ROTARY TABLE

 
Rotary table - Accuracy vs Resolution

A common misconception is that the resolution of the rotary table must also be its accuracy. For example, if a digital readout displays to four decimal places (0.0001), then it must also be accurate to that same value. That is usually not the case.  Although high resolution is a prerequisite for high accuracy, it does not guarantee it. Consider the two graduated scales:

Both scales have 15 graduations over equal arcs; therefore, both have identical resolutions of 1/15th arc. For arc A the resolution increments are equal; however, for arc B the resolution increments are obviously not the same.  That difference, scale accuracy, is a component of position accuracy, and while both examples have the same resolution, each will provide very different results. 

Accuracy is the difference between the actual position and the position measured by a reference measurement device. Rotary table accuracy is influenced by the feedback mechanism (rotary encoder, drive mechanism (ball screw, lead screw, linear/torque motor), and roundness/parallelism/run-out of the bearing guide-way. IntelLiDrives uses laser interferometers (for linear axes) and autocollimators (for rotary tables) as a reference measurement tools.

 

Repeatability is defined as the range of positions attained when the rotary table is repeatedly commanded to one location under identical conditions. Uni-directional repeatability is measured by approaching the point from one direction, and ignores the effects of hysteresis within the system. Bi-directional repeatability measures the ability to return to the point from both directions.

 

Resolution - The smallest possible movement of a rotary table. Also known as step size, resolution is determined by the feedback device and capabilities of the motion system.

 

Low Accuracy

High Repeatability

 

Low Accuracy

Low Repeatability

 

High Accuracy

High Repeatability

 

 
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Buying Tips for Rotary Table

A rotary table is used in precision metalworking industry. It is made of a solid base that can be clamped on to the other fixture. In simple words, rotary tables are discs, which rotate freely or by using a worm (hand crank).

Rotary tables are used in different applications like machining, assembly and automation. Other than this, these tables find usage in assembly and equipment positioning. When you are buying a table, there are a few things to consider. These include:

 

Diameter of the Table

The worktable diameter is the surface area of the rotary table.

Measurement of Through-Hole Diameter

It is the diameter of the breadth of the hole present at the center of the workstation.

Maximum Radial Load

When the load is pushed against the table, the heaviest amount it can support on vertical or horizontal axis is the maximum radial load.

Maximum Axial Load of the Table

Maximum weight tables are able to bear at the time of concentric operations.

Table Rotation Speed

Maximum rotation speed set b the manufacturer.

Minimum Indexing Increment

Smallest angle setting on the table.

 

Rotary tables can be mounted in horizontal, inverted or vertical styles. When the table is mounted horizontally, it is in a flat, horizontal and upright position. In vertical mounting, surface of the table runs up and down. When it is inverted, the table is upside down in a horizontal angle.

The location of drive on rotary table depends on the mount. You can place the drives below, behind, on the top or on the side of the table. When the drive is mounted horizontally, it is located above the surface of the table. When the table is mounted horizontally, the side-mounted drive is placed to the side of the surface of the table.

The rotary table can be driven manually, pneumatically, hydraulically and electrically. If you are driving manually, the table should be loosened and it must be turned manually with the crank.