PETpla.net Insider 07+08 / 2010

PREFORM PRODUCTION 16 PET planet insider Vol. 11 No. 07+08/10 www.petpla.net Getting to the Point Chinese company GDXL has recently patented a conical- base preform that saves weight and material. It has already been adopted for series production by a major beverage company. Preform production companies are constantly striving to reduce the weight of their products and cut the use of materials. However, the drive for light weighting has to be recon- ciled with the need to retain product strength. Guang Dong Xing Lian Precise Machinery Co., Ltd. (GDXL) is head- quartered in Fo Shan City in Guang Dong Province, which borders both Hong Kong and Macau and has the largest GDP of any province in the People’s Republic of China. GDXL’s design for a preform with a conical base was awarded patent certifi- cate no. ZL2009 3 0073607 2 from the China State Intellectual Property Office on March 10, 2010. “GDXL has had a conical base design on the market since 2006. This design is now being used by Coca- Cola Corporation in its operations in China,” said Simon Wu, sales del- egate for GDXL. “The primary driver for the new design is material saving – that is its strongest advantage.” Material reduction Dimensions of the neck, both in height and diameter, remain exactly the same for both a traditional round base and GDXL’s conical base; both are exactly the same length, also. Fur- ther down the preform, the walls are slightly thicker on the conical design than in the round base. The company says that the bottom property of PET bottles made to its design will be improved, through taking advantage of bottom stretching but weight sav- ings through the use of less material are in the region of 2 to 3% per bottle. A 500ml CSD preform weighing 22.2g with a round base, for example, will see weight reduction of 0.5g; a 2.0ltr CSD conical preform will weigh 1.67g less than the 45.03g typical of a round base. “The conical base design can reduce the amount of redundant material in round base design but,at the same time, it can improve the PET bottle’s stress cracking in the bottom, due to better stretching,” said Wu. Coca-Cola in China has been using GDXL’s conical base for a number of its products, including its 480ml asep- tic fill Yuanye tea series. “The weight of that PET bottle is lowered from 17.2g to 16.6g, using the conical base design. Its 2l Cola/Sprite bottle has seen, its weight reduced from 46.7g to 45.63g.” Despite using less material, the company says that the finished bottle has no need for additional support. However, during the design phase, manufacturers should ensure that the curve is smooth, in order that injection resistance is minimised. GDXL has designed its coni- cal base preform to run on existing equipment, although modifications are required to the core themselves, the cooling tube, gate insert and cooling insert of the takeoff tube. “As the shape of the preform bottom is changed, these components should be reformed to fit the conical base design,” Wu explained. “We esti- mate that the cost of modification is around RMB4000 per cavity.” The cost Comparison of round and conical pre- form: Both are exactly the same length