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How do CNC machine work and why do we need them


Have you ever thought about what powers a 3D printer, one of the most exciting tools to recently come out? What are the processes that make it possible for such machines to work effectively? And finally, what’s the role of ball screws in all this?

Read on and find out!


How do CNC machines work?

The thing behind all the processes we described above is called CNC, which stands for Computer Numerical Control. It is a system that automates machine tools by means of a computer executing pre-programmed command sequences.

The aim of any CNC machine is to control motion in a precise and automatic way. All of them operate in a similar fashion and consist of two (X, Y) or more axes facilitating either linear or rotary motion as well as a tool that can move in direction Z (depth). What differentiates them from your typical machine is that motion is caused by programmed commands and not by turning handwheels like in conventional mechanical tools. This allows for very rapid and highly precise movement along the axes. The motion rate, amount of motion and its type as well as the movement of axes can be programmed.


How to ‘communicate’ with a CNC machine

Programmers can ‘talk’ to a CNC machine using sentences made of CNC language. Each of these sentences describes what the operator would like the machine to do at any specific moment. It’s a bit like if you were given an instruction to a LEGO set or an Ikea wardrobe. To succeed you need to accomplish every step in a given order. CNC machines work in the same way. You need to upload the instructions and the tool will take care of the rest.

Make sure that, before you write a program with instructions, you make correct calculations and visualize the movements the tool will take. Make sure and double check that there are no mistakes. Otherwise, the machine will not execute the movements you want it to.


CNC operation

The axis motion of a CNC machine utilizes a coordinate system. The two most popular ones are rectangular coordinate system and a polar coordinate system. The former is found in a vast majority of machines and in this article, we will refer to it in our arguments.

The rectangular coordinate system works a bit like a graph. That means, every position on a coordinate system represents a certain value. The distances between the values are usually equal to 0.0001 inch or 0.001 millimeter.

The ‘graph’ always has a zero point, which is used by the program as the reference point. The motion of the tool is determined by a programmer who establishes the distance it needs to move from the zero point. For example, a command: X 3 and Y 5 would mean that the tool is supposed to move three inches along the X axis and five inches along the Y axis from the zero point.

Absolute and incremental motion

The task of a person programming a CNC machine is to determine how far should they move the tool. There are two ways for them to outline it.

H4 Absolute motion

In the absolute motion, the starting point for calculating every movement is the zero point. It’s a better method for beginning CNC programmers – it’s relatively easy to determine the ending points of motions using absolute motion. It answers the question “what position should the tool be moved to”.

H4 Incremental motion

A more advanced method, the incremental motion answers the question “How far should the tool be moved”. Instead of the zero point, it takes the previous tool position as its reference point. That means all the commands are relative to each other and if one mistake is made, all succeeding commands need to be corrected. It makes the incremental motion a more advanced method.


Why do we need CNC machines

CNC machines changed the manufacturing. The are used in many types of industries, from small businesses to massive corporations.

CNC machines allow for manufacturing of components needed in various areas of business, from aerospace to robotics. They vastly improved the production process allowing for a more precise and automated motion control that’s conveniently pre-programmed. That allows for creating complex components and then repeating the process using the same formula.  


What’s the role of ball screws in CNC machines?

The task of ball screws is to convert circular motion into a linear one. They do so with a low amount of friction. Ball screws can achieve efficiency of up to 90% (compared to the efficiency of around 40% of an ACME screw). They can also be extremely precise.

Ball screws require a thorough care. They need to be properly lubricated at all times to ensure smooth operation. Make sure you are using a lubricant that’s completely clean (bits of dust can damage the machine) and recommended by machine manufacturer.

We have already settled that the main task of a CNC machine is to control motion. Usually, CNC machines are made to perform really precise tasks like 3D printing or cut-outs. Ball screws, with their high precision and efficiency are perfect for such jobs. With their high efficiency they are the most suitable solution for industrial production, but also for more complex projects that could put a strain on less capable screws.


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