Roll Grinding Application

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precisionrollgrinders.com

Over 50 years of value-added service

Roll Grinding Application EngineeringPrecision Delivering Profitability

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


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


GROUND IN BEARINGS PRECISION GROUND ROLL

Roll Roundness Matters

OEM Specification on calender rolls = 0.0002”BARRING MUST BE REMOVED ENTIRELY


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)


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


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


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.


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.


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


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


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


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)


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.


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


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


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


adjusting to our new “virtual” partnership


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

precisionrollgrinders.comprecisionrollgrinders.com

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


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


Over 50 years of value-added service

thank you for your time.

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Roll Grinding Application

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