IENG 217 Cost Estimating for Engineers

IENG 217Cost Estimating for Engineers Operation Estimating

Tooling Estimated Operation Cost Direct Labor Prime Cost Direct Material Operation Cost Elements

Turning Operation

Operation Time tpr = total process time = machine time + handling time + tool change time = tm + th + tc(tm/T) where tm = machine time th = time to load/unload machine tc = time to change a tool (tm/t) = no. parts that can be produced before a tool change is required T = life of a tool

Operation Time cpr = production cost = batch cost + machine cost + tool cost

Machining Time • Function of rate of processing

Example • 3” diameter piece to be turned to 2.8” diameter, length of stock to be turned is 10”, f = 0.01”/rev., V = cut speed = 200 fpm, d = depth of cut = .2”. • Find machine processing time

Tool Life

Example • HSS cutter; at 250 sfpm tool lasts 30 min; at 100 sfpm tool lasts 60 min. Find tool life eq.

Operation Time tpr = total process time = machine time + handling time + tool change time = tm + th + tc(tm/T)

Operation Time tpr = total process time = machine time + handling time + tool change time = tm + th + tc(tm/T) Q: Do we want to minimize processing time or do we want to minimize part cost?

Example • Turning operation; L=10 inches, D = 3inches to 2.9 inches, feed = 0.1 inch/rev, load and unload = 2 min, cutter change = 3 min, tool life given by T = 1.7x105 V-1.7, Co = $35/hr, Cpt = $3 / cutter

Example

Operations Analysis • Factual time and cost estimating catalogues • Product design • Process knowledge • Operations sheet preparation • Time and cost finding

Time Elements • Setup time • Cycle time

Setup Time

Cycle Time Elements

Product Design

Process knowledge

Operations Sheet

Cost Estimates

IENG 217 Cost Estimating for Engineers