International Plastics News for Asia

Blow moulding small bottles the economical way

Today consumers want convenience. When they purchase products in the ready to serve food and drink packaging sector, they move towards resealable single serve containers.  This trend is making the single serve food and beverage packaging one of the fast growing segments for plastic bottles. 

Whether the need is for lightweight HDPE or PP bottles for milk, yogurts or other drink products or multilayer containers for oxygen barrier and hot fill applications, producers of packaging products are looking for the most economical blow molding options.  So how can a moulder save money blow moulding these small containers with Wilmington’s new SB (Small Bottle) blow molding system?

According to Jeff Newman, VP of Sales and Marketing for Wilmington Machinery, “We have found that moulders can save money by molding with our new ‘SB” continuous rotary extrusion blow molding systems. These systems utilise small individual molds with a unique design that eliminates hot flash and reduces the ‘log’ (untrimmed bottle with flash) weight that adds to the savings”.  Moulder can now produce containers ranging from 60ml to 1000ml for either monolayer or multilayer configurations. This technological break though reduces the operating cost while increasing the bottle quality.

The Wilmington SB rotary system can reduce the cost per bottle for the producer. It is necessary to remember that the top three costs typically associated with bottle production are material or resin, labour, and utilities such as electric consumption. Wilmington’s SB Blow Moulding System has the potential to reduce the amount of hot flash (typically tails and blow dome) by as much a 33 percent compared to other extrusion blow moulding processes. That is, for a typical single serve bottle, the flash is 30-40 percent of the bottle weight depending upon many factors. The SB system eliminates the typical tail at the bottom of the bottle and therefore allows us to achieve as much as a 33 percent reduction of flash. For a 32 gram bottles, this results in requiring only 38.5 grams per bottle with flash (32 gram +20 percent) versus a typical 41.6 gram requirement from standard processes (32 gram + 30 percent). At a rate of 300 bottles per minute, this requires 55 kg/hr less of melted HDPE plastic. Using a Kw rate of $0.12 USD per Kw hour, that is a saving of about $20,000 per year. The advantage in energy savings, however, does not stop there.

A monolayer Wilmington SB machine would most likely compete directly with reciprocating screw type blow moulding machines or shuttles as an alternative way to produce the bottles.  It requires 2 or 3 reciprocating / shuttle machines to match the capacity of one Wilmington single parison 40 cavity SB system. Most reciprocating shuttle machines have electric drives for the extruder, just like the SB system. However each those machine may have a 30-40 Kw hydraulic pump motor for the clamp and accumulator circuit.   The single SB system has only a single 3 Kw motor to drive the clamping system as compared to 60 Kwh for the two other machines. This could result in 60 Kwh savings over 8200 hours. At $0.12 per Kwh, this provides an additional saving of about $60,000 per year.

Additional energy-related cost savings include the cost associated with transporting extra resin, cost to regrind flash and store, plus labour involved with the movement, tracking and storing of the extra regrind. Utility cost is typically the second or third highest cost component in the cost of the bottle.  Labour savings is achieved because the SB system enables processors to use a single high output machines versus several smaller machines.  Previous methods to blow mould small size containers included reciprocating screw blow moulders, injection blow moulding, numerous shuttle blow moulders side-by -side and some competitor rotary systems that blow the bottles neck-to-neck configurations.  The reality is that a single SB 40 cavity system can produce the same number of containers as two reciprocating style machines. Therefore, a converter could possible reduce labor requirements by at least 1-2 operators per shift resulting in additional savings.

For more details on this system, read the International Plastics News - Middle East & Africa March issue.