Manufacturing Planning and Analysis
5.4 Costs of Manufacture
The costs of the whole manufacturing process can be split in two categories: material costs and worker related costs. The material costs cover the cost of the carbon itself and of the aluminium used on the inserts. As for the worker related costs, they count the total time spent on laminating the plies, the time spent debulking the laminates, the unmoulding time, the trimming time and the bonding time.
For the aluminium inserts these costs would be the machine usage and the time spent on cutting the aluminium plate. Since the aluminium inserts are a constant, their cost will not be accounted for on these next calculations.
Relying on the data from HyperMesh, the area of each ply was calculated to understand how many square meters of carbon are needed on the manufacture of the wing, these values can be seen in Table 5.1. Since not all the plies are made of the same material, in order to get the total cost of each component of the wing, the retailing prices for both SM [66] material and HM [67] material were found.
These costs are readily available by a simple internet search. With the cost of SM at 26e/m2and HM at 63e/m2, the cost of each component can be calculated and the results for the top skin laminate are presented in Table 5.1.
Despite giving a good approximation, this method to calculate the price of each ply is not 100%
accurate. Since all the plies are cut from a single roll, there is going to be some waste every time a ply is cut and this waste depends on the orientations of the ply. Figure 5.10 exemplifies this problem.
As can be seen from Figure 5.10, the ply with the orientation of 79.5ohas a bigger waste area than the ply with an orientation of 90o. Although they seem like they have no waste at all, since it is not
Table 5.1: Example of laminate material cost from ply area with top skin laminate. For the complete results please refer to Appendix B.
Ply Name Material Area [mm2] Number of
Cost per Ply [e] Ocurences
101100 SM 529140,88 0 0,00
101200 SM 345637,66 0 0,00
101300 SM 151215,92 1 3,93
101400 SM 16339,39 3 1,27
102100 HM 529140,88 0 0,00
102200 HM 277138,28 1 17,46
102300 HM 138938,18 1 8,75
102400 HM 29008,70 2 3,66
103100 HM 529140,88 1 33,34
103200 HM 305580,85 0 0,00
103300 HM 84100,19 6 31,79
103400 HM 33996,58 6 12,85
104100 HM 529140,88 0 0,00
104200 HM 317806,44 1 20,02
104300 HM 91005,22 2 11,47
104400 HM 34726,11 6 13,13
105100 HM 529140,88 0 0,00
105200 HM 317806,44 1 20,02
105300 HM 91005,22 2 11,47
105400 HM 34726,11 6 13,13
106100 SM 529140,88 1 13,76
106200 SM 331761,07 1 8,63
106300 SM 172284,32 1 4,48
106400 SM 50433,42 3 3,93
45 233,08
Number of Plies Total Cost
Figure 5.10: Influence of cutting directions on waste area.
possible with the roll presented on the image to cut a ply of 0onext to a ply of 90o, the area around the ply of 90o must be maximized by cutting, for example, more plies with an orientation of 90o. Despite having a smaller waste area, the smalls areas that are on each side of the ply with an orientation of 0o will probably be waste as well if a ply that is capable of fitting on that small space is not found.
When asking for a quotation for a part like this, all the plies outlines are supplied and then in-house, the manufacturer will assemble all the plies with their respective orientation on proper software. After assembling all the plies on a big sheet of “carbon”, it is possible to know how many linear meters of carbon are needed to manufacture a certain part. These linear meters already account with the wasted material.
With the price for the material of every single component, next the cost associated with the workers must be calculated. The values used for the manufacture work are described in Table 5.2.
Table 5.2: Table with assumptions made regarding work cost and manufacturing time.
Variable Value
Time Spent per Ply [minutes] 12 Time for Debulk [minutes] 40 Time for Trimming [minutes] 60 Time for Unmoulding [minutes] 10 Time for Assembly [minutes] 60 Debulk Interval [plies] 4 Worker Cost per Hour [e] 40
With the values from Table 5.1 and from Table 5.2, it is possible to estimate the total cost of the optimized model. The results are displayed in Table 5.3 and Table 5.4.
With everything taken into account, the final value for the cost of the optimized rear wing is 2463,35e.
Since there is no other value to compare it to, the same process was done to find the cost of the standard layup. The results of the cost evaluation of the standard layup are found in Table 5.6 and Table 5.7.
To have a better idea of the difference between the material and work related costs, Table 5.7 presents values for both the standard and optimized layup as well as the difference between them in percentage.
The increased number of plies reflects itself not only on the material cost but also on the total time cost. The material cost is simple to understand: there is no HM fibres used on the standard layup while this type of fabric is the foundation of the whole optimization process and with the HM fibers used on this part costing almost 2,5 times more than SM fibres, an increase in price is obviously expected.
The main difference appears in the time cost mainly to the time spent on debulks. Both of the models need to be trimmed and bonded but the time spent laying up the plies is increased on the optimized model and, while there are no debulks on the standard layup, the optimized model needs more than 5 debulks per component. These calculations do not reflect the reality perfectly since more than one mould can be laminated at the same time and the same thought process goes for the debulks.
Despite all its flaws, this calculation method is enough to demonstrate that the optimized model is simply too expensive to be manufactured to the light of the philosophty behind a LMP3 prototype. If the LMP3 category was not cost bound like Formula 1 and the hybrid LMP1’s, probably this solution would be feasible but since this is not the case, another solution must be found.