ABSTRACT
In this project we use a method to reduce the cost in supply chain management by analysis of job
drawings, the process flow related to their manufacturing, control plan for the part and finally
cost estimates using the current industry pricing for raw materials, machining operations and
processes.
This project addresses the issues related to the redundancy in design of the component and
checking for pricing of various components that are imported from other companies.
Chapter 6.1:
Introduction
Profit of any commercial organization is depends on its productivity and quality of the product.
To improve the profit they need to increase productivity without scarifying quality. To achieve
this, it is necessary for organizations to reduce cost in various departments.
Supply Chain Management (SCM) is the management of the flow of goods and services. It
includes the movement and storage of raw materials, work-in-process inventory, and finished
goods from point of origin to point of consumption.
Concentric Pumps Pvt. Ltd. is a tier 2 company meaning that the components required for
assembly of pumps (gears shafts plugs etc.) are supplied from local companies. The components
are only machined and assembled to the vendor specifications. Since the parts were taken in from
outside, the company faced a problem with the cost calculations and quotations of the parts.
Hence the parts bought were at a high price.
The possible solutions to the problem include:

Analysis of various processes involved in the manufacturing of that component to check
for its redundancy.

Check for the prices quoted for the processes against the actual market prices.

Check for a cheaper material without altering the mechanical properties.

Optimizing design of the parts to reduce material and hence price.
Out of the above listed; there was very little scope to change the material specifications of the
components. Hence we went ahead with the other three solutions. To implement the solutions,
we had to study of drawing of part, the process flow diagram, material specification and the cost
calculations of various CNC processes.
CHAPTER 6.2:
METHODOLOGY
A. STUDY OF JOB DRAWINGS
From the available job drawing at the company we study the dimensions, cross-section and
tolerances of various parts. These recorded dimensions are later used in time and cost
calculations of the CNC machine.
For instance, let us consider the drawing of ‘D-Plug’ as shown in the figure below. We find that
the dimensions are:

Root Diameter of the gear = 38.019 mm

Outer Diamter of Gear = 44.52 mm

Widhth of the Gear = 13 mm

Helix Angle of gear = 140

No. of teeth of gear = 17
Note: other required deminsions are duely mentioned on the left hand side of the job drawing.
Figure 6. 1: Job Drawing of Gear
B. STUDY OF PROCESS FLOW DIAGRAM
The process flow diagram enlists the various processes associated with the manufacturing of a
part. It includes the description of the process, incoming source of variation for the given
process, its desired outcome and the process characteristics.
For the considered part that is the gear, the processes involved are Bar Cutting, Pre Turning,
CNC Turning 1st Setup, CNC Turning 2nd Setup, Hobbing, Debburing & Chamfering, Shaving,
Punching, Heat Treatment, Bore Grinding and Roll Testing.
The process flow diagram for a few processes is attached below
Figure 6. 2 Process Flow of Gear
1. The job is put through CNC 1st Turning Setup, where the incoming sources of variation
are Gear Outer Diameter (OD), Bore Diameter, Gear Width, Chamfer etc. These
incoming sources result in desired outcomes. These desired outcomes are then generated
as

Gear OD = 44.60 ± 0.05

Bore diameter = 21.2 ± 0.025

Total width = 14.0 ± 0.20

Surface Roughness = 1.8Ra
2. The job is put through CNC 2nd Turning Setup, where the incoming sources of variation
are Gear Outer Diameter (OD), Bore Diameter, Gear Width etc. These incoming sources
result in desired outcomes. These desired outcomes are then generated as

Gear OD = 44.60 ± 0.05

Total width = 13.0 ± 0.10

Face parallelism = 0.02 max

Perpendicularity = 0.02 max

Surface Roughness = 1.8Ra
C. COST ESTIMATION OF THE GIVEN PART
The cost of CNC based parts can be calculated as follows:
Total price of component = Cost of Raw Material [BP + Tpt + Icc – ED – VAT] + Cost of
Machining [ Cutting + Turning + Hobbing + etc] + Cost of Tooling + Cost of Cleaning and
Washing + Cost Inspection and Checking + Cost of Packing and Freight + Over Head and Profit
+ Cost of Rejection – Cost of Scrap recovery and machining
For the previously considered Gear, we now evaluate the various cost involved in the
manufacturing of this product.
Cost Calculations
SR. NO.
DESCRIPTION
A
1
2
3
4
Bar Route
RAW MATERIAL
INPUT WEIGHT
Net Wt of Gears
SCRAP WEIGHT
RAW MATERIAL
5
B
Landed Price per Kgs
RAW MATERIAL COST
MACHINEING
Finish Weight of Blank
Cutting
Rough Turning
CNC Turning
Hobbing
Deburing & Chamfering
Shaving
Punching
Nitriding
Bore Grinding
Tooling
Cleaning & Washing
Inspection & Checking
Packing
Freight Upto Lonikand
Scrap Recovery in Machineing
OH & Profit 15% on RM & Machiening
Rejection
Round Up
Table 6. 1: Cost Calculation for Gear
Drive Gear 2559-27T
(INP. WT - NET WT)
BP
ED
VAT
Tpt
Icc
less Vat & ED
D50*22
EN19T
0.337 KG
0.088 KG
0.249
61.9 Rs/Kg
7.74 12.50%
2.48
4%
1
1
1.238
2%
-10.21
64.14
21.61
0.15
5
2.615
2.7
1
1.75
0.26 Kgs
2.946
50
200
450
150
300
2
1
150
300
5%
0.21
25
15%
2%
4.17
8.72
20.25
2.5
8.75
1
8.15
5
2
1
1
0.5
0.5
-5.29
58.24
11.99
0.24
92.08

Cost of Raw Material:
It is given by:
Landed Price per Kg = Buying price(BP) - Excise Duty (ED) – Value Added Taxes(VAT) +
Transportation Cost (Tpt) + Icc
Raw Material Cost = Input Weight * Landed Price (per kg)
 Cost of Machining
It is given by the time required for different processes multiplied by cost of machining
operation for a particular process.
The time computations for various processes are as follows:
I. Turning
Figure 6. 3: CNC Machine turning
A.
Machine Speed: To achieve a specific cutting speed:
N=
k*V
 * D1
N = machine speed in revolutions/minute (RPM)
k is a constant to “correct” speed (V) and part diameter (Di ) units
V is desired cutting speed, a Handbook Value
D1 is largest part diameter (initial size)
V given in surface feet per minute (SFPM), D1 in inches: k = 12
V given in meters per second (MPS), D1 in mm: k = 60000
V given in meters per minute (MPM), D1 in mm: k = 1000
If Cutting Speed for a given RPM rate is desired, solve above equation for V:
V = πND/k
B. Cutting Time: minutes per operation
CT is cutting time per “pass”
L is length cut
A is “allowance” or starting offset
fr is machine feed rate units/revolution, a Handbook Value
CT =
(L + A)
fr*N
II. Boring
Figure 6. 4: CNC boring
A. Machine Speed:
As above except D1 is the finished (larger) diameter
B. Cutting Time:
Same as above
III. Facing, Slot Cutting or Cut Off
Figure 6. 5: CNC Facing or Slot Cutting
In facing, slot (plunge) cutting and cut off, the cutting speed for a given RPM decreases
as the tool progresses toward the center of the piece being cut. This follows since most
(manual) lathes cannot increase spindle speed (N) during cutting operations. Thus, the
required N is calculated as above using the outside (largest) diameter of the part for a
given V.
A. Machine Speed
N =
kV
D
If Cutting Speed for a given RPM rate is desired, solve above equation for V:
V = πND/k
B. Cutting Time
CT =
(L + A)
fr*N
IV. Slab (Horizontal) Milling
Terms Used:
of Slab
CutterMilling
FigureN:
6. RPM
6: CNC
n: Number of Teeth on Cutter
W: Width of cut (may be full cutter or partial cutter)
t: depth of cut
V: cutting speed -- a Handbook value
L: Length of pass or cut
fm: Table (machine) Feed
ft: feed/tooth of cutter -- a Handbook value
D: Cutter Diameter
A. Cutting Speed:
N =
kV
D
If Cutting Speed for a given RPM rate is desired, solve above equation for V:
V = πND/k
B. Table Feed Rate:
f m = f t * N* n
C. Cutting Time:
CT =
L + LA
fm
LA is Length of Approach of Tool to Work
LA = t(D - t)
V. Face (Vertical) Milling:
Figure 6. 7: Face (Vertical) Milling
Terms Used:
N: RPM of Cutter
n: Number of Teeth on Cutter
W: Width of cut (may be full cutter or partial cutter)
t: depth of cutter engagement
V: cutting speed -- a Handbook value
L: Length of pass or cut
fm: Table (machine) Feed
ft: feed/tooth of cutter -- a Handbook value
D: Cutter Diameter
LA: Approach Length
LO: Length of “OverTravel”
A. Cutting Speed:
N =
kV
D
If Cutting Speed for a given RPM rate is desired, solve above equation for V:
V = πND/k
B. Table Feed:
𝑓𝑚 = 𝑓𝑡 × N ×
𝑛
C. Cutting Time:
Here several situation must be considered, these include:
1. Tool Not Fully Engaged with W<D/2
2. Tool not Fully Engaged but W> D/2
3. Tool Fully Engaged, Roughing Pass -- Doesn’t require “Full Wipe”
4. Tool Fully Engaged, Finishing Pass -- requires “Full Wiping Action”
CT =
(L+ LA + LO)
fm
1. LA = LO =
W(D - W)
2. LA = LO =
3. LA =
D
2
D
2
2
2
LO = - 0.5 * D - W
4. LA = LO =
D
2
VI. Drilling
Figure 6. 8: CNC Drilling
A. Drill Speed, RPM
N =
kV
D
k is a “Units Constant”
D is Drill Diameter
V is cutting speed, a Handbook Value, if Cutting Speed for a given RPM rate is
desired, solve above equation for V:
V = πND/k
B. Cutting Time (min)
CT =
A is allowance; usually
f r is drill feedrate
L is the length of Hole
D
2
(L + A)
fr*N
MACHINING TIME CALCULATIONS
CUTTING SPEED M/MIN
DIAMETER
RPM
CUTTING FEED IN MM/REV
TOOL TRAVEL IN MM
NO OF CUTS
CUTTING TIME
ALLOWANCES(LOAD/UNLOAD)
TOTAL TIME IN MINUTES
CUTTING SPEED M/MIN
DIAMETER
RPM
CUTTING FEED IN MM/REV
TOOL TRAVEL IN MM
NO OF CUTS
CUTTING TIME
ALLOWANCES(LOAD/UNLOAD)
TOTAL TIME IN MINUTES
CUTTING SPEED M/MIN
DIAMETER
RPM
CUTTING FEED IN MM/REV
TOOL TRAVEL IN MM
NO OF CUTS
CUTTING TIME
ALLOWANCES(LOAD/UNLOAD)
TOTAL TIME IN MINUTES
CNC Turning
150
150
150
150
150
47
47
47
47
47
1016 1016
1016
1016
1016
0.1
0.1
0.1
0.1
0.1
23
8
8
23
8
2
2
2
2
2
0.45
0.16
0.16
0.45
0.16
0.5
0
0.5
0
0.953 0.157
0.157 0.953 0.157
2.377
Minutes
With 90% Efficiency In
2.615
Minutes
156.9093
Seconds
Pre Turning
60
60
60
60
60
50
50
50
50
50
382
382
382
382
382
0.15
0.15
0.15
0.15
0.15
25
17
12
25
12
2
2
2
2
2
0.87
0.59
0.42
0.87
0.42
0.5
0
0.5
0
1.372 0.593
0.419 1.372 0.419
4.175
Minutes
With 90% Efficiency In
4.592
Minutes
275.5427
Seconds
Hard Turning
150
30
1592
0.1
16
3
0.3
0.5
0.801
0.801
Minutes
With 90% Efficiency In
0.882
Minutes
52.89504
Seconds
Table 6. 2: Machining Time Calculations
VII. Hobbing Time
Hobbing is a continuous gear generation process widely used in the industry for
high or low volume production of external cylindrical gears. Depending on the
tooth size, gears and splines are hobbed in a single pass or in a two-pass cycle
consisting of a toughing cut followed by a finishing cut. State-of-the-art hobbing
machines have the capability to vary cutting parameters between first and second
cut so that a different formula is used to calculate cycle times for single-cut and
double-cut hobbing.
Figure 6. 9: Hobbing of Gear
Single Cut Hobbing Cycle
The cycle time is given by the equation,
T=
Z *L
N *K *F
where
T = cycle time in minutes
Z = number of gear teeth
L = length of cut in inches
N = hob revolutions per minute
K = number of hob starts
F = feed rate in inches per revolution of work
HOBBING TIME CALCULATION
JD Gear 4287-27
SRNO. PARAMETER
1
NO. OF TEETH OF GEAR
2
NO. OF STARTS OF HOB
3
AXIAL FEED (MM/WORK REV)
4
HOB RPM
5
WIDTH OF GEAR
6
O.D. OF GEAR
7
ROOT DIA OF GEAR
8
HELIX ANGLE OF GEAR
9
LEAD ANGLE OF HOB
PRESSURE ANGLE OF
10
COMPONENT
11
O.D. OF HOB
12
LOADING / UNLOADING
HOBBING TIME IN MINUTES
Shaving Time
Table 6. 3: Hobbing Time Calculation
VALUE
17
1
1.6
250
13
44.52
38.019
14
2.17
17
80
1
2.7
1.75
NOTE: The cost of machining operation per hour is quoted by the company and those prices
cannot negotiated. The cost of cleaning and washing, Inspection and Checking, Packing and
Freight are also quoted by the company.

Cost of Scrap recovery and machining
Scrap weight = Input Weight (Weight of the Blank) – Net Weight (Finished weight of Gear)
Scrap Recovery = Scrap Weight * Cost of Scrap per Kg
NOTE: Cost of Scrap per kg varies from company to company. Overhead and Profit is
considered as 15% on Raw Material and Machining. Cost of Rejection is considered 2% of the
overhead and profit.
CHAPTER 6.3:
RESULT AND DISCUSSION
Part no.
Part Desc.
Raw Material
RM Rate
Table 1: Company Quotation
2523-27
Water Pump Drive Gear
Gross wt.
Cut weight
Forging wt.
Finish wt.
Scrap wt. (Forging)
RM cost
Scrap Cost
Bar Cutting
Hardening & Tempering
Rough Turning
CNC Turning
Hobbing
Tooling Cost
Shaving
Tooling Cost
Machine Deburring
Punching & Marking
Heat Treatment (Gas
Nitriding)
Hard Turning
Sub Total
ICC on RM
Rejection
Profit
Over Head
Packing & Freight
Total
Scrap machining
Total
Table 6. 4: Company Quotation
EN19T
60
Bar Route
0.32
0.26
Rs./Kg
Rs./Kg
15
220
450
2
2
275
2
100
1
105
290
3%
2%
10%
10%
Pune
1
0.123
0.042
19.2
-0.76
3.05
3.9
3
7.33
15
2
9.17
2
1.67
1
12.915
4.83
58.92
0.78
1.7
5.89
5.89
1.55
100.13
-2.19
102.32
Table 2: Cost Calculations
SR.
NO.
DESCRIPTION
A
1
2
Bar Route
RAW MATERIAL
INPUT WEIGHT
Net Wt of Gears
3
4
SCRAP WEIGHT
RAW MATERIAL
Drive Gear 2559-27T
D50*22
EN19T
0.337 KG
0.088 KG
(INP. WT - NET
WT)
BP
ED
VAT
Tpt
Icc
less Vat & ED
5
B
Landed Price per Kgs
RAW MATERIAL COST
MACHINEING
Finish Weight of Blank
Cutting
Rough Turning
CNC Turning
Hobbing
Deburing & Chamfering
Shaving
Punching
Nitriding
Bore Grinding
Tooling
Cleaning & Washing
Inspection & Checking
Packing
Freight Upto Lonikand
Scrap Recovery in Machineing
OH & Profit 15% on RM & Machiening
Rejection
Round Up
Table 6. 5: Cost Calculations for Drive Gear 2559-27T
0.249
61.9 Rs/Kg
7.74 12.50%
2.48
4%
1
1
1.238
2%
10.21
64.14
21.61
0.15
5
2.615
2.7
1
1.75
0.26 Kgs
2.946
50
200
450
150
300
2
1
150
300
5%
0.21
25
15%
2%
4.17
8.72
20.25
2.5
8.75
1
8.15
5
2
1
1
0.5
0.5
-5.29
58.24
11.99
0.24
92.08
Table 1 shows the quotation and cost break up of manufacturing the gear. The estimates were
analysed by us using the above mentioned methodologies and we found the following things that
added to the cost:

The quotation had redundant processes like hardening and tempering and hard
turning.

The cost of processes was quoted higher that what was calculated like nitriding,
tooling etc.

The scrap weight calculated was significantly low than what was expected.
To remove the above stated anomalies we recalculated the cost break up using maximum
possible values for raw materials and processes (time taken maximum). We even considered
processes like cleaning washing inspection etc. Even after the considerations we found a
significant difference in the pricing of the component. The changes in the above anomalies are
made and tabulated as shown in Table 2.
CHAPTER 6.4:
Conclusion Remarks And Scope For Future Work
By the implementation of solutions to the problems we find that the cost of manufacturing 1 gear
goes down by Rs. 10.24. The company requires 10000 gears per month so that the manufacturing
process is not stagnant. Hence,
Number of gears ordered per month = 10000
Difference in price per component = 102.32-92.08
= Rs. 10.24
Saving per month = 10.24*10000
= Rs. 10,2400
Savings per year = 102400*12
= Rs. 12,28800
Percentage savings = (10.24/102.32)*100%
= 10%
The price of component can be further brought down if the exact price of raw materials can be
determined. Moreover a detailed process study will show that some of the conventional
processes may be replaced by newer and fewer CNC operations. Also, there is scope to change
the material specifications by cheaper materials without compromising with the quality of the
finished product. Lastly the design can be optimised so that the part manufactured is made using
lesser material.