CNC Rotary Table Introduction and Product Guide

Posted on Jan 21, 2021

CNC Rotary Table

A CNC rotary table is the precision positioning accessory that can provide a reliable 4th axis or even 5th axis for modern machining centers. Utilizing a computer-controlled rotary table can turn the original 3-axis machine tools into 5-axis CNC machines, expanding the accuracy as well as decreasing the costs while performing complex machining operations at one time.

A CNC rotary table is the precision positioning accessory that can provide reliable 4 or even 5 axis cutting operation capabilities for modern machining centers. Utilizing it can turn the original 3-axis machine tools into 5-axis CNC machines, expanding the accuracy as well as decreasing the costs while performing complex machining operations.

1. The Basics

Rotary tables typically have rigid frames and coatings, and also excellent torque capacity, which makes the small device flexible and effective for a wide variety of turning, milling, drilling, and more metalworking operations. The easy setup and seamless interface allow the operators to easily add the rotary table to fit their 4-axis or 5-axis applications. .

The working principle is similar to the basic rotary tables, which is to support the workpiece by accurately rotating the workpieces on the axis in order to locate the parts for high precision tooling. Under rapid rotation, which is driven by CNC instructions, the cutting tools of larger machine tools or machining centers can remove the material and add the feature to the products at exact intervals. On rotary tables, there are vertical and horizontal axes for various tools to perform these high-performance metalworks. To enhance the accuracy and flexibility, there are models that employ additional dividing plates and come with additonal material handling mechanisms and features.

Rotary Table Explainer Video

Since 4-axis and 5-axis machining is increasingly popular today, adding the CNC rotary table as the 4th axis is an ideal solution to easily open up more complex machining options at a lower cost. Due to the arrangement, they are widely also called the 4th or 5th axis or tilt rotary. The 4th axis, which is the rotational operational direction, is added to the original three linear axes which are known as X-axis, Y-axis, Z-axis. In some cases, there are two rotational axes add to the original 3-axis machining center, achieving utmost accuracy as well as effective multiple face cutting to reach the difficult area on the surface. Rotary tables are usually mounted parallel to the ground or the bed, with the platter rotating around the vertical axis, for example with the most common vertical milling machine combination. Sometimes the machining application requires an alternative setup with the table mountet on its end so that it rotates around the horizontlal axis. Often, a tailstock is used in this configuration. Virtually all models today come with a clamping kit to mount it onto the bed of your machine tool.

:: Read more: What Is Automatic Rotary Table?

What about high precison positioning?

The function of the high precision rotary table is also to rotate the workpiece so the cutting tool can create the contour we desired out of the workpiece. However, a rotary table with higher precision has the ability to achieve great accuracy just as its name implies. There is also a major misconception between the resolution and the accuracy.

A common example is that if a digital readout displays to four decimal places, then the high precision rotary table must also be capable of achieving the accuracy to that same value. Even though for higher accuracy to be achieved, the resolution has to also be high, but there is no guarantee that the accuracy is going to be high. The accuracy is the concept which is the difference between the actual position and the position measured by a reference measurement device. The feedback mechanism such as the rotary encoder, and the drive mechanism can influence the accuracy of the advanced rotary table.

2. Structure and Components

A CNC rotary table can provide great rigidity for stable machining operations. It consists of the worktable where the metal parts are held, the rigid bearing that withstands the forces and loads during the rotation, the solid base which is used for attaching the rotary table to the machining center or other equipment, the motor, and the CNC system. 

● Worktable:

The worktable is the tooling surface where the workpieces are machined after accurate positioning. The worm gearing is the core mechanism of the table, which mesh with the steel worm which is submerged in the lubricants. Both the rigid bearings and the worm gears have large diameters. Excellent concentricity is the key to smooth operation, durability, and most importantly, accuracy. Driven by a computer and electric motor, the worktable can position the materials at exact intervals. For more flexible or critical operations, dividing plates can be added to this component.

● Computerized Control:

A CNC system regulates the simultaneous 4-axis motion of the rotary table. The instructions are programmed and transmitted via CAD software, reducing the time for adjustment and monitoring by human workers. 

● Motor:

The type and size of the electric motors utilized in can define the router accuracy as well as the efficiency of the device. Servo motor and stepper motor are two typical types that can be divided into more subtypes. The servo motor uses a closed looping variable circuit, the circuit will constantly run to keep the function. The brushes must be replaced every 2000 hours of operation in the servo motor. Compared to stepper motors, servo motors are more efficient in power consumption. On the other hand, the stepper motor has a simpler setup which are the wires that are attached to the driver. The bearing of the stepper motor is the only wearing component. However, the stepper motor consumes a great amount of energy.

Direct Drive Table, Solpower Taiwan

3, 4 and 5 Axis Models

There are currently several different types and models available in the industries. Each of them possess its own traits and abilities. Let us take a look at the most common ones other than standard three axis tables

4-axis Tables

The 4 axis CNC rotary table will process the workpieces by holding them in the same position while the cutting tool performs along the XYZ plane to trim away the unwanted material. In general, a 4 axis model is very versatile equipment that can be used for several different industrial processes such as engraving curved surfaces, continuous cutting, and intermittent cutting. Besides, people can also add other devices such as cam machining, blade machining, and helical grooves to the 4 axes rotary table. Such a feature is simply impossible to achieve with the machining center which has only 3 axes.

5-axis Tables

Besides the 4 axis ones, there are also 5 axis models. They have the ability to allow the workpiece to be processed automatically from five sides at one time. people usually utilized the 5 axes rotary table in the industries such as the automobile, the aerospace, and the boating industries. The reason that the 5 axes rotary table is commonly used in heavy industries is that the 5 axis machining is an important technique to be used when the components need better intricacy and quick precision. All of these have more than three axes are called the multi-axis rotary table.

Mounting Types

The installation method of the precision rotary table can be horizontal, vertical or inverted. When installed horizontally, the workbench surface is in a flat, vertical and horizontal position. When installed vertically, a rotary table is installed so that the surface of it can run up and down. In the reverse layout, itcan be rotated upside down in a horizontal position. The location of the drive of the rotary table can depend on the mount. The drive can be placed on the back, below, on the top or on the side.

When mounted horizontally, the spinning table top drive is positioned above the table floor. When the rotary table is horizontally placed, the side-mounted drive is located on the edge of the table board. The driving mechanism of the rotary table may be manual, electrical, pneumatic, hydraulic or non-driven. For manual revolving workbenches, release the workbenches and manually spin the workbenches with the crank.

4.Advantages and Applications

There are numerous benefits for utilizing a CNC rotary tables:

● Reliability and Consistency

Workpieces are gathered and machined through PC and fully programmed instructions. The 5-axis simultaneous operations will be measurably more reliable than products machined via different technologies. Also, the setup is simple and provides an indistinguishable process in every production cycle, the consistency of the quality of the metal products can be ensured under critical control and precision cutting. 

● Adaptability

Since the metalwork is driven by software, the preferred frameworks can be programmed and adapted by the rotary table. Saving both the cost and the room makes themis the ideal solution for potential users who don’t want to install larger equipment and new machines which may take up a great room for a wide variety of machining applications.

● Complex Parts

Another benefit is the utmost movements can be completed precisiely and faster. There are more favorable positions, operation angles as well as accessible machining that can be achieved through the technology. The complex operations are suitable for blade, helical grooves production, and other applications required to add complex features or require critical inspection in machining processes like the manufacturing of aerospace, automotive parts, and scientific equipment.

● Time-Saving

Addding a rotational table saves time because the extra finishing jobs or other sub-operations can also be performed at one time in the machining center. 

:: Read more: What Are 4th and 5th Axis CNC Rotary Tables?

A wide range of Applications

A rotary table can be used in many applications including manufacturing, inspection, and assembly. Indicators are used, for example, for assembly, manufacturing, and bottling equipment. They typically use a single item in workspaces or move relatively small layouts of items around stations for sequential work or assembly.

In automated assembly machines, the rotary tables implementation is widespread, and choosing the right mechanism is important for both improving efficiency and reducing the cost of this vital component. This guide discusses two common devices for rotating indexing and offers guidance on the right range. There are several ways to get mass mobilization when it comes to the development of rotary indexing tables. Regardless of whether the load or load in centuries of thousands of kgm2 is incredibly light. When choosing a robust rotary index solution that will match or meet your standards, there are several factors to take into account when spinning, elevating, or pushing.

5.Precision and Backlash Considerations

When determining the influencing factors on the postitioning  accuracy, the first thing to look at is the mechanical properties of the table itself. A rotary table contains six degrees of freedom. Each of these movements increases the total risk of positioning errors. Usually, a rotary table is driven by a worm gear, which is connected to the motor through a rotary encoder on the back. The position of the table can be determined by the number of pulses transmitted from the encoder to the control device.

The four main sources of error due to the semi-closed position loop are geometric errors, thermal deformation, elasticity, and wear. The sum of these errors is called angular positioning error. To greatly reduce the angular positioning error, the ideal position for installing the angle encoder is on the rotating shaft under test. The angle encoder is installed under the rotary table, and the rotary encoder is installed under the rear motor, the position loop is now considered a closed-loop system.

What exactly defines precision & accuracy?

Precision is a relative term. About a quarter of an inch is great and will meet the accuracy of its application. Others, for example, require micron-level accuracy in measuring and indexing devices. Then, some applications fall within these extreme ranges.

The misunderstanding is that you may have used an inaccurate indexing device and made it accurate by introducing a pin or wedge locking device. These devices increase the complexity and cycle time of use, and when they are used together with a high-precision positioning device, they may cause damage and reduce accuracy.

In the actual test, by selecting specific components, motion index drive, servo rotary indexer, the measurement accuracy is as high as 5-6 microns. These are not the results approved by Motion Index Drives, but the results of customer certification. When starting and stopping large amounts of data, it is important to know how fast it takes to stop the application with large amounts of data.

In a less rigid environment or the presence of higher recoil, a faster start and stop will bring many control problems. When moving masses (whether rotating mass or linear mass), starting and stopping in a system with a backlash of several arc minutes will cause a lot of back and forth movement in the gear system. The result is a force that is difficult or even impossible to calculate. In addition, when the gear head is used in rotating applications, the farther the mass is from the center of rotation, the greater the backlash. In applications with very slow deceleration times, recoil may not be a problem.

Precision & Backlash

Backlash in the positioning process is a big issue – when it comes to the beginning and stopping volumes, it's crucial to know how quickly you need to avoid the mass of your rotary indexing table applications. In a less rigid system or where there is an increased backlash, quicker start-ups and stops can cause a lot of control issues. When shifting a mass, whether rotary or linear, starting and stopping in a system with several minutes of backlash arc will create a lot of back-and-forth motion within the gearing system. The effect is a power that can be difficult and probably hard to quantify. In comparison, as the gear head is used for rotational applications, the more the mass is from the axis of rotation, the further the backlash is magnified.

The backlash may not be a concern in systems where deceleration times are incredibly long. In the case of cam indexers, there is " Zero Backlash." The cam indexer and rotary table dynamics give an incredibly rigid, highly regulated framework. A modern cam indexer system is capable of withstanding short cycle times with stop times in milliseconds.

6.How to pick the best model for your application

So you want to get the smart manufacturing going but are not sure of what to look for in rotary tables. The information provided in this section may be able to help. The primary factor is to determine the mass snapshot of inactivity. This is often overlooked when measuring a rotary table for the machine.

Another significant factor is the size of the workpiece being rotated, including how big it is and how substantial it is. You want your rotary tables to be large enough to handle enormous pieces. This is where tilling rotary tables may become handy so that the pieces can be handled without causing interior harm. They allow the quickening and decelerating of machining at appropriate rates.

The last factor is accuracy, the applications for which, for instance, pivoting a gigantic part to allow welding highlights on it where the individual stop positions can be genuinely free. On an additional note, when choosing direct drive rotary tables, factors that you should consider when selecting a rotary table for your CNC machinery include accuracy, backlash, mass moment of inertia, acceleration and deceleration, speed, and environment.

Rotary Indexing vs. Cam Indexing

Indexing system use is commonly possible in automatic assembly machines and the right process is important for both performance maximization and cost reduction.

● Cam Indexers

Cam indexers are an omnipresent tool used for several decades for rotary indexing tables. They are suitable for applications that often index the same angle and need a high degree of accuracy at a relatively low cost. To place the load, a cam indexer uses a mechanical cam. A math curve is pushed onto the cam and provides incredibly smooth and repeatable movement.

● Indexing Table

Another popular alternative is a fully programmable rotary index table. A rotary table is advantageous in two different situations. Firstly, a versatile movement pattern is important. An example is if two components are running on one computer, each of which requires different index patterns. For incredibly fast placement accompanied by a long period, another condition that matches the servo pointer is. The need to accelerate the camshaft while the cam indexing mechanism was operating before starting the output movement reduced the on-demand cam indexer. Acceleration of the camshaft is possible, but there is a delay before the movement begins. There are realistic restrictions.

With an indexing table, the output rotates as soon as the servo starts moving. This is not difficult for a continuous cam indexer or a zero-backlash servo indexer, but it can also be difficult for an on-demand cam indexer. For applications with high-speed servo indexing, smooth movements are crucial. A zero-backlash preloaded reducer can achieve this. The ideal alternative for correct positioning with high dynamic response would be the zero-backlash reel drive system.

Application parameters, like a moment of inertia, indexing angle, indexing period, and residence time, are required for each indexer style. The rotary indexing table for the application should also be sized correctly by a reputable manufacturer.

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