Weighing and batching machine from Scale-Tron

This article describes the weighing and batching machine manufactured by from Scale-Tron Inc.

A unique powder batching system was designed for Rehau Industries’ Baie D’Urfe, QC plant. The objective was to weigh up to 7 materials, with weights varying between 50g to 4 kg, into plastic bags and seal them. The soluble bags are then hand-added to plastic materials in a mixer, creating specific blends for different jobs.

The batches had to be completed within 120 seconds at most, with an accuracy of ±0.5% of each ingredient weight. These two conditions made it essential to use three separate weigh hoppers, discharging through a chute into the plastic bag which is held by a pneumatic clamp. Ingredients are stored in bins standing on seven vibratory screw feeders, supplied by Vibra Screw Corp. This type of feeder guarantees consistent feed of powders, some of which tend to clump and bridge. The feeder discharge tubes are closed positively at the end of feed by sealing pads on spring-return cylinders.

The three hopper scales, shown in the picture, have capacities of 300g, 1500g and 4000g, are mounted on a single load cell each and have removable hoppers. Discharge is activated from outside the hopper with a unique mechanism that only contacts the hopper during discharge, eliminating the forces and subsequent errors created by pneumatic tubing.

The batching system was controlled by our BatchTron-II batching controller, which handles both the speed and accuracy with ease. Innovations were too numerous to list here, but we can discuss them with you.

Our wide experience in load cells, coupled with integrated mechanical and electrical design skills, give the ability to design load cell-based systems from scratch and guarantee their performance in advance.

Bayer Premier Co. needed an automatic weighing system for their new plant near Bangkok.

The stainless steel weigh hopper had to be capable of withstanding an internal explosion without rupture and was to travel between 12 overhead hoppers, gathering materials, and four mixers where it would discharge the completed batches. Extendable seals were to make contact with hoppers and mixers before transfer of material, to contain dust. The hopper, mounted on load cells on a wheeled trolley and weighing over 10,000kg when loaded, had to travel on rails, powered by a variable speed AC motor. Weight data with an accuracy of 0.05% had to be transmitted over a festooned cable 200 ft in length to the controlling PLC.

The whole was to meet Class 3, Division 2, Group G requirements for hazardous areas.

The weighing system was delivered on time and was started up without requiring our presence on site. It has been operating successfully for five years.