W2_ANG_Material Selection

Problem Statement

As part engineering department of an automobile radiator manufacturer, an engineer in conceptual design phase is required to select material that will be used for its commercial off-the-shelf product.

This material selection shall consider the total life cycle of the car.

Feasible Alternatives

The design engineer has alternatives of using either a brass-copper alloy casting or a plastic molding. Either material provides the same service. However, the brass-copper alloy casting weighs 25 pounds, compared with 20 pounds for plastic molding. Every pound of extra weight in the automobile has been assigned a penalty of $6 to account for increased fuel consumption during the life cycle of the car. The brass-copper alloy casting costs $3.35 per pound, whereas the plastic molding costs $7.40 per pound. Machining costs per casting are $6.00 for the brass-copper alloy.

Outcomes/ Calculations of Each Alternative



brass-copper alloy casting

plastic molding





Cost per pound




Extra weight penalty




Weight penalty




Material cost




Casting cost




Total life-cycle cost




Setting Minimum/ Selection Criteria

The design engineer has to select the material based on the minimum total life cycle alternative he has, in this case he has to select the lower total life-cycle cost between using brass-copper alloy casting and plastic molding.

In life-cycle cost concept, a summation of all costs related to a product, structure, system, or service during its life span is considered. In general, life cycle may be divided into two general time periods: the acquisition phase and the operation phase. The greatest potential for achieving life-cycle cost saving is available in the acquisition phase of the life-cycle, because maximizing that potential life-cycle cost saving is critically dependent on effective engineering design and economic analysis that implemented during this (early) acquisition phase/ period.

Analysis/ Comparison of the Alternatives against the Criteria

Based on the calculation of each alternative above, shown that brass-copper alloy casting has disadvantage on weight and cost of casting, but its cost per pound make brass-copper alloy casting has lower total life-cycle cost compared to plastic molding.

Selection of the Best/ Preferred Alternative Compared against the Criteria

In term of total life-cycle cost, in above mentioned case, brass-copper alloy casting material is the preferred alternative compared to plastic molding.

Performance Monitoring and Post Evaluation of Result/ Follow up Assessment

The critical thing to be considered is whether all parameter related to the total life-cycle already properly put in the calculation. The consideration of what parameters and what quantitative number should put in those parameters are critical for the proper total life-cycle cost calculation.

References :

  1. Newel, Michael W. (2005), Preparing for PMP Certification Exam Chapter 1 Pp. 34, Third Edition, AMACOM.
  2. Sullivan, William G., Wick, Elin M., Koelling, C. Patric. (2012), Engineering Economy. Chapter 2 Pp. 20 – 66, Fifteenth edition, Prentice hall.
  3. Mulcahy, Rita, PMP, et al., (June 2013). PMP Exam Prep. 8th ed. USA: RMC Publication, Inc.

1 Comment

Filed under Anggono M, Week 02

One response to “W2_ANG_Material Selection

  1. Hi Pak Anggon, Sorry to have to tell you this but I have to REJECT your W2 posting….. Why? For TWO reasons- First, because the requirement is your blog must reflect a REAL CASE STUDY from your PERSONAL or WORKING life and I cannot see where this problem has anything to do with either. (It looks to me like a problem taking directly from some engineering economics book, which is NOT acceptable)

    Secondly, the MINIMUM requirement is for you to provide 3 references (citations) and you only provided 1……

    What I am expecting for your blog is to pick a REAL LIFE example either from your personal life (i.e saving for your retirement or your kids education) or some problem from your day to day working life. SURELY you can find a life cycle cost example from either your home or work? i.e. If you want an example from your home, how comparing the life cycle cost of two alternate refrigerators? Or washing machines? Or if you want an example from work, why not compare the life cycle cost of purchasing a new photocopy machine in your office? Which means you first have to obtain the performance data from the manufacturer then make your comparison…….

    See where I am going with this?

    BR, Dr. PDG, Shanghai, China

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