Magnetic chucks are one of the types of work holding systems in manufacturing and lathe machining. The work holding systems involve the applications of different mechanisms that hold an object in place securely. The object to be secured by the work holding systems is called the work piece. Magnetic chucks, though sharing the name of chuck, are nothing in common with the scroll chucks, modular chucks, 6 jaw chucks or the vacuum chucks; they are all work holding devices yet the mechanisms to secure the work piece by each one of them, the places of utilizing them, and the work piece itself to be hold by them are entirely different.
Unlike the most chucks that apply the clamping force to hold still a work piece, the magnetic chucks use the magnetic force instead. The magnetic force of the magnetic chucks comes from either a permanent magnet, an electromagnet, or an electro-permanent magnetic materials. The magnets in the magnetic chuck generate the magnetic field and the metal work pieces will be attracted toward the chuck to achieve the holding. The magnetic field can be turned on and off by a simple button.
When the magnetic chuck is on, the magnets inside the chuck induces the polarity to the ferrous work material which connects through the north and south poles of it. This way, when the work piece is placed across the poles of the magnet, the flux flows into the work piece. The work piece has the opposite polarity to that of the magnet and thus they attract each other. The flux can be amplified and controlled during the clamping operation in order to exert strong clamping force to the work pieces. The platform to place the work piece on the magnetic chuck is called a magnetic plate.
Consistent clamping magnetic force makes sure that the pressure to exert to the work piece is evenly spread to the whole thing. The magnetic chucks offer the full support to the work piece surface to that the cycle time is saved by focusing on the center area. The setup time and the time to take down the work pieces are also decreased because they are simply placed on the magnetic plate. In addition, the value of a magnetic chuck is not just securing the work pieces. It is also commonly used to secure multiple vices on it.
The magnetic chucks are excellent at holding flat work pieces for lathe grinding or drilling and they work especially better on the work pieces with smooth surfaces than those with rough surfaces because the magnetic flux is less effective through air gaps. Also, the magnetic chucks are not very good at clamping small work pieces however because the small pieces do not have enough surface area so that they are less likely to be held firmly.
The permanent magnetic chucks are made with magnetic materials with permanent magnetic fields. Therefore, they do not need electric current to induce the magnetic force. In other words, this type of magnetic chucks does not need power sources to run and it does not need the button or switch to turn on and off. It has great magnetic force and the life of it is permanent. A pole handle is needed to activate or deactivate a permanent magnetic chuck. This is the type that is best for light-duty machining.
The electromagnetic chucks need the electrical current to generate the magnetic field and induce the magnetic force; the current it takes is usually direct current (DC). The advantage of an electromagnetic chuck is the ease of use. It is magnetized and demagnetized by simply pushing a button. Moreover, there is control unit on this type of chuck so that the force can be controlled and adjusted as required. However, it needs power supply to ensure the reliability and sustainability.
The electro-permanent magnetic chuck is a hybrid of the other two types. It is more powerful and suitable for heavy-duty machining it requires less electricity to work. However, the price of an electro-permanent magnetic chuck is much higher than the permanent magnetic chucks and it is more sensitive to the air gaps between the work piece and the magnetic plate.
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