Advancement in technology has increased the capability of CNC tools more than before. This great nod has two sides of the same coin. While CNC tools can do more than before, it also means added pressure for users when choosing the right machine. Understanding the best machine suitable for your shop has become tricky, especially with the larger and more popular machines like the HMC and VMC. This blog post covers the differences between the two machines.
Machine Run
To understand how the two machines differ, it is first essential to understand how they run. A VMC removes metal from a workpiece and employs a vertical spindle using cutters. It typically works in a vertical work plane due to the vertical orientation. The columns of a VMC are designed to be non-moving. It is made as thick as possible to pursue rigidity during its manufacture. However, some VMC columns are designed to be moving.
HMCs, on the other hand, employ a horizontal spindle that works on a horizontal work plane and removes metal from the workpiece using cutting tools. From the names, the vertical machining center refers to the machining center where the main shaft is vertical, while in the HMC, the main shaft is horizontal. The HMC’s column moving structure requires it to be as large as possible to satisfy rigidity.
Work Table Form
HMCs workbench moves in X or Y direction. It is a rotary table and easy to choose and exchange the double table because of the lattice screw hole table. The horizontal columns are designed as a moving type, and the positive T-shaped HMC moves in the X direction while the inverted T-shaped HMC moves in the Z direction.
On the other hand, the workbench of a VMC is designed with a cross-slide structure.
Operation
HMC processes relatively larger workpieces than VMC. Clamping is also difficult with HMC, and monitoring the machining process is also not easy. Debugging is also difficult.
VMCs are relatively convenient and easy to operate, debug and monitor the entire machining process. They also require fewer tool holders and fixturing, and their operation tends to be like that of a regular machinist. They are generally tried and authentic all-purpose machines. They also have one work plane, and to reach all the sides of a five side squared block, it has to be flipped five times. The VMCs are used in great capacity and tend to be less expensive than the two machines. They also come in various types and sizes, from big to small.
Processing Objects
The HMC is suitable for processing box-like objects. It finishes the four parts of an object except for the top and the mounting surface. Pentahedron processing is possible after adding the angle head. It can be used to shape flat surfaces and is suitable for milling slots and grooves.
On the other hand, the VMC is limited by the tool changer and the height of the column. It is suitable for processing plate parts, sleeves, and discs and cannot be used on too high parts. To realize side machining of the workpiece, a CNC turntable or an angle head must be added since the volume of the workpiece is relatively small.
Machine Limitations
Even though they have great qualities, the VMCs also have limitations. There is a possibility for human error when using them, especially when flipping several times. However, this can be mitigated by equipping the 4th axis and fixtures. However, this may immensely decrease the working area, reduce efficiency, increase spindle downtime, and require technical skills.
The main drawback of HMCs is that they are relatively expensive. To make up for this, they promise a great return on investment. First, they limit the invention by the operator, therefore, reducing the chances of human error. It also has improved spindle utilization, productivity, chip flow, and a large tool magazine. Lastly, the HMCs come while already automated and work well with heavy workpieces.
Conclusion
Both the HMC and VMC have their own specific benefits and limitations. The choice of which machine to select depends entirely on the application. Even though they have certain things in common, they differ in other aspects. One main common thing about the two machining centers is that the milling function is the main function. However, they differ in structures, forms of machining the workpiece, and product positioning.
