MANUFACTURING

Description

Problem 1 :

A local company has received an order to machine 1500 parts. For quality assurance, one sample for  every 25 samples has to be tested for tensile strength. The starting work part costs 8.25 SR, each. Part  handling time for each cycle = 3.45 min, and machining time per part = 6.25 min. It takes 150 min to set  up the machine for the whole production. Equipment cost rate = 53.70 SR/hr, and labor cost rate = 37.50  SR/hr. The overhead cost is 41% of the labor and equipment cost rates. The cutting tool in the operation  costs = 152.00 SR, and it must be changed every 30 parts. Tool change time = 6.45 min. Availability of  the machine tool = 96.0%, in addition, the defect rate is 3%. Determine:

 a) required time (hours) to complete the batch;

 b) production rate of good parts;

 c) total cost of the batch;

d) cost of good-finished part.

Problem 2 :

A production machine was purchased six years ago for an installed price of 1735,000 SR. At that time it  was anticipated that the machine would last 8 years at a rate of 5500 hours per year. However, it is now in  need of major repairs that will cost 425,000 SR. After the repair, the machine will last five years, operating  4500 hours per year. The applicable overhead rate is 37%. Determine the equipment cost rate (SR/hr) for  this machine: a) before repair (original); b) after repair.

Problem 3 :

Aluminum is heated to 700ºC and poured into a mold. The length of the downsprue leading into the runner  of a mold = 125 mm. The cross-sectional area at its base = 112 mm2. Volume of the mold cavity = 750  cm3. Determine:

(a) velocity of the molten metal flowing through the base of the downsprue,  

(b) volume flow rate,   

(c) time required to fill the mold cavity.  

(d) What is the viscosity of the fluid at 700ºC (state your reference).   

Problem 4 :

Total solidification times of three casting geometries of the same volume are to be compared:  (1) a sphere with diameter = 9.15 mm; (2) a cylinder with a diameter = height; (3) a cube. The  same casting alloy is used for all three cases.  

(a) Determine the relative solidification times for each geometry.  

(b) Which geometric element would make the best riser? Why?  

(c) If the mold constant = 3.17 min/cm2 in Chvorinov’s rule, compute the total solidification  time for each casting