Question

A workpiece in the form of a bar 100 mm in diameter is to be turned down to 70 mm diameter for 50 mm of its length. A roughing cut using maximum power and a depth of cut of 12 mm is to be followed by a finishing cut using a feed of 0.1 mm and a cutting speed of 1.5 m/s. It takes 20 s to load and unload the workpiece and 30 s to set the cutting conditions, set the tool at the beginning of the cut and engage the feed. The specific cutting energy for the material is 2.3 GJ/m3 and the lathe has a 3-kW motor and a 70 percent efficiency. Estimate:

Answer 1

Hello your question has some missing part below is the missing part

Estimate The matching time for the Finish cut

answer: 79.588 seconds

Step-by-step explanation:

Calculate the matching time for the Finish cut

Diameter of workpiece before cutting = 100 mm

hence

Diameter of workpiece before Finishing cut ( same as after rough cut )

D2 = D1 - 2 * d = 100 - (2 * 12) = 76mm

step 1 : determine spindle speed

V =
`(\pi D_(2)N_(s) )/(60)` -------- ( 1 ). where : D2 = 76 mm , Ns = ? , V = 1.5 ( input values into equation 1 )

therefore Ns = 376.94 rpm

Finally : Determine the matching time

T =
`(L + A)/(Ft * Ns)` ---- ( 2 ) . where : Ft = 0.1 mm , Ns = 376.94 rpm, L = 50 mm , A = 0 ( input values into equation 2 )

note : A = allowance length ( not given ) , ft = feed rate

T = 50 / ( 0.1 * 376.94 )

= 1.3265 minutes ≈ 79.588 seconds