Misconceptions can lead to overspending and premature failure. Linear Motion and Assembly Technologies Ball screws come in a myriad of types and styles. Look at factors such as accuracy, preloading, and lubrication to help match the right product to a given application. With so many different ball screws on the market and the attendant flood of data from manufacturers, designers can have a tough time sorting out what truly affects ball-screw performance. Information often focuses on whiz-bang features that bring few real benefits, while more mundane but critical factors are missed completely. To help cut through the confusion, here's a look at four factors critical to successful ball-screw applications, as well as some related myths and misconceptions. Typically, an engineer's first and foremost concern is travel accuracy, which is possibly why so many standards address this single topic. Chief among them are DIN 69051, ISO 3408, JIS B1191, and ANSI-B5.48, which cover topics ranging from material specifications to geometric tolerances. The different norms can confuse the important issues. But common to all the specs is that lead error is the most critical indicator of travel accuracy. Lead error refers to the travel error over a given length as the nut travels along a screw. It is expressed in "mm per 300 mm" or "inches per foot" and determines a ball screw's accuracy rating. According to convention, a lower rating number means less lead error and, therefore, better accuracy. In other words, a Class 1 screw has a substantially higher accuracy than a Class 7 screw. Of course, the high-accuracy Class 1 screw also costs more and may take up to 10 weeks longer to produce. Designers should use accuracy ratings as the starting point for overall slide accuracy, but also weigh performance requirements against lead time and cost. MYTH #1: Accuracy
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Ball screws convert rotary motion to linear motion, or torque to thrust, and vice versa. They are primarily a power screw with a train of ball bearings riding between the screw and the nut in a recirculating track.
Lead Screws and ACME Screws
Lead screws and ACME screws are used to drive a nut in linear motion via direct contact between the screw and the nut. Lead screws usually incorporate proprietary screw and nut geometries and materials, and can be configured in zero-backlash arrangements.
Roller screws convert rotary to precise linear motion in a similar manner to ball screws or lead screws. Due to the greater number of contact points of the rollers compared to balls or thread on thread contact, a roller screw provides higher stiffness and smooth motion.
Schneeberger Inc is a distributor for Karl Hipp GmbH, manufacturer of precision miniature ball screws. All spindle and nut thread profiles are precision ground, providing smooth running performance...
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A ball bearing screw is just that: a screw which runs on ball bearings. The screw and nut have matching helical grooves or races, and the ball bearings recirculate in these races. There is no physical...
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Screw Accuracy Kerk uses a unique precision rolling process for screw manufacturing. Standard lead accuracy for Kerk screws is .0006 in./in. (mm/mm). Lead accuracies are available up to .0001 in./in.