Volumetric feed control for flexible filament

A volumetric feed control apparatus for use in a three-dimensional modeling machine of the type that builds physical objects from a solid build material element having a cross section by depositing molten build material element in multiple layers from the application tip of a dispensing head, said machine supplying the solid build material element to the dispensing head using an element advance mechanism operable at a variable controlled feed speed, the volumetric feed control apparatus comprising:

• sensing means positionable to be in sensing relation to the solid build material element, for sensing physical parameter data of the build element corresponding to the cross-section of the build element at a measured portion of the element, and for generating measurement signals corresponding thereto;
• variable-speed drive means operatively connectable to the element advance mechanism, for controlling the feed speed of the element advance mechanism;
• and
• a control operatively connected to the sensing means and operatively connected to the variable-speed drive means, for adjusting the speed of the element advance mechanism as a function of the measurement signals at times appropriate to compensate for a lag response between the sensing of physical parameter data of the build element and arrival of the measured build element portion at the application tip, to thereby control the volumetric flow of molten build material element through the application tip.

In a machine for making three-dimensional physical objects from a solid build material element having a cross section by depositing molten build material element in multiple layers through the application tip of a dispensing head, said machine supplying the solid build material element to the dispensing head using an element advance mechanism operable at a variable controlled feed speed, a method for controlling the volumetric flow rate of the molten build material element at the application tip comprising the steps of:

• sensing physical parameter data of the solid build material element corresponding to the cross section of the build element at a measured portion of the element, at a sensing position;
• generating measurement signals corresponding to the sensed physical parameter data;
• conveying the measurement signals to a control;
• using the measurement signals to compute an effective cross section of the build material element;
• providing the control with the distance between the sensing position and the application tip and the distance between the sensing position and the element advance mechanism;
• computing a lag response due to the time lag between the sensing of physical parameter data of the build element and arrival of the measured build element portion at the application tip;
• providing a variable-speed drive means operatively connected to the element advance mechanism for controlling the feed speed of the element advance mechanism;
• and
• supplying control signals from the control to the drive means to adjust the speed of the element advance mechanism as a function of the effective cross section, at times appropriate to compensate for the lag response.