Blow Molding: Enhanced Machines for Large & Complex Industrial Parts

New and upcoming machinery developments and advances in productivity, energy efficiency, ergonomics and safety highlighted WEX 2021, the Web Exhibition presented in late June by ST BlowMoulding. The machine builder (st-blowmoulding.com) has roots in Italy (consolidating the S.T. Soffiaggio Tecnica, Zaga and Meico brands), where its manufacturing, sales and service are currently located, though its headquarters are in Switzerland. Master of ceremonies for the virtual show was Ernie Hollo, of Hollo Plastics Equipment, Inc., Northfield, Ohio, the U.S. sales and service support team for ST BlowMoulding (holloplastics.com).

ST BlowMoulding specializes in large machines for automotive, industrial packaging (drums and IBCs) and specialty products. Hollo noted that 18 of its TA and ISIT series accumulator-head machines with up to 400-ton clamps and 100-lb shot capacity have been installed in the U.S. in the last three to four years. They are making products like outdoor furniture, sheds, kayaks and other large parts. One project in development is a calf shed. Four more large TA-series machines are due for delivery in the U.S. this year, with more to come in 2022 and 2023.

Big Machine for Automotive Ducts

The highlight of the Web Exhibition was the model ISIT 1320 Duo machine, which had been planned for a U.S. debut at the cancelled NPE2021 show in Orlando, Fla. That machine has been installed at Reyes Automotive Group in San Antonio, Texas, where it is dedicated to molding auto air-conditioning and ventilation ducts (and can be observed by visitors, according to Hollo).

This machine features dual 10-liter accumulator heads, each able to hold 16.5 lb of HDPE. They are fed by a pair of 75-mm adiabatic extruders, whose thermal insulation is said to reduce heat loss to the plant environment by 90%, and whose screw design reportedly prevents melt overheating at maximum output rate. According to the company, no barrel cooling is required for the extruder, and overall power consumption is significantly lower than for competing extruders for the same resin throughput. Thanks to these extruders and to variable-speed hydraulic pumps driven by an AC inverter motor, models of the ISIT series reportedly are ranked in Class 10, the highest category of energy efficiency under the Euromap 46.1 procedure for extrusion blow molding machines (less than 0.29 kWh/kg of HDPE).

Adiabatic extruders on these machines reportedly consume significantly less energy for the same resin throughput.

This machine has a 200-metric-ton clamp with dual tiebars, small hydraulic cylinders for open/close traverse movements, and a large cylinder for clamping. A rack and pinion on the frame supports the clamp and ensures repeatable positioning. Overall cycle time for this machine is said to be shorter than for any other press of comparable size.

The heads, with overlapping heart-shaped design, can support 300-mm (12-in.) tooling. The heads can accommodate direct gas injection for foaming—useful for weight reduction and thermal or sound insulation. They can also be configured for multilayer coextrusion with heads built by W. Müller. For example, the ISIT 1313 is a special 130-m.t. accumulator-head machine tailored for IBCs, where Hollo says ST BlowMoulding is a technology leader. This machine can be supplied with one or two extruders, the second to apply a thin outer layer (10-12% of total wall thickness) containing antistatic additive for industrial safety.

With two heads and two extruders, this machine can mold two different parts, even with different colors or materials, at the same time, limited by the part with the longer cooling time. The two extruders can run at different speeds for their respective parts.

Incidentally, Hollo noted that the company offers to retrofit its variable-speed pumps and high-efficiency extruders on existing machines—even those from competing manufacturers.

3D Suction Blow

Another specialty of ST BlowMoulding is under-hood automotive ducts and pipes with twists and turns and other geometrical complexities. A particular example is air-induction pipes for turborcharged engines. Its ASPI machines produce such shapes from engineering resins with no flash using 3D suction-blow molding (they can also perform conventional extrusion blow). Over 150 ASPI models are in use; two in the U.S. (the second installed in late 2020 in Northeast Ohio) are Duo models, which have a mobile extrusion platform that shuttles over two clamps. A model ASPI 400 (shown at NPE2018) is located in the DuPont lab in Troy, Mich.

ST BlowMoulding machines have molded coolant pipes of 18 mm diam. up to around 2 meters long. Developments are now focused on coolant lines up to 2.5 m long, with an ultimate goal of 3 m.

These machines control wall thickness continuously as they extrude, using exclusive 4WDS tooling for asymmetric radial parison programming. Coex capability is available for hard/soft sequential extrusion, such as to put elastomeric cuffs on a rigid tube body; or two-layer coextrusion, such as for a glass-filled/unfilled structure to provide noise reduction.

The latest development in the ASPI series is an “e-move” fully electric version that was introduced (via remote video link) at Chinaplas 2021 this spring. With 70-m.t. clamp and 0.5L accumulator head (torpedo type), it’s aimed at very small pipes, like coolant lines or possibly fuel lines with special geometries.

Other recent developments are aimed at production traceability—for example, the D-Print device, a new-generation parison marker to apply a QR code for data retrieval, which is said to be 100 faster than previous versions.
 

ASPI-series 3D suction-blow machines have made automotive coolant pipes of 18 mm diam. up to around 2 meter long. In the works are cooling lines 2.5 and 3 m long.

Better Ergonomics

Designing machines for safety and ease of use was a key focus of virtual presentations by ST BlowMoulding experts. One aspect was part take-out. One configuration shown uses an electric robot to demold the part and carry it to an operator station, where a second robot lowers the part to operator level—avoiding the need to reach and stretch to grab the part. A laser scanner ensures safety by halting robot movement while the operator is present.

Easy-to-use controls were also discussed. The newest touchscreen controls are said to resemble smart phones in their convenience of operation.

Another focus was safe and efficient tooling changeovers. On TA machines, a shuttling mold cart and a fixture for mold lifting enhance operator safety. On the ISIT machines (and on EC continuous-extrusion models), mold changeovers are carried out from above. The upper platform that houses the extrusion head moves backwards and clears the area over the clamp. All movements are by electric motors and controlled by position transducers. This greatly eases the rapid and precise return of the extrusion head to the correct position stored in the recipe for each mold. Electric motors on the die tooling are set from the operator screen.

Safer and easier die-core changeovers on the accumulator heads are facilitated by a swivel arm that supports the head and lifts it to free the mandrel body.
 

Remote Service

The company’s latest machines accommodate the converging trends of Industry 4.0 connectivity, widespread shortage of skilled personnel, and restrictions on travel brought on by the COVID-19 pandemic. Remote service capability is a feature of the ISIT 1320 machine at Reyes Automotive and is now on every new ST BlowMoulding machine. This allows a technician at the machine builder to access the control system remotely in order to configure, test and optimize the machine; diagnose and fix problems; and update software. Information gathered remotely from the machine can be processed through sophisticated diagnostics to predict potential failures before they occur. Live chat is available from each machine’s control panel.

These capabilities came together recently in the remotely assisted commissioning of machines in the U.S. and China. After the initial installations were made with a ST BlowMoulding technician on site, commissioning proceeded with only remote assistance.
 

On the horizon are blow molded nylon liners for composite pressure vessels and floating docks for solar panels.

What’s Next?

One of the company’s newest developments is an electric toggle clamp to replace its current variable-speed hydraulic units. The first version is an 80-ton unit currently in testing.

Other upcoming developments may be aimed at an application areas that ST BlowMoulding has identified as “future markets.” One nylon liners for composite pressure vessels, such as tanks for hydrogen fuels, LPG and CNG. Another is “floating docks” for solar panels. Company sources envision these as two-layer hollow HDPE parts with an outer layer containing UV stabilizers.