Indirect temperature monitoring for additive manufacturing

1 . A method for additive manufacturing of a dental appliance, the method comprising:

applying heat to a curable material conveyed on a carrier film of a printer assembly, wherein the heat is applied by one or more heat sources;

determining a current viscosity of the curable material while the curable material is conveyed on the carrier film of the printer assembly using one or more sensors;

determining a current temperature of the curable material, based on the determined current viscosity;

adjusting the heat applied to the curable material by the one or more heat sources, based on the determined current temperature, wherein the adjustment brings the current temperature closer to a target temperature; and

applying energy to the curable material to form a portion of the dental appliance.

2 . The method of claim 1 , wherein determining the current viscosity of the curable material comprises:

applying vibrations to the curable material using an agitator,

measuring a response of the curable material to the vibrations using the one or more sensors, and

determining the current viscosity of the curable material based on the response.

3 . The method of claim 2 , wherein the agitator is coupled to the carrier film.

4 . The method of claim 2 , wherein the agitator comprises a piezoelectric transducer or an ultrasonic transducer.

5 . The method of claim 1 , wherein determining the current viscosity of the curable material comprises:

positioning a flow restrictor in contact with the curable material,

measuring a first height of the curable material upstream of the flow restrictor using the one or more sensors,

measuring a second height of the curable material downstream of the flow restrictor using the one or more sensors, and

determining the current viscosity based on the first and second heights.

6 . The method of claim 5 , wherein the flow restrictor comprises a blade.

7 . The method of any claim 1 , wherein the current temperature of the curable material is determined at a first location of the printer assembly, and the energy is applied to the curable material at a second location different from the first location.

8 . The method of claim 7 , further comprising estimating a second current temperature of the curable material at the second location.

9 . The method of claim 1 , wherein the curable material comprises a polymeric resin.

10 . The method of claim 1 , wherein the energy comprises one or more of light energy or heat energy.

11 . The method of claim 1 , wherein the dental appliance is an aligner comprising a plurality of teeth-receiving cavities.

12 . The method of claim 11 , wherein the aligner is part of a series of aligners configured to reposition a patient's teeth according to an orthodontic treatment plan.

13 . A method comprising:

applying heat to a curable material to be used to form an additively manufactured object, wherein the heat is applied by one or more heat sources;

determining a current viscosity of the curable material while the curable material is conveyed on a carrier film using one or more sensors;

determining a current temperature of the curable material, based on the determined current viscosity;

adjusting the heat applied to the curable material by the one or more heat sources, based on the determined current temperature, wherein the adjustment brings the current temperature closer to a target temperature; and

applying energy to the curable material to form a portion of the additively manufactured object, after adjusting the one or more heat sources.

14 . The method of claim 13 , wherein determining the current viscosity of the curable material comprises:

applying vibrations to the curable material using an agitator,

measuring a response of the curable material to the vibrations using the one or more sensors, and

determining the current viscosity of the curable material based on the response.

15 . The method of claim 13 , wherein determining the current viscosity of the curable material comprises:

positioning a flow restrictor in contact with the curable material,

measuring a first height of the curable material upstream of the flow restrictor using the one or more sensors,

measuring a second height of the curable material downstream of the flow restrictor using the one or more sensors, and

determining the current viscosity based on the first and second heights.

16 . The method of claim 15 , wherein the flow restrictor comprises a blade.

17 . The method of claim 13 , wherein the current temperature of the curable material is determined at a first location of a printer assembly, and the energy is applied to the curable material at a second location different from the first location.

18 . The method of claim 17 , further comprising estimating a second current temperature of the curable material at the second location.

19 . The method of claim 18 , wherein the second current temperature is estimated based on one or more of the following: a movement speed of the curable material, an exposed surface area of the curable material, a radiant heat transfer coefficient of the curable material, or a convective heat transfer coefficient of the curable material.

20 . The method of claim 13 , wherein adjusting the one or more heat sources comprises adjusting one or more of the following: an amount of heat produced by the one or more heat sources, a direction of the heat produced by the one or more heat sources, an amount of time the heat is applied by the one or more heat sources, or a number of the one or more heat sources that are active.