Vertical Machining Centers

Vertical machining centers are much more suitable for complicated metal processing than conventional lathes or milling machines. Because of the complicated machining process involved in metal processing, vertical machining centers with vertically arranged machining tools are very popular on the market. They have very rigid vertical columns that can cope with various machining duties at very fast cycle times. Let us first define what exactly is meant by the term ‘Vertical Machining Center’.

1. What is a Vertical Machining Center?

Vertical Machining Centers are automated machine tools for metalworking applications where the main spindle is aligned vertically. Nowadays professional machine shops and manufacturing plants mostly use CNC Vertical Machining Centers (Computer Numerical Control). A VMC is a machine suitable for machining operations such as milling, drilling, boring, tapping, thread cutting, and more. Conventional vertical machining centers have 3 axes, more advanced machines for complex workpiece cutting can have four or even five. There are many different types of VMCs with different sizes, equipment, and applications.

2. Differences between Horizontal and Vertical Machining Centers

CNC machining centers can be divided into two main categories: vertical and horizontal. This distinction describes the orientation of the spindle (axis) in relation to the worktable, which is usually parallel to the ground (horizontal). The difference between a vertical and a horizontal machining center is illustrated in the image below.

Vertical Horizontal Machining Center
Fig.1 Vertical vs. Horizontal Machining Center
 

The axis of the main spindle of a vertical machining center is in a vertical orientation (up-down). The spindle holds the cutting tools and rotates them on this axis. Horizontal machining centers have their spindle and cutting tools set up horizontally over or across the worktable. HMCsare often used to mill grooves and slots or to shape flat surfaces.
 

3. Structure and Components of a VMC

Traditional milling centers and machining centers consist of at least three axes for machining, which is basically sufficient to cover most of the machining tasks described on the blueprint. However, the changes in the modern commercial market have led to changes in manufacturing and engineering. The modern commercial market now requires faster transportation and shorter delivery times, while requiring more varieties of products. As a result, the large-scale but less flexible production model has become less preferable.

Traditional milling centers and machining centers consist of at least three axes for machining, which is basically sufficient to cover most of the machining tasks described on the blueprint. However, the changes in the modern commercial market have led to changes in manufacturing and engineering. The modern commercial market now requires faster transportation and shorter delivery times, while requiring more varieties of products. As a result, the large-scale but less flexible production model has become less preferable.
 

How many Axes? 3, 4, 5?

A 3-Axis CNC Vertical Machining Center is the standard and can be used for various industrial components. The use of different cutters allows for a wide range of cutting operations. A 3-axis VMC works on three separate axes:
 

The X-Axis is the longitudinal axes for the left-right movement, the Y-Axis is the lateral axis for the front-back movement, while the Z-Axis is the vertical axis (for the VMC the axis along which the spindle moves) for up-down motion. Nore advanced vertical machining centers have an additional 4th or even 5th axis for more complex operations. CNC Vertical Machining Centers can include an additional axis to do specific cutting applications. A true 5-axis can perform continuous 5-axis machining simultaneously with increased accuracy and speed. It also significantly increases productivity as there is no need to unclamp, adjust and re-clamp the workpiece for different cutting operations.
 

Spindle - HSK, BT, CAT

vertical machinining center spindleThe Spindle on a VMC is perpendicular to the working surface and the worktable is the device that holds and rotates the cutting tools. The spindle cartridge moves up and down along the Z-Axis when approaching the component. The tool holder in the spindle usually only supports a certain standard. CAT & BT tooling also called V-flange is the most widely used one, especially in the USA. HSK is a german tooling standard that is also very popular, especially in Europe. IT is a more modern technology with a much shorter taper and different mechanism

Worktable - Standard, Rotary, Trunnion Type

rotary table vertical machineJust like any other machine tool the vertical machine has a worktable where the workpiece is mounted. Usually, you will have some fixtures like clamping vises. A standard worktable can move along the X-axis and Y-axis. A rotary table (see image) adds an additional axis as it can rotate. This tremendously increases the productivity of 3-axis machines. A Trunnion-type table even adds two additional exes, basically turning a 3-axis VMC into a 5-axis vertical machining powerhouse.

Automatic Tool Changer

chain type ATCAutomatic tool changers are a standard accessory of any modern vertical machining center and further add to its productivity. They can hold 20, 40, or even up to a hundred different tools for all kinds of cutting requirements.

4. Applications of Vertical Machining Centers

CNC vertical machining centers are typically used for flatwork that requires tool access from the top, for instance for mold and die cavities and large components for planes. VMCs are widely used in the manufacturing industry for the high-precision production of parts. The industries that make use of VMCs are quite literally endless: aerospace, automobile, molding, electronics, military, consumer products, etc.

Workpieces Vertical Machining Center
Fig.2 Vertical Machining Parts Examples (courtesy of Mecatron)
 

Big parts with complex curved surfaces such as cams or engine impellers and propellers require a lot of top-down machining and contouring. A multi-axis vertical machining center is ideal for these types of workpieces that are found in the aerospace and automotive industries. As it can ensure high precision and repeatability while not compromising on production efficiency. The same is true for dies and molds with a lot of cavities like engine blocks, gearboxes, and so on. With a vertical machining center, the vast majority of cutting steps can be performed with one setup, reducing production time.

5. The Future of Vertical Machining Centers

Vertical Machining Center Aerospace Part
Fig.3 Vertical Machining Center processing Aerospace Part
 

We have made clear the primary features of a vertical machining center. It can handle heavy-duty machining tasks where large-scale workpieces are involved. Through the work of the clamping system, large workpieces can be firmly secured on the worktable. With this advantage, many large-sized workpieces are transferred to the vertical machining center table for further processing, thereby improving work efficiency. In the future, it can be expected that CNC vertical machining centers will be further improved to make the machining processes even more advanced.

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