Understanding CNC Programming PDF

April 10, 2021

The need for CNC Part Programming PDF

Before automatic machines, industries relied heavily on manually operated machines to manufacture machine parts. As a result, it was relatively difficult to create complex profiles with high precision. The production costs were enormously high and the capacity of production also remained low. Moreover, the manufacturers always faced the challenge to produce parts on time while avoiding rejection rates. When semi-automatic machines were introduced in the late 1950s, the production rate took place and it was possible to produce parts with accuracy.

Computer Numerical Control (CNC)

Then in the 1970s, Computer Numerical Control (CNC) machining technology brought a revolution in the manufacturing process. These machines used computerized programs containing a set of instructions and parameters for machine tools to follow. These instructions are called CNC part programming pdf.  Today, every CNC machining begins with part programming. It increases productivity, eliminates human errors, saves money and time by reducing material wastes. Besides, it is easy to use and safe.

cnc part programming pdf

What is CNC Part Programming PDF?

The functionality of CNC programming in its basic shape is to control machining tools for automatic and accurate motion. The motion involves performing spindle, rotation, or coolant. The part programming prepares a program sheet from a drawing sheet.

It requires the collection of every machining data and its translation so that the machining control system can instrument the instructions after understanding them. The series of instruction in part programming actually the nature work for the tools to do on a part.

These instructions are usually written in functional format blocks, and contain symbols, letters, or numbers. The CNC operator feeds the data in the numerical control system in the G-code language, which is the standardized form. The control system understands this language and controls the tools in the required manner.

What is machining data in CNC programming?

Usually, the data pertains to:

  • Classification of the machining process in the sequential form including startup point for the tool, the depth for cutting part and the required tool path, etc.
  • The conditions to cut, speed of the spindle, the feeding rate, and coolant, etc.
  • Selecting tools for cutting

What should a CNC machinist do before CNC part programming pdf?

The quality of a CNC program depends upon complete synchronization between the programmer’s expectations and the actual working of the machining tool. CNC equipment is costlier and if the machinist does not program it properly, the automation will be inefficient and unfriendly. If he follows the following steps, there is a minimum chance of errors.

  1. Understanding commands in program header:

The program header explicitly contains the settings depending upon the type of machine tool, variation in the product line, and standards. It is good for the programmer to have a general idea about varying commands.

  1. Determining the startup procedure:

The machinist should extract dimensional data from part drawings so that he knows exactly which machining operations he should perform. The programmer or machinist needs to extract data pertaining to surface quality requirements. These requirements include feed rate of materials, positioning of tools, and their components’ speed.

The generic instructions regarding milling and machining will not work here. Some drawings are complex and, therefore, require the programmer to align the program’s coordinate systems with the machine’s coordinate system. The programmer may create a list of machined surfaces and relevant cutting tools to avoid missing anything while writing part programming.

  1. Determining the tool offset:

It is very important to define the order of machining operations. The machinist can select the right tools to make acceptable workpieces by listing out:

  • Step number
  • A detailed description of the operation
  • Name of the selected cutting tool (while separately listing the tool’s components)
  • The station number of the cutting tool
  • The speed of the spindle
  • Material’s feeding rate
  • Any issues involved in the step

The programmer will get a written version of what the program will do. The programmer should use it as a checklist in the CNC part programming pdf to avoid forgetting anything.

4.    Finding and setting the zero point:

Reference positions are critical in CNC programming. When the machinist works on drawing in CAD, he should know that the intersection of the X, Y, and Z-axis is the origin point. It is the point where he should position the part for cutting.

5.    Setting the speed and rotation of the spindle:

The machinist should know about the cutting speeds and feeds in order to operate the CNC machine efficiently. Moreover, cutting speed is the tool’s speed to cut the part in feet per minute. The distance a tool travels during one spindly rotation is the feed rate. When the programmer correctly writes the part program, he can repeatedly cut the same parts with precision.

6.    Setting up motion of the tools:

According to the required profile, the machinist should know about the system of three linear and three rotational axes to determine the motion and position of machine tools and workpieces. A good part of programming depends upon geometric information of a cutting tool in terms of its radius, diameter, and length.

7.    Returning the cutting tool to the reference point:

The CNC machine has a fixed reference point where the programmer stores the values. When he takes the CNC machine to the reference point, those values activate automatically and the machine knows its current axis position.

8.    Stopping the spindle and coolant to close the program:

Most commonly, M30 closes the CNC part programming pdf to automatically reset it to the beginning of the program. As a result, the operator can conveniently operate the machine for the next cycle.

Types of CNC Part Programming

There are generally two types of CNC part programming:

  1. Manual part programming

In this type of programming, the CNC programmer prepares a program manuscript using a device called flexo writer. He uses this device to write programming instructions too before preparing a punching tape. Simple machining parts developed on point-to-point machine tools need such type of programming.

Since CNC programming is an art form, it is never fully automated. IT is the manual programming that enables the machinist to have complete control over a part program. Obviously, it is directly applied in CAD/ CAM programming. A good manual part program requires the programmer to know about the workings of different CNC machines and various manufacturing processes. He should also know about the sequence of manufacturing operations, the cutting parameters, and editing the program for any design change. The knowledge about programming codes used in part programming is a must.

  1. Computer-aided part programming

For complex parts, the programming writes a computer program in the programming software inside computer attached to CNC machine. Computer-aided part programming requires the machinist to define the geometry of the work part, repetition work, and operation sequence.


Example of CNC Part Programming PDF for Machining

A CNC lathe uses CNC programming CNC Lathe – cnc-parts to manufacture high-precision parts. It does not even require too much interference from the operator. A CNC lathe machine multiple tasks of complex nature and optimizes production with improved processing speed.


CNC part programming pdf is considered to handle complex designs with greater speed and accuracy. It also has an edge over manual machining when manufacturers require repeated production in less time. In addition, part programming provides flexibility in work and allows the milling of contoured shapes, such as those created in 3D designs. Part programming certainly maximizes operational performance with efficient programming for a range of equipment.

cnc part programming pdf