How To Install Ball Screw Nut

CNC ball screw is a screw drive component rolling with the balls between screw and nut, it is a kind of precision, loftier efficiency, high stiffness, long service life and energy saving avant-garde manual components, can transform the motor rotary move into the table linear motion, thus widely used in machinery manufacturing, particularly CNC machine tools and machining centers, provides a good status for the master machine high-speed transmission.

With the increasing of precision requirements of CNC machine tools and machining centers, the loftier precision of ball screws becomes the inevitable trend of evolution, and its installation accuracy on the principal engine has gradually become a prominent trouble in associates. In lodge to achieve the accuracy requirements of the motorcar coordinate position, reduce the spiral deflection, to preclude radial first load, reduce the spiral shaft heating and thermal deformation, to minimize the transmission torque of the servo motor and improve the reliability of auto tools in continuous work, the installation accuracy of ball screw on the machine toll must be improved.

The mutual installation methods of brawl screw assembly in machine tools are usually the post-obit: double button – free; double push button – support; double push – double push.

Large horizontal machining center is an electromechanical integration high-efficiency machining equipment with high performance, high rigidity and loftier precision. Information technology is an ideal processing equipment for processing various loftier precision transmission box parts and other large moulds. Its 3 coordinate directions are used brawl screws manual driven by servo motors, and the three coordinate directions, namely 10, Y and Z, with larger operating stroke. Because of the structural characteristics of the brawl screw pair, the installation of the brawl screws in iii directions on the main engine becomes specially critical.

Starting time, there are defects for the old installation method of ball screws:

ane, According to the traditional method, the installation of the ball screw pair has been followed by the mandrel and the positioning sleeve connect both ends bearing support and the middle screw nut bracket together to right, with a dial indicator to parallel the mandrel axis and automobile tool slide guide and make mandrel drive freely and lightly. This installation method is more than convenient for small CNC machine tools and machining centers with less stroke in the 3 coordinate directions.

Every bit the fit clearance betwixt the mandrel and positioning sleeve, the positioning sleeve and the bearing hole at both back up ends and the middle screw nut bracket hole, the coaxial error of the bearing hole and screw nut bracket hole is larger, resulting in the increase of spiral deflection and radial commencement load, causing a series of serious consequences such as the temperature rise of the spiral shaft, the increase of the thermal deformation and transmission torque, resulting in the overloading and overheating of the servo motor, the servo system alarm, affecting the normal operation of the motorcar tool.

In addition, the actual difference between the bearing holes at the both support ends and the middle nut bracket hole tin can non exist accurately measured, thus affecting farther precise adjustment. For the larger CNC auto tools and machining centers with larger stroke, due to the required mandrel mostly above 1500mm, processing is difficult, not easy to ensure the accuracy, therefore cannot use the correct method of mandrel fit with positioning sleeve for ball screw installation.

In the product of horizontal machining heart, due to the automobile larger stroke of three coordinates, the use of traditional installation method, due to he coaxial fault of both support ends bearing hole and center nut bracket hole, resulting in ball screw radial offset load increases, servo motor overload and overheat, servo system alert and so on, so that the car tool can not run continuously, while seriously affect the service life and manual accurateness of ball screw, shorten the maintenance catamenia of the main machine.

two, The apply of other assembly methods, such as mobile saddle, shorten the altitude between nut bracket and begetting seat, the nut bracket and begetting seat corrected respectively, due to the two parts corrected separately, and the fit clearance of mandrel and positioning sleeve, the bodily application effect is not ideal, the aforementioned problems exist.

2nd, the new associates technology and method:

Through the technical research of this product, after repeated trial exploration and production verification, a more reliable assembly procedure method has been summarized.

1, First, use the integral special mandrel to right the nut bracket pigsty, and so that positive and lateral parallelism with the reference track within 0.01/1000;

2, After fixed the screw nut bracket, utilize the professional measuring fixture to measure the positive and lateral distance of the nut bracket hole and reference rail. Then, same performance every bit step 1, and use the professional measuring fixture to measure the positive and lateral altitude of the bearing hole from the reference track. It is required that the nut bracket hole and the reference rail positive and lateral distance is consistent, tolerance is 0.01, and fix the bearing seat. This method uses integral special mandrel, not only shorten the length, and combine the mandrel and positioning sleeve, eliminate the fit clearance between mandrel and positioning sleeve, reliable to ensure parallelism of bearing pigsty, nut bracket pigsty and guide rails;

3, Past measuring the bodily altitude, and then that both ends of begetting hole and the screw nut bracket hole coaxiality has also been reliable, thus reducing the brawl spiral deflection and radial offset load, improve the installation accurateness of ball screw.

4, In addition, in the process of installing ball screw, the axial move of the brawl screw must exist strictly controlled, and this technical index volition straight touch on the transmission position accuracy of the ball spiral feed system. Co-ordinate to the actual verification issue shows that: get-go, to install the end back up bearing at the servo motor end, it played a major function in the transmission procedure of ball screw, the axial movement of the ball spiral is controlled in the range of 0.015~0.02; so, and install the other end of the bearing, the axial move command in less than 0.01. In this fashion, the stiffness and accurateness of the ball screw feed system tin can be effectively guaranteed.

5, The pre-stretching of the ball screw shaft is also very necessary. In order to better the stiffness and accuracy of the ball spiral feed arrangement, pre-stretching of the screw shaft is very effective, but considering the different department of screw shaft, and the temperature rise tin non be accurately set, so the pre-tension force calculated past relevant literature can merely be used equally a reference. In production, often pre-stretching the screw shaft with negative value so that the positioning accurateness bend of motorcar tool table is shut to horizontal.

Third, the conclusion:

In the product, the no-load torque of the ball screw in the 3 coordinate directions of a large machining center assembled by the above-mentioned new process method is significantly reduced, the no-load current is also significantly reduced, the servo motor and the servo system are working normally, no servo alarm of the three coordinate directions, the machine tool can run continuously for more 72h. The above result fully shows that the use of new technology, tin can finer guarantee the ball screw assembly installation accurateness, moreover, this method is not express past the machine tool stroke. The larger the stroke of the machine tool, the more information technology tin highlight its advantages. It provides an effective and reliable method for the brawl screws installation of big CNC machine tools and machining center.

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Source: https://www.kosindustry.com/new-technology-of-ball-screw-assembly-installed-on-cnc-machine-tools.html

Posted by: freemanarche1959.blogspot.com

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