analysis of stackability of cfb boxes.pptx

7/27/2019 Analysis of Stackability of CFB Boxes.pptx

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Analysis of Stackabilityof CFB Boxes

ByRushikesh S. Aravkar (108PPT02)Narayan Iyer(108PPT08)

Shaikh Fehmida Begum(108PPT27)


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Stage - I

We discussed about :Objectives of project.Theory related to CFB boxes

ManufacturingTypesQuality control parameters and tests

McKees Formula. Theoretical Determination of Stackingstrength of CFB boxes.


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STAGE - II

7 BCT trials were done.Difference between theoretical andpractical values was standardized.RCT index was generated.MS-Excel based kraft paper estimator was developed.

A 3-ply box was designed as analternative for existing 5-ply box.


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Stacking Strength of CFB Box

The compression strength of a CFBbox is a direct measure of its stackingstrength and box performance.

BCT is the measure of the ability of CFB box to take top-down loadsDetermines how much load can be

stacked upon the box without the wallsbuckling


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McKees Equation BCT = 0.6 x ECT x Z x t

Where, BCT = Box Compression in kg,ECT = Edge Compression in kN/m,Z = Box Inside Perimeter in mm,t = Board thickness in mm

Relation between RCT and ECT:

ECT=1.28 x [RCT(L1) + TUF(F) x RCT(F) +RCT(L2)]where, ECT = Edgewise Compression in kN/m

RCT = Ring Crush Test in kN/mRCT in CD is to be considered.TUF = Take-up Factor L1,L2 = Liners;F=Flute


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BCT Trials

Seven trials were performedTo standardize the difference betweentheoretical and practical results was

done.

ReadingNo BCTTheoretical BCTPractical Factor Difference

1 438.39 371.9 15.17

2 387.79 272 29.86

3 344.26 262.6 23.724 344.26 256.4 25.52

5 332.38 238.4 28.28

6 385.54 282.2 26.8

7 402.12 328.6 18.28


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438.39

387.79

344.26 344.26 332.38

385.54402.12

371.9

272 262.6 256.4238.4

282.2

328.6

15.1729.86 23.72 25.52 28.28 26.8 18.28

0

50

100

150

200

250

300

350

400

450

500

1 2 3 4 5 6 7

B C T ( k g s )

Reading No.

BCT : Theoretical v/s Practical

BCT Theoretical

BCT Practical

Factor Difference


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BCT Trials

It was observed that the factor difference varies from about 15% to30%.

So we can standardize this differenceto be 30 % at the max.Significant box to box variation in BCT

valuesPaper properties are variabledepending on the amount and quality

of recycled content used and the


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CFB box is designed with regards toits performance during stacking.

The paper is selected on the basis of BF and GSM.Required BCT is approximately

achieved by altering the GSM BFcombination by trial and error method.But, BF is not directly related to

stacking strength.RCT ECT BCTStacking

(paper) (board) (box)


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RCT Index

Paper suppliers in India do not supplypaper as per the RCT.So an attempt was done to work out

an index which would give theapproximate RCT value of given GSMand BF paper.Variety of papers of differentspecifications in terms of GSM and BFwere tested for RCT.The samples contained papers from

different paper mills.


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RCT Index

It can be seen that RCT of paper of given GSM and BF varies significantlyfor different mills.

It is because of varying source of pulp. Also it is impossible to determine theno. of times the fibres are recycled .Recently some mills like Ruby Maconshave started providing Kraft Paper asper RCT specifications but there is stillinconsistency.


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RCT Index

It gives the range of RCT values for given specification of GSM and BF.

Paper Grade Range (CD) (kgf)

140 GSM 18 BF 9 14140 GSM 20 BF 13 17

150 GSM 20 BF 12 18

150 GSM 22 BF 13 20

150 GSM 24 BF 18 24

180 GSM 20 BF 18 23

180 GSM 24 BF 24 29

200 GSM 28 BF 26 - 32


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9

1312

13

18 18

2426

14

17 1820

24 23

29

32

0

5

10

15

20

25

30

35

140GSM18 BF

140GSM20 BF

150GSM20 BF

150GSM22 BF

150GSM24 BF

180GSM20 BF

180GSM24 BF

200GSM28 BF

R C T C D

( k g

f )

Paper Specifications

RCT Index

Minimum RCTMaximum RCT


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Designing 3-ply Box as anAlternative for 5-ply Box

A 5-ply box is always stronger than a3-ply box of same dimensions andspecifications.But if a stronger paper is used a 3-plybox can provide equal strength as thatof a 5-ply box of same dimensionscost savings and paper savings also.


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Steps

An existing 5-ply box was tested for BCT.New 3-ply box should provide thesame BCT value as that of existing 5-ply.BCT 5-ply = BCT 3-ply => ECT 3-ply => RCT

Thus using McKees Equation, RCT of paper was determined from requiredBCT.

Sample Boxes were prepared from the


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The 3-ply boxes made of 180 GSM24BF was tested for BCT and theresults were found to be matchingvery closely with existing 5-ply box.

BCT trial performed on 3-ply box made of 180GSM24BFReading No. BCT kgs

1 270 2 250 3 274 4 272 5 268

Average 266.8


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Static Load Testing of CFBBox

Compression strength is not equal to stackingstrength.Compression strength (BCT) is a laboratory

value measured under ideal conditions.

Although BCT typically overestimates by four to eight times the real stacking strength indistributionIt provides a starting point for estimatingstacking strength.So to determine the load bearing capacity of the box under actual stacking conditions thenewly designed 3-ply CFB box was tested for static load testing.


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Net weight of Box Contents: 8.5 kgsWeight of an empty box: 1.12 kgs

Gross weight of one box: 9.62 kgsNo. of boxes on the top of bottommostbox: 5 (as desired stack is 6 boxes)Total weight required for the test = 9.62x 5 = 48kgsThe test was conducted from 23 rd Aprilto 30 th April 2012. No deflection was

recorded.The box did not fail for 8 days. Hencewe can conclude that the box haspassed the static load test.


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Kraft Paper Estimator

Predicts the specifications of the KraftPaper, in terms of GSM and BF.This estimator is in the form of anexcel-sheet.It uses McKees formula and RCTindex.


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Inputs to be given: No. of plies and flute construction C-Box Specifications TUF Thickness of the board Weight of contents that the CFB box will

carry Number of boxes on the top of

bottommost box Factor of Safety (3 to 8, generally 5)


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Given the following inputs the estimator calculates

Box perimeter Weight of the box (150GSM paper as areference)BCT = (total load on top of bottommostbox) x( factor of safety)Then increasing this by 30 % as a

standard difference between theoreticaland practical value.This BCT value is used to estimate ECT of the board and RCT of the paper.Depending on the RCT found, the RCTindex is referred to suggest the paper thatis suitable for making the CFB box.


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DEMO


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Conclusions

According to our study we concludethat:

Theoretical BCT values are at the

max. 30% higher as compared to thepractical results.

RCT values vary significantly for paper of different paper mills.

Generated an RCT index.


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Conclusions

Kraft Paper Estimator was developed.

5-ply boxes can be replaced with 3-plyconstruction by using stronger paper.

The 3-ply box designed saves paper by about 40 % and cost is reduced byRs.16/box.


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THANK YOU

analysis of stackability of cfb boxes.pptx

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