Cdng nghiep rirng
XAC DINH CHIEU DAI BANG VAN MONO TRONG QUA TRINH BOC GO
Trinh Hien MaiTt-udng Dai hgc Ldm nghiep TOM TAT
Trong san xuat van dan, boc van la cong doan het sue quan trpng d£ tao ra nguyen lieu chu dao ciia day chuySn cong nghe. Chieu dai bang van mong trong san xuat van dan anh hucrng mang tinh quylt dinh &kn hieu suSt su dung ciia nguyen lieu trong qua trinh san xuat va gia thanh cua san pham van dan. Trong bai wik nay, chung toi xin gioi thieu hai cong thuc xac dinh chiSu dai bang van mong qua cac thong s6 duong kinh phoi go, ducmg kinh loi go b6c va chieu day van mong. Sai lech giiia cong thirc tinh toan ly thuylt va cong thiic tuong duong trong xac dinh chiSu dai bang van mong la khong dang kS, dao dong trong khoang tir 0,3 - 2,5% tuy timg truong hpp cu the._ Sai lech lon nhit khi duong kinh phoi go nho va chi6u day van mong lon. Trong pham vi nghien cuu nay, kSt qua sai lech Ian nhdt la 2,5% d6i voi trucmg hpp ducmg kinh khiic go sau khi got tron rat nho (85mm), chiSu day van boc 1,5 mm; va nho nhSt d6i vcri truang hgp dircmg kinh phoi go boc 270 mm, chieu day van boc 0,5 mm, khi do sai lech chua toi 0,3%. Vai kgt qua tinh toan do, tac gia bai bao khuyin nghi Tai hien truong san xudt nen xac dmh chiau dai bang van mong bSng cong thiic tinh tuong duang thong qua chu VI cac duang tron dong tam hoac sii dung dir lieu trong bang tra sin khi bilt dupc kicii thuoc phoi go boc va chieu day van mong.
Tu- khoa: Chieu dai bang van mong, cong thirc tinh tirmig duong, san xuSt van boc.
1. DAT VAN DE
Van boc la nguyen lieu chinh trong cong nghe san xuat van dan. Van boc la san pham ciia qua trinh san xuat dac biet ma phoi cua qua trinh gia cong (boc go) la san pham (Pham Van Chuong va Nguyen Hiru Quang, 2004). Chieu dai ciia bang van mdng trong qua trinh boc go la tong chieu dai phoi va bang chieu dai qui dao ciia dao tren phoi. Khi xac dinh chieu dai bang van mong trong nghien cuu ve dac diem ciia mgt so ioai go rimg trong trong san xuat van hoc o Viet Nam, tac gia Trinh Hien Mai va Adam Redman da dua quan diem tuong dong voi nhan djnh ciia nhieu nha khoa hoc khac, do la chieu dai bang van mong phu thuoc vao ducmg kinh phoi go, duong kinh loi boc va chieu day phoi (Trinh Hien Mai va Adam Redman, 2018). Hay noi mgt each don gian thi chieu dai bang van mong trong cong nghe san xuat van mong chinh la chieu dai ciia van boc san xuat dugc trong qua trinh boc go bang may boc. Trong cong nghiep san xuat van hoc 6 Viet Nam hien nay, hau het cac co so san xuat van hoc deu thuc hien buoc gia cong got tron phoi (bang may boc khong chau hoac may boc CO chau) boi cong doan dpc lap, san pham phoi go da qua got tron duoc de mgt khu neng biet va tai day, chung ta co the thong ke, tinh toan sail lugng van boc, nang suat ciia qua trinh san xuat...
Viec tinh toan chieu dai bang van mong trong qua trinh boc van se cho bi^t cu th^ hieu
suat sii dung cua nguyen lieu trong cong nghe san xuat. Tir do c6 co so de lap ke hoach va xac dinh dugic gia mua nguyen heu ciing nhu hach toan gia thanh cho san pham cuoi cimg CLia cong nghe. Viec tinh toan chieu dai bang van mong theo cong thirc ly thuyet ctia cac tac gia Pham Van Chuang va Nguyen Hiru Quang (2004) hay ciia WiUam va cgng su (2017) c6 tinh ly luan cao va iing dung tot trong dieu kien tieu chuan, trinh dp cong nghe san xuat dat muc dp cao va nguyen lieu dau vao (go tron) tuong doi dong nhat. Trong thuc te, san xuat van boc o hau het cac vimg nguyen lieu ciia cac tinh mien Bac Viet Nam dang sir dung may boc khong chau. Tiic la, truoc khi go dupc boc thanh van mong thi khiic go tron da qua cong doan gpt tron tren may boc co chau (doi voi go CO dudng kinh Ion hoac co do cong idn) hoac tren may boc khong chau (doi vdi khiic go d dieu kien binh thudng). Do vay, cimg vdi dieu kien cong nghe dac thii hien co, viec tinh toan chieu dai bang van mong doi hoi phai tinh toan nhanh ngay tai hien trudng san xuat, chinh vi vay neu ap dung each tinh ly thuyet se gap phai khong it kho khan. Trong bai viet nay, chung toi gidi thieu each tinh chieu dai bang van mong khi boc go don gian de phuc vu hieu qua cho cong tac chi dao san xuat. Cach tinh tuong duang, don gian do ciing dam bao dp chinh xac xap xi nhu tinh theo cong thuc ly thuyet.
2. PHUONG PHAP NGHIEN CUU
TAP CHI KHOA HOC VA CONG NGHE LAM NGHIEP S6 3 - 2019 129
Cdng nghiep rimg
- Tinh toan ly thuyet xac dinli chieu dai bang van mong trong qua tritih gia cong van boc theo so do bieu thi su tuong quan ciia qua trinh boc go the hien trong hinh 1 va theo cong thuc tinh toan cua Pham Van Chuong va Nguyen Hiju Quang, 2004 (cong thiic 1) nhu sau:
T/:i^
dx (1)Trong do:
L - Chieu dai bang van mong, mm;
t - Chieu day van mong, mm;
R - Ban kinh hinh tru Idn nhat trong khuc go, mm;
r - Ban kinh loi g6 boc, nun;
X - Ban kinh tai tpa do ta xet, mm.
Khiic go boc
Ru 16 trudc/
—-K* thudc nen
Van boc
Dao boc
. Mo ta quy dao dao cat va hiring cac doi tirong chuydn dong trong qua trinh hoc go - Trien khai cong thiic tinh toan theo ly thuyet
cua Vu-gdt-xki (1968) doi vdi mo hinh tinh toan
ly thuyet, chieu dai bang van mong bang quy dao ciia dao tren hinh tru phoi go.
Hinli 2. Mo hinh tinh toan tu'ong du-oTig (tinh theo chu vi cac vong tron d6ng tam) - Thuc nghiem- Xac djnh chieu dai bang
van mong bang phuong trinh tinh toan tuong duong la tinh don gian theo chu vi cac dudng tron dong tam (Hinh 2). Lap bang tra ket qua chieu dai bang van mong theo dudng kinh phoi, dudng kinh loi go boc va chieu day van mdng de cung cap nhanh dir lieu phuc vu cong tac chi dao san xuat
3. KET QUA VA T H A O LUAN
3.1. Tinh toan ly thuyet chieu dai bang van mong
Trien khai tinh chieu dai bang van mong theo cong thuc tinh ly thuyet cua Vu-g6t-xki (1968):
L = 2^ Jll Vx^ - {s/2n)Mx (2) Dat a ^ s/2n
L - 2 - { Vx^ - a^dx s •'rl
Trong do:
L: Chieu dai bang van mong;
s: Chieu day van mong;
n : Ban kinh ngoai;
(3)
TAP CHI KHOA HOC VA CONG NGHE ' "i" NGHIFP sn -i-tMa
Cdng nghiep rim,-,' TJ: Ban kinh loi go sau khi bdc;
x: Ban kinh hic thdi (ban kinh d thdi
diem dang xet).
Trien khai tich phan (3) ta co:
L ^ r V ^
Mx = i [ ( x ' 2 ) - ^ ( l n ( x + V J ^ (4) Trong tich phan xac dinh (4) bieu thiic x -gia ti Vx^ " a^ nam trong gia tri tuyet doi,
ciia X tai cac can vi va ri. Thay cac can ciia tich phan xac dinh bieu thitc co dang nhu sau:
L - '-^[{vl - a^) - ^(In (r, + V ? F ^ )] - ^ [(rf - ^')-j (ln(r2 + V i T = ^ )] (5) Tinh chieu dai van mong boc theo dudng ngoai hinh tru cua khiic g6 b6c (D|) va dudng kinh khiic go va chieu day van mong theo cong kinh loi go boc (D2) trong trudng hpp sir dung thiic (5). Ket qua tinh toan ly thuyet chieu dai phuong phap boc khong true chiu ghi trong bang van mong doi vdi cac cap dudng kinh bang 1.
Bang 1. Chieu dai bang van mdng tinh theo cong thirc ly thuygt (5)
Dircmg kinh ngoai.
Dl (mm) 270 180 130 140 90 150 130 80 90 95 190 130 85 170 120
Dirtmg l<inh loi go boc, D; (mm)
35 35 35 35 35 35 35 35 35 35 35 35 35 35 35
Cliieu day van mong, s ( m m )
0.5 0,5 0,5 0,5 0,5 1,0 1,0 1,0 1,0 1,0 1,5 1,5 1,5 1,5 1,5
0,007957
^
0,007957 0,007957 0,007957 0,007957 0,159155 0,159155 0,159155 0,159155 0,159155 0,238732 0,238732 0,238732 0,238732 0,238732
Cliieu dai bang van mong, L ( m )
112,587 48,970 24,622 28,863 10,799 16,709 12,311 4,064 5,400 6,126 18,260 8,207 3,141 14,490 6,898
3.2. Tinh chieu dai bang van mong theo each tinh tiroTig dircmg
Trong thuc te san xuat, viec sir dung cong thiic tich phan (2) hoac cong thiic trien khai (5) de tinh toan chieu dai van boc la kh6 thyc hien hoac tinh kha thi va tinh img dung khong cao.
Hau het cac co sd san xuat van boc da dugc chuyen mon hoa mirc do cao, khau boc van mong dupc thuc hien tir cac khiic go da dupc ggt tron qua may chuyen diing co true chau (Hinh 3) hoac khong true chau (Hinh 4), trong
nhieu trudng hpp sir dung may boc khong chau de boc lai nhung loi go boc (dudng kinh loi go khoang 70 - 150 mm) tir may boc c6 true chau.
Do vay, chiing toi de xuat phuong phap tinh toan chieu dai bang van mong tuong duong, gan diing bang each coi quy dao cua dao cat (chinh bang chieu dai bang van mong) bang tong chu vi cac dudng tron dong tam each nhau lien tiep co dudng kinh ldn han nhau diing bang chieu day van mong.
Hinh 3. True chau va may hoc van mong eo true chau
TAP CHI KHOA HOC VA CONG NGHE LAM NGHIEP SO 3 - 2019 131
Cdng nghiep rirng
Hinh 4. Boc van mong bang may Theo phuang phap tinh toan tuong duong nay, neu ggi dudng kinh khuc go da gpt tron la d, duong kinh loi go sau boc van mong la du chieu day van mong la s, ta co:
+ So vong tron dong tam c6 chieu day s la:
n - ( r - r , ) / s (6) + Chu vi vong tron ldn nhat co dudng kinh d, ban kinh r la: nd (hoac 2 TIT )
+ Chu vi vong tron nho nhat cua van mong boc dupc CO dudng kinh do, ban kinh ro la:
27i(r„ + s) ^
Gpi chu vi cua vong tron dau tien nho nhat cua van mong boc dupc sat vdi loi boc c6 dudng kinh d| la Li:
Ll = jrd| = 27r(ro + s) hay L|/27r ^ ro + Is L2 = 7ud2 ^ 27t(ro + 2s) hay L2/27r =^ ro + 2s L3 = 7rd3 = 2:i(ro + 3s) hay L^/ln = ro + 3s L4 = 7ud4 ^ 27r(ro + 4s) hay LA/ITZ = ro + 4 S L5 ^ Tidi ^ 27i(ro + 5s) hay L5/27r = ro + 5s
khdng true chau va bang van mong
Hay la:
Vln = ^ (Ll + L2 + L3 + L4+ Ls + ... + U ) LI2n = ro + Is + ro + rs + ro + 3s + ro + 4s +
ro + 5s + ... + ro + ns (7) Trucmg hgp n la so nguyen chan:
L/27r = nro + s (1 + 2 + 3 + 4 + 5 + ... + n)
= nro + s [ ^ ( l + n ) ] Truang hgp n la so nguyen le:
L/27r = nro + s [ ^ (1 + n) + {^)]
(8)
Lfl = Tidn = 27r(ro + ns) hay Lii/27r = ro + ns Chieu dai cua bang van mong boc dupe:
Khi d6: V2n - nro + s . [ - (n + 1)] (9) Nhu vay, trong mgi trudng hpp cua n nguyen, L/2Tr deu bang {nro + s [ - (n + 1)]}
Thay vao ta c6:
L = 2 7 r { n r o + s . [ j ( n + l ) ] } (10) Su dung cong thiic (10) tinh chieu dai van mong boc dupc theo cac dudng kinh khiic go trong bang 2.
Bang 2. Chieu dai bang van mong theo cong thii'c tinh toan ttfo^ng duong (10) d,
(mm) I s (mm) Nr„ • n)] L (mm)
270 180 130 140 90 150 130 80 90 95 190 130 85 170 120
35 35 35 35 35 35 35 35 35 35 35 35 35 35 35
0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 5 5 5 5 5 0 0 0 0 0 5 5 5 5 5
4112,500 2537,500 1662,500 1837500 962,500 1006.250 831.250 393,750 481,250 525,000 904,167 554,167 291,667 787,500 495,833
13865,000 5292,500 2280,000 2782500 770,000 1681,875 1151,875 264,750 391,875 465,000 2040,833 775,833 220,833 1552,500 623,333
17977,500 7830,000 3942,500 4620,000 1732,500 2688,125 1983,125 658,125 873,125 990,000 2945,000 1330,000 512,500 2340,000 1119,167
112898,700 49172,400 24758,900 29013,600 10880,100 16881,425 12454,025 4133.025 5483,225 6217,200 18494,600 8352,400 3218,500 14695,200 7028,367
132 TAP CHi KHOA H O C VA C O N G N G H E J A M N G H I E P SO .1 - 2ni<l
Cdng nghiep rimg 3.3. So sanh k^t qua ciia 2 each tinh chigu Trong do:
dai bang van mong v - ty Ie sai lech, %;
De CO the xac dinh su sai lech ket qua tinh L(3) - chieu dai bang van mong tinh theo toan giiia 2 each tinh, ta so sanh chung thong cong thiic (3);
qua ket qua tinh toan ty le % ciia chieu dai van L(io) - chieu dai bang van mong tinh theo mong tir cac cong thiic (3) va (10). cong thirc (10);
Ty le sai lech tinh theo cong thuc: Ket qua xac dinh ty le sai lech th^ hien
= [L(io)-L(3)]/L(3) (10) trong bang 3.
- L(3) |I-'(IOrI'(3|l"-'|3>
Bang 3. So sanh ket qua tinh toan tir cong thirc ly thuyet (3) va cong thiie tinh gan dung (10) (mm) (mm) =* V'"'"J (theo CT3) (theo CTIQ)
150 130 95 90 80 190 170 130 120
35 35 35 35 35 35 35 35 35
1,0 1,0 1,0 1,0 1,0 1,5 1,5 1,5 1,5 1,5
16,709 12,311 6,126 5,400 4,064 18,260 14,490 8,207 6,898 3,141
24,760 0,138 10,880 0,081 12,820 0,171 10,590 0,139 2,293 0,094 6,130 0,080 5,020 0,066 17,280 0,230 15,050 0,210 10,590 0,143 3,250 0,132 5,560 0.079
0,00278 0,00408 0,00509 0,00560 0,00750 0,01023 0,01129 0,01534 0,01481 0,01624 0,01260 0,01449 0,01742 0,01914 0,02515
0,278 0,408 0,509 0,560 0,750 1,023 1,129 1,534 1,481 1,624 1,260 1,449 1,742 1,914 2,515
Tir bang 3 cho thay ty le sai lech ve ket qua dudng kinh loi nho hon loi go de vd d dau tinh toan cua 2 cong thiic la khong dang ke. chau kep va bi cong do luc ep cua chau kep va Dudng kinh khiic go cang nho, chieu day van phan lire doi vdi ludi dao. De co the de dang mong cang tang thi ty le sai lech ve ket qua tinh toan san lugng van boc cung nhu sir dung tinh toan giua 2 cong thirc cang ldn. Neu cac dir lieu van boc cho nhieu chiic nang khac dudng kinh khuc g6 sau khi gpt tron rat nho trong thuc tien san xuat, chung ta co the lap (85inm), chieu day van boc 1,5 mm thi ty le sai bang tinh chieu dai bang van mong boc duoc lech ve ket qua tinh toan giira 2 cong thirc la theo cac chi tieu dau vao la dudng kinh hinh 2,5%. Trong trudng hpp dudng kinh khuc g6 tru ngoai ciia khiic go (da gpt tron), dudng kinh sau khi gpt tron 270 mm, chieu day van boc loi go boc va chieu day van mong theo each 0,5 mm thi ty le sai lech trong tinh toan giua 2 tinh tuong duong. Bang 4 la cac trj so tinh sSn cong thirc chua tdi 0,3%. theo cong thuc gan dung ciia chieu dai bang 3.4. Lap bang tra chieu dai bang van mong van mong theo dudng kinh ngoai da ggt tron, Hien nay, d Viet Nam hau het cac co sd san dudng kinh loi b6c (may boc kieu rulo) va xuat sir dung 2 loai may boc: May boc ru 16 chieu day van mong.
(boc khong true chau) dudng kinh loi g6 boc Bang 5 la chieu dai van mong boc dupe khi thudng b5ng 35 mm (nSu \ky dudng kinh loi boc tren may co chau kep go. Dudng kinh loi boc nho hon chat lugng van mong rat xau va go sau khi boc la 0,15 m. Loi nay co theb6c lai loi boc bi vd); may boc ru 16 con diing de boc tren may boc rulo (kliong chau kep) nhung luu lai loi g6 boc bSng may co ch4u kep dudng y: khi b6c lai, bang van mong bat dau chicu kinh Idn. Boc van b§ng may boc co true ch4u day bang khong tdi chieu day s ciia van. Khi thi dudng kinh ciia loi boc phu thupc vao chiSu ket thiic qua trinh boc, bang van mong lai giam dai khiic go b6c. Khi khiic go b6c co chi8u dai chieu day tir s den 0 va tong cpng 2 dau bang la 2,6 m thi dudng kinh loi go boc thudng tir van mong co chieu day tir 0 den s khoang 40 - 0,12 - 0,15 m, chiSu dai khiic go boc la 1,30 m 60 cm. Viec hao ton van mong nay da xay ra thi dudng kinh loi khoang 0,08 - 0,10 m. NSu khi boc ISn 1 tren may boc co chau kep.
TAP CHI KHOA HOC VA CONG NGHE LAM NGHIEP S 6 3 - 2019 133
Cdng nghiep rimg Bang 4.
Dirong Idnh ngoai phoi go
(mm) 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400
Bang 5 Dirimg kinh ngoai phoi go
(mm) 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400
Chi^u dai ban (tao Dirong kiab loi go boc (mm)
35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35
g van mong theo duo^g kinh go tron van bang may boc ru 16 - khSng true
Chieu da 0,8 mm
8,71 10,79 13,06 1553 18,20 21,06 24,11 27,37 30,82 34,46 38,31 42,35 46,58 51,01 55,64 60,46 65,48 70,70 76,11 81,72 8753 9353 99,73 106.12 112,71 11950 126,48 133,66 141,03 148,60 156,37
d bang van boc (m) 1.2 mm
5,84 7,23 8,75 10,40 12,19 14,10 16.14 18,32 20,62 23,06 25,62 28,32 31,15 34,11 37,20 40,42 43,77 47,26 50,87 54,61 58,49 62,50 66,63 70,90 75,30 79,83 84,49 89,28 94,20 99,25 104,44
va chiiu day van mong chau)
v6i chieu day van 1.5 mm
4,69 5,81 7,03 8,35 9,78 11,31 12,95 14,70 16,54 18,49 20,55 22,71 24,98 27,35 29,82 32,40 35,09 37,88 40,77 43,77 46,87 50,08 53,40 56,81 60,34 63,96 67,69 71,53 75,47 79,52 83,67 . Chigu dai bang van mong theo duofng kinh g6 tron va chieu day
Dutmg kinh ]5i go boc {mm)
150 150 150 150 150 150 150 150 150 150 150 150 ISO 150 150 150
(tao van bang may boc CO true chau Chieu dai bang van boc (m) O.Smm
39,41 44,43 49,64 55,06 60,66 66.47 72,47 78,67 85,06 91.65 98,44 105.42 112,60 119.98 12755 135,31
1.2 mm 26,32 29,68 33,16 36,77 40,52 44.39 48,40 52,53 56,80 61,20 65.73 70,39 75,18 80,10 85,16 90,34
0
khac nhau 2.0 mm
3,55 4,39 5,30 6,30 7,38 853 9,76 11,07 12,46 13,93 15,48 17,10 18,81 20,59 22,45 24,39 26,41 28,50 30,68 32,93 35,26 37,67 40,16 42,73 45,37 48,09 50,90 53,78 56,74 59,78 62,89 van mong voi chieu dav van khac nhau
7,5 mm 21,09 23,78 26,56 29,46 32,46 35,56 38,77 42,08 45,50 49,02 52,65 56,38 60,21 64,16 68,20 72,35
2,0 mm 15,86 17,87 19,97 22,14 24,40 26,73 29,14 31,63 34,19 36,84 39,56 42,37 45,25 48,21 51,24 54,36
Nhdn xet: mong khi boc van bang may boc mlo lan hon - Khi so sanh cac truang hgp ciing duong boc bing may boc co chau kep do phjn 161 g5 kinh phoi g6 boc va cung chieu day van ve con lai sau khi boc ciia may boc rulu co duong chi& dai bang van mong, so lieu tren bang 4 kinh nho hon loi go boc bang may co chau kep.
va bang 5 cho ta thjy: Chilu dai bang van Nhung ty le sai lech chieu dai bang vin mong 134 TAP CHI KHOA HOC VA CONG NGHE • « »'• M'^uirT> s r n . inr n
b6c tren 2 loai may b6c rulo va chau kep doi vdi mpi cap chieu day van gan nhu bang nhau.
Duong kinh g6 cang ldn thi ty le sai lech cua chieu dai bang van mdng boc dugc tren 2 loai may cang giam.
- S6 lieu tinh toan theo cac cong thiic tinh toan ly thuyet (3) hay tinh toan gan dimg tucmg duong (10) deu cho thay: Khi chieu day van mong tang (s tang) thi chieu dai van mong boc dupc se giam; Khi khiic go tron dua vao boc c6 dudng kinh tang thi chieu dai bang van m6ng boc dupc cung tang; Su sai khac ve ket qua giita 2 cong thiic do la khong dang ke, c6 the sir dung cong thiic tinh toan tuong duong (10) ap dung trong thirc te san xuat don gian va thuan tien hon cong thiic tinh toan ly thuyet (3) rat nhieu.
- Co the tinh chieu dai bang van mong cho bat ky khiic g6 b6c nao khi biet dudng kinh ngoai ciia khiic go da gpt tron, dudng kinh cua loi go sau boc va chieu day van mong bang cong thiic dcm gian hoac tra tir bang tinh san (bang 4 va bang 5) cho nhung trudng hgp cu the va dieu kien phii hpp.
4. KET LUAN
- Xac dinh chieu dai bang van mong qua cac thong so dudng kinh phoi go, dudng kinh loi go boc va chieu day van c6 y nghTa thiet thuc trong quy trinh san xuat van boc.
- Ty le sai lech giija cong thiic tinh toan ly thuyet va c6ng thiic tuong duong trong tinh chieu dai bang van mong la kliong dang ke.
Cong nghiep i •iw
dao dgng trong khoang tir 0,3 - 2,5% tiiy timg trudng hgp cu t h i Ty le sai lech ldn nh§t khi dudng kinh phoi go nho ma chi^u day van mong lai cao.
- Viec xac dinh chieu dai bang van mong qua c6ng thiic tinh tucmg duang bang each tinh thong qua chu vi cac dudng tron dong tam la CO the ap dung co hieu qua trong thuc tien, tai hien trudng san xuat.
- Chimg ta co the su dung dir lieu trong bang tra san de nhan duac ket qua tinh chieu day bang van mong khi biet dugc kich thudc phoi g6 boc va chieu day van m6ng th6ng dung neu chgn dudng kinh loi boc la 35 hoac 150 mm.
TAI LIEU THAM KHAO
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DETERMINATION OF VENEER RIBBON LENGTH DURING LOG PEELING PROCESS Trinh Hien Mai
Vietnam National University ofForestiy S U M M A R Y
In the plywood making, log peeling is a very important stage to produce key materia! for the technology process.
Veneer ribbon length in plywood production affects decisively the use efficiency of raw matenal m production technology and the cost of plywood product. In this article, we would like to introduce two formulas to determine the veneer ribbon length through the parameters of rounding billet diameter, core billet diameter and veneer thickness. The difference between the theoncal formula and the equivalent formula m veneer ribbon length calculation is negligible, ranging from 0.3 to 2.5% depending on the specific case. The biggest difference happens as the rounding biilet diameter is small and the veneer thickness is high. In this study, the largest difference is 2 5% in case the rounding billet diameter is very small (85 mm), and the veneer thickness 1.5 mm; and the smallest deviation is less than 0.3% m case the rounding billet is 270 mm in diameter, veneer thickness is 0.5 mm.
With these calculation results, the author recommended: At the production site, it is necessary to determine the length of veneer nbbon by the equivalent calculation formula through the perimeter of concentric circles or using data in the available table when knowing the rounding billet diameter and veneer thickness
Keywords: Equivalence formula, veneer peeling production, veneer ribbon length.
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