance intervals. Nominally, we recommend the first maintenance at 50 million revolutions or after one year of operation, whichever comes first. Subsequent maintenance intervals should be scheduled every additional 100 million revolutions or yearly.

The maintenance regimen itself is simple: Just vacuum out any dust that has accumulated on the slip ring load and signal contacts. The slip rings used in most packaging or industrial applications don’t even require any oil on the contacts.

While it’s true that engineers have little control over whether end-users will ultimately adhere to the recommended maintenance intervals, there are a couple of key upfront design factors related to maintenance:

Duty cycle. Nominal maintenance intervals may not be enough if you plan on running a slip ring at high rotational speeds, at elevated temperatures or in contaminated environments. These aggressive operating conditions can lead to signal degradation or even mechanical failures without an equally aggressive maintenance regimen (see Figure 3).

Figure 2

Months of Operation

Rev

olut

ions

, mill

ions

0 2 4 6 8 10 12 0

100

200

300

500

400

100 RPM

300 RPM

400 RPM

800 RPM

600 RPM

Maintenance Intervals vs. Operating Speed

1st

2nd

3rd

4th

5th

Figure 3

Horizontal Mounting Position

5245-3 Old Dowd Road, Charlotte NC, 28208 | T: +1 704 705 4711 | F: +1 704 733 9170

WHITE PAPER

https://www.kuebler.com

Easy access. All slip rings require some routine maintenance, but not all slip ring designs make maintenance quick and easy. It’s important to look for designs that have ready access to the power and signal contacts without requiring disassembly of the slip ring. Our designs, for instance, have a removable maintenance window adjacent to the contacts (see Figure 4).

Slip rings are so common nowadays that engineers tend to take their performance for granted. And in general, modern slip rings are reliable enough to tolerate some neglect. However, if you really want to get the most out of a slip ring, a little extra attention to mounting orientation and ease-of-maintenance will go a long way.

Slip Ring Design PrinciplesHigh-performance seals. Kuebler Safety-Trans™ design features an integrated labyrinth seal that separates the respective cavities for the power and signal channels. The labyrinth seal serves two roles—dust protection and electrical isolation between channels.

Advanced contact materials. Optimized materials ensure reliable signal and data transmission in different applications. For example, our silver alloy brushes and precious-metal contact surfaces have very low resistance of less than 0.1 Ohm, making it possible to transmit low voltage, low current signals.

Mechanically robust. Construction of the springs ensures power and signal transmission even with heavy vibration loads. Pick-off springs for load currents are made from copper graphite, which is highly abrasion resistant. The springs for signal currents are made from a resilient gold and platinum alloy with 50% gold content.

Easy Maintenance. All contacts are accessible through a removable maintenance window for easy cleaning. Brushes can also be accessed and replaced individually as needed.

Figure 4