Vertical Machining Center Guide

A vertical machining center is a machine tool much more suitable for complex metal processing than conventional lathes or milling machines. Because of the complex machining steps involved in metal processing, machines with vertically arranged tools are very popular among machinists and machine shop owners around the world. They are designed with a very rigid vertical columns that can cope with various machining duties at very fast cycle times. Let us first define what exactly the term ‘Vertical Machining Center ’means.

If you are looking for information on Vertical Lathes (also called Vertical Turning Centers) this article might be of interest for you!

1. What is a Vertical Machining Center?

VMCs are automated machine tools for metalworking applications where the main spindle is aligned vertically. Nowadays professional machine shops and manufacturing plants mostly use CNC controlled machine tools. 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. Vertical vs. Horizontal Machines

CNC machining centers can be divided into two main categories: vertical and horizontal. This distinction describes the orientation of the spindle (and 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 VMC 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 arranged horizontally over or across the worktable. HMCs are often used to mill grooves and slots or to shape flat surfaces.

3. Structure of a VMC

Traditional machining centers consist of at least three axes for machining, which is sufficient to cover most of the machining tasks described above. However, the changes in modern manufacturing have led to increased design and machining requirements: faster production cycles and shorter delivery times and increased accuracy for an even wider variety of products and parts. 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 Machining Center can be used for various industrial parts. 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. More advanced machines have an additional 4th or even 5th axis and pallet changers for more complex operations and specific cutting applications. A true 5-axis machine tool can perform continuous multi-side machining simultaneously with increased accuracy, speed and overall control. 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 part. 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. The spindle rotates the tool at high speed that is measured at revolutions per min, rpm.

The Worktable

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, depending on the size of the part. . A conventional 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 rotary table even adds two additional exes, basically turning a 3-axis VMC into a 5-axis powerhouse.

Automatic Tool Changer

chain type ATCAutomatic tool changers are a standard accessory of any modern vertical machine 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. Main Applications

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 Parts Examples (courtesy of Mecatron)

Big size 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 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 machine tool like that, the vast majority of cutting steps can be performed with one setup, reducing production time.

Let us take a closer look at some vertical machining centers from different manufacturers:

Okuma 5-Axis Vertical Machining Center Series

JV40 Vertical Machining Center Series

Z-MaT VMC Series

VMC 425 Series

5. The Future of Vertical Machining

Vertical Machining Center Aerospace Part
Fig.3  Aerospace Part Manufacture

We have made clear the primary features of a VMCs. They 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 table for further processing, thereby improving work efficiency. In the future, it can be expected that CNC machine tools will further improved to make the machining processes even more advanced.

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