How Do Mill Turn Centers Work?

Posted on Jan 5, 2021

Mill Turn Centers

Mill turning centers are essentially a lathe with multiple kinds of milling going on. A lot of things are happening inside the machine simultaneously, but the individual motions are not as complex as you might think.

What Are Mill Turn Centers?

CNC mill turn centers, often shortened to mill turning centers or turn-mill, are machine tools that rotate a workpiece on a rotary axis based on a turning method to carry out a variety of machining operations, such as cutting, deforming, drilling, end face machining and turning. These machining operations are achieved using machining tools to produce objects that are symmetrical to the axis driven by a spindle, which is the rotating unit of the machine consisting of a central shaft, sleeve, bearing, and the surrounding components.
 

What Does Mill Turn Actually Mean?

The history behind this uniquely named milling machine is that turning could only be done using a dedicated turning machine in the past, while milling could only be done with a milling machine. The two machining processes were never really integrated at the time due to technical difficulties. 

However, with the emerging existence of power turrets and live tools, the functions of both turning and milling have gradually been integrated into a single machine, making the process a lot easier and more efficient. These machines that are now capable of multi-tasking are called the CNC mill turning centers, 5 axis mill turn, or turn-mill in short. The most common arrangement of a turn-mill is the vertical mill turn centers which are characterized by the typical clamping mechanism.
 

:: Read More: Why bother with a CNC mill turn?

Vertical Mill Turning Centers

Following the above, workpieces are clamped vertically in a vertical mill turning center, and the cutting tool is mounted in an identical direction for vertical machining. Due to gravity, clamping is stronger and more stable for a vertical turning center. This type of mill turning machine is typically manufactured for processes that require high precision, such as the automotive industry, sports equipment, aerospace industry, and other industries working with larger projects.

The clamping mechanism of a vertical mill turning center involves placing the spindle behind the chuck of the machine. The spindle can either be driven by a belt or other types of driving mechanisms. Just like other machine tools like machining centers and milling machines, vertical mill turn centers can also be equipped with power tools to improve the versatility and functionality, thereby offering users more machining possibilities.
 

Programming of Mill Turn Centers

Mill turning centers are essentially a lathe with multiple kinds of milling going on. A lot of things are happening inside the machine simultaneously, but the individual motions are not as complex as you might think.

Besides the fundamental cutting, you will want the operations to be synchronized, such as performing cutoff, moving a part from the left spindle to the right, and so on. You will also want the operation on the right and left of the spindle to be balanced so that both take about the same amount of time. There is in fact immense time-saving potential of a mill turning center in which cutting can take place at both spindles simultaneously. 

With that said, you will need to create programs to minimize the downtime of your mill turning centers, using CAM (computer-aided manufacturing) software. You need to have your software produce the necessary codes that work on the turn-mill. 

The offline programming process actually comprises two aspects: one for creating a program that guides the actions of the turning center, and the other converts the program into code that will work on a specific model of your turn-mill. The combination of the two is called post-processing and is very essential. You always want to make sure the codes are working as intended or you may have to tweak them. Below is a list of tips outlined for your reference pertaining to selecting the right software for your mill turning centers:

● One size does not fit all, meaning you cannot use one software across all models of mill turn centers.

● Programming is approached differently among different shops and vendors, including the part documentation, electronic files, drawings, etc. 

● When dealing with machine tools that require substantial investments, always obtain some fundamental knowledge yourself by doing research. Do not take the vendor or manufacturer's word for everything.

● Make sure that the manufacturer offers a software demonstration service, which should be undertaken at a moderate pace with an easy-to-understand language.

● Make sure that there is an independent and dedicated counterpart whom you can contact and consult whenever the software isn't working as it should.
 

Tooling of Mill Turn Centers

The unique thing about a mill turning center is that the turn-mill system has a spindle that is sometimes milling or holding a static tool for turning. Such setup can eventually be a burden on the tool holding hardware.

This is why experts have advised that your mill turning centers are bought from manufacturers that are willing to offer milling spindles with various types of tool connection systems. As a matter of fact, the demand for tool connection capability is much higher than that of a turning machine or a milling machine alone. 

With the above said, indexing is very critical because you are practically using the spindle to hold both the rotating and static tools. Fortunately, many manufactures nowadays have dedicated engineers who specialize in tooling for multi-function machining. They will be a good source for related information and advice. Some of these companies even offer accessories and tools that are designed for multi-function machines, such as turning spindles, fixed chucks, hydraulic cylinders, etc., all of which have been widely distributed across industries around the globe.

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