Illig has developed a new technique for thermoforming small polystyrene beverage bottles that it claims can undercut the cost of blow molding while also providing performance benefits.

The Heilbronn-based company claims that its thermoformed bottles provide these 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 company’s thermoformed bottles provide a weight savings of 50 percent over blow molded alternatives. He said typical weights of around 4 grams are possible for a thermoformed part compared with 7 grams to 8.5 grams for equivalent blow-molded bottles.

Part of this weight savings is attributed to the more uniform side wall thicknesses that are achieved using thermoforming. This is achieved despite the process involving high draw depths.

Tests performed at Illig show that thermoformed bottles made from 1.4-millimeter-thick PS sheet on its BF70 in-line system meet the load-bearing requirements expected for conventional blow molded bottles in spite of their lower weight.

Albrecht said the key to the success of Illeg’s bottle-forming process is use of special forming tools with moveable lower elements capable of dealing with the 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 the thermal energy to be applied only in the area to be formed. This 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 either 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 provides more easy 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
  
• 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 upwards 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 well with conventional fill-and-seal lines, according to the company. Albrecht expects cost of nonsleeved thermoformed beverage bottles to come out around 8 euros (85 yuan) per 1,000, compared with a claimed 28 euros (298 yuan) per 1,000 for blow molded equivalents.

Illig expects its production technology to open up new design opportunities in other thermoformed products, such as food packaging cups and tubs with pronounced undercuts.

European Plastics News is a sister publication to Plastics News.