• Spindle Speeds (Number) Range: 0–2,200  RPM

• Motor & Electrics: 750  W

• Machine Dimensions W/O: 600 mm 9 900 mm X 2100 mm

• Floor Space Required - Max.: 600 mm 9 900 mm Alignment and Calibration Tests

Following tests are carried out on the proposed CNC Lathe

machine.

• Spindle speed test

• Tailstock to spindle  alignment

• Machine tool backlash adjustment and compensation parameters

• Rigidity test

The results obtained are given  below.

For tailstock and spindle alignment, a workpiece is placed on the chuck and its matching with the quill of the tailstock is visually examined. A perfect alignment is observed between the two  ends.

A digital tachometer is used to check the available spindle speed (rpm) with the input speed. Figure 17 shows, almost exact speed is achieved with the respective inputs. The final results of the calibration are given   below.

• (Actual/programmed) Average% backlash error = 0.98

• (Actual/programmed) conversion factor in x-axis = 0.94

• (Actual/programmed) conversion factor in y-axis = 0.96

• (Actual/programmed) conversion factor in x-axis = 0.93

• (Actual/programmed) conversion factor in feed rate =

0.99

• (Actual/programmed) conversion factor in spindle speed = 0.95

With these corrections, the CNC lathe becomes ready for operation.

Experiments on the CNC Lathe Work Material-Perspex.

Tool Material- High speed  steel.

The cylindrical specimens were prepared, from the Perspex rod (length 120 mm, diameter 15 mm) to get mounted on the fixtures of the  lathe.

Operations carried out.

• Basic CNC lathe operations (plain turning, step turning, taper turning, arc turning,  threading)

• Manufacturing of a bolt (16 TPI  threads)

Fig. 17  Actual speed versus preset spindle speed for   servomotor

194 J. Inst. Eng. India Ser. C (April–June 2013)   94(2):187–195

Prior to the operations, some tests were carried out to find out the optimum parameters for the machining of the Perspex. The optimum values found  are:

• Spindle Speed = 600 RPM

• Depth of Cut = 0.6 mm per pass

• Longitudinal feed of workpiece to the tool = 12 mm/ min

Machining with these parameters gave a very fine sur- face finish during the machining of Perspex rod. So the above machining operations were carried  out.

One of the CNC program used for the operation is given below (unit: mm with multiplication factor of   10).

Program (Plain Turning).

Work Material: Perspex, H.S.S  Tool.

Work Dimension: Cylindrical Perspex Rod (length  =

150 mm, Diameter = 15 mm).

•    N1 S500 M4

•    N2 G00 X00 Y00 Z00

•    N3 G00 X00 Y400 Z00

•    N4 G01 X-6 Y400 Z00 F80