A lathe is a machining tool that consists of a high-speed rotating workpiece and a cutting tool that moves along the X and Z axes to remove the material.
This rotary motion of the workpiece is provided with the help of a lathe spindle.
So what happens when a lathe machine has multiple spindles? Can it provide additional functionality?
This article discusses multi-spindle lathes in detail and talks about the advantages they offer over their single-spindle counterparts.
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What is a Multi-Spindle Lathe?
A multi-spindle lathe, as the name suggests, has more than one spindle arrangement that can provide independent rotational motion to the workpiece. These spindles are generally arranged in a circular array, and each spindle has a designated index number, with different turning operations being performed at each spindle.
The ability to provide different spindle speeds on the same lathe machine, without the need for constantly modifying the program, makes these lathes ideal for large-scale production of complex parts, where quick cycle time is of key importance.
Generally, a multi-spindle configuration is found in CNC lathe machines like Swiss lathe, where multiple cutting tools are used for performing different operations like turning, boring, drilling, threading, etc.
These lathes have almost all the basic parts of a lathe with a multi-spindle configuration and tool holding system.
Unlike traditional lathes, these multi-spindle lathes generally have a higher axis system, such as 6-axis system.
Automatic multi-spindle lathes can be found with 6 to 8 spindle configurations. However, as the number of spindles increases, the complexity of the program also increases.
Working of a Multi Spindle Lathe
Multi-spindle lathe consists of a spindle drum that houses multiple spindles.
Each spindle has its dedicated tool post that holds multiple lathe cutting tools to perform different machining operations on the workpiece.
The working of a multi-spindle lathe consists of different steps, such as loading, machining, and unloading.
Loading consists of mounting the desired workpieces on the spindles of the lathes.
After mounting the workpieces, the lathe starts machining the workpiece as per the part program.
In a multi-spindle lathe, each spindle acts as a machining center where different machining operations can be performed.
The workpiece moves from one spindle position to another while undergoing different machining operations at each position.
For example, let us consider a six-spindle lathe with a facing tool at spindle 1, a turning and drilling tool at spindle 2, a boring bar at spindle 3, a grooving tool at spindle 4, a knurling tool at spindle 5, and a parting tool at spindle 6.
The workpiece first undergoes facing operation at spindle position 1, followed by a rotation of the spindle drum to position the workpiece at spindle 2.
At spindle 2, the workpiece undergoes simultaneous turning and drilling operation.
The workpiece is then shifted to spindle 3 where a boring tool enlarges the drilled hole to the desired diameter.
After completion of boring operation, the spindle drum moves the workpiece to spindle 4, where a grooving tool cuts the desired grooves on the surface of the workpiece.
Similarly, at spindle 5 the workpiece undergoes knurling operation, and at spindle 6, a parting tool parts the workpiece at the desired length.
Apart from this, a multi-spindle lathe can perform multiple operations at the same time.
This means that while one workpiece undergoes facing at spindle 1, another workpiece can undergo drilling and turning operation at spindle 2.
As a result, the workpiece undergoes multiple machining operations without the need to halt the operation for tool change.
This enhances the productivity of the system and results in high-quality output with quick cycle time.
However, the time spent in loading and unloading the workpieces on these lathes is almost equal to the time taken for machining the workpiece.
Therefore, a multi-spindle lathe is practical for applications that otherwise would take very long machining hours when machined on a traditional lathe.
Advantages of Multi-spindle Lathe
A multi-spindle lathe provides the functionality of multiple machining centers in a single machine and therefore offers various advantages over traditional single-spindle lathes.
The ability to perform multiple operations at each spindle enhances the productivity of the system. It enables a multi-spindle lathe to perform the function of multiple lathe machines in a single setup.
Apart from that, the ability to work simultaneously on multiple workpieces further enhances its productivity and facilitates a quick cycle time.
Generally, a 6-spindle lathe provides 3 times higher productivity than a single spindle lathe, whereas an 8-spindle lathe provides 5 times higher productivity.
Multi-spindle lathe provides the feasibility to rotate the single drum and position the workpiece to undergo different machining operations.
This eliminates the need for frequent loading and unloading of workpieces between different machining centers, which affects the accuracy of the machining process.
Therefore, the ability to perform different machining operations in a single setup ensures high accuracy in the final product.
A multi-spindle lathe provides multiple machining centers in a compact design.
It is equivalent to a series of single-spindle lathes and therefore requires less space when compared to its equivalent single-spindle lathes.
Furthermore, running a multi-spindle lathe is comparatively more energy efficient than running multiple single-spindle lathes for performing a similar operation.
Therefore, multi-spindle lathes are ideal for small workshops with limited shop floor availability.
Limitations of Multi-spindle Lathe
Despite their high productivity and quick cycle time, multi-spindle lathes have their drawbacks.
High Initial Cost
Multi-spindle lathes are automatic lathes with complex designs.
These lathes consist of a rotating spindle drum and multiple cross-slides that guide the cutting tool along X and Z axes at every spindle station.
Apart from that, these lathes can also consist of a rotating tool that moves along Y-axis and performs milling operations on the workpiece.
This complexity of the structure results in a high initial cost of the machine.
Generally, the cost of a multi-spindle lathe is much higher than the cost of standard lathes, but provides better productivity, making it suitable for large-scale industries.
As the complexity of the machine increases, the need for a complex program also increases.
CNC machines require a programming code that determines the movement of various elements of the machine in order to perform the desired machining operations.
However, with multi-spindle lathes, the complexity of the program increases as it has to ensure a smooth transition between different spindle positions and control the movement of multiple cutting tools.
Need for Expertise
Operating such a complex machine requires an expert CNC machinist who is well informed about its different parts and functions.
Apart from that, the quality and accuracy of a multi-spindle lathe operation are also dependent upon the skills of the CNC programmer who prepares the part program for the desired operation.
Multi-spindle lathes are ideal for applications where multiple operations are to be performed on a single workpiece.
These lathes enhance productivity and save time and space by providing quick cycle time and compact design.
Multi-spindle lathes can perform complex machining operations with high accuracy but require highly skilled individuals to attain the desired machining results.
Frequently Asked Questions (FAQ)
Is a Swiss lathe a multi-spindle lathe?
No, a swiss lathe is a single spindle automatic lathe that is generally used for machining small-size cylindrical workpieces. However, certain special swiss lathes can have multi-spindle arrangements to enhance their productivity.
Can we perform off-center drilling on a multi-spindle lathe?
Yes, a multi-spindle lathe is capable of performing off-center drilling operations on the workpiece.
Apart from lathes, what other machines are found in multi-spindle configuration?
Apart from lathes, multi-spindle configurations can be found in drills and milling machines.
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