Checkweigher Design
Concept
All-Fill Inc.
Dan MacGuigan, Matt Griffith,
Phil Mitchell, Richard Maurer
Introduction of Project
• Weighs Products
• Rejects out-of-spec Products
• Quality Control
•Up to 200 products/min.
Improvement Objectives
(Wants)

Decrease Cost



Material
Manufacturing/Machining
Time
Assembly Time



Fewer Parts
Fewer Required Tools
Increase Marketability

Easier Maintenance

“Tool-less” Belt Changes



Drive Belt
Conveyor Belt
Faster Order Turnaround
Design Constraints

Safety
Protection From Moving Parts
 Design Against Catastrophic Failure


Weight


Footprint


Cannot Increase Overall Weight
Cannot Change Current Footprint
Life

Service Life Cannot Decrease
Improvement Metrics
Metric
Material Cost
Current
Target
Achieved
$290/$740 $230/$590 $220/$184
Manufacturing Time
18.5 hrs
14 hrs
10 hrs
Assembly Time
17 min
14 min
14 min
Number of Parts
86/208
75/100
80/99
1
2
2
3
0
0
# of Rollers
# of Tools Required
for Belt Change
How to Meet Wants
 Divide
Checkweigher into Subsystems
 Each Subsystem Offers Benefits
 Some Subsystems Interrelated
 Compounded Improvements
Identification of Subsystems




Motor Mount
Roller Attachment
Knife-Edge
Sidebars & Tie Bars
Current Design
Motor Mount

Wants
 Lower Cost (Benefits Sponsor)




Fewer Small Parts (Nuts, Washers, etc.)
Less Costly Manufacturing
Faster Assembly
Increase Marketability (Benefits Customer)


Easy Tensioning of Timing Belt
“Tool-less” / Fast Belt Change
Metric
Curren Target
t
Time to Change Belt
7.3 min
5 min
3.3 min
2 min
1 min
0.5 min
# of Tools to Change Belt
3
0
0
Number of Parts
6
5
4
Time to Properly Tension belt
Achieved
Motor Mount - Current
Motor Mount - New
Thumb Screw

Wants

Lower Cost (Benefits Sponsor)


Roller Integration
Lower Manufacturing Cost
Increased Marketability (Benefits
Customer)


“Tool-less” Belt Change
More Versatile
Metric
Curren Target Achieved
t
Time to Assemble
17 min
13 min
14 min
# of Rollers Types
1
2
2
# of Tools to Change
Belt
3
0
0
Roller Integration – Current
Roller Attachment
Current Attachment
Points of Rollers Points
Roller Integration – New
End Caps
Drive End Cap
Knife-Edge End Cap
Conventional Idler End Cap
End Cap Integration
Snap Ring and Pliers
Concept Roller
Attachment Points
Cotter Pin
Knife-Edge

Wants

Lower Cost (Benefits Sponsor)



Lower Cost
Simpler
Increased Marketability (Benefits
Customer)



Less Vibration
Less Belt Wear
Shorter Transition Distance
Metric
Curren Target Achieved
t
Time to Manufacture
7 hr
5 hr
3.7 hr
Material Cost
$740
$590
$184
# of Parts
208
100
99
Knife-Edge - Current
Nylon Spacer
Bearing

Problems
Many Small Parts
 Expensive
 Difficult to Assemble

Knife-Edge - New

Material – PTFE (Teflon®)




Low Coefficient of Friction
High Melting Temperature
Inexpensive
Few Parts
Sidebars & Tie Bars

Wants

Lower Cost (Benefits Sponsor)




Lower Material Cost
Shorter Manufacturing Time
End Cap Integration
Increased Marketability (Benefits
Customer)


FDA Approved
Lighter
Metric
Material Cost (per pair)
Mass/Length
FDA Approved
Current
Target
Achieved
$20
$10
$6
0.05 lbm/in 0.03 lbm/in 0.03 lbm/in
Yes
Yes
Available
Sidebars - New

Polycarbonate






Lighter
Less Expensive
Easily Machined
Sufficient Mechanical
Properties
FDA Approved Available
End Cap Integration
Tie Bars - New

Redesigned for Compatibility
with Polycarbonate Sidebars


Single Attachment to Sidebar
Material Change
From Aluminum to
Polycarbonate
 Less Costly
 Lighter

Assembled Prototype
Testing



Weight
Assembly Time
Maintenance Time
Drive Belt Change
 Conveyor Belt Change


Accuracy & Precision

Product Weight Measurements
Weight

Current Weight


New Weight


7lbs 4 ounces
6lbs 3ounces
Current
17.4% Weight Reduction
Prototype
Assembly Time
Current
Current Assembly



Assembly Time
17 Minutes
4 Tools Needed
New Assembly


14 minutes
2 Tools Needed
18
16
14
12
Time (min)

Prototype
10
8
6
4
2
0
Current
Prototype
Design
18% Reduction In Assembly Time
Maintenance Time

Conveyor Belt Change Time Increased



Due to Sidebar Material Change
Introduce Helicoils in Next Prototype
Drive Belt Change Time Decreased





Old Time: 7:30
New Time: 3:30
47% Decrease in Time Required
“Tool-less”
Less Hardware Required
Accuracy and Precision Testing

Sample Products Run on Actual Machine



Three Different Products
Representative of a Range of Weights
Three Conveyor Units Tested



Old Design
Conventional Prototype
Knife-Edge Prototype
Accuracy Results
49
Average Online Mass - Tube in Box
Average Online Mass - Canister
48.5
49
48
47.5
47
48
47.5
Old Design
372
Mass (g)
Mass (g)
48.5
Mass (g)
Offline Mass
374
370
Prototype
368
Knife Edge
366
364
46.5
100
200
Conveyor Speed (fpm)
47
362
100
200
Conveyor Speed (fpm)
46.5
Average Online Mass - Weight in Box
Offline Mass Compared to Data From:
2250
•Old Design
• Prototype of New Design with Knifeedge
Mass (g)
•Prototype of New Design
2240
2230
2220
2210
2200
100
Conveyor Speed (fpm)
Precision Results

At Least 1 New Design Outperformed
Current Checkweigher in Every Test
Overall Benefits

Tool-less Belt Change



Motor Mount
Cotter Pin
Versatile




Lighter



Sidebars
Tie Bars

Less Expensive
Fewer Parts


End Caps
Knife-Edge
Sidebars
Knife-Edge
Motor Mount
Component
Money Saved
Motor Mount
$11
Knife-Edge
$480
Sidebar (2)
$14
Tie Bar (3)
$21
Manufacturing Time $510
TOTAL SAVED:
(60% of Current Checkweigher Cost)
$1036
(~33% of Retail)
Conclusion

Design





Prototyping



Lighter
More Versatile
Easier Maintenance
Less Expensive
Fully Functional Prototype
100% Scale
Testing




18% Assembly Time Reduction
“Tool-Less” Belt Changes
More Accurate
More Precise
Implementation Plan

Provide to All-Fill:
Bill of Materials
 Complete Electronic Drawing Package
 Checkweigher Prototypes



Manufacture Three Complete Improved
Checkweigher Designs
Run Mock Production Line
 Questions
 Acknowledgements
 Nate
Cloud
 Ha Dinh
 Ed
White
 Dave Kendell
 Steve Beard
BoM - Conventional
Conventional Roller
Quantity
Hardware
6
1/4-20x1/2" Hex Socket Bolt
N/A
9
5-40x1/4" Flat Head Screw
Motor Plate
MM1
2
1/4-20x1" Hex Socket Bolt
2
Spacer
MM2
2
1/4-20 Washer
1
Motor Mount
MM3
2
1/4-20 Lock Washer
3
Tie Bar
S1
4
1/4-20 Thumb Wheel
2
Sidebar
S2
2
10-32x1" Hex Bolt
2
Drive End Cap
EC1
4
10-32 Washer
2
Idler End Cap
EC2
1
Idler Roller with Bearings
N/A
4
10-32 Lock Washer
2
10-32x1" Wing Bolt
1
Drive Roller with Bearings
and Sprocket
N/A
2
10-32 Thumb Wheel
2
Roller Shaft
S3
4
10-32x1/2" Hex Socket Bolt
1
Table Top
S4
4
Brass Washer (ID 3/8", OD .75")
1
Drive Belt
N/A
1
Conveyor Belt
N/A
4
Hairpin Cotter Pin (Wire
Diameter = 0.1")
8
1/8"x1" Steel Dowel
Quantity
Part
Drawing Number
1
Motor with Sprocket
1
Sidebar
Right End Cap (Knife-Edge)
Left End Cap (Knife-Edge)
Lateral Support
Knife-Edge Support
End Cap – Drive
End Cap - Idler
Motor Mount
Motor Plate
Spacers
Tie Bars
Table Top
Roller Shaft
Sidebar Deflection
Analysis
Assumptions:
Height = 1.15”
Length (support to support) = 4.5”
Width (plastics) = .5”
Width (Aluminum) = .5”
Package weight = 12 Lb.
Elastic Moduli =
Aluminum - 57,000 ksi
UHMW PE - 100 ksi
Nylon 66 – 200 ksi
Polycarbonate – 392 ksi
Schematic
Sidebar side view
Package
weight
Support from
below
checkweigher
Support from
below
checkweigher
Sidebar Deflection Analysis
.063 in4
IAluminum = .048 in4
Max deflection at center of sidebar:
 Iplastic =


Aluminum .0000084”
 UHMW PE - .0036”
 Nylon 66 .0018”
 Polycarbonate .00092”

Worst Case Scenario
Sidebar Deflection Analysis
Standard loading


Assume 2 equally loaded sidebars
Deflections:
UHMW PE
.0018”
 Nylon 66
.0009”
 Polycarbonate .00046”
 Aluminum
.0000042”


Machining precision is .0005”, greater than
potential deflection of Polycarbonate.
Raw Data – Tube (Slow Speed)
Mass (g)
Scatter in Data
50.0
49.5
49.0
48.5
48.0
47.5
47.0
46.5
Conv. Prototype
Old Design
Knife Edge
Offline Mass
0
10
20
Trial
30
Raw Data – Tube (Fast Speed)
Mass (g)
Scatter in Data
52.0
51.0
50.0
49.0
48.0
47.0
46.0
45.0
44.0
Conv. Prototype
Old Design
Knife Edge
Off Line Mass
0
5
10
15
Trial
20
25
30
Raw Data – Box (Slow Speed)
Scatter in Data
2300.0
Mass (g)
2280.0
Conv. Prototype
2260.0
Old Design
2240.0
Knife Edge
2220.0
Off Line Mass
2200.0
2180.0
0
5
10
15
Trial
20
25
30
Raw Data – Canister (Slow Speed)
Scatter in Data
373.0
Mass (g)
372.0
371.0
Conv. Prototype
370.0
Old Design
369.0
Knife Edge
368.0
Off Line Mass
367.0
366.0
0
5
10
15
Trial
20
25
30
Raw Data – Canister (Fast Speed)
Mass (g)
Scatter in Data
382.0
380.0
378.0
376.0
374.0
372.0
370.0
368.0
366.0
364.0
362.0
360.0
Conv. Prototype
Old Design
Kinfe Edge
Off Line Mass
0
5
10
15
Trial
20
25
30
Suggested Improvements




Introduce helicoils for easier threading
Hole in Motor Mount to allow access to screw
covered by Motor Mount
Screws through Knife-edge end caps into knifeedge lateral support
Consider replacing more aluminum parts with
polymer
Material Cost
Material
Vendor
Height (in.)
Width (in.)
FDA-Approved?
Cost per ft.
Aluminum (anodized)
McMaster-Carr
1.5
0.375
no
$9.07
Aluminum (non-anodized)
McMaster-Carr
1.25
0.375
no
$4.35
Aluminum (non-anodized)
Metals Depot (MetalsDepot.com)
1.25
0.375
no
$2.75
Polycarbonate
McMaster-Carr
1.5
0.5
no
$3.23
Polycarbonate
San Diego Plastics (www.sdplastics.com)
1.5
0.5
yes
$3.00
UHMW Polyethylene
McMaster-Carr
1.5
0.5
yes
$3.16
UHMW Polyethylene
Modern Plastics (www.modernplastics.com)
1.5
0.5
yes
$2.50
Nylon 66
McMaster-Carr
1.5
0.5
yes
$6.30