1.1 two parts; one is fixed cost which

1.1      
High Speed Shaft

High speed shaft is modeled as per the designed dimensions
done in the start of the report. Keyways were made in the shaft for coupling of
pinion and standard key is used for coupling.

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Figure 11 CAD model of high speed shaft

1.2      
Low Speed Shaft

Low speed shaft is modeled as per the designed dimensions
done in the start of the report. Keyways were made in the shaft for coupling of
gear and standard key is used for coupling.

 

Figure 12 CAD model of low speed shaft

1.3      
Standard Parts (Bearings, Seals, Bolts, Keys)

Standard parts are downloaded from Trace parts online CAD
database from different vendors and incorporated into the CAD model.

Following is BOM of all the standard parts in the gearbox
assembly including standard parts.

 

1.4      
Gearbox Assembly

All the parts imported from standard catalogue and modeled
in Creo parametric were assembled in assembly module of the software. Following
is a 3D render image of the complete assembly in exploded format for better
understanding.

 

Figure 13 CAD Model Assembly of gearbox

 

2      
MANUFACTURING DRAWINGS

Drawings of all the parts and assemblies were made in
drawing module of Creo Parametric using the already generated CAD models. Assembly
drawings have all the information including dimensional details, interface
details, bill of material and material of each and every part. Following are
screen shots of all the drawings including part drawings as well as assembly
drawings.

 

Figure 14 Assembly drawing snapshot (Sheet 1)

 

Figure 15 Assembly drawing snapshot (Sheet 2)

 

Figure 16 Gear drawing screenshot

 

Figure 17 Pinion drawing screenshot

 

Figure 18 High speed shaft drawing screenshot

 

Figure 19 Low speed shaft drawing screenshot

 

Figure 20 Lowe casing drawing screenshot

 

Figure 21 Upper casing drawing screenshot

2.1      
Cost Estimation

The estimated cost of the project is divided into two parts;
one is fixed cost which is based on the price listing for different standard
and outsourced components used in the gearbox while the 2nd part is
the variable cost which comes from the custom manufactured parts like gear,
pinion, casing and shafts.

Both cost estimations are discussed in following paragraphs.

2.1.1    
Fixed Cost

Standard components that are used in the project include
bearings, seals, fasteners and electric motor. These components usually come
from a manufacturer and comes at a fixed cost from certain supplier. Cost of
these components from selected suppliers is listed in the table below along
with the total number of components being used and total cost for each
component.

Table 8 Cost estimation for standard components

2.1.2    
Variable Cost

Components which are to be custom manufactured have variable
cost and it depends upon the manufacturing method/technique, quantity and labor
cost etc. including many other variables. The optimum method for manufacturing
of the casing is using sand casting and then doing machining operating later
for finishing. Similarly suitable manufacturing method for shafts is using
conventional or CNC machining on lathe and milling. As far as pinion and gear
is concerned, they can be manufactured on hobbing machine for tooth profile
cutting and CNC or conventional lathe and milling machine for rest of the
operations.

3      
CONCLUSION AND RECOMMENDATIONS

The
design process of gearbox is carried out in two parts. First part is based on
listing down the user requirements and then making certain assumptions for the
design variables input followed by design calculations for different components
of the gearbox including input shat, output shaft, pinion and gear. All the
critical design aspects of components have been verified by calculations. Two
different methods have been used for the design of input and output shaft and
the results from worst case have been selected as the design parameter.
Similarly selections of gear and pinion parameters have been made incorporating
a reasonable factor of safety keeping in view the dynamic loading conditions of
the gearbox. Different modes of failure for pinion and gear have been
considered and forces were calculated to ensure the design safety and life
requirements.

2nd
part of the report involves bringing the designed gearbox onto paper in
the form of manufacturing and production drawings. CAD software (Creo
Parametric) is used to create CAD models of all the components involved in the
gearbox, dimensions from the calculated results were used for CAD modeling.
Standard parts were imported from online resources of manufacturer’s catalogue
and assembled with the custom design components in assembly module of the CAD
software. Once the CAD modeling is completed, drawings module of CAD software
was used to create 2D manufacturing/production drawings of all the custom parts
with dimensional details, tolerances and material data. Assembly drawing of
gearbox shows all the components in exploded format with bill of material and
mass properties in a tabular format. The part numbers of all the standard
components is mentioned in the BOM table.

Although a rigorous design procedure has been followed in the design
process of gearbox, there are areas which can be improved further. Individual
components have been designed using conventional design method of calculation
but for verification of these calculations, FEA software can be used and design
can be verified. Also the geometry of upper and lower casing can be optimized
for weigh reduction and weight of pinion and gear can be reduced by removing
material from certain less stressed areas to minimize the rotational inertia of
the components hence minimizing the starting torque and load on the motor.