solved problems on shaping machines

SOLVED PROBLEMS ON SHAPING MACHINES

Problem 3.1

A shaper is operated at 125 cutting strokes per minute and is used to machine a workpiece of 300 mm in length and 125 mm in width. Use a feed of 0.6 mm per stroke and a depth of cut of 6 mm. Calculate the total machining time for machining the component. The forward stroke is completed in 230°. Calculate the percentage of the time when the tool is not contacting the workpiece and the ratio between the cutting time and return time. 

Given data:

S = 125 strokes/min

Workpiece length, l = 300

w = 125 mm

f = 0.6 mm/stroke

d = 6 mm

Forward stroke angle, θf = 230°

Solution:

Let us assume the approach and over run = 25 mm

Stroke length,

L = l +25 = 300 + 25 = 325 mm

The percentage of time when the tool is not contacting the workpiece,

Problem 3.2

Calculate the power required for shaping the steel with a depth of cut of 2.8 mm, cutting speed 65 m/min and the work length 50 mm. The feed rate is 0.5 mm/rev. Take the machining constant k as 79×10-6.

Given data:

d = 2.8 mm

V = 65 m/min = 65 × 1000 = 65000 mm/min

l = 50 mm

f = 0.5 mm/rev

k = 79 × 10-6

Solution:

Problem 3.3

Estimate the shortest machining time required to machine a plate of 200 mm × 90 mm in a shaper under the following conditions.

Cutting speed = 13.3 m/min

Feed = 0.57 mm/double stroke

Number of passes = one

Approach + over run (longitudinal) = 20 mm

(Lateral) = 4 mm

Ratio of cutting speed to rapid return = 0.83.

Given data:

Work length, l = 200 mm

Work width, w = 90 mm

Cutting speed, V = 13.3 m/min

Feed, f = 0.57 mm/double stroke

Number of pass, n = 1

Approach + over run, A = 20 mm

Lateral = 4 mm

Ratio, m = 0.83

Solution:

Problem 3.4

The cross-feed on a shaper consists of a lead screw having 0.2 threads per mm. A ratchet and pawl on the end of the lead screw is driven from the shaper crank such that the pawl indexes the ratchet by one tooth during each return stroke of the ram. Ratchet has 20 teeth.

(a) Find the cross feed in mm.

(b) If a plate 100 mm wide has to be machined in 10 minutes, find the cutting speed in m/s. The ratio of return to cutting speed is 2:1 and the length of the stroke is 150 mm.

Given data:

Lead screw threads = 0.2 Thread/mm

Ratchet teeth = 20

Plate wide, w = 100 mm

Machining time, T = 10 min

Ratio of return to cutting speed, 1/m = 2

Stroke length, L = 150 mm

Solution:

Problem 3.5

A 75 cm × 20 cm surface of cast iron block of 15 cm thick is to be machined on a shaper. The ram speed is 25 mpm, length of stroke is 500 mm, depth of cut is 4 mm, feed is 1.5 mm/stroke, stock to be removed is 6 mm, side cutting edge angle of the tool is 45°, ratio of time taken in return stroke to the time taken in cutting stroke is 0.5. Determine the metal removal rate and the total cutting time.

Given data:

Cast iron block of 75 cm × 20 cm × 15 cm

V = 25 mpm

L = 500 mm

d = 4 mm

f =1.5 mm /stroke

Stock to be removed = 6 mm

α = 45°

m = 0.5

Solution: