MACHINE TOOL TESTING
The accuracy of manufactured parts depends on the accuracy of machine tools. The quality of work piece depends on Rigidity and stiffness of machine tool and its components. Alignment of various components in relation to one another Quality and accuracy of driving mechanism and control devices.
It can be classified into
· Static tests
· Dynamic tests.
· Static tests
If the alignment of the components of the machine tool are checked under static conditions then the test are called static test.
If the alignment tests are carried out under dynamic loading condition. The accuracy of machine tools which cut metal by removing chips is tested by two types of test namely.
o Geometrical tests
o Practical tests
· Geometrical tests
In this test, dimensions of components, position of components and displacement of component relative to one another is checked.
In these test, test pieces are machined in the machines. The test pieces must be appropriate to the fundamental purpose for which the machine has been designed.
Purpose of Machine Tool Testing
The dimensions of any work piece, its surface finishes and geometry depends on the accuracy of machine tool for its manufacture. In mass production the various components produced should be of high accuracy to be assembled on a non-sensitive basis. The increasing demand for accurately machined components has led to improvement of geometric accuracy of machine tools. For this purpose various checks on different components of the machine tool are carried out.
Type of Geometrical Checks on Machine Tools.
Different types of geometrical tests conducted on machine tools are as follows:
3. Parallelism, equi-distance and coincidence.
4. Rectilinear movements or squareness of straight line and plane.
Main spindle is to be tested for
1) Out of round.
3) Radial-throw of an axis.
4) Run out
5) Periodical axial slip
Various tests conducted on any Machine Tools
· Test for level of installation of machine tool in horizontal and vertical planes.
· Test for flatness of machine bed and for straightness and parallelism of bed ways on bearing surface.
· Test for perpendicularity of guide ways to other guide ways.
· Test for true running of the main spindle and its axial movements.
· Test for parallelism of spindle axis to guide ways or bearing surfaces.
· Test for line of movement of various members like spindle and table cross slides etc.
Use of Laser for Alignment Testing
· The alignment tests can be carried out over greater distances and to a greater degree of accuracy using laser equipment.
· Laser equipment produces real straight line, whereas an alignment telescope provides an imaginary line that cannot be seen in space.
· This is important when it is necessary to check number of components to a predetermined straight line. Particularly if they are spaced relatively long distances apart, as in aircraft production and in shipbuilding.
· Laser equipment can also be used for checking flatness of machined surface by direct displacement. By using are optical square in conjunction with laser equipment squareness can be checked with reference to the laser base line.