Customer preferences featured in new small hydraulic presses.

A new line of hydraulic-clamp injection machines for small-tonnage applications has been developed by Van Dorn Plastic Machinery Co., Strongsville, Ohio. These additions to Van Dorn's HP series break new ground for Van Dorn, both in hardware innovations and in the company's approach to product development. The new machines will be introduced formally at Plastics USA in Chicago next month.

The new line, which replaces the HP Jr., Van Dorn's previous offering in small machines, was developed from scratch. Its design was based on a detailed assessment of customer needs obtained in a "quality function deployment" (QFD) study, conducted as part of the company's Total Quality Management process. The QFD study identified customer needs from interviews with a wide range of processors at their plants. Those customer preferences were then prioritized and translated into technical requirements by a crossfunctional product design team encompassing various disciplines from engineering to manufacturing to sales and marketing. Van Dorn says it is making QFD a standard practice in its development of major new products.

Interestingly, the small-tonnage HP line is designed in metric units. The series initially will be available in a 55-(U.S.) ton machine, with production of 33-ton and 44-ton models to be phased in during the first half of 1993. Additional larger tonnages will become available in the future. Several key customer priorities have been implemented into the overall design:

* Fewer components--half the number of some competing models to simplify maintenance and repair.

* Compact design--55-tonner has a footprint of 11.9 x 3.3 x 5.5 ft high.

* Quiet operation, due to a low-noise screw motor and axial piston pump. The HP operates at a noise level of under 75 dbA at the screw motor.

* Large windows around the machine for improved visibility, and space around the clamp and injection unit for better access.

* Machine base with large drop area and three-way access.

* Full line of pre-engineered options.

QUICK-CHANGE INJECTION UNIT

The HP's newly designed injection unit is more compact, which helps to minimize the machine footprint. The injection unit also includes quick-change features to maximize uptime. Clear access to the barrel area and front-end mounting system simplify changing the screw and barrel. A quarter-turn release feature on the screw, simple locking nut on the barrel, and swiveling injection unit also are said to provide easier cleaning and changeover. Heater bands are equipped with quick disconnects also to facilitate changeover. Three barrel heat zones and a nozzle heater zone reportedly provide effective and uniform temperature control.

The unit has a standard injection pressure of 25,000 psi, capable of running stiff engineering materials such as liquid-crystal polymers (LCPs). Although the machines are still undergoing beta site testing, cycle times are said to be under 4 sec, depending on the application.

Twin centerline nozzle pull-in cylinders line up the injection nozzle accurately and prevent bending of other components. Four interchangeable injection units with three screw diameters are available for each injection unit. Shot sizes are available from 0.66 oz to 8.46 oz. Standard screw, barrel and non-return valve are offered with 20:1 L/D and 3:1 compression ratio. Screws are ion-nitrided for extended life, and options are available for specific applications and materials.

RIGID CLAMP UNIT

The clamp is designed for extra rigidity. Platens are cast, and tiebar supports shorten the span of deflection, which is said to provide more precise and consistent mold alignment. In addition, the main ram is designed to prevent platen tipping. PTFE bearings provide support along the length of the ram, which is firmly attached all the way to the moveable platen. The clamp provides generous spacing between ion-nitrided tiebars. The 55-ton machine has horizontal and vertical spacing of 12.9 in.

A single, internal rapid-advance cylinder minimizes the number of clamp parts and eliminates external leakage to simplify maintenance and help to ensure clean parts. All pistons and hydraulic cylinders use PTFE seals to reduce friction, enhance repeatability, and extend the life of the clamp. The hydraulic ejector system with rigid cast ejector plate is equipped with position potentiometers, and is adjustable to stop the ejector short of full stroke. The ejector is designed for easy access and uses quick disconnects for the center coupling to facilitate quick mold change.

Full SPI mold mounting is standard, as is the ability to eject-on-the-fly. A chain slot in the gate allows the operator to easily load and unload the mold. The stationary platen is predrilled for easy mounting of auxiliary equipment such as robots and sprue pickers. For added accessibility, an area has been designated on the side of the clamp, rather than underneath, for placement of water lines.

NEW-GENERATION HYDRAULICS 

A new generation of Vickers variable-volume piston pumps is said to be highly energy efficient with improved reliability and quiet operation. The pump is located under the base (not in the oil tank), where it is easily accessible. Circuitry design is said to keep the number of proportional valves used on the machine to a minimum. HP series machines are equipped with two Vickers proportional directional control valves and one Vickers proportional pressure valve, with a single valve dedicated to clamp action to ensure good repeatability.

All hoses are attached with O-ring fittings to prevent leakage. A compact manifold design at the back of the machine is accessible, reduces the need for piping, and minimizes leak points.

The new line initially will be offered with the Pathfinder EL control, but eventually a range of Van Dorn control options will be available. Power and control cabinets are separated to prevent electrical noise interference. Price will vary depending on machine size and control type. Base price of the 55-ton unit with controls is from $50,000 to $58,000.