We evaluate an American National Standards Institute (ANSI) standard 14-tooth sprocket (shown in Figure 1.1 (a) and Figure 1.1 (b)), which is mainly used in chain- driven products such as automotive and pumps, to transmit rotary motion between shafts, where using gears are a misfit.
The sustainability analysis of the sprocket requires us to establish the environ- mental baseline first. The SolidWorks workflow to establish the baseline is
◾ Evaluate (Ribbon Tab).
◾ Select Sustainability or Tools (menu).
◾ Sustainability Xpress.
The detailed steps are as follows:
Step 1: Select material, based on Class (Steel) and Name (Alloy Steel) criteria in the tool (Figure 1.2).
Step 2: Select the appropriate Manufacturing Process (CNC Milling) and Manufacturing Region (China, Asia) (Figure 1.3).
Step 3: To complete the baseline setting process, SolidWorks Sustainability tool requires the transportation and use region of the product to be specified.
North America was selected as the “Use Region,” considering it is one of the largest consumers of automobiles (Figure 1.4; as per CNBC’s recent global survey for World’s Largest Auto Markets - http://www.cnbc.com/
id/44481705/World_s_10_Largest_Auto_Markets?slide=10).
Step 4: Baseline can be set using this icon, located at the bottom of the tool.
The Sustainability tool makes calculations and reports the results as per metrics.
The values of the impact factors are based on every input considering all stages in the life cycle of the product being assessed.
The consolidated reports are generated in a pie chart format (Figure 1.5).
The total environmental impact caused due to the ANSI standard 14-teeth sprocket is 0.51 kg CO2, 5.72 MJ of energy, 2.92 × 10−3 kg SO2 (equivalent) of sulfate, and 3.92 × 10−4 kg PO4 (equivalent) of phosphate. SolidWorks also provides the flexibility to assess an impact metric at every stage of a life cycle, individually.
Figure 1.6(i) shows the carbon footprint. The emissions predominantly include carbon dioxide and greenhouse gases. Figure 1.6(ii) shows the energy consumed in procuring the iron (the material considered in this case is steel), manufacturing the sprocket, as well as disposing of it after its life. The energy consumed includes all nonrenewable energy resources and energy used in conversion such as hear, power, and so forth. Figure 1.6(iii) shows air acidification caused in the entire life cycle
(a) Sprocket CAD model
(b) Sprocket engineering drawing
14 Tooth Sprocket
Figure 1.1 Sprocket CAD Model and Engineering Drawing.
of a sprocket. Figure 1.6(iv) shows water eutrophication caused in the entire life cycle of a sprocket. The sum of an impact metric at every stage (as shown above) gives the total of each impact metric for the entire product life cycle.
A sustainability assessment and evaluation of the sprocket were made using the SolidWorks® sustainability tool by considering several design alternatives. Tables 1.2 through Table 1.4 show the result. In Table 1.2, we change the sprocket material from iron to aluminum while holding the other parameters constant. The impact metrics shown in the table indicate that using iron is a better sustainable design of the sprocket. Note that the water eutrophication for both materials is almost the same. Table 1.3 shows the effect of the manufacturing process. It shows that mill- ing is much more environment-friendly than sand casting. Finally, Table 1.4 shows manufacturing in India is better for the environment than manufacturing in other Figure 1.2 Step 1 of Establishing the Baseline.
Figure 1.3 Step 2 of Establishing the Baseline.
parts of Asia including China. This is due to the transportation distance. India is closer to the United States than is Asia.
The assessment of the six design alternatives is shown in graphical form in Figure 1.7, with designs (cases) shown along the X–axis and all four corresponding impact metrics shown along the Y–axis.
Figure 1.4 Step 3 of Establishing the Baseline.
Figure 1.5 The Consolidated Report.
In Figure 1.7, A & B represent the effects due to change in material, C & D represent the effects due to change in manufacturing processes, and E & F represent the effects due to change in manufacturing region. Sustainability using the LCA approach helps in evaluating the environmental effects of a product holistically, that is, material through use of the product. Each case plots four impact metrics with the appropriate units along the Y–axis.
The results indicate assessment case D shows the highest levels of environmental impact, including all effecting factors such as carbon footprint, energy consumption, air acidification, and water eutrophication. Thus, the set of materials and processes followed throughout the life cycle in D should be avoided. Let us consider the comparison of D and C as they have the most life cycle stages in common. This comparison focuses on the manufacturing processes selected in each case. It indicates that the selection of manufacturing processes is a crucial parameter to preclude
(i) Carbon footprint (ii) Energy consumption
(iii) Air acidification (iv) Water eutrophication
Figure 1.6 Impact metrics of a sprocket.
Table 1.2Material Effect CaseDesign CriteriaCarbon Footprint (kg CO2)Energy Consumption (MJ)Air Acidification × 10−3(kg SO2)Water Eutrophication × 10−4(kg PO4) AMaterial: Iron (Ductile Iron) Manufacturing Process: Sand Casting Manufacturing Region: Asia Use Region: North America
0.423.772.012.16 BMaterial: Aluminum (1060 Aluminum Alloy) Manufacturing Process: Sand Casting Manufacturing Region: Asia Use Region: North America
0.809.715.331.99
Table 1.3Manufacturing Process Effect CaseDesign Criteria
Carbon Footprint (kg CO2)Energy Consumption (MJ)Air Acidification × 10−3(kg SO2)Water Eutrophication × 10−4(kg PO4) CMaterial: Steel (Alloy Steel) Manufacturing Process: CNC Milling Manufacturing Region: Asia Use Region: North America
0.515.722.923.92 DMaterial: Steel (Alloy Steel) Manufacturing Process: Machined Sand Casting Manufacturing Region: Asia Use Region: North America
1.1212.219.41 7.20
Table 1.4Manufacturing Region Effect CaseDesign CriteriaCarbon Footprint (kg CO2)Energy Consumption (MJ)Air Acidification × 10−3(kg SO2)Water Eutrophication × 10−4(kg PO4) EMaterial: Steel (ANSI 4130 Steel) Manufacturing Process: CNC Milling Manufacturing Region: Asia Use Region: North America
0.485.502.93 3.97 FMaterial: Steel (ANSI 4130 Steel) Manufacturing Process: CNC Milling Manufacturing Region: India Use Region: North America
0.354.211.33 3.33
such high levels of impacts to the environment. Case C results show a significantly low contribution to environmental impact. With this information, it can now be concluded that machined sand casting may be avoided for better environmental benefits for a particular PLC. The results also indicate that the assessment case A shows the best overall performance and the most optimized approach to develop a product like Sprockets. Case B follows the same set of processes and procedures except for a change in material of the product. This change has resulted in significant use of energy, and higher air acidification and carbon footprint. Cases E and F exhibit almost the same results, and the change in results is due to the change in manufacturing region.