‘HID­DEN LOSS FAC­TORS’ IN OVER­HEAD MA­TE­RIAL HAN­DLING SYS­TEM

MIS­MAN­AGE­MENT OF UPS CAN DO MORE HARM

Stitch World - - NEWS -

Over­head ma­te­rial han­dling sys­tem, in sew­ing or pop­u­larly called as Unit Pro­duc­tion Sys­tem (UPS), is a favourite among many gar­ment man­u­fac­tur­ers in Asia. On an av­er­age, cost per sew­ing work­sta­tion can be US $ 1,000 to US $ 4,000 for im­ple­ment­ing over­head ma­te­rial han­dling sys­tem in sew­ing. But it seems cost is no de­ter­rent for many gar­ment man­u­fac­tur­ers. If we ask our­selves why any or­ga­ni­za­tion would like to im­ple­ment over­head ma­te­rial han­dling sys­tem on shopfloor? The an­swers can be man­i­fold – to in­crease pro­duc­tiv­ity, to re­duce op­er­a­tor han­dling time, to re­duce the through­put time (which is a myth), for bet­ter ac­count­abil­ity of WIP, to re­duce soil­ing of pieces, re­duce floor space uti­liza­tion and in­crease ver­ti­cal space uti­liza­tion, vir­tu­ally ev­ery­thing that a fac­tory man­ager can wish for. But in re­al­ity, what is achieved can be far dif­fer­ent from what is promised or claimed, if the sys­tem is dealt with mis­man­age­ment. The ar­ti­cle is a re­search project car­ried out by a NIFT stu­dent un­der the guid­ance of Dr. Pra­bir Jana, NIFT Delhi, which shows that an over­head ma­te­rial han­dling sys­tem could also be dis­ad­van­ta­geous if not im­ple­mented prop­erly.

Afac­tory was cho­sen for anal­y­sis where the same style was run­ning in both – the PBU sys­tem as well as the UPS sys­tem – us­ing over­head ma­te­rial han­dling. On man­age­ment’s re­quest, the ad­van­tages and dis­ad­van­tages of both the sys­tems on six dif­fer­ent pa­ram­e­ters were an­a­lysed. These pa­ram­e­ters were floor area uti­liza­tion, through­put time, WIP, bal­ance ef­fi­ciency ( line uti­liza­tion), labour pro­duc­tiv­ity and SMV.

Floor Area Uti­liza­tion

The very first shock that hit was when the floor area uti­liza­tion un­der the two sys­tems were an­a­lysed. There were two types of UPS lay­out in the fac­tory: Type 1 and Type 2 as shown in the fig­ure be­low. There were six lines of Type 1 and two lines of Type 2. Sim­i­larly, there were six lines of PBU Type 1 and three lines of PBU Type 2.

UPS ac­tu­ally in­creases through­put time. This is be­cause in PBU, you work si­mul­ta­ne­ously on one gar­ment, but in UPS, the sys­tem be­comes lin­ear and is bound to take more time. – Dr. Pra­bir Jana, NIFT, Delhi

The av­er­age area oc­cu­pied by one sew­ing ma­chines in the two sys­tems was cal­cu­lated and com­pared in the ta­ble be­low. Against the claim, it was shock­ing to see that the UPS sys­tem uti­lizes about 1.8 times more floor space than its equiv­a­lent PBU sys­tem. No doubt, the floor area in the line was neat and clean; the WIP count­ing was easy, but floor area uti­liza­tion was al­most dou­ble. Although the or­ga­ni­za­tion was able to uti­lize the ver­ti­cal space, the typ­i­cal pre- U-shaped over­head rail made the floor space uti­liza­tion very poor. In­ci­den­tally, all the com­put­er­ized over­head ma­te­rial han­dling sys­tems have rigid pre- de­signed struc­tures re­sult­ing in very lit­tle op­tions for the man­u­fac­tur­ers to change the lay­out struc­tures.

Shorter the through­put time, the bet­ter the re­sponse time (or lead time)

In or­der to un­der­stand which of the two sys­tems give a shorter through­put time, it was de­cided to cal­cu­late the through­put time by not­ing down the date and time of load­ing a par­tic­u­lar hanger ( in case of UPS) and a

All the com­put­er­ized over­head ma­te­rial han­dling sys­tems have rigid pre-de­signed struc­tures re­sult­ing in very lit­tle op­tions for the man­u­fac­tur­ers to change the lay­out struc­tures.

Over­head ma­te­rial han­dling sys­tem should be im­ple­mented only in as­sem­bly sec­tion where the half-fin­ished sewn com­po­nent is larger in size and pos­si­ble to sew in hang­ing con­di­tion. Sew­ing in hang­ing con­di­tion re­duces pick up and dis­pose of time re­sult­ing in re­duced SMV in UPS sys­tem.

par­tic­u­lar bun­dle ( in case of PBU) in a line and un­load­ing time and date of the same hanger/bun­dle. We cal­cu­lated the time for five hang­ers/bun­dles each day for three days and for three dif­fer­ent styles. To the man­age­ment’s sur­prise, the av­er­age through­put time for the UPS sys­tem came out to be ap­prox­i­mately six times higher than the PBU sys­tem. “I am pro­fess­ing this point for last so many years ( against the claim of over­head ma­te­rial han­dling sys­tem sup­pli­ers) that UPS ac­tu­ally in­creases through­put time. This is be­cause in PBU, you work si­mul­ta­ne­ously on one gar­ment, but in UPS, the sys­tem be­comes lin­ear and is bound to take more time. Although six times may be a lit­tle too high in this fac­tory, fac­tory can try to keep it un­der check by re­duc­ing the amount of WIP dras­ti­cally,” avers Pra­bir Jana.

Lower the Work in Progress, lower the through­put time

Ide­ally, low WIP means low over­all cost of gar­ment. Work in Progress ( WIP) was cal­cu­lated in the line by not­ing the ini­tial WIP, daily in­put and out­put for con­tin­u­ous 15 days for one line each. The av­er­age WIP for UPS came out to be 386 against an av­er­age of 432 pieces for PBU sys­tem. The only thing hap­pen­ing right in the fac­tory for UPS is low WIP.

The rea­son be­hind main­tain­ing higher WIP in PBU is cush­ion­ing for the non-trans­parency of count­ing the ac­tual WIP in the line, but in UPS, no pieces are hid­den in boxes or trol­leys, and it is easy to count the hang­ers. This trans­parency en­ables the com­pany to main­tain low WIP in the UPS line. This is also a unique case to prove that only lower WIP can­not en­sure quicker through­put. The lin­ear­ity of all oper­a­tions and higher SMV have out­weighed the ad­van­tage of low WIP fi­nally re­sult­ing in higher through­put time for UPS.

Bet­ter the line uti­liza­tion, bet­ter the pro­duc­tiv­ity

In the next step, three months data on line uti­liza­tion and labour pro­duc­tiv­ity was taken into ac­count to be mea­sured. Uti­liza­tion of lines for 8 hour shift was cal­cu­lated us­ing the for­mu­lae ( Out­put X SMV) / ( Man­power X 480) X 100.

It came as a shock to an ex­tent to see that PBU was fea­tur­ing bet­ter both in terms of uti­liza­tion and labour pro­duc­tiv­ity. It was in­ter­est­ing to note that the mean SMV that is pro­vided by the com­pany for the UPS line was con­sis­tently higher than the PBU line.

The mis­take the com­pany did was in im­ple­ment­ing over­head ma­te­rial han­dling sys­tem in ev­ery sew­ing op­er­a­tion of the style, which re­sulted in mul­ti­ple prob­lems. In the first phase, over­head ma­te­rial han­dling sys­tem should have been im­ple­mented only in as­sem­bly sec­tion where the half-fin­ished sewn com­po­nent is larger in size and pos­si­ble to sew in hang­ing con­di­tion. Sew­ing in hang­ing con­di­tion would have re­duced pick up and dis­pose of time re­sult­ing in re­duced SMV in UPS sys­tem. If over­head ma­te­rial han­dling sys­tem was im­ple­mented only in as­sem­bly sec­tion, the small parts prepa­ra­tion could have fol­lowed PBU and hence par­al­lel pro­cess­ing would have oc­curred, re­sult­ing in re­duced through­put time. Sew­ing small parts us­ing over­head ma­te­rial han­dling sys­tem in­creases the pick up and dis­pose of time, hence lead­ing to in­creased SMV.

Ev­ery fac­tory should em­pha­size on ju­di­cious use of tech­nol­ogy rather than a show­case (to im­press buy­ers or fel­low man­u­fac­tur­ers).

The floor area in case of UPS is neat and clean, but it uti­lizes al­most dou­ble floor area com­pared to PBU (photo for rep­re­sen­ta­tion pur­pose only)

Against all the claims, PBU sys­tem of pro­duc­tion fea­tures op­ti­mum floor uti­liza­tion, low through­put time and high pro­duc­tiv­ity (photo for rep­re­sen­ta­tion pur­pose only)

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