Abstract: An example method for estimating a media level of a media stack in a printer includes storing a media level model correlating a picker metric of a media picker to pick media from the media stack to the media level; measuring a current picker metric when the media picker picks the media from the media stack during a print job; adding the current picker metric to a historical data set; updating the media level model by generating a regression for the historical data set; and based on the current picker metric and the updated media level model, estimating a current media level of the media stack.

Abstract: In one example, a carriage control process using rotary encoder counts includes: reading an outbound rotational count for a carriage drive when the carriage reaches a first translational reference position in an outbound pass along a path; reading a return rotational count for the carriage drive when the carriage reaches a second translational reference position on a return pass back along the path; advancing a rotational start count for the carriage drive at the beginning of a next outbound pass if the outbound count is less than the first reference count and the return count is less than the second reference count; or retarding a rotational start count for the carriage drive at the beginning of the next outbound pass if the outbound count is more than the first reference count and the return count is more than the second reference count.

Abstract: In one example, a roller control process for a 3D printer includes stopping the layering roller rotating at angular home before the roller reaches linear home at the end of a fusing pass, measuring the duration between when the roller reaches angular home and when the roller reaches linear home, and, if the duration exceeds a threshold, then stopping the roller rotating at angular home at a distance closer to linear home in subsequent fusing passes until the duration does not exceed the threshold.

Abstract: In one example, a roller control process for a 3D printer includes stopping the layering roller rotating at angular home before the roller reaches linear home at the end of a fusing pass, measuring the duration between when the roller reaches angular home and when the roller reaches linear home, and, if the duration exceeds a threshold, then stopping the roller rotating at angular home at a distance closer to linear home in subsequent fusing passes until the duration does not exceed the threshold.

Abstract: An example of an apparatus is provided. The apparatus includes a vacuum source to draw gas and a build material from a build process. The apparatus includes a filter to separate the build material from the gas. A filtered portion of the build material is to be deposited on the filter and a collected portion of the build material is to be redirected. The apparatus includes a storage container to receive the collected portion of the build material. The apparatus includes a mass estimation engine to determine a total mass of the build material. The mass estimation engine is to estimate a mass of the filtered portion.