Direct Drive Rotary Table is basically a type of rotary table most often used for the constant operation that is multiple times more accurate and agile than traditional rack and pinion rotary table. It has the capacity to provide infinite degrees of angular position control at any given time. Rotary tables are designed to be very precise and easy to use, making them ideal for small shops and manufacturing shops with little or no floor space. In addition, they are very economical and can be easily mounted on a rack or fixed on a wall. Their main advantage over rack and pinion tables is that they can work in any position and any angle, while they are less prone to mechanical or physical problems.
These innovative machines use two sets of unequal rotors. The lower set has a shaft attached to it that is fixed directly to the table top. It rotates with the aid of an idler and the upper set of rotors is fixed to the shaft and rotate around it. A potentiometer is fitted on the end of the shaft and it helps to monitor the torque applied on the upper set. In order to operate these machines, there is need for an accurately measured force. Hence the designing principle of the direct drive rotary table is to allow the application of any appropriate force on the two sets of rotors, without affecting the other.
The drive is usually a two stroke unit that utilizes high-speed rollers. High-speed rollers are very suitable for applications where high precision is required. However, due to their high speed and large-sized dimensions, they require large sized bearings. This means that they need to have a very large surface area available. Therefore, they are normally found in high-performance machinery like presses and industrial grinders.
Some disadvantages of using a rotary table that uses high-speed rollers are: there is a high friction between the rollers, which leads to high wear and tear of the bearings and grinding wheels; free cooling of the bearings leads to early damage; and the inner ring gear and the roller chemicals tend to slip slightly. High-speed operations need considerable holding time and this results in early wear and tear of the bearing components. Further, free-cooling of the bearings leads to early failure of the outer ring gear.
The other type of direct drive rotary table is the zero backlash one. The design of the zero backlash table is quite similar to the high-speed ones, except that there is no need for free cooling of the bearings. The main advantage of the zero backlash tables is the absence of the operation time errors that are observed with the former. The main disadvantage is that they cannot hold a particular torque value. Further, they can only accommodate a certain amount of rolling force. The maximum speed of the device is limited by the performance capabilities of the motor.
There are different types of direct drive rotary tables available on the market today. Each of these is designed to suit a specific purpose. Some examples of these are: