Skip to main content

Computer Numerical Control

A computer controller is used to drive an NC machine directly. (more on Numerical Control ),

The need of CNC program is be able to direct the position of the cutting tool. As the tool moves we will cut metal (or perform other processes). I we plan to indicate positions we will need to coordinate systems. The coordinates are almost exclusively cartesian and the origin is on the workpiece.

Cartesian Coordinate System

Primitive people used their 10 fingers and 10 toes to count numbers and from this
evolved our present decimal, or Arabic system where "base ten," or the power of 10, is used to
signify a numerical value. Computers and MCUs, in contrast, use the binary or base 2 system to
recognize numerical values. Knowledge of the binary system is not essential for the programmer or operator since both the computer and the MCU can recognize standard decimal system and
convert it to binary data.

Almost everything that can be produced on a conventional machine tool can be produced
on a computer numerical control machine tool, with its many advantages. The machine tool
movements used in producing a product are of two basic types: point-to-point (straight-line
movements) and continuous path (contouring movements).

The mathematician and philosopher Rene Descartes invented the Cartesian or rectangular
coordinate system. With this system, any point can be located in mathematical terms from any
other point along three perpendicular axes. CNC systems use rectangular coordinates because
the programmer can locate every point on a job precisely and independently from each other.

Eg :-


For a lathe, the infeed/radial axis is the x-axis, the carriage/length axis is the z-axis. There is no need for a y-axis because the tool moves in a plane through the rotational center of the work. Coordinates on the work piece shown below are relative to the work.


For a tool with a vertical spindle the x-axis is the cross feed, the y-axis is the in-feed, and the z-axis is parallel to the tool axis (perpendicular to the table). Coordinates on the work piece shown below relative to the work.


For a tool with a horizontal spindle the x-axis is across the table, the y-axis is down, and the z-axis is out. Coordinates on the work piece shown below relative to the work.


The advantages of CNC machines are

1. They are located very close to machine tool

2. CNC allows storage/retrieval/entry of NC programs without preprocessing of NC code

3. CNC program is only entered into memory once, so it is more reliable

4. The programs can be tested and altered at the machine

5. Increased flexibility and control options on the local computer

6. Easy to integrate into FMS systems



Popular posts from this blog

esprit software specifications

ESPRIT programming system is one of your DP Technology, a world leader in CAD / CAM software.For twenty years, DP Technology has an established position in the engineering industry, which is due to continuous development and use of the benefits of NC control systems.ESPRIT uses more than twenty years of experience in programming in the language of the ISO command and knowledge of machines working in the CNC system and its tools.DP Technology is investing 20% of its revenues in research and development.This ensures that the company always keep the leading position among the world's leading manufacturers of CAD / CAM.ESPRIT is an optimal system for operators and programmers looking for a friendly CAM system.It allows the programming of processing: milling (3, 4 and 5 axis)machine tools electroeroding WEDM wire.The program has a friendly Windows ® interface. The result is that the service and learning is easy and pleasant, often intuitive.The time needed to deal with the environ…

Multi cut threading macro program example using G76

Multi cut threading macro program example using G76

Custom Macro – Using variables for the Programming :

Ideal application for the use of Variable programming (i.e. Custom Macro Programming) on a CNC Lathe :

As such the usage is covering very vast application area. You name it and it can be coded using macros. But, by and large following are the core application areas :

1) Threading applications like variable lead threading, Multi start threading,

Square and Trapezoidal threading, circular form non-standard type

threading ;

2) Multi-start worm cutting ;

3) Face and radial grooving of non-standard type;

4) Design one’ s own cycle of any type.

Example : Carrying out 4 start threading of the size – M16 x 2.0 mm pitch. Write a custom Macro “A” Program for the same. Use Multi-cut threading cycle – G76. Use following data :

Data :

i) O. D. = 15.8 mm
ii) δ1 = 30.0 mm
iii) δ2 = 5.0 mm
iv) 1st cut depth = 0.3 mm
v) Lead = Pitch x no. of starts = 2 x 4…

desktop milling machine

There is an interesting product for hobbyists and cnc students "a desktop milling machine" listed in portable cnc

Freezone jobs