Parker Hannifin Corporation

Daedal Division
1140 Sandy Hill Road
Irwin, PA 15642
Phone (800)  245-6903
Phone (724) 861-8200
Fax  (724) 861-3330

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Electromechanical Positioning Systems

High Precision Construction

Overview
The vast majority of precision tables in use today employ rolling element (ball or cross roller) linear bearings. These are grouped into two primary categories: recirculating bearings (square rail and round rail), which facilitate very long travel distances and nonrecirculating (ball and rod, and cross roller) which offer the smoothest translation. Here you will find a condensed description of each style. The pages which follow describe Daedal’s screw driven, high precision table product offering. For an in-depth discussion

Square Rail Linear Tables
Square rail bearings are recirculating ball bearings designed to move heavy loads on a precise linear path. Linear guides which house several rows of re-circulating ball bearings ride on a square or rectangular steel rail. The rail cross section enables bearing ways to be ground into the sides of the rail. These bearing ways are shaped in an arch which approximates the same radius as the ball bearing. This increases the contact surface between the ball and the rail, thereby increasing the load capacity of the linear bearing. Travel with this bearing type is only limited by the available base, rail length, and drive mechanism. These tables are driven by a precision ground ballscrew, which is performance matched to the linear bearings to optimize load/life performance as well as positioning precision.

Round Rail Linear Tables
Round rail bearings are a re-circulating type linear bearing system consisting of two large diameter ground steel rods on which ball bushings ride. These bushings, have several rows of recirculating ball bearings, which support the moving carriage and permit very long travel lengths. The ball bushings provide good load capacity with very low friction and its modular design permits easy replacement of bearing components. A rolled ball-screw is normally employed as the drive mechanism. With characteristics of low friction, high-speed, long travel and low cost, this drive is well suited for tables utilizing a dual round rail bearing system. These tables are ideal for assembly and automation applications where higher speed, long life and easy, low cost maintenance is important.

Linear Ball Bearing and Cross Roller Tables
The nonrecirculating linear bearings found in both Linear Ball and Rod, and the Cross Roller style tables provide the smoothest translation (least mechanical noise) of any mechanical bearing table. The bearing system in the linear ball bearing (ball and rod) style table consists of two rows of hardened steel balls located on either side of the table. Each row is captured between two sets of ground steel rods (two stationary, two moving) and preloaded to provide ultra smooth, very straight, extremely low friction motion. The cross roller style functions in a similar manner except the balls are replaced by cylindrical rollers and the rods by ground "V" groove ways. The result of this difference is an increased load capacity of two to three times the equivalent size ball bearing table. The ball bearing tables utilize either leadscrew or ballscrew drive-depending on load ratings. Both tables are limited in travel as a result of the nonrecirculating nature of the bearings. moves the positioner and is the principal element in  determining positional accuracy,

Rotary Indexing Tables
Precision rotary tables, used for precise angular indexing, employ an integral angular contact ball bearing or cross roller bearing system. The bearing system is preloaded to eliminate any eccentricity and provide smooth, flat rotary motion. The drive mechanism is a precision worm gear assembly which is compliantly preloaded to minimize backlash and assure positional accuracy and repeatability.

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