The development of a technical costmodel for composites : Adapted to the automotive industry

Detta är en Master-uppsats från KTH/Lättkonstruktioner

Författare: Mathilda Karlsson; [2013]

Nyckelord: ;


Composites are light, durable and can be designed to have mechanical properties rivaling those of steel. In order to use composites in more cost-sensitive fields their manufacturing-cost must decrease. One way of decreasing this cost is to manufacture larger volumes. Large manufacturing volumes means high investment costs but low cost per manufactured part. Cost-efficient thinking also brings about less environmental impact as the goal is to manufacture as many parts as possible, for the smallest amount of resources - a necessary part of a sustainable society.

The overarching goal of this master thesis is to investigate and evaluate the investment costs at different manufacturing volumes, as a function of component size and other influencing variables. The investigation is carried out through the development and utilization of a basic technical cost model. The investigation involves three manufacturing methods commonly used for structural composites: High-Pressure Resin Transfer Moulding (HP-RTM), Compression moulding of thermoplastics (CM-TP) and Advanced Sheet Moulding Compound (A-SMC). A fully automated material system is chosen and simulated for each method in order to manufacture large annual manufacturing volumes.

The developed technical cost volume is designed using a bottom-up perspective where the steps of each manufacturing method is analysed separately from each other. For each sub-step its corresponding lead-time and containing costs is deduced and passed on to the final sum of all sub-steps. The manufacturing cost consists of the investment cost, operator cost, the material cost as well as further fixed costs such as electricity and plant costs. Hydraulic presses are one of the highest cost-contributes to the total investment cost, for all three studied manufacturing methods. HP-RTM has the highest investment cost while CM-TP has the lowest, correlating with the fact that a higher pressure is necessary in the former. CM-TP has the highest material cost whilst HP-RTM has the lowest. The operator cost is also a large contribution to the total manufacturing cost.

Decreasing this will decrease the final cost per part. The cost per part decrease with increasing annual manufacturing volume. At lower manufacturing volumes the cost is closely related to the size of the investment cost as well as other fixed costs. At higher manufacturing volumes material cost dominates for all three studied processes. A process using a more expensive raw material therefore has a clear disadvantage at these higher annual production volumes. The cost per part decrease could be described as a finite sum. At a large enough annual production the lowest cost part is reached and further increase in volume will not affect the cost noticeably.

Dividing a large component into several smaller pieces for later merging is costsaving at lower manufacturing volumes. How cost-saving depends on the manufacturing method. Manufacturing methods with a high investment cost has a higher cost-save by dividing the component into several smaller parts.

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