The various test performed on the alignment tests on milling machine are,
- Cutter spindle axial slip or float.
- Eccentricity of external diameter.
- True running of internal taper.
- Surface parallel with longitudinal movement.
- Traverse movement parallel with spindle axis.
- Centre T-slot Square with the arbor.
- Tests on column.
- Over arm parallel with spindle.
This are various performed of the alignment tests on milling machine.
Cutter spindle axial slip or float
When the axial slip of a spindle is tested, the feeler of the dial gauge rests on the face of the locating spindle shoulder and dial gauge holder is clamped to the table. Change in reading is taken by rotating the spindle shoulder. It is done at the two spots diametrically opposite to each other.
Eccentricity of external diameter
The feeler is placed on the cylindrical surface of the shoulder. The shoulder is rotated and any deviation in reading is noted by dial gauge. It is due to eccentricity of the spindle in the hole in which it fits.
True running of internal taper
The table is set in its main position and the mandrel is fixed in the spindle taper about 300mm long. A dial gauge is set on the machine table. The dial gauge feeler is adjusted to touch the lower surface of the mandrel.
The mandrel is turned and readings at two points are noted. The error measurements are
1) Axis of the spindle and the axis of taper may not be parallel.
2) Eccentricity of the taper hole indicates same error at both the places.
Due to this type of errors, cut will not be shared equally between teeth of cutters and therefore, vibrations and poor finish will result.
Surface parallel with longitudinal movement
In this test, the dial gauge is fixed to the spindle. The deviations from parallelism between the table surface and longitudinal motion are noted down. Due to this error, the surface of the table will fluctuate up and down, and cutter will not take equal cuts on the job.
Traverse movement parallel with spindle axis
The traverse movement parallel with spindle axis is done in horizontal plane as well as vertical plane. The dial gauge is fixed on the table. The deviation of table movement in the direction of crosswise and deviation on reading are noted by the dial gauge with feeler. On one side of mandrel is in horizontal plane and under the mandrel for error in vertical plane.
Centre T- Slot Square
Cut on the machine will not be parallel to the axis of job, if the central T – slot is not perpendicular to the arbor, the key way etc. To check this error, a dial gauge is fixed on the mandrel, the feeler being adjusted to touch the vertical face of the bracket.
The reading on the dial gauge is observed when the bracket is near at one end of table. It is done by swing over the dial gauge and moved the tension block so that the corresponding reading can be taken near the other end of the table.
Test on column
The tests on column are,
- Column ways of knee square with table inclination front to rear.
- Side inclination.
First, the table is arranged in its central position and fixes a square with an arm about 3mm long. A dial gauge is attached to the spindle mandrel so that feeler is rest on the arm of the surface. Now, the reading is taken on the dial gauge. The table is moved upwards about 300mm and the reading S noted on the dial gauge. So, the difference in reading is a direct indication of the error of perpendicularity of the table surface and knee support. Alignment tests on milling machine.
The test is conducted for two positions of the square. Dial gauge touches the square in front of the first position and it faces the side of the square at 90° to the first position in the second position.
Over arm parallel with spindle
It is done on horizontal plane as well as vertical plane. To check the parallelism of the over arm and the spindle, the dial gauge is fixed on the table and its feeler under the mandrel. The table is moved crosswise and change in reading is noted.
For error in the horizontal plane, above readings are repeated so that feeler is under over arm and the two sets of readings are compared.