As machining centres are far more expensive than ordinary machine tools, they are subject to more constraints, and the choice of machine tool is more important than ever. Correct selection is the key to using a machining centre well and making it effective. When buying a machining centre, it is particularly important to carefully examine these five key points.
1, the rigidity of the machining centre
As the machining centre stiffness will directly affect the productivity and machining accuracy of the machine, machining centre processing speed is much higher than ordinary machine tools, motor power is also higher than the same specifications of ordinary machine tools, so its structure is designed to be much higher than the stiffness of ordinary machine tools. When ordering, the machine can be tested according to the process requirements, the permissible torque, power, shaft force and feed force maximum, according to the values provided by the manufacturer. In order to obtain the high rigidity of the machine, often not limited to the size of the parts, but the relative size of the parts to choose 1 to 2 specifications of the machine.
2, machining accuracy of the machining centre
Machining accuracy will directly affect the quality of the product, many people question the accuracy of the machine tool, will directly affect the decision of the buyer. Be aware that machining accuracy and machine tool accuracy are two different concepts. It is wrong to take the positional accuracy on the manufacturer’s brochure or product certificate as the machining accuracy of the machine tool. The sample or certificate of conformity indicates that the position accuracy is the accuracy of the machine tool itself, while the machining accuracy is the sum of the errors generated by various factors of the entire process system, including the error allowed by the machine tool itself. In the selection, you can refer to the process capability kp assessment method as the basis for the selection of accuracy. Generally speaking, the calculation result should be greater than 1.33.
3, machining centre CNC system selection
CNC system is the core brain of the machining centre operation, CNC functions are divided into basic functions and selection functions. The basic functions are inevitably provided, and the selection of functions will only be provided by the manufacturer when the user has selected these functions. The functions of the CNC system must be selected according to the performance needs of the machine tool, when ordering both the functions needed to order the full range, can not be missed, while avoiding waste caused by low usage, but also need to pay attention to the correlation between the functions. In the available CNC system, the performance varies greatly. Should be selected according to the need, can not unilaterally pursue high indicators, so as not to cause waste. Multiple machine selection, as far as possible, the same manufacturer’s CNC system, so that the operation, programming, maintenance can be more convenient.
4, the number of axes and the number of linked axes
The number of coordinate axes and linked axes should meet the typical workpiece processing requirements, the number of coordinate axes is also one of the signs of the grade of the machine tool. In general, the same manufacturer, the same specifications, the same precision machine tools, increase a standard coordinate axis, the cost of about 35% increase. Although the increase in the number of axes can strengthen the function of the machine tool, the final or pay attention to the process requirements and the balance of funds.
5, automatic tool changer and tool magazine capacity
The choice of automatic tool changer mainly considers tool change time and reliability. Short tool change time can improve productivity, but the tool change time is short, the general tool change device structure is complex, high failure rate, high cost, excessive emphasis on tool change time will make the cost significantly higher and make the failure rate rise. According to statistics, about 50% of the machining centre failures are related to the automatic tool changer, therefore, under the premise of meeting the requirements of use, try to choose a highly reliable automatic tool changer to reduce the failure rate and the cost of the whole machine. The quality of work of the automatic tool changer and the capacity of the tool magazine will directly affect the performance and quality of the machining centre. The tool magazine capacity is based on the principle of satisfying the need for tools for a complex machined part.