Question

1. List and explain the factors that contribute to poor surface finish in machining operations.

   Hint: By the student. Recall, for example, in turning or milling, as the feed per tooth increases or as the tool radius decreases, the roughness increases. Other factors that contribute to poor surface finish are built-up edge, tool chipping or fracture, and chatter. By the student. Recall, for example, in turning or milling, as the feed per tooth increases or as the tool radius decreases, the roughness increases. Other factors that contribute to poor surface finish are built-up edge, tool chipping or fracture, and chatter. Each of these factors can adversely affect any of the processes described in the chapter.

Answer 1

Following factors that contribute to poor surface finish in machining operations.

1) Cutting speed

2) Depth of cut

3) Feed

4) Material removal rate.

1) Cutting speed :

It is the rate at which cutting edge of tool passes over the surface of workpiece in unit time.

unit - m/min

If the cutting speed is too high, then because of high heat generation the tool may get blunt.

If the cutting speed is too low, then machining time is more results in low productivity.

2) Feed :

It is defined as distance travelled by the tool along or into the workpiece, for each pass of tool point in unit time.

e.g. lathe machine : in lathe machine the advancement of tool in work piece is feed.

3) Depth of cut :

It is the penetration of cutting edge of the tool into the material of work piece in each pass, measured perpendicular to the machined surface.

depth of cut = (D−d)/2

4) Material removal rate (MRR) :

MRR is the volume of material removed in unit time.

It indicates the time required to remove the specific amount of material from workpiece.

unit - mm3mm3 / min

MRR = f x t x VcVc

f = feed in mm/rev

t = depth of cut in mm

VcVc = cutting velocity

please good rate

thanks