Devices, systems, and methods for monitoring the operation of an injection molding machine, for example, a wax injection molding machine, are disclosed. The devices, systems, and methods may be used for injection molding machines having an injection die, a molding medium injection cylinder, and a control cylinder coupled to the injection cylinder, the control cylinder having a fluid supply conduit. Monitoring and/or control are practiced by monitoring the fluid pressure and the flow rate of the fluid in the conduit. This flow rate and pressure are used to calculate the fluid pressure and flow rate of the molding medium injected into the injection die. A data acquisition system may be used to calculate and output the calculated data. The system can be portable and adaptable for use with any type of injection molding machine and for any injection molding medium.