Elements of Machining Cost

The costs that go into machining a part can be broken into three categories:

• Material removal cost.
• Tool cost
• Non-productive cost

Total machining cost = Material removal cost + Tool cost + Non-productive cost.

Material Removal Cost

This is the cost incurred while the job is being actually cut (it excludes all non- productive movements of both machine and man).

Material removal cost = Metal cutting time per piece × (labour + overhead) rate

Metal cutting time = Length of cut/ (Feed/rev. × rpm ) for turning

Labour rate = Rs./hr.

= Rs./hr. for machine or for a cost center or as a percentage of direct labour

Non-Productive Cost

This is the cost incurred through non-productive time of labour and machine. Non-productive cost = Non-productive time × machine (labour + overhead) rate

Non-productive Time of Labour

• Movement of tool towards job and away
• Indexing of turret, etc.