A melt system configured to convert a solid polymer into a molten polymer, the melt system comprising: at least one melt unit having: a reservoir; a melt grid positioned above said reservoir, said melt grid configured to expose said solid polymer to a temperature sufficient to form a molten polymer and to deposit said molten polymer into said reservoir; a hopper disposed above said melt grid and configured to hold a supply of the solid polymer, said hopper having a lower end, an upper end opposite said lower end, and a wall that extends from said lower end to said upper end, said lower end being proximate to and open to said melt grid, said upper end and said wall defining an internal chamber that holds said supply of said solid polymer; and a thermal isolation region disposed below said melt grid and above said molten polymer in said reservoir, said thermal isolation region configured to thermally isolate said solid polymer in said hopper (60, 61) from molten polymer in said reservoir, wherein the thermal isolation region comprises an isolation chamber disposed below said hopper, characterized in that said hopper further has an access door (80a, 80b) disposed on said wall, said access door (80a, 80b) being moveable between a closed position where said hopper is closed and an open position where said internal chamber is accessible to receive said solid polymer. at least one melt unit having: a reservoir; a melt grid positioned above said reservoir, said melt grid configured to expose said solid polymer to a temperature sufficient to form a molten polymer and to deposit said molten polymer into said reservoir; a hopper disposed above said melt grid and configured to hold a supply of the solid polymer, said hopper having a lower end, an upper end opposite said lower end, and a wall that extends from said lower end to said upper end, said lower end being proximate to and open to said melt grid, said upper end and said wall defining an internal chamber that holds said supply of said solid polymer; and a thermal isolation region disposed below said melt grid and above said molten polymer in said reservoir, said thermal isolation region configured to thermally isolate said solid polymer in said hopper (60, 61) from molten polymer in said reservoir, a reservoir; a melt grid positioned above said reservoir, said melt grid configured to expose said solid polymer to a temperature sufficient to form a molten polymer and to deposit said molten polymer into said reservoir; a hopper disposed above said melt grid and configured to hold a supply of the solid polymer, said hopper having a lower end, an upper end opposite said lower end, and a wall that extends from said lower end to said upper end, said lower end being proximate to and open to said melt grid, said upper end and said wall defining an internal chamber that holds said supply of said solid polymer; and a thermal isolation region disposed below said melt grid and above said molten polymer in said reservoir, said thermal isolation region configured to thermally isolate said solid polymer in said hopper (60, 61) from molten polymer in said reservoir, wherein the thermal isolation region comprises an isolation chamber disposed below said hopper, characterized in that said hopper further has an access door (80a, 80b) disposed on said wall, said access door (80a, 80b) being moveable between a closed position where said hopper is closed and an open position where said internal chamber is accessible to receive said solid polymer.