Calibrating deposition rates in selective deposition modeling

A closed loop selective deposition modeling system for dispensing a build material to form a three-dimensional object in a layerwise fashion, the system comprising:

• means for generating data descriptive of the three-dimensional object;
• means for supporting the three-dimensional object as it is formed;
• means for dispensing the build material according to the data to form a layer of the three-dimensional object, the dispensed layer having a thickness greater than a desired layer thickness by an excess amount;
• means for dimensionally normalizing the layer to remove the excess amount of build material and thereby establish the desired layer thickness;
• means for measuring the power utilized in dimensionally normalizing the layer to obtain a measurement indicative of the amount of excess material removed.

A closed loop selective deposition modeling apparatus for forming a three-dimensional object by dispensing a build material in a layerwise manner, the apparatus comprising:

• a platform for supporting the three-dimensional object as it is being formed;
• a dispenser for dispensing the build material to form the layers of the three-dimensional object as it is being formed;
• a planarizer for dimensionally normalizing the layers of the three-dimensional object by removing excess build material to establish a desired layer thickness, the planarizer being rotated at a substantially constant angular velocity utilizing a substantially constant power level when dimensionally normalizing the layers;
• a means for measuring the substantially constant power level utilized by rotating the planarizer at a substantially constant angular velocity when dimensionally normalizing the layers;
• a waste collection system for collecting the excess build material from the planarizer;
• at least one controller in communication with the platform, dispenser, planarizer, and means for measuring the substantially constant power level, the controller for selectively dispensing the build material according to data descriptive of a layer for each layer of the three-dimensional object and for dimensionally normalizing the layers;
• and wherein the controller adjusts the amount of excess build material collected by the waste collection system in response to the measurement of the power taken by the means for measuring the substantially constant power level.