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Convert Rotary to Linear Motion

Tech Talks by igus helping solve design engineering problems with motion plastics

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Learn more at www.igus.com/drylinSD rotary tolinear motion Convert Lead screws are a common technology used to convert rotary motion into linear motion, and are often used to provide actuation to a set of linear bearings. Plastic lead screw nuts are an excellent alternative to ball screws in many applications where extreme precision (micron level) is not required. They require no external lubricant, which makes them suitable in applications ranging from sensitive lab instruments to packaging machines. Trapezoidal lead screws are also ideal for 3D printers, as the industry is standardized on metric motion profiles and components. They are also very easy to customize, and are found in a number of geometries, from coarse threads for higher torque output, to high-helix designs for higher speed applications. Traditional materials for lead screw nuts are typically brass, oil-impregnated bronze, and simple plastic materials. igus ® tribo-plastics, such as iglide ® J and iglide ® L280 are composite plastic materials, which offer lower friction and wear values than many other materials across a whole range of applications. These composites operate free of any oil and grease, and do not require maintenance. They are able to operate on traditional ferrous lead screws, as well as low-weight anodized aluminum lead screws. ACME and trapezoidal lead screws The single-start ACME thread is the most common form of the lead screw nut in North America. Developed in the mid-1800s, they can be found on all types of machines, and are most suited to low-cycle or positioning applications. Their trapezoidal shape makes them better suited for the axial loading found in power transmission applications. Standards for single-start ACME nuts apply to the inner thread dimensions. ACME lead screws are called out by their diameter, and then the threads-per-inch (TPI). For example: A ¾-20 ACME has a major ID of 0.75" and 20 TPI To calculate the lead (linear travel in inches per one screw revolution) simply divide 1 inch by the TPI. In the above example a 20-TPI nut 0 1 2 3 4 5 POM PA J L280 Wear test with 100 N (45 lbf) axial load using a cold rolled screw 0 20 40 60 80 100 J/1018 Wear test with 200 N (90 lbf) axial load and 50% duty cycle J/1045 L280/1018 L280/1045 Common CNC Drive Forms 30º 29º

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