Functions of CNC Milling Machine Parts and Components Explained
Frame lies above the ground or foundation of CNC milling machine. It works as a support and also damper for the machine vibration. The material of the frame may be Cast Iron or granite filled welded structure. Barely steel is not used generally as a milling machine frame because it has some spring properties and very less dampening ability. Though steel is very stiff, Cast Iron is a better choice. Another innovative idea is using epoxy resins with different sizes of stones in a welded steel container. Epoxy granite mixture is a good damper and when it is confined in a steel container the strength is also improved. At times aluminium is also used in the mixture. There are arrangements for putting foundation bolts on the frame so that it is rigidly connected to the ground.
CNC milling machine axes are connected to the frame for providing motion to each direction. As the machine is computer controlled it is done by the program. It can also be done manually. A common CNC is called 3 axis CNC. and can move in 3 directions. The components attached to a CNC axis include motor, different types of ways, table, limit switches and lead screw. Generally, the axes move in X, Y and Z directions but sometimes optional 4th Axis is necessary and it is kept in the list of accessory. 5 axes millings are also seen but not very common. The motor provides the motion to the table and the ways provide smooth sliding motion. Dovetail ways and linear ways are frequently used in the axes assembly. Leadscrew provides the linear motion while it is extracting the rotary motion of the motor.
The table is placed on the top of the saddle. It holds the jobs and also the job holding devices. A number of T slots are there for holding the workpiece and jigs and fixtures. In CNC milling operation the table is moved by the motor which gets signals from the program codes.
The spindle is the rotating tool holder. The tools are installed in the tapered part of the spindle. The spindle has different RPMs. From the main transmission speed, the spindle speed may vary. The spindle speed is set up according to the properties of the material needed to be machined. Mainly three different types of spindles are seen. These are cartridge spindles, self-contained spindles, and fabricated spindle.
The CNC controller in a CNC milling machine gives signals to the motor of the machine to move in CNC axes. It is the electronic control that works as the brain of the machine. This electrical and electronics equipment executes the code given as the input.
The role of coolant in CNC milling machine is vital. It improves tool life and ensures smooth machining of the work. The different coolant used in CNC milling includes Mist Coolant, Flood Coolant, Cool Air Gun or Air Blast coolant and Dust Collector. Actually, the dust collector is not a coolant but it creates the initial condition for the coolant to work. It collects the chips and clears the surface. Mist coolant is used where the machine is not in a closure and requires pressure. For the closed conditionof the machine flooding coolant is better.
Like any moving engine or machine CNC milling also needs lubrication. The guideways need lubrication to allow the smooth motion over the table. The leadscrew is needed to be lubricated as it is getting engaged with gears and motors and also handing heavy loads. In a CNC machine, oilers are generally automated. But it can be done manually too. Automated oilers are good as they ensure timely lubrication.
Drawbars are good if you need to change your tool frequently. If automatic tool changer is used then drawbars are required. Capture and release of the tool holders from the spindle can be done by the means of powered drawbars. Drawbars include Impact wrenches, Pull Stud and Tormach TTS Style. With powered drawbars, you don’t need an operator each time when you want to loosen the drawbar. It reduces the time required by half.
Enclosures create a cover for the machine. A milling machine is always cutting and throwing cheaps. It can be very messy. So an enclosure comes in very handy and the chips or the chips mixed with coolant keeps inside and the production floor remains clean.
As the name implies it gives another movement in a direction different from the direction of X, Y and Z. It is required in many cases. With this, the operator can hold extra parts on the table and can do some extra work on the workpiece.
According to the functionality, CNC millings can be small or large. And also according to the position of the spindle the CNC milling can be divided into two classes. Vertical and Horizontal milling machines. In vertical milling the tool axis is vertical and in horizontal milling, the tool axis is horizontal to the WP. In horizontal milling, you can do the up milling and down milling. We will discuss the different cutting processes of milling machines in a different article. Hope you have got a good idea about the CNC Milling Machine Parts.