Liquifier pump control in an extrusion apparatus

In an extrusion apparatus having an extrusion head including a liquifier which receives a solid element of a modeling material, heats the modeling material, and outputs a flow of the modeling material at an output flow rate while the extrusion head moves along a predetermined tool path at an extrusion head velocity, the apparatus using a material advance mechanism to supply the solid element of modeling material to the liquifier at an input rate which controls the output flow rate, a method of controlling the output flow rate comprising:

• determining an extrusion head velocity profile and an extrusion head acceleration profile based on the tool path;
• calculating the input rate of modeling material to the liquifier required to achieve an output flow rate of modeling material from the liquifier that is proportional to a current extrusion head velocity corresponding to the extrusion head velocity profile, the input rate being calculated based on the extrusion head velocity profile, the extrusion head acceleration profile and a time constant;
• and
• controlling the input rate of modeling material to equal the calculated input rate.

An extrusion apparatus comprising:

• an extrusion head movable along a predetermined tool path at an extrusion head velocity;
• a liquifier carried by the extrusion head which receives a solid element of a modeling material, heats the modeling material, and outputs a flow of the modeling material at an output flow rate;
• a material advance mechanism which supplies the solid element of modeling material to the liquifier at an input rate that controls the output flow rate;
• a modeling system for determining an extrusion head velocity profile based on the tool path;
• and
• a control system for providing control signals to the material advance mechanism, the control signals commanding operation of the material advance mechanism to have an input rate of modeling material to the liquifier that produces an output flow rate of modeling material from the liquifier that is proportional to a current extrusion head velocity corresponding to the extrusion head velocity profile.

An extrusion apparatus comprising:

• an extrusion head movable along a predetermined tool path at an extrusion head velocity;
• a liquifier carried by the extrusion head which receives a solid element of a modeling material, heats the modeling material, and outputs a flow of the modeling material at an output flow rate;
• a material advance mechanism which supplies the solid element of modeling material to the liquifier at an input rate that controls the output flow rate;
• and
• a control system for providing control signals to the material advance mechanism, the control signals commanding operation of the material advance mechanism to have an input rate of modeling material to the liquifier that produces an output flow rate of modeling material from the liquifier that is proportional to a current extrusion head velocity corresponding to an extrusion head velocity profile based on the tool path.