Human-Machine Interfaces (HMI) are used where people and machines or systems (often within an industrial context) interact during a given task. The goal of this interaction is for the user to operate and control the machine in an effective manner, while receiving helpful and timely feedback. In some contexts, an HMI may also function as a decision support system (DSS), or include DSS components, aiding users in making effective decisions about some aspect of the industrial operation. In this paper, we discuss the iterative design of an HMI-DSS based on a mathematical model for an icecream manufacturing operation. We chose ice-cream manufacturing as a working example because it is a multi-modal system, containing sufficient process complexity to be generalizable to many other kinds of industrial operations. One of our design goals is to provide users with a display that includes both quantitative and qualitative information types related to the situation requiring a decision. In addition, we aim to provide users with an exploratory environment that enables them to experiment with decision alternatives, their past and potential consequences, prior to actually carrying out the decision.