Energy efficiency improvement in stretch blow moulding

Gujarat-based Shyam Plastic Machinery was founded in 1993 with extrusion lines as main products, then expanded into PET stretch blow moulding machines four years later in 1997. Starting with a humble production rate of 12 bottles per minute (BPM), Shyam today supplies blowing machines up to 300 BPM speed. The fully automatic range of Shyam includes those of 2 and 4 cavity machines, with production up to 100 BPM.

Shyam’s SP Pristine series, a fully electric PET stretch blow moulding machine, was introduced to provide a mid-range production with high energy efficiency levels. The objective was to offer energy efficient cost-effective line to control rising production cost of the final product.

“Shyam has always been a customer centric company and keeps developing products to fulfil the needs of customers to make them more competitive, by reducing energy and maintenance costs, in the continuously evolving market place,” said Samir V Khakharia, Director, Shyam Plastic Machinery.

Shyam’s SP Pristine series, a fully electric PET stretch blowing moulding machine.

SP Pristine Series-I was introduced to cater to emerging customer needs for a range of machines from 150 to 300 BPM. The Pristine series reduces the energy consumption by 35 to 40% compared to other linear machines by increasing the efficiency of the heating oven (continuous moving rotary type oven) by pitch reduction and completely eliminating low pressure air requirement.

The company further introduced the upgraded SP Pristine series II by developing a unique heating oven design which further reduced heating load by 40% making it one of the most energy efficient machines in this range. The popular line adds significant volumes each year, launched in new oven design to ensure longer life (practically life-long) of majority moving parts significantly reducing maintenance cost. The machine is a Reheat Stretch Blow Moulding type that uses pet preforms that are reheated, stretched and blown to the final container. 

What contributes to smooth operation

In SP Pristine series II, preform hopper (preforms to be dumped in to this hopper) is connected to elevator conveyor, which takes preforms to unscrambler (orientation unit). The roller type unscrambler orients preforms and sends into loading channel, which supplies preforms to loading turret wheel, which in turn loads preforms to oven mandrels.

Loaded preforms are heated using 8 heating modules, each comprising of 7 heating lamps, while module 1-3 are penetration zone and module 7-8 are distribution zone.

Preform spreading is done by servo-controlled spreader assembly while preform transfer and bottle ejection are done by servo-controlled transfer mechanism. Servo operated mould clamp system, together with blow air compensation ensures fast movement of mould platens, and also minimal parting line. Blown bottles are inserted into the air conveyor connected with machine. 

The model is available in five variants from 6, 7, 8, 10, 12 cavity configurations. The 10-cavity configuration model (other cavity configurations possible based on variant) produces 14,500-15,000 per hour for 1000 ml water bottle. Output varies with bottle design and preform weight and design, with guaranteed production efficiency at 95%.

The quality of blow moulds highly contributes to the bottle quality and production rate, and hence Shyam recommends that blow moulds are manufactured by the company, or procured from registered suppliers. The mould material provided is made from aluminium HE 20 Grade as standard supply. On customer request, Alumec 89 can also be used at additional cost.

The all-electric machine uses multiple servo axes, in synchronous mode to optimise mechanical movements and timings, resulting to reduced mechanical functions time and allowing more process time leading to higher productivity of the machine.

The SP Pristine series guarantees energy-savings plus a host of benefits for efficient operation.

Preform loading and heating conveyor is based on continuous movement, which removes the conventional pneumatic reciprocating movements, eliminating abnormal wear & tear of moving parts and also reducing air consumption.

The entire machine is based on Neck Hold system, right from preform entry to bottle ejection, which has great advantage against body holding of preforms and blown bottles, reducing the number of changing parts and also reduces mould change over and efforts spent to perform those tasks.  

Penetration zone followed by precise power-controlled zones provides accurate and efficient heating of preforms. Auto controlled variable speed ventilation blowers also greatly contribute to precise heating control. This close loop heating system contributes to making it a unique feature in its segment. 

Servo stretching system, with individual fast response blowing valve sets per cavity, provides precise stretch-blow process control, which is a primary requirement for better material distribution.

Reduction of pneumatic components and reciprocating movements, together with the use of servo motors for all major functions, result in reduction of impact and noise level.

The machine is enclosed on all sides and also from the top. This prevents dust from settling on to machine components. Reduction of dust level cuts down maintenance requirements and increases life of all moving components. Machine covered from top is again a unique provision in the segment.

Ease in mould change over and maintenance is one of the primary criteria taken care while designing of this machine. The ergonomically designed machine provides a safe and convenient working level for the operators and maintenance personnel.

Necessary safety features like easily visible emergency mushroom buttons, machine mode switch limit switches in guards are part of standard equipment.

Blow air recovery is provided in all cavities so that part of high-pressure blowing air is re-collected back before exhaust. The same air can be used either for pre-blow or supplied back to booster compressor as designed and desired.

The use of servo motors replaces major pneumatic components that consume enormous compressed air, resulting in negligible air consumption, and hence highly reducing production cost. The operation air, less than 8 CFM (which is 115th to 1115th as compared to conventional machines) is easily recovered by the blow air recovery feature, still leaving extra air for other re-use.  Reduced pitch in oven allows more number of preforms in the given heating area, and hence efficiently heat preforms using less heat, with minimal heat loss. 

Special provisions for higher productivity

The interactive user interface allows the authorised user to use the machine interface (industrial PC), to order spares, access machine manuals, and also to track spares order status. During office hours, the industrial PC can also be used by the operator to communicate with online support personnel.

Pre-designed daily/ batch production reports can be automatically generated and emailed to predefined personnel/ higher production authority. The interface (under development) of machine provides reminders for preventive maintenance based on usage hours of the machine.

The company also offers robust after sales support as it has dedicated team of engineers ready to respond to the customer requirements without delay. Updating, maintenance and integration of new developments and technologies in the installed machines are also provided by the Ahmedabad-based company.  

SP Pristine series caters to all the customers in various industries like, packaged drinking water, carbonated drink, fruit juice, edible oil, cosmetics, liquor & pharmaceutical sectors. To date, the Shyam has installed more than 450 machines spanning in over more than 45 countries that includes Indian sub-continent, European, Gulf and African countries. The number of installations of SP Pristine series alone is more than 60.   

- This article also appears in the International Plastics News for Asia - February issue. To view the e-zine, click here.