Gang Saw Gang
Mohammad Jeelani
Richard Thrift
Barton Pate
Michael Knoblett
Jeremy Patterson
Mark Herndon
Justin Owens
Joseph Perry
Mike Hudgens
Problem
To design a reliable machine to cut various sizes
of scrap wood into survey stakes of specific
dimension
To reduce labor
To maximize production
Constraints
$1500 Budget
10 x 10 square ft. area
Compatibility with Indexer Design
Size of lumber
Gang Saw Layout
Input
conveyor with board
alignment device
Gang Saw Assembly
Exit Slide
Saw Blade and Power Rollers
Blades
Adjustable for 1
or Cut
1 Stakes for up to 12
Board Width
Stakes for up to 6
Board Width
Minimum Board Length
12
Feed Rollers
Spring
Loaded Free
Spinning Top Rollers
Powered Knurled Bottom
Rollers
Powered Exit Roller
Circular Saw vs. Band Saw
Low
cost of equipment
Low cost of maintaining
them
Low cost of saws
High
initial cost
High cost of saws
More susceptible to
damage from hard
materials embedded in
wood
Blade Constraints
According
to Rip Saw Applications,we needed to
meet a rim speed of 9000.
Kerf for carbide tips-.15
Teeth must clear wood
8 inch blade for cutting 12 in. long pieces
Larger the blade, the more maintenance
Standard Blades
Cheap
Will
not last long
Blade tips break easy
Diamond Tip Blades
Mostly
used for cutting steel.
Diamond is very hard, but edge is not as sharp.
Higher cost
Extremely fragile
There is a need for an increase of 15 to 30% in power
consumption because of the increase in cutting
pressure.
Not using the right power,you can run into problems
like:
a. Premature edge wear
b. chipped or broken teeth
Carbide Tip Blades
Powder-like
material in its raw state.
It is shaped by compressing it at high temperatures.
Increasing the content of carbide, wear resistance
increases but resistance to shock decreases.
Harder and more resistant to corrosion.
Much cheaper
Lasts 20 times as long as the standard blade
Saw Calculations (8 in.)
R.P.M. = 3.8197 (Rim Speed)
Saw Diameter
= 3.8197 (9000 ft/m)
8 inches
=
4297.16
Tooth Bite = Feed Rate (12)
RPM (Teeth)
= 16 ft/m(12)
4297.16(8)
=.0055
Arbor RPM = 12 (Rim Speed)
Saw Diameter(3.14)
=12 (9000)
8 in.(3.14)
=4299.36
Circumference =3.1416 (Diameter)
=3.1416 (8 in.)
=25.13
HP per saw =D of C(Kerf)(FPM)(Factor)
144
= 1.5(.15)(16ft/m)(45)
144
=1.125
Total HP= 1.125(7)
=7.875
Saw Calculations (10 in.)
R.P.M. = 3.8197 (Rim Speed)
Saw Diameter
= 3.8197 (9000 ft/m)
10 inches
=
3437.73
Tooth Bite = Feed Rate (12)
RPM (Teeth)
= 16 ft/m(12)
3437.73(10)
=.0055
Arbor RPM = 12 (Rim Speed)
Saw Diameter(3.14)
=12 (9000)
10 in.(3.14)
=3439.49
Circumference =3.1416 (Diameter)
=3.1416 (10 in.)
=31.416
HP per saw =D of C(Kerf)(FPM)(Factor)
144
= 1.5(.15)(16ft/m)(45)
144
=1.125
Total HP= 1.125(7)
=7.875
8 inch Carbide Tip w/8 teeth
Cost,
most suitable for
woodworking
12 inch boards would jam
machine
8 teeth to carry load out of
cut
Shaft Design
Bending
and Torsion
1045 Steel-industry recommended
Torque on shaft from motor
Calculated value of
0.632
inch diameter shaft
Shaft Design Contd
Industry
experts recommend a diameter of 1
15/16 Inches
Compare with calculated value
inch shaft selected based on calculations and
bearing availability
Shaft Selection
Keyed vs. Splined
Keyed
Catalog
item
1045 Shafts Available
Supplier
Cheap if purchased
Easier to machine
Easy to replace
Splined
Not
catalog item
Expensive to purchase
Difficult to machine
Long wait if shaft fails
Shaft Prices
Keyed
3/4
inch diameter
24 inch length
Keyway dim. of 3/16 IN.X
3/32 in.
$ 30.00
Splined
Have to be custom made
Finding machinist
Custom job more
expensive
Bearing Selection
Self
aligning for deflection
Eccentric lock for one direction of rotation
Load and rpm rating
Supplier
$30.00 per bearing
Cost of two - $60.00
Major Motor Constraints
Single
Phase Motor
Maximum 15 hp Motor
Advantages of the 15 hp motor
15
hp motor results in a feed rate of 30 ft/min
2.1
hp = (45)(.15in)X(1.5in)
144
= 30 ft/min
7 blades x 2.1 hp = 15 hp
Disadvantages of the 15 hp motor
TEFC
motor unavailable
The Cost of a 15 hp motor is $800
Eliminates the fast feed rate of 30 ft/min
This eliminates the possibility of a 15 hp
Advantages of 2 x 5 hp motors
Efficient according to hp calculations
Hp per saw = 1.5(.15)(16)(45)
144
= 1.13 hp
7 blades x 1.13 hp = 8 hp
2 x 5 hp motors are equal to 1 x 10 hp motor
Disadvantages of 2 x 5 hp motors
The
Cost of 2 x 5 hp motors is $974
Hassle as far as one of the motors failing
Motors have to be coupled together
More space required for the two motors
Advantages of 1 x 10 hp motor
The
Cost is only $650
The motor is the most efficient according to hp
calculations
Hp
per saw = (1.5)(.15)(16)(45)
144
= 1.13 hp
7 blades x 1.13 hp = 8 hp
1
motor is less hassle as coupling and failure are
concerned
A TEFC motor is available in a 10 hp electric motor.
Feeder System
Gravity
Belt
Conveyor
& Chain Conveyor
Power
Feeder
Overhead
Conveyor
Machined
Power Conveyor
Feeder Considerations
Cost
Analysis
Final Decision
Alignment Mechanism
Outlet
Ramp
Feed Rollers
Rough
knurled surface to
grip the surface of the
wood as it is being
pushed through the saw
blades
Chrome coated to prevent
wear
Mounted just before and
after saw blades
Driven by sprocket
connected to gearbox
Smooth
roller will be
mounted directly above
each of the rough rollers
2 inch diameter roller
Does not need coating
Spring loaded allowing it
to be forced up by the
board
Feed Roller Power Supply
Torque
= Force X Radius
Torque = 140 lb X 0.0833 ft = 11.6 lb-ft
Horsepower = (Torque X rpm)/5252
hp = (11.6 lb-ft X 30 rpm)/5252= 0.066 hp
0.066 hp to force board through saw blades
Power supplied from a gearbox connected to
main motor
Feed Rate = 16 ft/min or 30 rpm
Cost of Purchased Rollers
Rough surface
Smooth surface
$100-$150
$50-$100
At least 4 rollers needed 2 smooth, 2 rough
Total - $300-$500
Cost of Chain Feed System
14
inch wide chain made from cast steel with
race guide - $2500
Must have a forced lubricating system which will
cost extra
Must have more horsepower to run
Cost to Fabricate Rollers
1
stick of cold roll steel
20 feet long
2 inches in diameter
$100 or $5 per foot
$75-$100 for chrome coating
Time
Blade Spacing Mechanism
Requirements of Spacing
Mechanism
Adjustment
of blade spacing: 3/4 - 1.5
Ease of operation
Short changeover time (< 5 min)
Reliability
Low maintenance
Low cost
Alternatives
Babbitt
Guide System
Set Collars
Dual Arbors
Compression Springs between blades
Pneumatic
Actuation
Rack and Pinion (Human Powered)
Babbitt Guide System
Consideration of Babbitt Guide
System
Advantages
Proven
Technology
Simple adjustment of
Blade Spacing
Disadvantages
Babbitt
guides must be
periodically re-poured.
Cost Exceeds Budget
Not available in 3/4
spacing
Consideration of Set Collars
Advantages:
Simple
Inexpensive
Reliable
Low
maintenance
Disadvantages
Difficult
and time
consuming to adjust
Consideration of Dual Arbors
Advantages:
No
blade adjustment
necessary.
Relatively simple to switch
from 1.5 to 3/4 blade
spacing(2nd arbor
pneumatically actuated)
Disadvantages
Horsepower
doubled - 2
motors required
15 Blades required
Additional shaft and
bearings required
Pneumatic Cylinder and
Control Valves required
Increase in cost = $1360
Compression Springs with
Pneumatic Actuation
Advantages:
Blade
adjustment simple
and quick.
Disadvantages:
2
pneumatic cylinders and
control valve required
($150)
Latching mechanism still
required
Compression Springs with Rack
and Pinion
Advantages:
Rack
and Pinion-Proven
technology
Simple to adjust blade
spacing
Low maintenance
Inexpensive to machine.
Disadvantages:
Expensive
if purchased
Compression Springs with Rack
and Pinion
Compression Springs with Rack
and Pinion
Spring Calculation
F
F
Spring Rate(k) = 111 lb/in
Blade Spacing
1.5"
3/4"
Compressed Length
1.25"
.5"
Free length = 2 in
Delta L
.75"
1.5"
Force(K*Delta)
83.25 lb
166.5 lb
Calculation of Crank Force
Pinion
Rack
F
Crank Arm (L)
Handle
At Full Spring Compression F = 166.5 lb
Torque(pinion) = F*r
Crank Force = Torque/L= F*r/L
For r=1 and L = 8 :
Crank Force = 18.5 lb
Cost Analysis
Part
Purchased or Machined(P/M) Cost Per Unit($)
8" Blade
5/8" Shaft
pillow block bearings
Shaft Bearings
Rack
2" Pinion
Crank Arm
Compression Springs
10 hp Electric Motor
Drive Pulleys
Drive Belts
Feed Rollers
Frame Steel
P
P
P
P
M
P
M
P
P
P
P
M
M
Total Units
60
50
18.61
30
5
9.64
5
2
650
9
10
5
75
Cost($)
7
1
10
2
2
2
1
6
1
7
5
5
1
Total Cost
420
50
186.1
60
10
19.28
5
12
650
63
50
25
75
1625.38
OSHA Regulations
Guards
All
belts, pulleys, gears, shafts, and moving parts shall
be guarded
Feed Rolls and saws shall be covered with an exhaust
hood or with a guard that shall be so arranged as to
prevent accidental contact with the rolls or saws
Shafting under bench machines shall be enclosed by a
stationary casing or trough
Belts where both runs of the belt are 42 inches or less
from the floor shall be fully enclosed
Power
The
saw shall be provided with a disconnect switch that
can be turned off, locked out, and tagged out in the off
position while repairs or adjustments are being made
A mechanical or electrical power control shall be
provided on each machine to make it possible for the
operator to cut off the power from each machine without
leaving his position at the point of operation
Power
Provision
shall be made to prevent machines
from automatically restarting upon restoration of
power
Power controls and operating controls should be
located within easy reach of the operator while he
is at his regular work location, making it
unnecessary for him to reach over the cutter to
make adjustments
Maintenance
Dull
or badly set saws shall be removed from
service, before they begin to cause the material
to stick, jam, or kick back when it is fed to the saw
Saws to which gum has adhered on the sides
shall be immediately cleaned
Bearings shall be kept free from lost motion and
well lubricated
Maintenance
Arbors
of all circular saws shall be free from play
Pulleys with cracks, or pieces broken out of rims,
shall not be used
All power transmission equipment shall be
inspected at intervals not exceeding 60 days and
be kept in good working condition at all times
Questions?
