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Posted on Jan 17, 2021
4th and 5th axis rotary tables can increase a machine tool's versatility. A standard CNC milling machine has three machining axes, the X, Y, and Z axes, enough to handle general-purpose machining tasks. However, they are not able to create complex profiles on the workpiece unless they make use of CNC rotary tables...
CNC rotary tables are a cost-effective alternative for the shops that cannot afford those high-end multi-axis machining centers. Though less versatile and efficient than a CNC machining center, a typical milling machine that incorporates a rotary table is able to carry out many more intricate tasks. In this article, we will walk you through the basic knowledge of the 4th and 5th axis CNC rotary tables, including how they work and what they can do for the shops.
In essence, it is a mechanical device that offers an additional rotational axis to a machine tool. It is typically designed to work with a milling machine so that the machine has the ability to carry out more complex cuts. Provided with a rotational axis, in a sense it combines a milling machine with a lathe. Besides giving an extra axis, rotary tables are also used for indexing and positioning tasks.
Rotary tables were invented in the early 20th century. The construction has not changed much since the invention except the way they are driven. At first, chains were used. But from 1918 on the shaft-driven mechanisms replaced them. As the technology of powered machines and computer control advanced, NC and CNC models hit the market in the late 20th century. CNC controls facilitated precision positioning and indexing.
The primary benefit is the indexing accuracy. In the past, millimeter-scale accuracy was enough for general-purpose machining applications since the part tolerance requirements were not high. Today, medical equipment, military, and automotive components require higher precision. That is why CNC tables with micrometer precision prevail across industries.
The standard CNC rotary tables are also called the 4th axis or 4-axis rotary tables. The 4th axis refers to the rotational axis, their most important feature. It upgrades an existing machine tool with x, y, z dimensions by adding an additional axis.
Fig. 4-axis Rotary Table, Solpower Machine Electronic Corp.
As mentioned earlier, the working principle of a 4th axis CNC rotary table is similar to the headstock of a lathe. They are both electrically powered to clamp a workpiece and make turns. The CNC system enables precision positioning so that the milling machine can make cuts on the desired surfaces of a workpiece.
An additional fourth axis is beneficial because it can be adjusted for particular amounts of rotary motion. The degrees the table rotates are pre-programmed and accurately controlled by the computer. The other benefit is that it allows the milling machine to work on cylindrical parts. The milling machine can cut grooves, slots, and planes on the outer diameter of a bar.
The precision indexing ability of the rotary table enables the machine tool to cut equidistant holes in a workpiece around 360 degrees across its surface. Repositioning of the workpiece is not required during such an operation. Similar operations such as arc cuts and curved contours can be performed in a run as well.
A 5th axis CNC rotary table provides two additional machining axes to a machine tool. Besides the rotational axis, the 5-axis rotaries have another swinging axis. In other words, the table not only turns but also tips. With two more axes, the machine tool is able to perform multi-plane machining.
Fig. 5-axis Rotary Table, Goushin Machinery
The working mechanism of a 5-axis CNC rotary table is simple. As you can see in the image above, the rotary is mounted onto a swivel base. In addition to the swivel, other designs such as a swing bed are also available to provide a tilting axis to the table. Here is a video showcasing the moving axes.
Rotary Tilt Table, Bart Christopher
A 5th axis CNC rotary table not only features precision positioning but also eliminates multiple setups that are required for complex machining applications. Compared to the standard CNC rotaries, the 5-axis table covers more surfaces on the workpiece. The milling machine can machine a workpiece on any four of the five axes at the same time, which reduces the production lead time significantly.
One of the key applications of 5-axis machining is mold-making. The ability to achieve intricate surface designs on the workpiece allows for the machine to manufacture molds used in industries including aviation/aerospace, automotive, military/defense, and medical.
:: Read More: What to Consider When Buying a Rotary Indexing Table
The 4th and 5th axis CNC rotary tables have their own pros and cons and are suitable for particular applications. The 4th axis rotaries are apt at precision indexing for simpler designs whereas the 5th axis tables excel at complex designs but the rigidity is compromised and chatter or deflection may take place accordingly. The shops should choose a model that meets their actual requirements.
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