Finally, rolled ball screw systems are especially vulnerable to dimensional distortions as a result of die tooling wear. These sources of error can lead to a ball/nut system that possesses excessive backlash, which occurs due to a mismatch between the bearing diameter and screw shaft threads, and it also sharply decreases the positional accuracy that can be achieved.
Conversely, the thread grinding process is inherently more time intensive than the rolling process, partly because of the specialized grinding tools required for the cutting operation. This translates into a significantly higher “off the shelf” price tag for ground ball screws compared to rolled ball screws. However, there is a significant benefit achieved for the higher cost process because the ground threads can be held to tighter tolerances in relation to the centerline of the material blank because each thread is ground one at a time. For these reasons, ground ball screws are almost exclusively employed in applications where high degrees of precision and repeatability are required.
Rolled ball screws Ground ball screws
Rolled ball screw systems will generally cost significantly less than ground ball screws, and should be more than serviceable for use in most applications. Both rolled and ground balls screws are available in a wide variety of lengths, diameters, and load capacities to fit a broad range of applications. However, if very high degrees positional accuracy is required, to a high degree of repeatability, it may be more than worth the cost to opt for a precision ground ball screw system. The engineer must carefully consider these distinctions when tasked with selecting between the two for any given machine application.
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