Rotary indexing table

Types of rotary indexing tables

An automatic indexing table is built like a segment of a circular disk, which is usually a horizontal sliding plate mounted on vertical posts that form a center point. The rotary table is one of the oldest forms of motion economy, but it is still common now.

With the input of an electric motor, normally fixed on a machine or work center, the rotary indexing table can be used for vending pick-and-move operations or workstations where, on average, 90 right-angle rotations are required to fetch or place an article.

With the assistance of a PLC program, the number of right-angle turns and the time taken to make each turn can be set and programmed as desired.

Generally, there are three kinds of rotary indexing tables:

• Cam-driven tables

  Due to their affordability and prevalent usage, cam-driven tables are commonly employed in various setups. However, it's important to acknowledge that these tables possess certain constraints in terms of their accuracy and rapidity of operation.

• Cylinder-driven tables

  Tables driven by pneumatic or hydraulic cylinders offer an impressive capacity for handling heavy loads and achieving swift rotations. Nevertheless, it is essential to recognize that these tables are inherently limited to providing continuous rotary motion.

• Servo motor-driven tables

  The versatility of servo motor-driven tables allows for the accommodation of diverse rotational movements, including the possibility of indexing, which refers to the ability to precisely control the table's position and rotation speed. Furthermore, these tables are characterized by their rapid speed and high accuracy, making them suitable for applications that demand precision and efficiency.

Specification and Maintenance

• Sizes and Weight: Heavy-duty rotary index tables come in different sizes. Bigger ones can be as wide as 800 mm and support more weight. For example, a table with a 600 mm diameter can easily hold parts weighing up to 500 kg. Smaller rotary index tables used for light work may only be about 400 mm across but are good for lighter loads of 200 kg or less.
• Motor Torque: A strong motor with enough torque to move the table smoothly is very important. The torque rating of the motor should ideally be between 20 and 50 Nm or higher, depending on the weight the table has to carry. Higher torque means the motor can handle heavier loads without straining.
• Speed Control: How fast the index table moves from one position to another is very important. The motor must be able to turn the table at different speeds, from 0.5 to 5 RPM or even slower and faster if required. It should also have smooth acceleration and deceleration so that parts can be gently picked up and dropped off.
• Gear Ratio: The gears inside the rotary indexing table reduce the speed of the motor while increasing the torque to turn heavier loads. A gear ratio of 1:60 will allow the motor to turn the table once for every 60 turns of its input shaft. Higher gear ratios, like 1:90, give it more multiplying power to turn heavier weights. Lower gear ratios are good for faster speeds.

Maintenance

The proper functioning and durability of rotary tables are directly proportional to the regularly scheduled maintenance. Allow the indexing table to come to a complete stop before applying. Lubrication must always be given before the application. Doing so will ensure the oil reaches the manways. Allow all the oil to drain out of the indexing table before starting and then, in between, upon stopping, to allow it to ventilate properly and avoid any pressure or vacuum formations within the table.

Due to the very high speed of the bear or the bushing, the oil has to be of the highest quality to offer the stable viscosity required to ensure a smooth and excellent indexing function. Abnormal oil temperatures should be closely monitored. If the oil temperature rises above 70 degrees centigrade, immediately examine the oil to see if it is smoking or presenting any unusual characteristics. In some cases, air-cooling indexing tables could be used to lower the oil temperature, which otherwise may always be above 40 degrees centigrade during use.

In some cases where the load of the rotary index table is considerable, or very high-speed rotation is required, it may be worthwhile to examine the oil seal critically. Specialized oil seals or the use of Viton could be used as an alternative if very high speeds of rotation are desirable. One should always look for signs of wear or slurry formation while working with oil seals and ensure that any dirt or slurry does not enter the machine as it could damage it.

Any unusual noises or signs during operation should be immediately examined to adjust the braking force if it is present in the indexing table or the direction of movement so that all the components can work towards a common goal.

Applications of rotary indexing tables

Automation: Rotary indexing tables are widely used in various automation industries. The workpiece can be fixed on the rotary indexing table, and the corresponding processing procedure can be indexed at different angles. This simplifies automation tasks.

Manufacturing: Rotary indexing tables are also commonly used in manufacturing industries. Machines can be arranged along the indexing table so that the workpiece can be processed one by one on different machines. For example, in CNC machining centers, rotary indexing tables allow multiple machining operations on a single machine.

Assembly: In assembly applications, rotary indexing tables can be used as assembly platforms or assembly lines. Workpieces can be indexed at specific positions for assembly operations, improving assembly efficiency and accuracy.

Welding: In some welding scenarios, rotary indexing tables can be used as welding jigs. Workpieces can be indexed to different welding positions for welding operations, such as spot welding, seam welding, etc., achieving uniform and efficient welding.

Quality inspection: Rotary indexing tables can also be used in quality inspection processes. Workpieces can be indexed at specific inspection positions for quality inspection and testing operations, such as dimensional measurement, functional testing, etc.

Sort and package: Rotary indexing tables can be used for sorting and packaging operations. Workpieces can be indexed at specific positions for sorting operations, such as classification, weighing, packaging, etc. For example, in food processing factories, rotary indexing tables are used for sorting and packaging.

Laboratories: Rotary indexing tables can be applied in laboratory automation. For instance, in biological or chemical analysis, rotary indexing tables can be utilized to perform dilutions, samples, or reactants' addition, modification, or observation at predetermined intervals.

How to choose a rotary indexing table

When choosing a rotary indexing table, a few things need to be considered to ensure a worthwhile investment.

• Work requirements analysis

  Investigate the existing work processes to understand the overall machinery, feeding methods, and desired priority-up techniques. Identifying the process's priorities, such as job mies and feeding rate, will assist in selecting an indexing table that fits. Considering what kind of automation desired will help select an indexing table that suits those needs.

• Availability of resources

  Take stock of the available human and financial resources. An automatic indexing table may be preferred if more human resources are available to operate and maintain the machinery. It is also essential to determine whether enough capital is at hand to purchase the required machinery and any ancillary equipment.

• Compatibility with existing equipment

  Ensuring that the indexing table selected is compatible with the existing machinery will help a smooth integration. Considering any additional equipment that may be needed will also help in understanding the total cost of setting up a solution.

• Space constraints

  A thorough investigation of the available space is needed, especially the height, length, and width. The rotary indexing table's dimples should match the parameters of the space available in the work area.

• Supplier support

  It is crucial to select a table from a supplier with a good reputation and record of providing post-purchase support. Suppliers with a track record of offering good post-puppishcarell keep savings operational and reduce downtime.

Q&A

Q1: How does a rotary indexing table work?

A1: The working process of a rotary indexing table may vary depending on the type. For example, a cam-driven rotary indexing table functions by using a rotating cam to drive the indexing movement. The cam has a profile designed to create step-like movements. Then, each step moves the table. On the other hand, a friction-driven rotary indexing table works by using a friction drive to move the table. The friction drive consists of a disc or wheel that creates a force of friction to move the table. However, regardless of the type, all indexing tables are driven by motors. The motor provides the power needed to rotate the table. Some rotary indexing tables have gears that increase or reduce the speed at which the table rotates.

Q2: What are some advantages of rotary indexing tables?

A2: One of the main benefits of a rotary indexing table is that it provides a fixed work location. This means that operators don't have to move workpieces or tools to achieve different angles. Secondly, these tables are durable. They can support heavy workpieces and withstand the stresses of frequent rotation and positioning. More importantly, a rotary indexing table can improve productivity. The tables provide quick and easy access to all sides of a workpiece without moving it.

Q3: Are there any disadvantages of a rotary indexing table?

A3: A major drawback of a rotary indexing table is the cost. These tables can be expensive. As a result, they are only used in applications that require high efficiency and accuracy. Also, while a rotary indexing table offers precise positioning, the precision may be lower than dedicated CNC machining.