Wednesday, November 3, 2010

GENERAL FLOW OF OPERATING CNC MACHINE

When machining the part using the CNC machine tool, first prepare the program, then operate the CNC machine by using the program.

1) First, prepare the program from a part drawing to operate the CNC machine tool.
How to prepare the program is described in the Chapter PROGRAMMING.

2) The program is to be read into the CNC system. Then, mount the workpieces and tools on the machine, and operate the tools according to the programming. Finally, execute the machining actually.



How to operate the CNC system is described in the Chapter OPERATION.


Before the actual programming, make the machining plan for how to machine the part.
Machining plan
1. Determination of workpieces machining range
2. Method of mounting workpieces on the machine tool
3. Machining sequence in every machining process
4. Machining tools and machining
Decide the machining method in every machining process.

Sunday, November 15, 2009

Tool coordinate system

If you want to create a CNC Program, you must know also about tool coordinate system.


dont forget to adjust the tools.

Coordinate system

There are easy ways to remember the coordinate system in programming Cnc.
1. Cartesian Coordinate Systems



2. Right hand rule


Kind of axis coordinate in CNC Machine

Before we go to create a cnc program, we must know that every machine have a axis coordinate.
If the machine only have 3 axis coordinate, then it should be look like this

and axis coordinate in lathe machine, generally look like this



and this



You must know the philosophy of the axis coordinate

Information needed in CNC programming

There are information needed in CNC programming, such as :

1. Preparatory Information: units, incremental or absolute positioning
2. Coordinates: X,Y,Z, RX,RY,RZ
3. Machining Parameters: Feed rate and spindle speed
4. Coolant Control: On/Off, Flood, Mist
5. Tool Control: Tool and tool parameters
6. Cycle Functions: Type of action required
7. Miscellaneous Control: Spindle on/off, direction of rotation, stops for part movement

This information is conveyed to the machine through a set of instructions arranged in a desired sequence – Program

Information needed by a CNC Machine

Friday, August 14, 2009

Programming CNC Machines With G-Codes

Ever since the industrial revolution started, the demand to create precise instruments and products is an important factor in large scale manufacturing. Belts, screws, Drills and all movable parts needed to create other products in the assembly line must all be exact and compatible, thus extra care must be taken in order to ensure that all moving parts match perfectly. Computer Numerical Controlled programming has become an extremely important part of this process.
Computer Numerical Controlled Machines are useless without any programming. CNCs rely on pure hard codes in order to execute commands that the Machine Operator wants to do, therefore not only is it needed to learn the mechanics of the whole Computer Numerical Controlled Machine but it is also at the utmost importance that the Machine operator knows how to communicate with the machine, and that is by using G-codes.
Preparatory code/ functions or much commonly called as G-codes are functions in the Computer Numerical Control programming language. The G-codes job is to manage the position of the tool as well as control the step by step commands during the actual work. Basically the G-codes are the most important part of the Computer Numerical Control Programming algorithm.
There are other codes involved in the programming of CNCs such as M-codes that manages the machine, T-codes for managing the tools, and F-codes for the tool feed and tool speed controls. All of these codes are created in a Computer Aided Manufacturing (CAM) software.
G codes as well as the others use the RS-274D as the recommended standard for the Computer Numerical Controlled Machines. This standard was developed by the Electronic Industry association during the 1960s. These standards provide a basis for the creation of Computer Numerical Controlled Programs.
First designs of these standards came from punched paper tapes as the medium standard for data interchange, but now ASCII character bit patterns are the standard for the representation.
G-Codes
Lets discuss the g-codes further, as what I have said earlier G- codes constitute only a part of the Computer Numerical Control Program, in the whole programming algorithm, they are denoted by the letter G, Basically it is a code telling the machine what kinds of actions to perform in a step by step basis, examples of these actions would be rapid move, controlled feed moves that would bore holes, a work piece cut routed to a specific dimension, change a pallet, and set a tool information such as offset.
After creating each part of the codes, the algorithm is compiled in the Computer Aided Manufacturing (CAM) software. The CAM software basically use translators called post processors to output the code optimized for a certain machine type. Often times, post-processors are often used to allow users to enable further customization.
G-codes can also be used to create outputs for Computer Aided Design systems used to design printed circuit boards (PCB). Any software must be customized for each type of machine tool that it will be used to program. Some G-codes are written by hand for volume production jobs.
Some Computer Numerical Controlled machines use conversational programming. Conversational programming is an easier way to program CNC machines because it is more user friendly because it uses a wizard like program that hides the G-codes into plain view. Some Popular examples of this kind of CNC machines are the Southwestern Industries Proto TRAK, Mazaks Mazatrol, and Mori Seikis CAPS conversational software.
Conclusion
With these kinds of further sophistication in programming Computer Numerical Controlled Machines, it is expected in the future that programming would be much easier for its machine operators.