MR 2 Shearing Process
Unit Process Life Cycle Inventory
Dr. Devi Kalla, Dr. Janet Twomey, and Dr. Michael Overcash
August 16, 2009
Shearing Process Summary................................................................................................. 2
Methodology for unit process life cycle inventory model (uplci) ...................................... 3
Shearing Process Energy Characteristics ............................................................................ 4
A. Parameters effecting the Energy required for shearing operation.................................. 7
Shearing Energy .............................................................................................................. 8
Shearing force calculation........................................................................................... 8
Idle Energy .................................................................................................................... 10
Basic Energy ................................................................................................................. 11
B. Method of quantification for mass loss: ....................................................................... 12
Tool set usage ............................................................................................................... 12
Case Study on Shearing process ....................................................................................... 14
Product Details .............................................................................................................. 15
Process Parameters........................................................................................................ 15
Shearing process ........................................................................................................... 15
Time, Power and Energy calculations for shearing operation ...................................... 15
Summary: .......................................................................................................................... 16
References Cited ............................................................................................................... 17
Appendices ........................................................................................................................ 17
Manufacturers Reference Data ..................................................................................... 17
1
Shearing Process Summary
Shearing is a frequent metalworking unit process in manufacturing as a mass
separating step, which involves cutting or shearing metals, as well as plates, bars, tubing
of various cross sections without formation of chips. When the two cutting blades are
straight, the process is called shearing. In the separating step, portions of the workpiece
are “separated” from the workpiece. Hence this life cycle inventory is to establish
representative estimates of the energy usage from the shearing unit process in the context
of manufacturing operations for products. The shearing process is used as the preliminary
step in preparing stock for stamping processes, or smaller blanks for CNC presses, Figure
MR2-1. The shearing unit process life cycle inventory (uplci) profile is for a high
production manufacturing operation, defined as the use of processes that generally have
high automation and are at the medium to high throughput production compared to all
other machines that perform a similar operation. This is consistent with the life cycle goal
of estimating energy use and mass losses representative of efficient product
manufacturing.
Straight-blade shearing is used for squaring and cutting flat stock to a required
shape and size. In straight-blade shearing, the work metal is placed between the
stationary lower blade and a movable upper blade. As the upper blade is forced down, the
work metal is penetrated to a specific portion of the thickness, after which the
unpenetrated portion fractures and the work metal separates Figure MR2.2. Usually the
clearance between the two blades is 5 to 10% of the thickness of the material, but is
dependent on the material. Clearance is defined as the vertical separation between the
blades, measured at the point where the cutting action takes place and perpendicular to
the direction of blade movement. It affects the finish of the cut (burr) and the machine
power consumption. This causes the material to experience highly localized shear stresses
between the two blades.
Figure MR2.1. Computer numerical control (CNC) shearing machine (Photograph from
Xinya Machine tool manufacture Co.Ltd, China)
2
Figure MR2.2. Shearing Process Schematic (Todd et al., 1994)
Figure MR2.3 shows an overview of the developed environmental-based factors
for shearing operations.
Figure MR2.3. LCI data for shearing process
Methodology for unit process life cycle inventory model (uplci)
In order to assess a manufacturing process efficiently in terms of environmental
impact, the concept of a unit operation is applied. The unit process consists of the inputs,
process, and outputs of an operation. Each unit process is converting material/chemical
inputs into a transformed material/chemical output. The unit process diagram of a
shearing process is shown Figure MR2.4.
3
The transformation of input to output generates five lci characteristics,
a. Input materials
b. Energy required
c. Losses of materials (that may be subsequently recycled or declared waste)
d. Major machine and material variables relating inputs to outputs
e. Resulting characteristics of the output product that often enters the next unit process.
Machine tool, Fixing, Cutting Fluid
Work Piece
Cutting Tools
Cutting Fluid
Energy
Shearing
Product after
shearing
Noise
Waste Coolant
Scrap
Mist
Figure MR2.4. Input-Output diagram of a shearing process
Shearing Process Energy Characteristics
In shearing processes the tooling and setup are relatively simple. A shear machine
basically consists of a shear table, shear blades both upper and lower, workpiece holding
devices, and gaging devices. Because high production shearing is a semi-continuous
process, the lci is based on a representative operational sequence, in which
1) Work set-up generally occurs once at the start of a batch in production. Set-up is
made on the shearing machine as the first work piece is introduced into the
machine. The work piece is positioned, all drawings and instructions are
consulted, and the resulting program is loaded. The total set-up time must then be
divided by the size of the batch in order to obtain the set-up time per sheared part.
The energy consumed during this set-up period is divided by all the parts
processed in that batch and is assumed to be negligible and is discussed in the
example below.
2) During loading, the workpiece is fed onto the shear table and hold-down devices
are used to fix the workpiece in position. At each cut hold-down devices used for
the part to be positioned correctly with respect to the cutting tool. This is at the
level of Basic energy and is labeled Loading.
3) Relative movement of the cutting tool and the workpiece occurs without changing
the shape of the part body (Upper blade moving downwards), referred to as Idle
Energy and is labeled Handling.
4) Actual shearing process occurs and is labeled Tip Energy.
5) Upper blade moves upwards and the workpiece is repositioned for subsequent
cutting, thus the energy per piece is repeated. (Idle Energy for Handling and then
Tip Energy for shearing).
4
6) Put workpieces away or rearrange them for other operation and typically sent
forward to another manufacturing unit process. This is at the level of Basic
Energy and is labeled Unloading.
The machine considered in this study is a hydraulic shear machine because the
degree of control is greater compared to other shear machines like mechanical, squaring
machines etc. Hydraulic machinery are machines and tools which use fluid power to do
work. Hydraulic shears are actuated by a motor driven pump that forces oil into a
cylinder against a piston; the movement of the piston energizes the ram holding the upper
knife. Hydraulic shears are designed with a fixed load capacity. This prevents the
operator from shearing material that exceeds capacity and, therefore, saves costly damage
to the machine structure; this is a basic advantage of hydraulic shear (ASM International,
2002). The hold-downs are the devices that hold the workpiece firmly in position to
prevent movement during shearing. The hold-down pressure must be greater than the
force generated in cutting the material. These forces depend on the knife clearance, rake
angle, and depth of material back piece. The back gages are adjustable stops that permit
reproducibility of dimensions of sheared workpieces in a production run. Most gages are
controlled electrically. The operating speeds of hydraulic shears are limited to speeds of
8-21 strokes per minute and capable of shearing a 1.5 inch plate up to 420 inch long.
Computer numerically control (CNC) system permits dimensional accuracy and
repeatability, increased productivity, and hands-off safe operations. For thin sheet,
magnetic overhead rollers eliminate sag and support the sheet for accurate gaging.
In this representative unit process, the life cycle characteristics can be determined
on a per shear basis or on a per piece basis if there are multiple shearing steps per piece.
Since this is a high production process, the start up (at the beginning of a batch or shift) is
deemed to be small and not included. In this uplci, there are three typical power levels
that will be used, Figure MR2.5. Correspondingly, there are times within the shearing
sequence from which these three power levels are used, Figure MR2.5.
5
P
Servo motor for axis
drive
Idle Energy
Tip Energy
Basic Energy
Ptotal
Pidle
Pbasic
tshearing
t
tidle
tbasic
Figure MR2.5. Determination of power characteristics and energy requirements of
Shearing machines.
The steps 2), 3), 5), and 6) are estimated as representative values for use in this
unit process lci and energy required of cutting material by shearing, step 4), is either
measured using shearing force values. High production shearing operation involves
multiple sub-operations illustrated in Table MR2.1. There are thus many variables which
have some influence on the overall energy of the shearing unit process. The system
boundaries are set to include only the use phase of the shearing machine, disregarding
materials processing, production, maintenance and disposal of the machine. Stock
decoilers, straighteners, feeders, part handling, and scrap removal systems are known as
shearing machine auxiliary equipments. Moreover, the functioning of the manufacturing
machines is isolated, disregarding the influence of the other elements of the
manufacturing system, such as material handling systems, feeding robots, etc. Other
consumables such as lubricants and coolants are included.
6
Table MR2.1
Machine Units and its functions
Energy Consuming Units
M1
M2
Hydraulic pump1 (Main Pump
with continuous circulation)
Hydraulic pump2
Drives Axis Movement servo motors
PC
computer+control panel1
(screen etc) Machine operation
(pedal with instruments)
Functions
Type of Energy
Move the pistons
connected to the blades
basic
Clamp the dies
basic
Move backguage with
respect to the table
idle
basicControl Panel2
basic
The energy consumption of shearing is calculated as follows.
Etotal = Pbasic * (tbasic ) + Pidle * (tidle) + Pshearing * (tshearing)
(Basic energy) (Idle energy) (Shearing energy)
(1)
where power and time are illustrated in Figure MR2.5.
A. Parameters effecting the Energy required for shearing operation
An approximate importance of the many variables in determining the shearing energy
requirements was used to rank parameters from most important to lower importance as
follows:
1. Thickness of the material
2. Mechanical properties of the sheet metal
3. Length of shearing
4. Knife penetration
5. Speed of the punch
6. Clearance
7. Bottom force
8. Geometry
9. Production rate
10. Friction at the punch, die, and workpiece interfaces.
11. Machine energy during standby and idling
From this parameter list, only the top 5 were selected for use in this unit process life
cycle with the others having lower influence on energy. Energy required for the overall
shearing process is also highly dependent on the time taken for idle and basic operations.
7
Shearing Energy
Shearing time (tshearing) and power (Pshearing) must be determined for the shearing
energy and it is calculated from the more important parameters given above.
Shearing setup is illustrated in Figure MR2.6. Actual shearing process time is the
thickness of the sheet metal divided by shear blade velocity (shear speed, mm/sec). In
order to shear a sheet metal, the blade must pass through the thickness of the workpiece.
This means the travel of the blade is more than the thickness of the sheet. Thus in actual
practice, we add the thickness of the sheet “T” to the length of approach and length of
shear to give overtravel for the calculation of total time.
Figure MR2.6. Shearing setup
Shear blade velocity mm/sec (in/sec) = V
workpiece thickness mm(in) = T
Length of the cut mm (in) = L
Feed rate of stock to be sheared mm/sec (in/sec) = F
Width of the stock to be sheared mm (in) = W
T
Shearing time (tshearing) =
V
(2)
Shearing force calculation
Shearing force for straight-knife is basically the product of the shear strength of
the sheet metal and the cross-sectional area being sheared. Shearing force Fs for straight
blades in metalworking can be determined by (George et al., 2000):
 S * P * T 2 *12   P 
(3)
Fs  
1  
R *100   2 

Where,
Fc = Shearing force lbf
S= shear strength of the sheet metal, Psi
T= stock thickness, in. and
R = rake of the knife blade, in./ft.
Standard blade rakes are 1/4, 3/8, 1/2, 5/8, 3/4 and 7/8 in./ft.
P = penetration of knife into material, fraction of T (range 0 – 1)
Rake is the angular slope formed by the cutting edges of the upper and lower knives. It
has been found that increase in rake leads to a corresponding nearly linear decrease in
shearing force (Cincinnati, Inc and Hydrapower International, personal communications,
8
2009). Thus the energy equation can be simplified, so that a rake angle does not have to
be specified. Thus the effective energy FS is dependent on S, P, and T as given in (4).
 S * P * T 2 *12   P 
Fs  
1  
100

 2 
(4)
Where,
Fs = Shearing force lbf
S= shear strength of the sheet metal, Psi
T= stock thickness, in. and
P = penetration of knife into material, fraction of T (range 0 – 1)
For metric usage, the force is multiplied by 4.448 to obtain newtons (N).
Table MR2.2. Values of percent penetration and shear strength for various materials
(Kalpakjian, et al., 2008)
Material
Lead alloys
Tin Alloys
Aluminum Alloys
Titanium Alloys
Zinc
Cold worked
Magnesium alloys
Copper
Cold worked
Brass
Cold worked
Tobin bronze
Cold worked
Steel, 0.10%C
Cold worked
Steel, 0.40%C
Cold worked
Steel, 0.80%C
Cold worked
Steel, 1.0%C
Cold worked
Silicon steel
Stainless steel
Nickel
Percent
Penetration (%)
50
40
60
10
50
25
50
55
30
50
30
25
17
50
38
27
17
15
5
10
2
30
30
55
Shear Strength,
psi (MPa)
3500 (24.1) – 6000 (41.3)
5000 (34.5) – 10,000 (69)
8000 (55.2) – 45,000 (310)
60,000 (413) – 70,000 (482)
14,000 (96.5)
19,000 (131)
17,000 (117) – 30,000 (207)
22,000 (151.7)
28,000 (193)
32,000 (220.6)
52,000 (358.5)
36,000 (248.2)
42,000 (289.6)
35,000 (241.3)
43,000 (296.5)
62,000 (427.5)
78,000 (537.8)
97,000 (668.8)
127,000 (875.6)
115,000 (792.9)
150,000 (1034.2)
65,000 (448.2)
57,000 (363) – 128,000 (882)
35000 (241.3)
9
Shearing force Fs for all non-straight tools in metalworking can be determined by:
Fs=LTS (for any shape cut)
Where L is sheared length, in inches (mm); T is material thickness, in inches (mm); S is
shear strength of material, in pounds per square inch (MPa); and D is diameter, in inches
(mm).
So for circular shear Fs=πDTS (for round holes)
The product of force and the distance moved gives the energy associated with that
particular operation. Using the shearing force calculated in the above, we can estimate the
energy required to perform the operation by using the following:
E = Fs  L
(5)
Where: E = Energy (inch lbf /shear)
Fs = Shearing force, lbf
L = sheared length, in.
For metric usage, the energy is multiplied by 0.113 (4.448*25.4/1000) to obtain joules
(J).
Power required for shearing process P = Fs*V
Where V = shear blade speed in/sec or (mm/sec) (machine specification)
The shearing energy is thus E (Joule/shear) = shearing time*Pshearing
With a given material to be sheared, shear strength given in Table MR2.2. Thus with only
the material to be sheared, the thickness of the workpiece, and the length of shear, one
can calculate the lci shearing energy per shear, equation 5. This then must be added to the
idle and basic energies, see below.
Idle Energy
Energy-consuming peripheral equipment included in idle power (Pidle) are shown
in Table MR2.1. The idle power characterizes the load case when there is relative
movement of the tool and the work-piece without separating the metal (e.g. axis
movement) - Handling. For shearing, the handling times are the air time of approach and
retraction after shearing. The idle time (tidle) is the sum of the handling time (thandling) and
the shearing time (calculated above as tshearing, equation 1), see Figure MR2.5. For
shearing machines, the handling times are the air time of approach and retraction after
shearing. We can calculate the handling times and energy as follows.
Idle energy = [ timehandling + timeshearing]* Pidle
(6)
During the shearing process, the tool is considered to be at an offset of 6 times the
thickness above the work piece and so the approach distance is 6T. We also assume the
overtravel is 6T. Every time while shearing a sheet the blade comes down from a height
of 6T and again retracts back to an offset position after completing the shearing process
with a vertical traverse speed (VTR). The approach and overtravel distance used here is
10
12 times the thickness of the sheet and so the shearing approach and overtravel time is
12*T/ V. While the retraction time may be longer than the shearing time, this is estimated
as the sum of the approach, overtravel, and shearing times. We use the machine retract
rate (mm/sec) and the approach and overtravel distances to establish the handling time. In
the handling time, the feeding time is also be added for continuous processes, but this
uplci is for the more common batch loading. From Figure MR2.6
Approach distance mm(in) = A
Overtravel distance mm(in) = O
Retract rate mm/sec (in/sec) = R
Feeding time = W/F for next cut
Time for handling is
Approach + Overtravel + retraction times = timehandling
(7)
AO
Approach and overtravel time =
= 12*T/ V
V
T  AO
Retract time =
= 13*T/ VTR
VTR
The shearing time was previously calculated and is not included in the handling time.
timeidle = thandling + tshearing
(8)
From these calculations the idle energy for shearing with a single shear cut is
E (Joule/shear) = (tapproach/overtravel + tretraction) + tshearing]* Pidle
(9)
The average idle power Pidle of automated CNC shearing machines is between
400 and 10,000 watt*. (* This information is from the CNC manufacturing companies,
see Appendix 1). Approximately Handling time will vary from 0.1 to 10 min.
Basic Energy
The basic energy of a shearing machine is the demand under running conditions
in “stand-by mode”. Energy-consuming peripheral equipment included in basic energy
are M1, M2 and PC from Table MR2.1. There is no relative movement between the tool
and the work-piece, but all components that accomplish the readiness for operation (e.g.
machine control unit (MCU), unloaded motors, servo motors, pumps) are still running at
no load power consumption. Most of the automated CNC shearing machines are not
switched off when not shearing and have a constant basic power. The average basic
power Pbasic of automated CNC machines is between 400 and 6,000 watt* (* From CNC
shearing machine manufacturing companies the basic power ranges from 1/8th to 1/4th of
the maximum machine power, see Manufacturers Reference Data in Appendix). The
largest consumer is the hydraulic power unit.
Ostwald, 1986 has shown that the time to load a blank or part into a machine and
then remove the part is proportional to the perimeter of the rectangle which surrounds the
part. This time can be given by t = 3.8 + 0.11 (L + W) (seconds)
Where L, W = rectangular envelope length and width, cm.
In summary, the unit process life cycle inventory energy use is given by
11
Etotal = Pbasic * (tbasic ) + Pidle * (tidle) + Pshearing * (tshearing)
(10)
This follows the power diagram in Figure MR2.5. With only the following information
the unit process life cycle energy for shearing can be estimated.
1. material of part being manufactured
2. Thickness of the sheet
3. Length of the shear
4. Table MR2.2
B. Method of quantification for mass loss:
For ordinary shearing operations such as straight cutting, coolant oil is not
commonly used. Hydraulic shearing machines use fluid power to do work. In this
machine, high pressure liquid called hydraulic fluid is transmitted throughout the
machine to various hydraulic motors and hydraulic cylinders. In addition to transferring
energy, hydraulic fluid needs to lubricate components, suspend contaminants and metal
filings for transport to the filter, and to function well to several hundred degrees
Fahrenheit. Hydraulic fluid replacement occurs so infrequently that on a per shear or per
1,000 shear basis, this mass loss is neglected.
Lubricant oil is commonly (but not always) used on the metal surface in contact
with the knife. Lubricant is applied along the sheared line and then is some subsequent
processing step, it is removed before a final product is used. In order to link this mass
loss directly to shearing, it is included here. Note the energy or ancillary waste for
lubricant removal (solvent degreasing, rag wipe, etc) would be captured in the uplci of
those processes and only the lubricant mass is assigned to shearing. Lubricant applied and
removed is estimated (Madavan, Wichita State University, 2009, personal
communication) as 5cm width x L (cm) x (2.54/1000) cm thickness x 0.9 g/cm3 = 0.11
g/cm length of shear.
Tool set usage
Tool Life information can be found from the cutting tool manufacturer. For
shearing harder or thicker metals, blades with hardnesses nearer the low end of this range
are used in order to compensate for increased shock loading. Table MR2.3 gives some
typical hardnesses of blades used in ten different plants for cold shearing of specific
ferrous and nonferrous products. Service data on life of shear blades are scarce because
maintenance programs employed in most high-production mills call for removal and
redressing of blades, regardless of condition, during scheduled shutdowns. Available data
report blade life in terms of number of cuts, linear footage (in slitting), tonnage, or time
between redressings. The service data in Table MR2.3 encompass all of these variables.
Hard-faced blades are satisfactory, and in some plants are used exclusively, for hot
shearing. Table MR2.4 summarizes data on blade life in one steel plant where hard-faced
blades are used for most hot shearing operations (ASM International, 2002). With these
12
large number of shear cuts between regrind and even longer between actual replacement
of the shearing blades, the shearing blade as is not included as a waste.
Table MR2.3. Service data for shear blades (ASM International, 2002).
Type of
Shear
Material
Thickness of
material sheared
mm
Blade
steel
Blade
Blade service
Hardness before regrind
HRC
Cold shearing of steel
Sheet metal
Low-carbon steel
5
W2
58-60
30,000 cuts
Sheet metal
Low-carbon steel
5
A2
58-60
55,000 cuts
Sheet metal
Low-carbon steel
5
D2
58-60
100,000 cuts
Bar shear
1025 & 1040 steel
25
W2
58-60
20,000 cuts
Bar shear
1025 & 1040 steel
25
L6
40,000 cuts
Bar shear
1025 & 1040 steel
25
S5
100,000 cuts
Sheet and strip
1010 steel
5
D2
58-60
150,000 cuts
Sheet and strip
Stainless steel
12
D2
58-60
65,000 cuts
Sheet
2 to 5% silicon steel
0.8
D2
58-60
45,000 cuts
Slitter
carbon, silicon and galvanized
0.16-4
D2
58-60
1 week (a)
Slitter
Stainless steel
0.8-1.5
D2
58-60
15,000 ft
Blade 1.5 x 100 x 25 mm
Stainless silicon steel
2-2.5
D2
60-62
2 weeks (b)
steels
Hot shearing of steel
Slab shear
various steels
30,000-40,000
tons
Cold shearing of copper alloys
Sheet
Brass
0.16-5
S1
54-58
5,000 cuts
Slab
Brass
25-60
S1
54-58
25,000 cuts
upto 45
H11
42
15,000 cuts
Hot shearing of copper alloys
Slab
Brass
Hot shearing of aluminum alloys
Automatic flying cutoff shear
Aluminum, alloys
7
H25
43-46
10,000 cuts
75 mm shear
Aluminum, alloys
76-140
H25
43-46
17,000-20,000
Cuts
(a)
Blades were reground weekly, with about 0.025 mm of stock being removed.
(b)
Maximum. Blades usually were changed weekly.
13
Table MR2.4. Life of hard-faced blades for hot shearing of steel in a specific steel mill
(ASM International, 2002).
Steel for blade
Hard facing
Blade life, tons of steel
Type of shear
(a)
body
alloy
sheared
Billet, 300 by 300 mm (12
1030 cast
by 12 in.)
1B new, 2B repair,
29,000
3A ribs
Billet, 250 by 250 mm (10
1030 forged
by 10 in.)
2B
5,800
Billet duplex
1030 cast
None; inserts of
H21 or M2
26,000
Billet
H21
None
3,584
Bloomer, 1 m (40 in.)
1045 plate
1B new, 2B repair
7,680
Bloomer, 1.1 m (44 in.)
1045 plate
1B
87,000
Slab, 900 mm (36 in.)
1045 plate
1B
71,000
Plate
6150 (mod)
None
6,000
Rail, 250 by 250 mm (10
by 10 in.)
1030 cast
1B new, 2B repair,
12,960
3A ribs
Rail
1045 plate
2B
5,400
Billet
1045 plate
2B
10,800
(a) Nominal compositions. Alloy 1B: 0.5 C, 0.9 Si, 4.75 Cr, 1.2 W, 1.4 Mo, rem Fe.
Alloy 2B: 0.75 C, 0. 5 Mn, 0.65 Si, 4 Cr, 1 V, 1.2 W, 8 Mo, rem Fe. Alloy 3A: 3 C, 1 Si,
28 Cr, 4 Mo, rem Fe
Case Study on Shearing process
In this report we analyze the detailed energy consumption calculations in shearing
process. The shearing process is performed on BAILEIGH CNC shearing machine (BP –
5060). The machine specifications are listed below:
Table MR2.5 Machine specification
Specifications
BAILEIGH
Model Number
BP-5060
Max. shearing force, kN
500
Approach Speed, in/sec
3.15
Shearing Speed (V),
0.28
in/sec
Return Speed, in/sec
2.4
Main motor, kW
3.7
Motor 2, kW
0.4
3 Axes motor
0.75
output(X,Y,Z), kW
Total Maximum Power
6kW
consumption
14
Product Details
For this example we are assuming a steel sheet (0.1 Carbon cold worked) as the
work piece. The work piece is of sheet-metal part of 0.25 X 120 X0.8 (T x L x W) in. has
a shear strength of 43,000 psi. The steel chart also tells us for this grade steel the
elongation factor is 38%.
The term “rake” is used to designate the angel of the upper blade and is usually expressed
in inches per foot. A 1/4-inch rake means that the upper blade slopes at a rate of 1/4
inches per foot of length. The objective of the study is to analyze the energy consumption
in shearing machine.
Process Parameters
The shearing conditions and the process parameters are listed in Table MR2.6.
Table MR2.6. Process Parameters for Example Case
Process Conditions
Sheet thickness (T)
0.25 in
Shear strength (S)
43,000 psi
Penetration
38%
Rake, in/ft
0.25
Length, in
120
Width, in
0.8
Feed, F in/sec
0.4
Shearing process
During shearing operation the tool is considered to be at an offset of 1.5 in (6
times the workpiece thickness) above the workpiece. Every time while shearing the blade
comes down from a height of 1.5 in. Similarly we assume the overtravel to be 1.5 in. It
retracts (T+1.5+1.5) in. back to the offset position after completing the shearing process.
Time, Power and Energy calculations for shearing operation
The total processing time can be divided into the 3 sub groups of basic time (Load
and Unload), idle time (Handling), and shearing time.
Shearing time:
The time for shearing is determined by
ts = (T)/V (sec)
Where V is the Shear blade speed in mm/sec, and T is the thickness in mm.
T = 0.25 in
V = 0.28 in/sec
Time to shear will be,
ts = (0.25)/ 0.28
= 0.9 sec/shear
Energy required for each shear,
E = L * Fs
15
The force required for shearing a 0.135 in thick and 120 inch long of a steel sheet (0.1
Carbon cold worked) can be estimated using the following calculation:
 S * P * T 2  P 
1  
Fs  
R
2


Fs = 43,000 * (0.38) * (0.25)2 *12 * (1-0.38/2) = 39,706 lb or 176.62 kN
0.25
Shearing energy for each shear
E = 39,706 * 120 = 47,64,720 inch-lbf or 538.34 kJ
Power required P = Fs * V
= 39,706 * 0.28 = 11,117.68 in-lb/sec or 1.26 kW
Idle Time:
Handling Time:
The air time for shearing is approach, feeding and retracts time
Approach time = 0.7/3.15 = 0.225 sec
Retracts time = 18 + D /60 = 25.5/60 = 0.425 sec
Total air time = 0.65 sec
Total idle time = tshearing + tair
= 0.65+0.9 = 1.55 sec
Idle power from Appendix 1 can be assumed as = 2.5 kW
Idle energy = 2.5 * 1.55 = 3.875 kJ/shear
Basic time:
Loading and unloading time t = 3.8 + 0.11 (L + W)
= 3.8 + 0.11 (304.8 + 2)
= 37.55 sec
Pbasic = 1.25 kW
Ebasic = Pbasic * ttotal
ttotal = tbasic + tidle = 37.55 + 1.55 = 39 sec
Ebasic = 1.25 * 39 = 48.75 kJ
Etotal = 538.34 + 3.875 + 48.75 = 590.96 kJ
Summary:
This report presented the models, approaches, and measures used to represent the
environmental life cycle of shearing unit operations referred to as the unit process life
cycle inventory. The four major environmental-based results are energy consumption,
shearing process, lubricant oil, and cutting tool. Calculations for product manufacturing
are presented, based on knowing only the cutting length, number of cutting, and the
material sheared. The life cycle of shearing is based on a typical high production scenario
(on a CNC shearing machine) to reflect industrial manufacturing practices. The energy
can be calculated from a basic list of variables, likely to be known for each part to be
brake formed
1. material of part being sheared and Table MR2.2
2. thickness of the material
3. length of the sheet to be sheared
4. Shearing speed, using representative manufacturers’ values
16
References Cited
1. Abele, E.; Anderl, R.; and Birkhofer, H. (2005) Environmentally-friendly product
development, Springer-Verlag London Limited.
2. ASM International. (2006) Metalworking: Sheet Forming Hand book, Vol. 14B,
American Society of material.
3. Clarens, A.; Zimmerman, J.; Keoleian, G.; and Skerlos, S. (2008) Comparison of
Life Cycle Emissions and Energy Consumption for Environmentally adapted
Metalworking Fluid Systems, Environmental Science Technology,
10.1021/es800791z.
4. Erik Oberg. (2000) Machinery’s Handbook, 26th Edition, Industrial Press.
5. George, F.S; and Ahmad, K. E. (2000) Manufacturing Processes & Materials, 4th
Edition, Society of Manufacturing Engineers.
6. Groover, M.P. (2003) Fundamentals of Modern Manufacturing, Prentice Hall.
7. Kalpakjian, S.; and Schmid, S. (2008) Manufacturing Processes for Engineering
Materials, 5th Edition, Prentice Hall.
8. Piacitelli, W.; Sieber, et. al. (2000) Metalworking fluid exposures in small
machine shops: an overview, AIHAJ, 62:356-370.
9. Phillip Ostwald. (1991) Engineering cost estimating, 3rd Edition, Prentice Hall.
10. Schuler GmbH. (1998) Metal forming Handbook, 1st Edition, Springer.
11. Todd, R.; Allen, D.; and Alting, L. (1994) Manufacturing processes reference
guide, Industrial Press, New York.
12. Tschatsch, Heinz. (2006) Metal forming practice: Processes-machines-tools,
Springer.
13. Wlaschitz, P. and W. Hoflinger. (2007) A new measuring method to detect the
emissions of metal working fluid mist, Journal for Hazardous Materials,
144:736-741.
Appendices
Manufacturers Reference Data
The methodology that has been followed for collecting technical information
on CNC machines has been largely based in the following:
The documentation of the CNC shearing machine and the technical
assistances collected from the manufacturing companies through internet. The
shearing machines are brakeforming machines with a change in the moving tool and
so the same machine data as brakeforming is included here. Several interviews with
the service personnel of the different CNC manufacturing companies have been
carried out. After collecting the information from the different companies it has been
put together in the relevant document that describes the different approaches the
different companies have regarding the technical information on the CNC shearing
machine. Telephone conversations allowed us to learn more about basic power and
idle power. Companies that involved in our telephone conversations are Baileigh,
Ronmack, Trumpf, and Cincinnati. These companies manufacture different sizes of
17
CNC machines, but this report shows the lower, mid and highest level of sizes. For
our case study we picked machine at the highest-level.
Specifications
Model Number
Shearing force, kN
Approach Speed,
mm/sec
Shearing Speed, mm/sec
Return Speed, mm/sec
Main motor, kW
Motor 2, kW
3 Axes motor
output(X,Y,Z), kW
Specifications
Model Number
Shearing force, kN
Approach Speed,
mm/sec
Shearing Speed, mm/sec
Return Speed, mm/sec
Main motor, kW
Motor 2, kW
3 Axes motor
output(X,Y,Z), kW
Specifications
Model Number
Shearing force, kN
Approach Speed,
mm/sec
Shearing Speed, mm/sec
Return Speed, mm/sec
Main motor, kW
Motor 2, kW
3 Axes motor
output(X,Y,Z), kW
Specifications
Model Number
BP-3360
330
80
7
60
2.2
0.4
0.75
RM-2050
600
120
9
100
5.5
1
1
TB V-50
560
150
12
120
6
1
1
90MX6
BAILEIGH
BP-5060
500
80
7
60
3.7
0.4
0.75
RONMACK
RM-3100
1500
120
9
80
11
1
1
TRUMPF
TB V-130
1440
150
12
120
18
1
1
CINCINNATI
175MX10
BP-9078
900
80
7
60
7.4
0.4
0.75
RM-8000
5000
120
9
80
37
1
1
TB V-320
3570
150
12
120
35
1
1
350MX12
18
Shearing force, kN
Approach Speed,
mm/sec
Shearing Speed, mm/sec
Return Speed, mm/sec
Main motor, kW
Motor 2, kW
3 Axes motor
output(X,Y,Z), kW
500
300
1200
275
4000
250
30
200
15
2
1
25
180
20
2
1
20
150
25
2
1
19