Roll Grinding Application
Transcript of Roll Grinding Application
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WEBINAR SERIES
precisionrollgrinders.com
Over 50 years of value-added service
Roll Grinding Application EngineeringPrecision Delivering Profitability
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precisionrollgrinders.comprecisionrollgrinders.com
X
y
slope = m
y=mx+b
y-intercept
bXLS
BEFORE
AFTER
D Joint design of experiment to reduce variation
M Measurement of current process before/after change
A Analyze data with 6s rigor (MiniTab) – confidence levels
I Improve process with change
C Control process = predictive equation
Process variation improvement, roll life = $Analysis (6s) Providing Real Economic Value
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Precision Rolls: What MattersPre-grinds and grinds for proper tolerances and shape
Maintaining the surface and optical properties you need to produce high-quality product
Value-driven results through material savings, product quality and roll life• Reducing Variation
• World-Class Product QualityBEFORE
AFTER
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GROUND IN BEARINGS PRECISION GROUND ROLL
Roll Roundness Matters
OEM Specification on calender rolls = 0.0002”BARRING MUST BE REMOVED ENTIRELY
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Roll Roundness PerformanceThe Reason for 0.0002” OEM Roundness and Surface Finish Specifications
• Machine direction variation or barring
Calender Roll Performance = Caliper Variation Performance • This can also cause strength variation
Tens
ile (k
m)
MD position (mm)
Thic
knes
s (m
icro
met
er)
3.2
3
2.8
2.6
2.4
2.2
2
70
65
60
55
50
45
400 200 400 600 800 1000
Breaking Length Thickness
Caliper variation 0.0002” – 0.0004” = Strength variation of 20%
(FPInnovations Study)
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Roll Shape MattersCentered roll crowns are critical!
+0.00500
+0.00400
+0.00300
+0.00200
+0.00100
+0.00000
-0.00100
-0.00200
-0.00300
-0.00400
Measure in inchCurve zero point: +67.3300 inch
(Diameter)
Before Grind ProfileAfter Grind Profile
Target Crown Profile
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Target Moisture Average
Machine speed is dropped to control streaks to within
moisture variation specification
Reel
Moi
stur
e %
Moisture Profile
6%
Front Middle Back
7%
Actual Moisture Average
Actual Moisture Average after reducing streaks shifts up
Reduced streaks allow for moisture average to increase = increased production
Reel
Moi
stur
e %
Moisture Profile
6%
Front Middle Back
7%
Roll Shape MattersPress Roll Performance = Improved Moisture Variation = Energy Reduction
Moisture streaks = lost productionReduced moisture streaks =
increased production
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Roll Shape Performance Press Roll Performance = Reduced Variation = Run to Target & Speed Up
Reduced Streaks = Higher Moisture = Increased ProductionDescription Variable Amount
Average reel moisture before (%) 6.2Average reel speed before (fpm) 2500
Average production rate before (T/hr) 50.5
Average reel moisture after (%) 7.0Average reel speed after (fpm) 2525
Average production rate after (T/hr) 51.0Increased production per day (tons) 12
Increased revenue per incremental ton $250Increased revenue/year (350 days) = $1,050,000
DON’T DRY UP THE SHEET WHERE IT IS MOST EXPENSIVE (DRYER SECTION) TO COMPENSATE FOR MOISTURE STREAKS IN THE PRESS SECTION.
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Reducing Variation – Roll Concentricity Matters
• Concentricity must be attained to ensure roundness and shape.
• Poor concentricity leads to material losses and shorter roll life.
• Concentricity is often overlooked.
concentricityConcentricity is a tolerance that controls the central axis of the
referenced feature, to datum axis.
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before/after capability comparison for thickness t1 vs thickness t2summary report
50%Reduction in % Out of Spec% Out of spec was reduced by 50% from 98.06% to 48.74%.
Before: Thickness T1 After: Thickness T2• The process standard deviation was reduced significantly (p < 0.05).• The process mean changed significantly (p < 0.05).
Actual (overall) capability is what the customer experiences.Potential (within) capability is what could be achieved if process shifts and drifts were eliminated.
Customer Requirements
Process Characterization
Comments
Was the process standard deviation reduced?
P < 0.001Yes No
0 0.05 0.1 >0.5
Did the process mean change?
P < 0.001Yes No
0 0.05 0.1 >0.5
BEFORE AFTER
Actual (Overall) CapabilityAre the data inside the limits?
Lower Spec Target Upper Spec
0.012 * 0.016
Statistics Before After Change
Mean 0.024614 0.015142 -9.47E-03
StDev(overall) 0.0042289 0.0026244 -1.60E-03
Actual (overall) capability
Pp 0.16 0.25 0.10
Ppk -0.68 0.11 0.79
Z.Bench -2.07 0.03 2.10
% Out of Spec 98.06 48.74 -49.32
PPM (DPMO) 980600 487440 -493159
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Roll Life and Start-UpROLLS THAT START CLOSER TO PERFECTLY ROUND START UP FASTER & RUN LONGER!
Regrind Point
0.0008”
0.0002”
6 Months 12 Months 15 Months
Roll Performance and Savings Over Time
2.5XLONGER
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Roll Performance = strengthReal-World Case Study
Tens
ile (k
m)
MD position (mm)
Thic
knes
s (m
icro
met
er)
3.2
3
2.8
2.6
2.4
2.2
2
70
65
60
55
50
45
400 200 400 600 800 1000
Breaking Length ThicknessSTFI VARIATION IMPROVEMENT OF 54%allowed for bwt reduction of 0.2#/msf
Potential speed increase
Before PRG Calendar Grinds – 3.7After PRG Calendar Grinds – 1.754% improvement led to BWT reduction 35.3# to 35.1# = $500,000/YR
Potential fiber cost reduction
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Calender Roll Performance = Less ScrapReal-World Case StudyImproved spool losses by 250# per reel
• 250# per reel (approx. 12 seconds of run time)
= 1,000 tons per year = $300,000 (This mill also realized $100,000 per year in reduced winder breaks)
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Cost Analysis Driven from 6s AnalysisDESCRIPTION VARIABLE AMOUNT
Grind Cost 1 $20,000.00
Roll Life (months) 1 14.00
Grind Cost 2 $10,000.00
Roll Life (months) 2 6.00
Annual Savings due to Extended Roll Life $2,857.14 Production Hours Lost due to Improperly Ground Roll 2.00
Lost Revenue Per Hour $3,500.00
Total Lost Revenue due to Improperly Ground Roll $7,000.00 Scrap While Running Improperly Ground Roll (pounds) 50.00
Cost per pound $50.00
Total Scrap Cost due to Improperly Ground Roll $2,500.00 Revenue Per Hour at Normal Production Speed $3,500.00
Percent Production Lost due to Degraded Speed 0.10
Hours Run at Degraded Speed 24.00
Revenue Lost Due to Degraded Speed $8,400.00 TOTAL COST OF IMPROPERLY GROUND ROLL $17,900.00
To use this justification tool simply insert the values appropriate for your operation into the green cells. Your projected savings will be automatically calculated and displayed in the lowest cell on the right.
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Roll Life and Start-Up – Mechanical Excellence• Bearing Inspection • Bearing Seat Grinding• Bearing Replacement• Complete Roll Inspection• Complete Rebuilds/
Reconditioning• Dynamic Balance• Dynamic Leak Test• Grinding
• Head Fit Repairs• Journal Repairs• NDT• New Housings• New Journals• New Rolls• Roll Modifications • Vacuum Testing
of Suction Rolls
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Roll Life and Start-Up – Mechanical Excellence
• Thorough inspection of bearings and housings
• Proper assembly of bearings and housings
• Replacing worn or damage bearings and bushings
• Journal repair and replacement
• On-time start-up and profitable production
Precision maintenance is more than just precision grinding
BEFORE AFTER
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Roll Life and Start-Up – Mechanical Excellence
• Temperature control
• Reduce sheet scorching and hot spots
• Prevent “thermal” runout (TIR) due to plugged passage• Can cause machine direction material variation
• Increase production speeds
Uniform roll surface temperature: temperature transfer and roll TIR
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adjusting to our new “virtual” partnership
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What are “Virtual Value-Added” Services?Partnering with your roll service provider to improve your process reducing variation• Data analysis, sampling and testing• Statistical validation of real benefits ($$)• Virtual troubleshooting (pics/video)
Send us your data, samples, pics, video
XLS
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X
y
slope = m
y=mx+b
y-intercept
bXLS
BEFORE
AFTER
• Joint Design of Experiment to reduce variation
• Data analysis on current process
• Implement plan for variation improvement
• Data analysis on improved process – predictive equation
Process variation improvement = $
Promise to provide real economic Value
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adjusting to our new “virtual” partnershipAllentown, Pennsylvania (610) 395-6966
Carrollton, Georgia (770) 830-6323
Lewisport, Kentucky (270) 295-4990
Texarkana, Arkansas (870) 216-4000
ALLENTOWNPennsylvania
LEWISPORTKentucky
TEXARKANAArkansas
CARROLLTONGeorgia
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precisionrollgrinders.com
Over 50 years of value-added service
thank you for your time.
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