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Twin Sheet Thermoforming Provides One-step Solution
T W I N S H E E T T E C H N O L O G Y PROVIDES AN EFFICIENT SOLUTION TO THE PRODUCERS OF VERY DIFFERENT PLASTIC PARTS . WE LEARN MORE IN THIS INTERVIEW WITH ZVI RAPAPORT OF CANNON ERGOS .
Cannon News : Could you define in few words the Twin Sheet thermoforming technology ? Zvi Rapaport : It is a production method of manufacturing thermoformed parts by bonding two heated sheets of plastics in a single operation using a double female mould , resulting in a hollow three dimensional structural part . This space inside the part may remain hollow , contain structural inserts or expanded foam bonded to the hot sheets during the forming stage . Compressed air or gas can be injected and sealed after the part is cooled to create an actively responsive part .
CN : Which advantages can you highlight for this technology ? ZR : The structures obtained by the two bonded sheets can solve numerous functional and aesthetic problems , providing an industrial finished solution in a single process that often also has economic benefits . It is a smart alternative to blow-moulding , rotational moulding and other plastics processing technologies , since it allows for the positioning of inserts within the hollow part , allows for the use of different compatible thermoplastic materials in addition to the ability to use different thicknesses and colours on each of the side of the part .
CN : Could you illustrate the most recent achievements in this specific niche of the thermoforming market ? ZR : I can disclose some details of an interesting project we delivered this year to an Italian Tier One supplier of mechanical components to the automotive industry . Cannon Ergos was commissioned to develop a large and flexible Twin Sheet thermoformer for the manufacturing of custom industrial pallets . These custom-made rectangular supports are used to hold large mechanical components or bulk materials precisely and safely on their trip from the Tier One production plant to the OEM ' s car assembly line . Thermoformed by Twin Sheet technology , they are composed by two sheets of HDPE ( High Density Polyethylene ) bonded during the forming operation . The hollow structure obtained is able to withstand the substantial weight and severe impacts while protecting a number of mechanical assembled components during the trip and in intermediate storage areas . The client manufactures these pallets in different sizes and shapes using a dedicated Cannon Twin Sheet thermoformer designed to optimise the cycle time while keeping high flexibility in terms of final product . This machine features a forming area of 2,500 by 1,500 mm and has a closing force of several hundreds of kN . The thermoformer is designed to handle plastic sheets in the 1 to 10 millimetres thickness range , this specific application typically uses 4.5 mm thick HDPE sheets . Two banks of halogen heating elements efficiently heat the sheets according to a user defined heating pattern . A precise , highly responsive , computer temperature control system guaranties correct temperature is maintained
throughout the heating process . Dual sag control is achieved as the lower mould box and the volume between the two sheets are sealed and pressurized . An array of sensors monitors the sag of the sheets and opposes it by increasing the pressure in the sealed spaces . This feature is extremely useful to optimally heat the material and optimize material thickness distribution during the forming process . The forming clamp locks the two mould halves and a closing force of hundreds of kN is applied to bond the two sheets into a cohesive three dimensional structure . Pressurized air is blown between the two sheets , to ensure the best reproduction of the mould details and to provide an initial cooling effect . After cooling , the mould and the moving intermediate frame ( the “ cartridge ”) open , to release the formed pallets . A robot in the heart of the production cell unloads the formed parts from the machine and immediately puts in place another set of four pre-heated sheets to restart the cycle . A production cadence of 5 minutes and a generous working area – to simultaneously produce two pallets of 1,200 by 1,000 mm side by side – contribute to high production rates . Fast tool change is achieved by automatically adjustable reduction plates and clamp frames . All tooling has automatic quick locking systems . Servo movements with encoders and proportional valves for process control ensure the process is stored and retrieved when needed . The ability of producing single sheet parts complete the flexibility of the machine . I can disclose only a few details of another project , a machine designed for high-speed , high-precision , extremely repeatable production . It makes small parts that require a high degree of accuracy . The machine uses two independent sheet transport rails with ample space between them . The independent transport rails allows for flexible forming sequence and the space allows the ability to place inserts inside of the Twin Sheet part . A robot places inserts inside the cavities of the first formed sheet while the second sheet is still heating in the oven . Once the inserts are placed the second sheets is transported to the forming area to be formed and bonded to the first sheet . The latent heat bonds the inserts
Twin Sheet thermoforming equipment requires a special design to guarantee perfect handling and bonding of two hot plastic sheets .
Industrial plastic pallet obtained with Twin Sheet forming technology , using two thick HDPE sheets .
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