The encoder wheel is not one of those one-size-fits-all elements. Which is something you might know all too well if you have an engineering problem that goes beyond standard measurements. In this blog, we break down different types of encoder wheels, their applications, and why you might need a custom wheel for your product.
Encoder wheel tech
Encoder wheels are necessary optical components in everything from industrial to commercial designs. These rotational discs are also “part of a closed-loop feedback system that collects and processes information, such as position, direction, and speed.” And because rotary encoders track motor shaft movement, precision is necessary. In fact, overall accuracy traces back to the encoder disc, which why understanding encoder wheel technology is so important.
That said, we develop our varied encoder wheels on materials and with processes optimized for a specific application. To achieve the necessary measurement precision, we use methods like laser cutting, optical fabrication, and microlithography. Accuracy matters, so we work with our customer’s end-goals and specifications throughout the entire process.
Why are custom encoder wheels needed?
Depending on the encoder sensor used, the track optical radius, counts per revolution (CPR), lines per inch (LPI), and index options are all variable as is the diameter of the disc. Absolute and commutation track patterns designed for specific applications and must be exact and precise.
Different types of materials used
As versatile products, encoder wheels use several different materials depending on the application. The primary considerations when choosing a material are temperature, humidity, shock, and cleanliness. If you choose a material that cannot withstand high temperatures, you risk thermal expansion that could result in position errors.
We adjust the materials used based on customer specifications and engineering goals. At a basic level, the most common materials include glass, metal, and mylar film. However, we go beyond these materials and also commonly use:
For applications that need higher performance than glass, we often use ultra-flat quartz. These synthetic quartz substrates have extreme flatness and optical transmission that translate to ultra high resolution for applications like sine wave encoders. Quartz is also very robust in extreme environments. Although an expensive option, for some applications there is no other substitute.
In general, glass encoder wheels are resistant to humidity and temperature, but they’re also very delicate. Borosilicate glass, on the other hand, is thermal shock resistant so “it will not crack under extreme temperature changes like regular [sodalime] glass.”
Soda-lime glass is often used instead of borosilicate glass because it is “less expensive and readily available.” In fact, soda-lime glass is about 90% of the manufactured glass across the globe. But the combination of silica, soda (sodium oxide), and lime (calcium oxide) make this material only “relatively durable at normal temperatures.”
High reflective chrome (HRC)
High reflective chrome, or HRC, is a glass encoder wheel coating type. We use HRC when the disc pattern needs to be highly reflective. For reflective mode encoders, HRC glass is the most precise material available.
Low reflective chrome
Low reflective chrome, or LRC, is the standard coating used for transmissive mode encoder discs. It can also be specified for the backside of reflective glass encoder discs to eliminate unwanted reflections from other components.
Unlike glass, Mylar encoder wheels “have low mass and can withstand high levels of shock without distortion.” Mylar film is a polyester film used for its strength, stability, and transparency. Code wheels made from this material are cost-effective and user friendly. However, this material is not as temperature resistant as its counterparts.
What type of encoder wheel do you need?
Sometimes it’s challenging to know which photonic product is the right fit for your engineering project. We offer a variety of different encoder products to suit the needs of practically every industry. But if none of these options is the exact fit, we are happy to create a custom solution for you.
Glass encoder discs
Our chrome on glass encoder discs offers the highest degree of accuracy due to the etched photo pattern’s extreme flatness and precision. We use CAD data to create the discs from your specifications. This generates a high-resolution glass master from which we print the parts.
Transmissive mode glass discs
We create transmissive glass discs for OEM and high-performance applications. Our standard disc configuration includes soda-lime glass with low reflective chrome, but we can adjust materials and optical density as needed. If you need discs for extreme performance (like sine wave applications) or higher temperatures, we use ultra-flat quartz or borosilicate glass.
Reflective mode glass discs
For this encoder wheel product, our material configurations include high reflective and transparent patterns. Options include ultra-low reflective chrome on the back of the disc and gold coating for high-performance applications.
Mylar encoder discs
If you need a low-cost application, mylar encoder discs are a great choice. Our automated process saves you money in both production and prototype quantities without sacrificing quality and precision. Using our die punch or laser cutting systems, we can create cutouts to precisely align the photo pattern to your device. Additionally, we can rapidly deploy these parts, shipping them to you in under two weeks upon approval.
Reflective mylar encoder discs
We offer our PET (Mylar) composite discs with pressure-sensitive adhesive for easy device mounting. We also provide peel-and-stick discs and scales with protective liners and laser-cut registration features for easy installation. One option includes bonding to acrylic substrates to increase thickness.
Aluminum code wheels
For applications requiring the highest environmental performance, we recommend reflective aluminum encoder discs. This is because they’re able to withstand shock and extreme temperatures. Another advantage is the ability to mount to a hub or shaft using the disc ID for alignment similar to PET discs. But, like glass discs, they do not need to be fully supported and can use smaller diameter hubs. Although not as user friendly as PET discs during assembly they are an affordable option when compared to glass code wheels.
It’s worth noting that, as the cost of automation drops and optical encoders find their way into more consumer and other mass-produced products, custom reflective code wheels are a very competitive solution.
Encoder wheel applications
If you’re reading this, you likely have an encoder wheel application in mind. However, we often work with our clients to find the exact wheel type, material, process, and measurements to fit their project. Some of these applications include:
Factory/warehouse automation: One of our fastest-growing applications include automation for warehouse robotics. Another example is encoder wheels applied to a drive motor or lead screw in factory conveying.
Medical components: Optics and imaging help medical providers see what was unavailable without current technology. Encoder wheels help make medical components highly sensitive and precise.
Aerospace craft and sensors: The aerospace industry uses optics like encoder wheels for accuracy, security, and precision. These include products like drone sensors and aiming and tracking systems.
Metrology calibration standards: Optical encoder discs used in metrology help make the measuring systems more accurate and automated. This is especially important for things like calibration standards and targets.
Photo Solutions for all your optoelectronic needs
At Photo Solutions, we’ve spent the last few decades perfecting our custom tooling and production process for mission-critical designs. We offer precision manufacturing in various encoder materials, including glass, quartz, film, and aluminum. Whatever your application or industry, we create custom encoder wheel orders on special composite configurations that enable easy and accurate installation at your facility. Get in touch to see what we can design for you!