a flask assembly that includes a cope flask, a drag flask, and a changeable match plate, wherein said match plate has top and bottom surfaces on which patterns are formed;

an upper squeeze member adapted to be inserted into said flask assembly from said cope flask-side to oppose said top surface of said match plate and for defining an upper molding space, which is to be filled with molding sand, together with said cope flask and said top surface of said match plate;

a lower squeeze member adapted to be inserted into said flask assembly from said drag flask-side to oppose said bottom surface of said match plate and for defining a lower molding space, which is to be filled with the molding sand, together with at least said drag flask and said bottom surface of said match plate;

a first hydraulic cylinder system for driving said upper squeeze member to the top surface of said match plate to squeeze the molding sand within said upper molding space;

a second hydraulic cylinder system for driving said lower squeeze member to the bottom surface of said match plate to squeeze the molding sand within said lower molding space;

a hydraulic power unit for extending the first and second cylinder systems;

said molding machine being characterized in that said hydraulic power unit comprises:

a source for supplying oil;

a piping system for fluidly communicating with said first and second hydraulic cylinder systems to supply the oil from the source;

an accumulator that is provided within said piping system;

first and second electromagnetic directional control valves for controlling the flow of the oil from said source to the first and second hydraulic cylinder systems;

first and second pressure sensors located in said piping system to associate with the first and second hydraulic cylinder systems for measuring pressures of the oil within said piping system while the first and second hydraulic cylinder systems are extended, and for generating output signals that correspond to the measured values of the first and second pressure sensors; and

a controller for receiving the output signals from the first and second pressure sensors, and for controlling the turning of the first and second electromagnetic directional control valves based on the received output signals and the predetermined value within a range below the pressure holding said accumulator against the oil.