Choosing the right machining center

A machining center is an advanced machine tool that enables the machining of parts, usually metal, by material removal. In general we refer to milling or machining in a general way. This guide focuses on CNC (Computer Numerical Control) machining centers and milling machines.

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  • How to choose a machining center?

    COMAU 4 axis machining center

    The choice of your machining center will depend on several criteria: the shape and complexity of the part to be made, the material to be machined and of course the size of the machine.

    Depending on the complexity of the shape of the part to be machined, you can choose:

    • The number of axes: a machine tool has a minimum of 3 linear axes and a maximum of 7 axes. The vast majority of machines in the industry are equipped with 5 axes.
    • The spindle orientation: vertical or horizontal.

    Lastly, the size of the machine will depend on the space you have in your workshop or factory.

  • How many axes do you need for a machining center?

    Maschinenfabrik Berthold Hermle AG 5 axis machining center

    The number of axes you need for a machining center depends on the geometry of the part to be machined. Machine tools are most often equipped with 5 axes, but there are also 3-axis and 4-axis machines as well as ones with up to 7 axes. In this section, we will deal with 5-axis machines because they are the most common in the industry. We will go over:

    • 5-axis simultaneous machines
    • 3 + 2 axis machines

    In a 5-axis machine, the cutting tool moves in the three linear axes X, Y and Z and rotates in the two rotary axes A and B simultaneously. This is called 5-axis simultaneous machining. The advantage of 5-axis simultaneous machining is the ability to machine complex parts in a single operation. The part is machined on 5 sides while the cutting tool is moving on the 5 axes. This configuration is especially advantageous for the machining of complex parts, but it is costly.

    Another 5-axis configuration that is possible and less expensive is the 3 + 2. In this configuration, the machine performs a 3-axis milling operation. The two rotation axes are used to orient and lock the cutting tool in a fixed, inclined position. This configuration is suitable for parts that are not very complex to machine, for roughing operations or for producing molds.

  • Should you choose a vertical or horizontal machining center?

    Mazak horizontal machining center

    The spindle orientation of a machining center is either vertical or horizontal. Both systems have advantages and disadvantages.

    Horizontal machining centers

    • The spindle is oriented horizontally and allows for low angle cutting, especially on the side of the workpiece.
    • This type of machining is suitable for milling slots or shaping flat surfaces.
    • It is suitable for machining very large parts and complex geometries.
    • This configuration facilitates chip evacuation.
    • Tool change time is fast.
    • It offers a pallet change function.
    • This type of machining is more suitable for heavy parts requiring machining on several sides.

    Vertical machining centers

    • The spindle is oriented vertically so tools are cut from the top of the workpiece.
    • It allows the machining of large parts by working all sides of a part without the intervention of an operator.
    • This type of machining is suitable for the grinding of dies and the machining of tool parts.
  • What different materials can be machined?

    Different materials can be used in machining. The choice of material will determine the power required as well as the spindle rotation of your machine. There are a few points to consider for each material.

    Material Power
    Required
    Rotational Speed (RPM) Required Necessary Characteristics
    Aluminum High High High speed spindle drive motor
    Cast iron High torque Low speed High torque spindle motor

    Drive system

    Rigidity

    Vibration damping

    Graphite / Composites Low torque High High speed spindle drive motor

    Thermal stability

    Dust retention system

    Plastic Low torque High High speed spindle drive motor
    Titanium High torque Low speed High torque spindle motor

    Drive system

    Rigidity

    Vibration damping

    Steel High torque Low speed High torque spindle motor

    Drive system

    Rigidity

    Vibration damping

    Geometry of the tool path

    Glass / Ceramic / Stone High torque Very low
    (to avoid microcracks)
    Sintered diamond tool
    Wood Medium torque High Chip evacuation system
  • What are the other selection criteria?

     There are some other selection criteria when choosing a machining center:

    • The speed: as we’ve seen, the speed you will need depends on the material to be machined. Materials with low rigidity require high rotation speeds, especially for finishing. Harder materials require lower speeds.
    • Whether it has a pallet loader: this facilitates unattended operations and shortens part cycle times.
    • Automated loading/unloading: this allows unattended machining.
    • The number of spindles.
    • Digital control: allows you to program the movements that the machine tool must carry out to shape a particular part.
      • A digital system can control the machining tool, the pallets where the parts are fixed, the part change system and the storage system.
      • Digital control enables the automation of all operations.
  • How to choose the size of a machining center?

    Determining the strokes required for machining allows you to anticipate the manufacturing and dimensions of the parts. You will need to take into account the 3 linear axes X, Y and Z, expressed in millimeters.

  • What are the latest trends for machining centers?

    Haas Automation Machining Center

    Machine tools play an important role in industrial production. With the advent of Industry 4.0 and the factory of the future, which is smarter, more efficient and cleaner, we are being forced to rethink our manufacturing processes.

    New trends are emerging on the market. These include connected machining centers, green machining centers and hybrid machining centers.

    Connected machining centers

    With the rise of the Internet of Things and connected objects, machine tools are no exception. Machining centers are increasingly sophisticated and equipped with sensors (speed sensors, temperature sensors, etc.) that regularly transmit data. The data collected in this way can be used, for example, to predict possible machine breakdowns and carry out preventive maintenance.

    Another important characteristic of connected machines is the possibility to control them remotely from a tablet or a cell phone and be alerted 24/7 in case of a problem so you can launch an intervention immediately. As a result, connected machining centers offer higher productivity and reduced downtime.

    Green machining centers

    In order to make manufacturing processes more environmentally friendly, several manufacturers have developed new machining centers with lower energy consumption and environmental impact.

    The manufacturer BENZ, for example, has integrated energy recovery technology into its machines to operate its sensors. The speed of the tool, the vibrations and the heat generated by the machine are all elements that allow energy to be recovered and thus avoid the use of batteries, which are inevitably less environmentally friendly and often have to be replaced.

    Hybrid machining centers

    These machining centers combine turning and milling or milling and 3D printing in one machine. DMG MORI is a pioneer in this field with its Lasertec 65 3D which combines milling and additive manufacturing.

    Hybrid machine tools can be more efficient by reducing production cycles. They also offer the possibility of creating parts with designs that would be impossible otherwise. Lastly, because of their combined functions they allow you to save space by having one machine instead of two.

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