The scope and structural characteristics of CNC machine tools
1.Scope of application of CNC machine tools
In general,CNC machine tools are particularly suitable for applications where the machining of parts is complex,the accuracy requirements are high,product updates are frequent,and production cycle requirements are short.
The complexity of the parts and the production batch,the application range of the three machine tools changes,when the parts are not too complicated,the production batch is small,the general machine tool should be used;when the production batch is large,special machine tools should be used;The degree of progress,the more suitable CNC machine tools.At present,with the popularization of CNC machine tools,the application range is extended from the BCD to the lower complexity of the EFG line.
The relationship between the processing volume and the production cost of general machine tools,special machine tools and CNC machine parts.In the case of multi-variety,medium and small batch production,the total cost of using CNC machine tools is more reasonable.
According to the advantages and disadvantages of CNC machining and a large number of application practices at home and abroad,parts can generally be divided into three categories according to the degree of application:
(1)The most suitable class
1.Parts with complex shapes and high processing precision,which can not be processed by general-purpose machine tools or can be processed but difficult to guarantee product quality.
2.Complex curves or surface contour parts described by mathematical models.
3.There are shells or box-type parts that are difficult to measure,difficult to control,and difficult to control in size without opening the inner cavity.
4.It is necessary to combine the parts of the multi-process such as milling,boring,hinge or thread in the sequential clamping.
(2)More suitable class
1.In the processing of general-purpose machine tools,it is highly susceptible to human factors(such as mood swings,physical strength,technical level,etc.),and the value of parts is high.Once the quality is out of control,it will cause major economic losses;
2.It is necessary to manufacture complex special tooling parts when machining on general purpose machine tools.
3.It is necessary to change the parts that can be finalized after designing multiple times.
4.Machining parts that require long-term adjustment on a general-purpose machine.
5.Parts that have low productivity or high physical labor when processed with a general-purpose machine.
(3)Not applicable class
1.Production of large batch parts.
2.Parts that are difficult to install or that are completely positioned to ensure machining accuracy.
3.The machining allowance is unstable,and there is no online detection system on the CNC machine that can automatically adjust the parts at the coordinate position of the part.
4.The processed parts must be coordinated with specific process equipment.
2,the structural characteristics of CNC machine tools
1.The main motion is commonly used for AC or DC motor drag,adopting frequency conversion speed regulation,which simplifies the mechanical structure of the main drive system,and has high speed,high power,rapid and reliable speed change,and stepless speed change.Fair choice of cutting amount.
2.Both the main shaft component and the support member adopt a new structure with good rigidity and vibration resistance.For example,the main shaft component of the message pressure bearing is used,and the support member of the steel plate welded structure is used.
3.The plastic sliding guide rail,rotating guide rail and static pressure guide rail with low friction factor are adopted to improve the sensitivity of the machine tool movement.
4.In the feed drive,on the one hand,the gears and components without gaps,such as ball screw pair,static worm and worm gear pair,preloaded double gear rack and so on.On the other hand,the gap-removing measures,such as eccentric sleeve type,taper gear type and helical gear spacer,are used.
5.The structure of multi-spindle and multi-tool holder is adopted to improve the cutting power per unit time.
6.Devices with automatic tool change and automatic exchange of workpieces to reduce downtime.