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Linear guides (bearings) play an essential role in many linear motion systems. They support the load, constrain travel, manage friction, and directly affect system parameters such as accuracy, repeatability, and lifetime. Properly specifying the linear guide requires a detailed understanding of the static and dynamic conditions of the system. Even for simple layouts, that can involve complex and time-consuming calculations. THK America, a Motion Solutions partner, provides an alternative. “THK has a great calculator for determining safety factors in lifetimes for a variety of relatively straightforward layouts,” says Wally Logan, VP of engineering at Motion Solutions. Logan and colleagues in the Motion Solutions Engineering Services team take advantage of the tool to provide initial information for simpler systems. The time saved enables them to focus their efforts on more complex custom systems.

The calculator is fast and easy to use. Users enter basic configuration information (number rails, number of blocks), adding details like dimensions, load configurations, and basic information on speed and frequency of use. The tool will suggest several appropriate THK linear guides, giving safety factor, nominal life, and service life for each model (see figure 1) . Users can output the results to a PDF or save them for future reference. The latter option is particularly useful, given that most designs develop and can change over time. Users can add additional details to a saved design to update information.

Figure 1: The output of the THK Online Lifetime Calculator tool includes safety factor and estimated lifetime.

“It’s great for preliminary direction, to get a baseline of where to start,” says Take Grzyb, corporate engineer at THK America. “Few engineers have full system information available at the beginning of a project. They can use our tool to get started. Once they have more information from their own end-user and application, they can run the calculation again.”

Users should be aware that the tool is intended for basic systems. If you’re designing a five-axis machining center, calling a sales engineer is the best approach. If you are building a system based on a single axis with two rails and four blocks, for example, the online calculator will probably be effective. “THK is a technology focused company, says Ed Johnson, VP of sales at THK America. “We wanted to build a tool that would make it faster and easier for people to specify and use linear guides. Our Online Service Life Calculation tool does just that.”

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