Due to the rise of CNC machine tools, metal processing is now more accurate than ever. Machinists can use computers to program the tool path into microns, which almost eliminates the inaccuracy caused by human error. As long as the CNC machine tool is set correctly, it should be able to cut metal parts with high precision.
But there are many factors that affect the precision of metal processing. Machine quality, material selection and even room temperature can play a role, and some customers may have very different accuracy requirements for other customers.
This paper discusses the ins and outs of precision metalworking and explains the concepts of precision, precision and tolerance.
What is machining accuracy?
Although precision and precision seem to be synonymous, they have different meanings in machining. Therefore, it is important to understand the meanings of the different terms we are talking about.
In metalworking, accuracy refers to the degree to which the machine matches the measured values specified in the design.
If the machine can cut the precise position specified in the design, then it has high accuracy.
If it misses occasionally, but hits the right position on average, then we can say that it still has high accuracy.
But the important thing is that a good CNC machine tool can not only reach the general level. ...
What is machining repeatability or machining accuracy?
Machining accuracy refers to the similarity of measured values between multiple attempts or multiple copies of parts.
In other words, if a machine accurately hits the same point on 100 copies of a part, then it has high accuracy.
This is different from precision, because precision does not pay special attention to whether the "point" is the same as the point specified in the design! A machine can be very accurate, even if it always cuts 3 mm to the left of the expected mark.
Obviously, it is important to be accurate as well as accurate.
Accuracy means that you are reaching the coordinates specified in the design, and accuracy means that you hit them consistently in multiple units.
What is machining tolerance?
In machining, tolerance refers to the deviation from the cutting value. So it is related to accuracy, but this is the value specified by the customer, not the property of the machine itself.
If customers require a feature of a part to be very consistent between different units, they will set strict tolerances on the feature to allow the smallest deviation. In practice, this means that the machine must operate more slowly and carefully.
For example, if looser tolerances are specified on non-mechanical features, machining can be carried out faster.
Although tolerances are defined by customers, machines usually specify their standard tolerances and minimum possible tolerances.
What contributes to the accuracy of CNC machine tools?
The accuracy of CNC machine tools depends on several factors, some of which are decided by the manufacturer of CNC machine tools, while others can be controlled by machinery.
In order to achieve accurate metal processing, the following factors must be considered:
Machine quality: excellent machines with high-quality parts usually produce more accurate parts than low-quality machines.
Machine conditions: CNC machine tools contain many parts, so correct maintenance is very important to maintain its accuracy.
Tool condition: Passivated wear tools with flank wear and crescent wear will reduce the accuracy of CNC machine tools, so they must be kept in good condition. Blunt objects will also increase the cutting temperature, which is another factor that reduces the accuracy.
Airborne inspection: feedback tools such as airborne probes can tell mechanics whether the machine is cutting accurately during work. These tools can also be used to correct any deviation in real time, thus improving accuracy.
Temperature and humidity: the working environment will affect the machining accuracy. Although the machine can cut parts in warm conditions, it must maintain thermal consistency to avoid deviation.
Calibration: The machine tool should be calibrated regularly to maintain accuracy.
What is the best metal for precision metalworking?
Accurate metal machining is best achieved by using materials suitable for CNC machining.
Because even the hardest metals and alloys can be machined accurately, some materials that are difficult to machine will have a negative impact on machining accuracy.
Machinability of metal means that cutting tools can cut it easily. This highly machinable metal can be cut quickly at low power, thus obtaining high-quality finish without causing significant wear on cutting tools.
Some highly machinable metals include:
Aluminum 606 1
Aluminum 7075
Aluminum 2024
Stainless steel 303
Stainless steel 304
Brass C35300
Theoretically, a good CNC machine tool should still be able to cut difficult-to-machine metals, although it needs more time and power.
However, these difficult-to-machine metals will have an indirect negative impact on accuracy.
Non-machinable metals will significantly increase tool wear, while passivated tools will reduce the accuracy and precision of the machine.
In addition, most customers want to find a good balance between speed and accuracy. If accurate metal machining requires extremely low cutting speed because metal is difficult to machine, then this project may not be worth the trouble.
When do you need accurate metalworking?
For many reasons, accurate metal processing is very important, from ensuring customer satisfaction to ensuring the mechanical function of parts.
Items requiring high accuracy may include:
The metal prototype promoted by investors is obviously inaccurate and may leave a negative impression on senior professionals.
Mechanical parts that interact with other parts. Proper functions can be controlled by specifying proper tolerances, but good accuracy is still needed to ensure compatibility between components.
Parts are made of rare or expensive metals, and excessive waste will damage the economic feasibility of the project. Of course, it is always good to minimize waste. )
Provide jobs for potential long-term partners. When working with new customers, providing them with accurately processed parts from the beginning will increase the chances of establishing long-term cooperative relations. In some cases, customers will only accept orders if they can guarantee a certain degree of accuracy.