MAnu İmalat yöntemleri, Lecture notes of Engineering Dynamics

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MANUFACTURING PROCESSES II

PROCESSES AND COST

ESTIMATIONS IN CASTING

EQUATIONS IN CASTING

Reminder: Let’s make calculations!

Problem 1: Riser Design

Problem 3: Sprue Calculations

Problem 4: Sprue Calculations A sprue is 30 cm long and has a diameter of 12. 7 cm at the top, where the metal is poured. The molten metal level in the pouring basin is taken as 7. 6 cm from the top of the sprue for design purposes. If a flow rate of 655 cm 3 /s is to be achieved, what should be the diameter of the bottom of the sprue? Assume that the flow is frictionless.

Total cost of part manufacturing

The total cost of manufacturing a component

consists of following elements:

1. Material cost

2. Labor cost

3. Direct other expenses

4. Overhead expenses

1. Material Cost (a) Cost of material required for casting is calculated as follows : (i) From the component drawing, calculate the volume of material required for casting. This volume multiplied by density of material gives the net weight of the casting. (ii) Add the weight of process scrap i.e. weight of runners, gates and risers and other material consumed as a part of process in getting the casting. (iii) Add the allowance for metal loss in oxidation in furnace, in cutting the gates and runners and over runs etc. (iv) Multiply the total weight by cost per unit weight of the material used. (v) Subtract the value of scrap return from the amount obtained in step (iv), to get the direct material cost. Note: The casting drawing is made by adding various allowances like- shrinkage, draft and machining allowance, etc., to the dimensions of finished component.

Total cost of part manufacturing

2. Labor Cost Labor is involved at various stages in a foundry shop. Broadly it is divided into two categories: (i) The cost of labor involved in making the cores, baking of cores and molds is based on the time taken for making various molds and cores. (ii) The cost of labor involved in firing the furnace, melting and pouring of the metal. Cleaning of castings, fettling, painting of castings etc., is generally calculated on the basis of per kg of cast weight.

Total cost of part manufacturing

3. Direct Other Expenses

Direct expenses include the expenditure incurred

on patterns, core boxes, cost of using machines

and other items which can be directly identified

with a particular product. The cost of patterns, core

boxes etc., is distributed on per item basis.

Total cost of part manufacturing