Reduced manufacturing cost, reduced weight and improved wall-thickness control are all among the claimed benefits for a new bottle thermoforming technology developed by Illig Maschinenbau GmbH & Co. KG. The technology is designed to produce small polystyrene bottles for applications such as yogurt, juice and isotonic drinks.
The Heilbronn, Germany-based company claims its thermoformed bottles provide those benefits while being virtually indistinguishable from blow molded alternatives. Only the absence of pinch-off marks gives an indication of the different production technique employed.
Illig sales manager Reiner Albrecht said the firm's thermoformed bottles are 50 percent lighter than blow molded alternatives. Typical weights of around 4 grams are possible for a thermoformed part, compared with 7-8.5 grams for equivalent blow molded bottles.
Part of the weight savings is attributed to the more uniform side-wall thicknesses achieved using thermoforming, despite the process's high draw depths.
Tests performed at Illig show thermoformed bottles made from 1.4-millimeter-thick PS sheet on its BF70 in-line system meet the load-bearing requirements expected of conventional blow molded bottles in spite of their lower weight.
Albrecht said the key to the success of its bottle-forming process is use of special forming tools with movable lower elements capable of dealing with pronounced undercuts in the bottle design, as well as the use of a servo-driven sheet pre-stretching unit and tightly controlled sterile forming air.
Typically, a tool configuration for thermoformed bottle production involves two rows of cavities arranged across the machine operating direction.
The Illig process involves heating the sheet selectively using contact heating plates, which allows thermal energy to be applied only in the area to be formed. That method ensures minimal shrinkage of the remaining skeleton material, which can be reground and recycled into the system.
Once the bottle has been formed, it is punched out from the remaining sheet material using steel rule cutters.
The BF70 production system can be linked to existing or new fill-and-seal machines at beverage and dairy companies. Illig said the smooth, wide edge achieved at the top of the thermoformed bottle allows for easier sealing to the circular aluminum foil lids used on fresh dairy packages.
Albrecht said the thermoformed bottle technology involves just five production steps: roll purchasing, transport and storage, bottle forming, transfer to fill-and-seal lines and transport to the customer. A typical blow molding system includes additional empty-bottle transport, two sorting processes and pre-fill cleaning, he said, all of which add cost and complexity to the manufacturing system.
Initial Illig bottle thermoforming systems offer the ability to apply decoration after filling, either using shrink sleeves drawn upward from the bottom of the bottles or via roll-fed applicators. However, the company sees potential in the future to apply sleeves between the forming and punching operations within the BF70 machine.
A BF70 production system designed to form 18 bottles a cycle at a rate of 25 cycles a minute would be capable of turning out 27,000 cups an hour, which integrates with conventional fill-and-seal lines, the firm said. Albrecht expects the cost of nonsleeved thermoformed beverage bottles to come out at around 8 euros ($12) per 1,000, compared with a claimed 28 euros (about $42) per 1,000 for blow molded equivalents.
Illig officials said they expect the technology to open up new design opportunities in other thermoformed products, such as food cups and tubs with pronounced undercuts.