What is application of ball screw in high speed CNC machine tool?

High speed machining is a high and new technology of the 21st century.It is with high efficiency,high precision and high surface quality as the basic characteristics,in the aerospace,automotive industry,mold manufacturing,photoelectric engineering and instrumentation industries gained more and more widely in application,and has made significant technical and economic benefit.It is an important part of contemporary excellent manufacturing technology.In order to achieve high speed machining,the first to have high speed CNC machine tools.High-speed CNC machine tools need both a high-speed spindle system and a high-speed feed system to realize the high-speed material cutting process.To achieve high speed feed,domestic and foreign manufacturers continue to take measures to improve the high speed performance of ball screws.The main measures are:

1.Appropriately increase the speed of the lead screw,lead and thread head number.At present,the common use of large lead ball screw nominal diameter and lead matching:40mm×20mm,50mm×25mm,50mm×30mm,the feed speed can reach more than 60m/min.In order to improve the stiffness and bearing capacity of the ball screw,the ball screw with large lead is generally used double head thread to improve the effective bearing number of balls.

2.Improve the structure to increase the fluidity of ball movement.The reverse ball circulation device is improved,the curve parameters of the ball groove are optimized,and the three-dimensional guide tube and ball returning device are used to introduce the ball into the nut body along the guide angle direction of the internal thread,so that the direction of ball movement is tangent to the raceway rather than intersecting.This minimizes impact loss and noise.

3.using"hollow strong cooling"technology.High temperature of high speed ball screw is generated by friction during operation,resulting in hot deformation of the lead screw,which directly affects the machining accuracy of high speed machine tool.The use of "hollow strong cooling" technology is to pass the constant temperature cutting fluid into the hole of the hollow lead screw to forcibly cool the ball screw and keep the temperature of the ball pair constant.This measure is an effective way to improve the high speed performance and working accuracy of medium and large ball screws.

4.For the high-speed feed system with large stroke,the drive mode of screw fixation and nut rotation can be adopted.At this time,the nut rotates,while one side moves axially along the fixed lead screw.Since the lead screw does not move,it can avoid the critical speed limit and avoid various problems when the slender ball screw runs at high speed.Nut inertia is small,flexible movement,high speed can be achieved.

5.Further improve the manufacturing quality of ball screw.By adopting the above measures,some of the problems that exist in the traditional ball screw can be largely overcome.Japan and Switzerland have been in the international leading position in the high-speed ball screw,its maximum fast moving speed can reach 60m/min and even 90m/min in individual cases,and its acceleration can reach 15m/S2.Because the ball screw has a long history,mature technology,wide application,low cost,so in the medium load,feed speed requirements are not very high,stroke range is not too large (less than 4~5m) in the general high-speed machining center and other economic high-speed CNC machine tools are most widely used.

Complete design and selection of ball screw,in addition to considering the transmission stroke(indirectly affecting other performance parameters),guide(combined with the design speed and motor speed selection),the use of state(affecting the force),In addition to the rated load(especially the dynamic load will affect the life),component stiffness(affecting the positioning accuracy and repeated positioning accuracy),installation form(force system composition and mechanical model),load pulsation(considering the safety together with the static load),shape characteristics(affecting technology and installation)and other factors,It is also necessary to check the repeated positioning accuracy,positioning accuracy,stability,limit speed,peak static load and limit rate of circulation system(Dn value)of the selected specifications.After correction and selection,the fully applicable specifications can be obtained,and then the characteristic parameters of the motor,bearing and other associated parts can be determined.

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