The Accuracy in CNC Machining

Talking about accuracy is talking about CNC machining

There is a wide variety of technical terminology, but there is a great deal of confusion about its meaning. Are you interested in knowing the meaning of this technical term used in CNC machining? The following post will give you a clear idea of ​​the term: accuracy.

What is accuracy in CNC machining?

Accuracy, vital in any engineering development, refers to the difference between the actual measurement and the measurement of your system. If the difference between the two is extremely small, the precision of that measurement is said to be high. It is also known as the degree of conformity.

Furthermore, this term defines the reliability of a tool. Basically, precision is a measure that defines the ability of a measurement system to return the same measurement over and over again. In addition to this, it is pretty crucial that a measurement system is accurate and precise.

Precision machining is a process that removes excess raw material from a workpiece, while it maintains critical tolerance finishes, to create a finished product. In short, it means molding large pieces of material into more precise parts, so they can comply with very exact specifications. This process involves cutting, milling, turning and is generally performed using computer numerical control (CNC) equipment.

Today, the machining industry produces a great deal of large and small objects that we use in daily life. From the production of automobiles to surgical devices and aircraft parts, accuracy  machining is present in all technologies, engineering and industries. So basically, if a product contains parts (components), it requires precision machining.

Precision machining requires the ability to follow extremely specific drawings made by computer-aided design (CAD) or computer-aided manufacturing (CAM) programs. This CNC (Computerized Numerical Control) machining technology creates 3D diagrams or outlines needed to produce a machine, object or tool. Drawings must be created in great detail to ensure quality and success.

CNC (Computerized Numerical Control) machine operators work with a variety of materials such as bronze, glass, graphite, plastics, steel, and other metals. Depending on the size of the project and the materials involved, several Quality Control tools will be used, such as the measuring arm and different IMEs (Measurement and Test Instruments), compiled in the corresponding Metrology Room. In addition, 3D Mapping (3D mapping software that allows you to create, analyze, view and share measurements with third parties) will sometimes be necessary.

Factors that take part in the machining precision

Physical factors

The influence of physical factors in the processing of parts is mainly manifested in two aspects:

On the processing side

Geometric accuracy requirements are very high. If there is an error in the geometric accuracy, it will directly cause the measurement obtained with the machining to be out of range.

Currently, most of the CNC machinery refers to combined equipment and the precision of the assembly between its mechanical components directly affects the degree of precision of the machining of the parts that are made, so there are certain hidden dangers in the process of machining

At the same time, the aging of machinery will also reduce the accuracy of machined parts. If the CNC machinery is used for a long time, it will cause erosion and aging of its different internal components, especially if the preventive maintenance is not adequate.

The influence of human factors

The machinery must be controlled by staff. The incorrect or irregular operation of the employees  will affect the final precision of the machined product.

Thermal deformation factors

When the machine is working, a large amount of heat is generated due to friction with each other, and the mechanical system will be deformed by heat, which will affect the accuracy.

Thermal deformation mainly involves the structure of the machine tool, the workpiece, the clamping device and the tool. First of all, the deformation of the machine tool includes the deformation of itself and the structure.

The long-term operation of the machine tool makes  the temperature of the structure of the machine tool to increase linearly, which affects the fit between the various parts of the machine tool, and then the machining accuracy of the workpiece.

In addition, the machining process by chip removal also generates a large amount of heat, whose control is essential to obtain the required final machining precision. Due to this, today all CNC machines have internal cooling systems during the machining process, which mitigate the effects of the heat generated.

Force deformation factors

Within machining there are many factors that cause the system to be deformed. For example, machine tools, fixtures, and work pieces can generate various forces such as gravity, clamping force, and cutting force during operation.

In addition to bearing their own working pressure, the parts must also bear the forces generated by them and the friction between the equipment.

Certain elements such as tools (equipment to fix the part to be machined in the machine), clamps and tools are subject to high working pressures, and the components will move during the machining process. In addition, certain pressures between the components will cause different degrees of machining deformation, including changes in shape and position.

These deformations will affect the operation of the system and will have a certain impact in the machine´s lifetime, which will shorten its years of life and affect the accuracy of the parts.

As in the previous factor, correct preventive maintenance will increase the useful life of the CNC machine.

CNC programming factors

Scheduling properly can prevent machining errors, especially those caused by dimensional tolerance conversion.

Therefore, at the first stage of CNC programming, it is necessary to properly choose the programming origin. In addition, the programmed path cannot be ignored and its correct choice will improve the efficiency and the machining of the part. Otherwise, it will directly affect the precision of the machining.

Internal factors

The internal factors that affect the precision of the pieces are manifested mainly in the irregular installation of machinery and in the precision errors of the machining systems. If the machine tool has many defects and deficiencies, the machine will produce parts with large errors in the production process.

Machinery at Asimer Group

Trevisan horizontal machining centers

CNC vertical lathes

CNC Horizontal Machining Centers

CNC horizontal lathes

The Technical Department at Asimer Group collects the specifications and requirements of each customer  and we evaluate the need or not of having external suppliers. Each phase of the project is negotiated and coordinated, and logistics is managed, guaranteeing maximum compliance with the desired technical requirements.