Control Advances Give Rotomolders A Better Handle on Their Process

Internal mold-temperature monitoring, advances in process simulation, and new European machine entries were among the news presented to more than 450 attendees at the annual spring conference of the Association of Rotational Molders (ARM) in Barcelona, Spain.

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'Seeing' in the mold

Minimizing cycle time and eliminating guesswork is the aim of two new devices that look at temperatures inside the mold. One is a battery-powered temperature profiler that relays data from up to eight in-mold thermocouples to a portable data recorder mounted on the outside of the mold. STP CorrecTemp from STP Equipment Inc., Bromptonville, Que., has an insulated stainless-steel enclosure that can protect the electronics from temperatures up to 500 F for 2 hr. The user must wait until after the cycle ends before retrieving the data for analysis or downloading. Windows software allows data sampling for periods from 1 sec to 24 hr and storing up to 65,000 data points in memory.

A simple approach to mold-temperature monitoring comes from Just Roto Inc., Rolling Meadows, Ill. Its Just-Right in-mold sensor uses thermographic crystals to show mold temperature. The crystals change color (from gold to bluish-green) at specific temperatures from 331 to 488 F. The color crystals are impregnated into a label resembling a thermometer. The label is placed on a special machined-PTFE vent-tube assembly (from Wheeler Boyce Co., Stow, Ohio) and held in place by O-rings. The tube is placed in the mold vent and removed after each cycle. A vent tube with O-rings and 10 labels costs $30.

Predict your process

Rotocycle version 1.1 is a new software simulation tool from Ferry Industries Inc., Stow, Ohio, used to predict and optimize production rates for any type of rotomolding machine. Rotocycle 1.1 allows users to choose from 12 machine types--shuttle, turret, and multi-station independent-arm. After all relevant machine settings are entered, the computer calculates the maximum output achievable at those settings. The system can show the effect on productivity of changing times for arm movement and door opening and closing. It can pinpoint delays and bottlenecks and help you balance station times for machines with multiple ovens and coolers. "It acts as a diagnostic tool and can give you clues when to get a bigger machine," says Ferry president Harry Covington. The software runs on a PC and costs $395.

Ferry's Rotocure 2.3 System Manager, the standard controller on its Rotospeed machines, has been upgraded with a faster PLC. It now monitors and records 50 operator and machine functions and can index individual arms through a cycle without mold rotation. New oven and cooler door switches enable selective or automatic operation of any door. It provides separate on/off control of cooling air and water and has four thermocouple temperature-input modules to measure additional temperature points such as ambient air.

New European machines

A year ago, Crossfield Excalibur Ltd., a maker of rotational molds in Rochdale, England, developed its own line of open-flame, rock-and-roll molding machines for container sizes from 200 to 10,000 liters. Since then, the Merlin line has been upgraded with a self-contained hydraulic unit in place of a chain drive. The oven has adjustable gas nozzles that reportedly allow tighter control of heating profiles than in a conventional oven. The cooling station has two fans that swivel to direct cooling air at any area of the mold. This feature is said to help trim cycle time by 25%. The unit is PLC controlled. Crossfield makes custom machines and two standard models, the Merlin 200 for 200-500 liter containers and the Merlin 5000 for 500-5000 liters.

Three new machines were developed by SAT of Aix-les-Bains Cedex, France. First, SAT added two new models to the top end of its M line of fixed-arm turret machines. Both units accommodate three or four straight or offset electrically driven arms, one or two cooling areas (each with air or air/water cooling), and one or two load/unload areas. The M-4000 has a swing diameter of 4000 mm, max. weight capacity of 4400 lb, and gas heating capability of 500 kw. Model M-4500 has a 4500-mm swing diam., 5500-lb max. arm weight, and heating power of 600 kw.

The firm also offers the new C-4500 carousel machine, which has similar features as the M-4500 plus the advantage of independent arm movement.

There's also new machine features from Caccia Engineering S.p.A. of Italy (represented by E.A.P. Machinery Systems Inc., Erie, Pa.). First, an operator can now program the arm to tilt the molds after cooling for loading/unloading. New automated fan control permits more efficient modulation of air temperature in the cooling chamber. And new software for rock-and-roll machines lets you enhance wall thickness in selected areas of the part by stopping rotation while the major axis oscillates at a preset angle.

The firm also now offers the Rotodex quick-change system for spider arms on shuttle or carousel machines. Caccia's new Easy Drive System lets you store the number of cycles for a particular arm and mold. The cycle setting is recalled by entering the code for the spider. The system is interfaced with Caccia's automatic mold-feeding system.