There are two distinct chocolate mixing systems at the Toronto facility, one that produces the Neilson product line and one that supplies chocolate to make the Cadbury product line. While these systems are not exact copies of each other, they are sufficiently similar to be grouped together for this discussion.
The process begins by mixing and blending raw materials based on a predefined recipe. The mixing system consists of two horizontal mixers fed with raw materials through a shared system of inlet pipes and valves. The operators also manually add certain other small volume ingredients. The industrial mixers discharge a chocolate paste onto a shared conveyor that transports the product to a set of refiners. The refiners comprise of a set of heated rollers that remove lumps and deposit a fine chocolate flake onto another conveyor that moves the chocolate to one of several large blending conches. Each conche has roughly four times the capacity of one of the industrial mixers, so a single batch is made up of four mixer loads or 'mixes'. Normal operation is to make a different type of chocolate in each batch. This means there is often a case where each of the industrial mixers contains a different recipe. In these instances, it is very important to control the release of the mixers to the refiners so that product mixing is avoided.
Another problem was the slight variations in the quantities of ingredient automatically added to the mixers by the operator. These variations were caused by the mechanics of the ingredient piping network and the manual nature of the operation (the operators held a button down on the PLC control panel until they received the weight called for in the recipe). If a more stringent control of the ingredient addition system could be designed whereby slight shortfalls in one mix could be compensated by changing the target weight of the next mix then in all likelihood, product consistency could be improved.