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Dynamically controlled screw-driven extrusion

  • US 10,684,603 B2
  • Filed: 01/13/2016
  • Issued: 06/16/2020
  • Est. Priority Date: 01/13/2015
  • Status: Active Grant
First Claim
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1. A screw-drive extrusion system comprising:

  • a toolhead, the toolhead comprising;

    a screw-drive extruder, the screw-drive extruder comprisingan upper housing portion defining at a proximal end at least one feedstock port for receiving a flow of feedstock material;

    a lower housing portion defining at a distal end an extrusion die defining an extrusion opening, said lower housing portion cooperating with said upper housing portion to define an elongated inner bore having a sidewall;

    an elongated screw having at least one flight, said screw comprising a shank portion and a drive portion, said drive portion riding within said elongated inner bore, said at least one flight cooperating with said sidewall to advance feedstock material received via said at least one feedstock port toward said extrusion opening;

    a bearing assembly joined to said upper housing portion and comprising support bearings for supporting said shank portion of said screw; and

    a heater positioned about said lower housing portion intermediate said upper housing portion and said extrusion opening;

    a motor, said motor comprising a drive shaft coupled to the elongated screw;

    a hopper for receiving feedstock pellets, anda conduit extending from a lower end of said hopper to the at least one feedstock port of said screw-drive extruder, said conduit being adapted for conveying feedstock pellets from said hopper to said screw-drive extruder;

    anda control system for dynamically controlling operation of the toolhead, said control system comprising;

    a motor speed sensor configured to monitor motor drive shaft position over time and send corresponding motor position data signals to a control processor;

    a motor driver configured to send a motor control signal to the motor;

    a temperature sensor configured to monitor temperature over time and send corresponding temperature data signals to the control processor;

    a heater controller configured to send a temperature control signal to the heater;

    said control processor comprising a microprocessor, a memory, an input/output data acquisition connector, firmware, and instructions stored in the memory and executable by the microprocessor to provide a motor control loop and a temperature control loop,said motor control loop comprising instructions stored in said memory and executable by said microprocessor to send a first control signal to said motor driver to cause said motor to operate in accordance with a speed set point;

    said temperature control loop comprising instructions stored in said memory and executable by said microprocessor to send a second control signal to said heater controller to cause said heater to operate in accordance with a temperature set point; and

    an extrudate flow controller comprising instructions stored in said memory and executable by said microprocessor to determine, repeatedly over time, a current temperature set point and a current speed set point,the extrudate flow controller further comprising instructions stored in said memory and executable by said microprocessor to receive, from an external control system, a command for filament length and motor speed for a wirefeed extrusion system, and for determining said current temperature set point and said current speed set point as a function of said filament length and motor speed instructions, said current temperature set point and said current speed set point being determined by calculating a desired volumetric flow rate as a function of said filament length and motor speed instructions and by referencing calibration data stored in said memory to determine said set points.

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