An extruding system, comprising: a hot-melting unit configured to convey a polymeric material; a mixing unit configured to receive the polymeric material from the hot-melting unit and configured to mix the polymeric material with a blowing agent and to form a mixture of the polymeric material and the blowing agent; a blowing agent supply unit connected to the mixing unit and configured to convey the blowing agent into the mixing unit; an injection unit configured to inject the mixture, the injection unit includes a hollow metering cartridge configured to accommodate the mixture and a discharging member slidably disposed in the hollow metering cartridge and configured to discharge the mixture out of the hollow metering cartridge; a first flow control element disposed between the hot-melting unit and the mixing unit and configured to control flow of the polymeric material from the hot-melting unit to the mixing unit; and a second flow control element disposed between the mixing unit and the injection unit and configured to control flow of the mixture from the mixing unit to the injection unit; wherein the hot-melting unit includes a hollow pressing cartridge configured to accommodate the polymeric material and a pushing member rotatable within the hollow pressing cartridge, the mixing unit includes a hollow mixing cartridge and a mixing rotor rotatably disposed in the mixing cartridge, the mixing rotor is immovable in a direction parallel to the longitudinal axis of the mixing cartridge and is axially rotatable relative to the hollow mixing cartridge, the discharging member is movable in a direction parallel to a longitudinal axis of the hollow metering cartridge, the pushing member has a first groove annularly arranged over a surface of the pushing member, the first groove is in a first depth, the mixing rotor includes a first groove portion having a second groove and a second groove portion having a third groove, the first groove portion is arranged at one end adjacent to the hot-melting unit, the second groove portion is annularly arranged at the other end adjacent to the injection unit, and a groove depth of the second groove and a groove depth the third groove are different from the first depth, characterized in that the hollow metering cartridge is not axially rotatable relative to the hollow metering cartridge. a hot-melting unit configured to convey a polymeric material; a mixing unit configured to receive the polymeric material from the hot-melting unit and configured to mix the polymeric material with a blowing agent and to form a mixture of the polymeric material and the blowing agent; a blowing agent supply unit connected to the mixing unit and configured to convey the blowing agent into the mixing unit; an injection unit configured to inject the mixture, the injection unit includes a hollow metering cartridge configured to accommodate the mixture and a discharging member slidably disposed in the hollow metering cartridge and configured to discharge the mixture out of the hollow metering cartridge; a first flow control element disposed between the hot-melting unit and the mixing unit and configured to control flow of the polymeric material from the hot-melting unit to the mixing unit; and a second flow control element disposed between the mixing unit and the injection unit and configured to control flow of the mixture from the mixing unit to the injection unit; wherein the hot-melting unit includes a hollow pressing cartridge configured to accommodate the polymeric material and a pushing member rotatable within the hollow pressing cartridge, the mixing unit includes a hollow mixing cartridge and a mixing rotor rotatably disposed in the mixing cartridge, the mixing rotor is immovable in a direction parallel to the longitudinal axis of the mixing cartridge and is axially rotatable relative to the hollow mixing cartridge, the discharging member is movable in a direction parallel to a longitudinal axis of the hollow metering cartridge, the pushing member has a first groove annularly arranged over a surface of the pushing member, the first groove is in a first depth, the mixing rotor includes a first groove portion having a second groove and a second groove portion having a third groove, the first groove portion is arranged at one end adjacent to the hot-melting unit, the second groove portion is annularly arranged at the other end adjacent to the injection unit, and a groove depth of the second groove and a groove depth the third groove are different from the first depth, characterized in that the hollow metering cartridge is not axially rotatable relative to the hollow metering cartridge.