MATLAB/ dishwasher.- plastic injection molded
Manufacturing Cost Estimate and Method Selection
Authors
Gerald Angle II
Engineering 102
Submitted To
ENGR 102 Students
Fundamentals of Engineering Statler College of Engineering and Mineral Resources West Virginia University Morgantown, WV
Spring 2017
Todd Hamrick 2013
Abstract
The first project in ENGR 102 this semester is to analyze a series of fabrication methods, in order to recommend one method for implementation. The analysis team will
have the choice of three parts to analyze: an automotive bumper, the platform of a baby jumper, or a silverware tray for a dishwasher. Each of the potential parts has
two fabrication methods with two possible materials that need to be evaluated for fabrication cost.
There are several individual components to the project, namely conducting background research into their fabrication and material combination as well as creating the
Matlab code needed to find the total cost of fabrication. These individual components are then combined in the group final report and presentation to determine which
of the four studied parts is the best option for the company. The analysis team has the ability to set is own criteria for optimal method.
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Contents Abstract
……………………………………………………………………………………………………………………………………… ii 1
Introduction ………………………………………………………………………………………………………………………… 1 2 Background
Research ……………………………………………………………………………………………………………. 2 3 Methodology
……………………………………………………………………………………………………………………….. 3 3.1 Replacement Automotive
Bumper ………………………………………………………………………………….. 3 3.2 Replacement Baby Jumper Platform
……………………………………………………………………………….. 5 3.3 Replacement Dishwasher Silverware Tray
………………………………………………………………………… 7 4 Results
………………………………………………………………………………………………………………………………… 9 5 Discussion
………………………………………………………………………………………………………………………….. 10 6 Conclusion
…………………………………………………………………………………………………………………………. 11 7 Recommendations/Future
Work ………………………………………………………………………………………….. 12 8 References
………………………………………………………………………………………………………………………… 13 Appendix 1
……………………………………………………………………………………………………………………………….. 14
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1 Introduction The assigned first project of the semester is to analyze different ways to build the same replacement part and to recommend which method should be used.
There are several possible parts to be considered by each group and one part analyzed, as listed below:
1. Replacement Automotive Bumper o Additive Manufacture Steel Aluminum o Conventional Manufacture Aluminum Composite (fiberglass/carbon fiber) 2. Baby Jumper
‘Tray’ o Additive Manufacture Plastic Metal o Conventional Manufacture Plastic (vacuum formed) Wood (machined) 3. Dishwasher Silverware Tray o Additive
Manufacture Plastic Metal o Conventional Manufacture Plastic (injection molded) Metal (machined/welded)
**Note, traditionally, the number/bulleted list and a note like this do not appear in the introduction to the report.**
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2 Background Research As part of this project each group member will research one of the fabrication method/material combination listed with your group’s selected
part, such that all four are reviewed and each member is expected to be able to describe how the method is performed in at least one full page of the technical report
and a slide of the final presentation. Each of the background research sections will be submitted individually prior to the final due date of the project, and combined
for the final report.
Please do not forget to utilize resources such as the Engineering Library, and Engineering Librarians in addition to the internet. It is expected that each member find
at least 4 sources that are cited in their individual background portion, and at least two of these sources have to be from a journal article or conference
proceedings.
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3 Methodology The methodology portion of this report is subdivided into the respective parts in an attempt to make understanding each of the different parts analysis
requirements easier. For all of the parts it is assumed that there are no existing tooling in the company and thus the estimated cost of tooling needs to be included
in the manufacturing costs. In the manufacturing world, the term tooling represents all the jigs, molds, etc. that are needed in order to build the component(s) in the
device. Looking into the cost determination of building a part and for this project, a Parametric Cost Estimate technique uses historical data and statistics to
predict the cost.
3.1 Replacement Automotive Bumper For the replacement bumper for a car, there are several options in consideration for the material of the bumper but the shape and
size of the part is the same for all the materials as the same mount points are used no matter the material choice. The parameters to be factored in for the bumper
problem are the raw material, tooling, consumables and labor costs.
To estimate the raw material costs, an estimate of the raw material used in the part is needed. To get a rough estimate for the bumper consider it as an open
rectangular box with a defined thickness, as illustrated in Figure 1. The volume, V, of this approximated shape can more easily be estimated based on the thickness of
the material, t, and the dimensions of height, h, depth, d, and width, w, as listed in Equation 1. Once the volume of material is known, then the mass, m, can be found
based on the material density, ρ . A standard bumper would have dimensions of 8 inches in height, 7 inches in depth, and 6 feet in width.
Figure 1. Illustration of the rectangular estimated shape of the automotive bumper. =83−(4ℎ+4+4)2+2(ℎ++ℎ) Equation 1 = Equation 2
Width
Height
Depth
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Table 1. Cost of respective materials per metric ton of material Material Density (kg/m3) Cost US$ per metric ton Steel 8050 500.00 Aluminum 2800 1600.00 Fiberglass
1800 1800.00 Carbon Fiber 1600 10000.00
Tooling costs are also somewhat dependent on the material thickness in that the forms/molds need to be stronger to account for the higher pressure needed to form the
materials. For this part analyze thicknesses ranging from 3 mm to 10 mm. But the tooling costs also vary by manufacture method and material. Thus, the relationships
shown in Equations 3 – 6 represent the four scenarios for the automotive bumper, with the thickness t supplied in mm.
Table 2. Tooling cost estimates for manufacture method and material options being considered. Manufacture Method Material Tooling Cost Relationship (per 1000 parts)
Additive Steel =1000�1.25 �2+500t+8000 Equation 3 Additive Aluminum =1250�1.5 �1.5+375+7500 Equation 4 Traditional Aluminum
=250� 1.125�3+500+1250 Equation 5 Traditional Fiberglass/Carbon Fiber =400� 1.1�2.5+350+2500 Equation 6
The consumables to be considered for this part depend on the manufacture method and material choice as well. For the additive manufacture methods the consumable of
“support” material that is utilized to hold up hollow features of the part and are the same for both material options, historically average $2 for every cubic
centimeter of printed volume of the part. Thus, the volume estimate from determining the mass can be re-used to find the consumable cost. However, traditional
manufacturing methods have a higher consumable cost because of the safety aspects of the finishing process, such as dust masks, gloves, etc., in addition to the
sandpaper, grinding wheels, etc that are used as part of the process. It has been estimated that for this application, the consumables would be ~$15 per part built.
Likewise, the labor costs are considerably different for the manufacturing methods, with the additive manufacturing method having the lower of the two labor costs.
Based on preliminary manufacturing estimates, it will take a 24 hour print cycle for each part in the additive manufacturing methods, with
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one operator monitoring the machine, at a cost of $45 per hour. As for the traditional manufacturing methods, material choice changing how much labor is required.
For the aluminum part, the casting of the general shape takes 3 employees 2 hours to prep, and ½ hour to pour the molten aluminum. There is then a minimum of a 4 hour
cooling period in which no employees are needed, followed by a 4 hour sanding and finishing process with 2 employees. The average hourly cost for these employees is
$40 per hour. In contrast, the composite (fiberglass or carbon fiber) part requires a 4 hour, 4 employee prep session to build the layers of the composite and a
minimum of an 8 hour baking cycle to cure the composite followed by a 2 employee, 3 hour process to remove the part from the mold and finish the part. 3.2 Replacement
Baby Jumper Platform Replacing the platform in a baby jumper can be done in two possible manufacturing methods, with two possible materials in each method. In order to
determine the fabrication cost of the platform the volume of material used needs to be estimated. In additional to the raw material costs, the tooling cost, labor cost
and consumable costs need to be estimated to determine the most effective fabrication method.
To find the part volume, the shape can be simplified to a hollow cylinder open on one end, as illustrated in Figure 2. Using the height of the cylinder, h, and the
inner and outer diameters, Di and Do respectively, and a uniform thickness, t, the volume can be estimated using Equation 7 and thus find the mass, m, based on the
material density, ρ , Equation 8. Table 3 provides the density of the respective materials, as well as the cost of each material per metric ton. The standard baby
jumper has a height of 1.5 inches, an outer diameter of 2 feet and an inner diameter 16 inches.
Figure 2. Pictorial representation of the baby jumper platform volume estimate shape. = 4(+)(−+4ℎ−4) Equation 7 = Equation 8
Hollow Center
Solid Top
Open Bottom Solid Outside and Inside Walls
h
Di
Do
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Table 3. Cost of respective materials per metric ton of material Material Density (kg/m3) Cost US$ per metric ton ABS Plastic (additive manufacture) 1050 600.00
Aluminum 2800 1600.00 Polycarbonate Plastic (vacuum form) 1190 750.00 Wood (Teak) 640 34000.00
Tooling costs are also somewhat dependent on the material thickness in that the forms/molds need to be stronger to account for the higher pressure needed to form the
thicker materials as well as by the manufacture method and material used. Thus, the relationships shown in Equations 9 – 12 represent the four scenarios for the baby
jumper platform, with the thickness t supplied in mm. For this part, the thickness should be studied from one millimeter to seven millimeters.
Table 4. Tooling cost estimates for manufacture method and material options being considered. Manufacture Method Material Tooling Cost Relationship (per 1000 parts)
Additive ABS Plastic =300�1.25 �2+50t+4000 Equation 9 Additive Aluminum =1250�1.5 �1.5+375+7500 Equation 10 Traditional Polycarbonate
Plastic =275� 1.125�3+45+10250 Equation 11 Traditional Teak =180� 1.1�2.5+120+3750 Equation 12 The consumables to be considered for
this part depend on the manufacture method and material choice as well. For the additive manufacture methods the consumable is support material that is utilized to
hold up hollow features of the part and are the same for both material options, are historically average $0.50 (plastic) or $2 (metal) for every cubic centimeter of
printed volume of the part. Thus, the volume estimate from determining the mass can be re-used to find the consumable cost. However, traditional manufacturing methods
have a higher consumable cost because of the safety aspects of the finishing process, such as dust masks, gloves, etc., in addition to the sandpaper, grinding wheels,
etc that are used as part of the finishing process. It has been estimated that for this application, the consumables would be ~$15 per part plastic part built, and $35
for the finishing of the teak part.
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Likewise, the labor costs are considerably different for the manufacturing methods, with the additive manufacturing method have the lower of the two labor costs. Based
on preliminary manufacturing estimates, it will take a 13 hour print cycle for each part in the additive manufacturing methods, with one operator monitoring the
machine, at a cost of $45 per hour. As for the traditional manufacturing methods, material choice changing how much labor is required.
For the polycarbonate part, the forming of the general shape takes 2 employees 1 hour to prep, and ½ hour to set the plastic. There is then a minimum of a 2 hour
cooling period in which no employees are needed, followed by a 3 hour trimming process with 2 employees. The average hourly cost for these employees is $40 per hour.
In contrast, the teak part would require a one hour, one employee prep session to rough cut and attach to the machining jig, and 8 hours machining to create the part.
This would then need to be followed by a 2 employee, 3 hour process to finish and stain the part for sale. 3.3 Replacement Dishwasher Silverware Tray A replacement
silverware tray for a dishwasher can be fabricated by either additive manufacturing or traditional manufacturing methods of injection molded plastic or bent and welded
metal. In evaluating the fabrication costs for this device it is assumed that all methods of fabrication will use the same volume of material, which can be estimate
using the ‘box’ approach as outlined for the automotive bumper but assume that only half of the box surfaces are filled with actual material for the basket. For basket
in this analysis, the dimensions are width of 9 inches, a depth of 4 inches, and a height of 4 inches. The thickness of the metal wire being considered, and thus
assumed for all manufacturing techniques, range from 0.020 to 0.2 inches. Use this range of thickness for your analysis. After using Equation 1 to find the volume and
Equation 2 for the mass with the material details listed in Table 5 the material cost can be estimated. In addition, the tooling cost, consumable cost and labor cost
need to be considered.
Table 5. Cost of respective materials per metric ton for the dishwasher tray Material Density (kg/m3) Cost US$ per metric ton ABS Plastic – Additive manufacture 1050
600 Acetal (POM) Plastic – Injection molded 1560 950 Stainless Steel – Both methods 7900 2450
The tooling costs will factor in the machines and jigs that are needed to build the part and vary depending on both the method of manufacture and the material being
used. In addition, the thickness of the part requires different strength and forces which also impacts the tooling requirement for the part.
Table 6. Tooling cost estimates for manufacture method and material options being considered. Manufacture Method Material Tooling Cost Relationship (per 1000 parts)
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Additive ABS Plastic =300�0.0125 �2+50t+4000 Equation 13 Additive Stainless Steel =1450�0.014 �1.5+435+5500 Equation 14 Traditional
Acetal Plastic =275� 0.0125�3+65+12500 Equation 15 Traditional Stainless Steel =180� 0.011�2.5+120+3750 Equation 16 Another cost issue
with building the dishwasher tray is the consumables needed for fabrication methods, which also depend on the material. In the additive manufacturing methods support
materials need to be used to help support the actual part features and can be averaged to get an estimate of $0.50 (plastic) or $2.38 (stainless steel) for each cubic
centimeter of actual print material used. Thus, the volume estimate from determining the mass can be re-used to find the consumable cost.
However, traditional manufacturing methods have a higher consumable cost because of the safety aspects of the finishing process, such as dust masks, gloves, etc., in
addition to the sandpaper, grinding wheels, etc that are used as part of the finishing process. It has been estimated that for this application, the consumables would
be ~$10.50 per part plastic part built, and $12.75 for the finishing of the stainless steel part.
Likewise, the labor costs are considerably different for the manufacturing methods, with the additive manufacturing method have the lower of the two labor costs. Based
on preliminary manufacturing estimates, it will take a 7.5 hour print cycle for each part in the additive manufacturing methods, with one operator monitoring the
machine, at a cost of $45 per hour. As for the traditional manufacturing methods, material choice changing how much labor is required.
For the Acetal part, the forming of the general shape takes 2 employees 1 hour to prep, and ½ hour to inject the plastic into the mold. There is then a minimum of a 2
hour cooling period in which no employees are needed, followed by a 6.25 hour trimming process with one employee. The average hourly cost for these employees is $40
per hour. In contrast, the stainless steel part would require a two and half hour, one employee prep session cut and attach the wires to the forming machine, and 3.5
hours for the machine to create the part. This would then need to be followed by a single employee, 3 hour process to finish and inspect the part for sale.
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4 Results The results for this project are going to be the stating of the costs for the four different manufacturing method and material combinations of the part
chosen by your group. This should include a graphical representation costs and how the thickness of the part impacts that cost.
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5 Discussion For the discussion of the results, it is expected that each group recommend a sale price for the part, and determine the payback period for the equipment
investment that is the constant term in the tooling cost formulas based on the profit per part. For this estimate assume that the parts are sold as fast as they can be
built, and should be conducted for all four scenarios.
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6 Conclusion In addition to concluding which of the four options is the best for the company, provide a summary of additional capabilities that the equipment for the
best method would provide the company.
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7 Recommendations/Future Work The Recommendations section, sometimes referred to as the Future Work section, should contain a description of what the next step(s) are
in the implementation of the results of this study.
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8 References References should be listed according to MLA format and a minimum of 10 should be used overall.
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Appendix 1
Deliverables:
Description Group/Individual Point Value Due Date Team Planning(Team Charter and Gantt Chart) Group 10 Feb 3 Background Research for Report Individual 10 Feb 10
Project Code Individual 30 Feb 20 Powerpoint File Group 15 Feb 27 Presentation Group 10 Week of Feb 27 Final Technical Report Group 25 March 3
Individual Code Grading Scale: Grade Level Performance Expectation A • All of the “B” Level • Create properly formatted graph of cost –vs- thickness • Determine the
percentage breakdown of each type of cost to make the part B • All of “C” Level • Create a single variable that contains a table that includes all the different cost
categories and the total cost C • Create thickness vector • Calculate material costs, tooling costs, consumable costs, labor costs
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