CNC Machining: Understanding the Process, Programming, and Tools That Power Modern Manufacturing
What is CNC Machining
Computer Numerical Code (CNC) Machining is a modern mainstay of the manufacturing process and uses programmable machines to custom-design parts for a variety of uses.
CNC programs and software can control most machining tasks including spindle speed, coolant temperature, and more to remove layers of material from a stock piece. This stock piece is typically known as a blank or workpiece. The process of removing layers from a workpiece can be tailored to a wide range of materials that include metals, plastics, wood, glass, and composites.
A CNC machine is a programmable machine that can perform CNC machining tasks autonomously and is used widely across industries that manufacture parts for different end purposes. The high-precision parts made by CNC machines are cost-effective and extremely accurate, thereby by providing a range of options and applications.
History of CNC Machining
While the machining techniques used in CNC machining stretch back to the middle decades of the 20th century, today’s techniques are far more advanced and specific and involve entering 3D files into a computer, which runs a program that controls the motion of the machining tools.
Present-day CNC machines follow a set of procedures based on a numerical control (NC) system pioneered in the metal industry in the late 1940s. The NC system relied on paper punch-tape applications (known as G-codes) to program instructions included in the manufacturing process. More advanced programs evolved over the next fifteen years and in the late 1960s led to the start of the mature CNC systems used today.
The advantages of CNC Machining include precision, automation, and speed. This leads to faster turnaround times, a fully automated quality controlled process, a reduced number of machines required to complete multiple tasks, and enhanced capabilities overall. Without the advent of NC machining and the systems it utilized, the foundation for CNC machining would not have been established. NC machining represents a direct correlation to the benefits manufacturers can provide through CNC machining in today’s marketplace.
Overview of the CNC Machining Process
CNC machining has touched almost all aspects of the manufacturing process. In today’s engineering marketplace, everything from large corporations to small machine shops can take advantage of the precision, speed, and automation CNC machining offers. The possibilities CNC machining provides are seemingly endless, and the sophistication with which the machines complete jobs grows greater with each passing year. To gain a clear understanding of the CNC machining process, it is important to review its key concepts. These concepts can be applied to virtually any kind of CNC machines, which plays a pivotal role in adapting and upgrading a machine’s capabilities.
Fundamentals of CNC: as mentioned, CNC delivers greater speed, automation, and accuracy. Additionally, most CNC machine tools increase flexibility. Since the machines run on different programs, operators can run different workpieces simultaneously while attending to other tasks. Once a program is verified and proves its ability to execute its project, it can be recalled and reapplied to future projects with ease. CNC machines are easy to set up and operate, which leads to faster turnaround times on projects that need to be completed quickly.
Motion control: CNC machines have two or more directions of motion, called axes. These axes can be positioned precisely and automatically on linear and rotary paths. CNC machines allow motions that are programmed through commands. The motion types are rapid, linear, and circular, and the amount of motion and rate at which the axes move is also computer-controlled.
The CNC programmer must know the programmable motion directions (axes) available for the CNC machine tool. The axes names will vary from one machine tool type to the next. They are always referred to with a letter address. Common axis names are X, Y, Z, U, V, and W for linear axes and A, C, and C for rotary axes.
Motion types: There are many motion types available to CNC machines, but most utilize three basic motions regardless of your application. These three motions have commonalities. They are modal, meaning they stay in effect until changes, and the “end point” of the motion is specified in motion commands.
The first motion type is rapid motion. This motion uses a command that determines the machine’s fastest possible rate. This minimizes non-productive time. Typically, rapid motion comes into play while positioning the tool in and around cutting positions, clearing obstructions, and any other non-cutting motion that occurs during the program.
Straight line motion allows the programmer to command a perfectly straight line movement and control the feed rate that is used during the movement. Straight line motion aids in drilling, turning straight diameters, face or taper, and milling straight surfaces.
Circular motion causes the machine to follow a circular path. This motion generates radii during machining. Clockwise and counterclockwise motions occur in circular motion, or interpolation, as it is sometimes called. The programmer defines the radius on which the circular motion travels. For example, if a programmer were milling the outside of a workpiece contour, he could use a circular command that tells the control the radius of the arc control on the location of the center point.
Programming Control Examples
Programming controls vary by machine and motion type, but there are essential controls which dictate generalized motions.
The programmer must also know what functions of the CNC machine are programmable (as well as the commands related to programmable functions).
These include:
- Spindle control
- Automatic tool changer
- Coolant control
- Automatic pallet changer
Programs are made up of commands and commands are made up of words. Each word has a letter address and a numerical value. The letter address tells the control the word type. CNC control manufacturers do vary with regard to how they determine word names (letter addresses) and their meanings.
These include:
- O – Program number (Used for program identification)
- N – Sequence number (Used for line identification)
- G – Preparatory function
- X – X axis designationY –
- Y axis designation
- Z – Z axis designation
- R – Radius designation
- F – Feedrate designation
- S – Spindle speed designation
- H – Tool length offset designation
- D – Tool radius offset designation
- T – Tool Designation
- M – Miscellaneous function
Compensation and Offset Tools
CNC Machine tools require some form of compensation. Compensation allows the user to mitigate unpredictable conditions related to tooling as a program is developed. The same concept is illustrated if you imagine an airplane pilot compensating for wind velocity and direction as a heading is set.
Various compensation types exist. These include:
- Tool length compensation
- Cutter radius compensation
- Tool nose radius compensation
Offsets in the CNC control are storage locations where numerical values are stored and given meaning by the CNC operator. Offset tools can be used for a number of reasons depending on the style of the machine tool and its type of compensation. Common applications for offsets include:
- Specifying each tool’s length
- Specifying the radius of the cutting tool
- Assigning program zero
- Allowing swing on turning centers
Conclusion
This article touches on some of the basic components of CNC machining and provides an overview of its processes and uses.
While it does not comprehensively cover every facet of CNC machining, it does discuss the key elements that power CNC machining in the 21st century.
Align Machine Works can Help with Your Next CNC Machining Project
If you’ve spent any time looking for the right CNC parts at the right price, you know how frustrating the experience can be. What’s worse, when you do finally find the right part, it’s either out of stock or takes a long time to ship.
At Align Machine Works, we’re committed to helping our customers get the right part fast. We have a global network of CNC machining supplies that can provide a variety of parts in as little as one (1) week.
If you’re looking for a CNC machining part or service for your next project, we make the process simple.
Here’s how it works:
- Upload your part: Simply upload your CAD file and our quote engine will calculate everything needed to make your part
- Choose your material: Choose from over 30 materials in both plastic and metal categories
- Choose your features: Need threaded taps or other features? Simply tell us how many of each and upload a drawing specifying where you’d like them
- Choose your finish: We offer several finishes and any Pantone paint color you may require
Follow these four simple steps and you’ll be on your way to completing your next CNC machining project quickly and successfully.
