The machines are numerically controlled cutting machines. If we compare the structure of a conventional cutting machine and numerical control, observe the following differences:
• The measurement system for controlling the distance it must travel carriage along an axis consisting of a numerical scale.
• On CNC machines the scale has been replaced by alinear measuring system is coupled to the guidelines and indicates the distance traveled in analog form (voltage variation) based on the principle of beam.
• The transmission system consisted of conventional machine screw drive nut. The game that existed between these elements did not allow more precise positioning than specified (0.01 mm).
• The transmission system used in the numericalcontrol machines consists of transmission type of ball screw-nut.
• Motors in traditional machines were cutting phase AC motors. The motors used in numerical control machine tools are direct current motors.
• The numerical control machine tools have a control panel. This panel acts as interface between user and machine and through it enters the NC program.
From the above statements we canconclude that the NC is a language of manufacturing. The structure of language and its semantics are defined according to traditional generation of machined surfaces using conventional machines. The semantics and structure are established in international standards
The steps for NC programming are similar to those established in manufacturing.
1. Understanding the definition drawing of thepiece, which must contain:
The tolerances on dimensions and shape allowed.
The surface finish of the workpiece
The material of the workpiece
2. Once known:
The set of surfaces to be machined in the process
The cutting tools.
The dimensions of the blank.
The dimensions and tolerances of the finished part, the NC program can bewritten.
3. Once generated NC program is necessary to introduce to the memory of the 'machine. In this process uses the control panel.
4. When the program was introduced over the manufacture of the part can start. Tools should be placed in their positions. The reference system used in the programming defined. Compensators tool introduced in the corresponding memory of the machine and therefrigerant contained in the reservoir corresponding
COORDINATE SYSTEMS IN CONTROL NUMERIC
When the position at which the tool has to move is programmed, the system moves the Computer Numerical Control tool that position using the coordinates in the words dimensional block. For the particular machine under consideration, defines three different types of coordinate systems:
• The coordinatesystem of the machine. The origin of this system is known as machine zero. This point is defined by the manufacturer of the machine. The machine coordinate system is established when it is turned on and the tool is brought to the reference point.
• The coordinate system of work. The coordinate system used in the machining of the workpiece coordinate system is known as work. The origin of this systemis defined in a useful point for programming the geometry of the workpiece.
• The reference coordinate system. The position of this point generally coincides with placing markings on measurement rules, because these marks are generally found at the ends of the rules, the machine zero point of origin is defined at the ends of the stroke of the machine .
There are many possibilitiesto transfer their designs to the manufacturing end of the piece
Milling machines frequently used
This mill is widely appreciated by optical, radio enthusiasts and model makers to manufacture their parts, including steel. With a very robust machine frame, made of cast iron, fixed column for the movement of Z-cast aluminum table and transverse displacements of X and Y...