A method for forming a hollow cylinder, in a single step, into a quartz glass tube with a large outer diameter and high dimensional stability is provided. To produce the tube, the cylinder, while rotating, is softened in portions in a heating zone which is moved at a relative feed rate Va and the softened portion is radially expanded by a centrifugal force and/or internal overpressure applied in the hollow cylinder bore so as to form a deformation zone. The radial expansion of the softened portion is carried out at a location-dependent radial expansion rate Vr, the profile of which along the deformation zone has a maximum value Vr,max which is smaller than 20 cm/min. The temperature in a rear heating portion of the heating zone, assigned to the end of the deformation zone, is lower than in a front heating portion assigned to the beginning of the deformation zone.

A method for shaping the mouth of a hollow precursor made of glass is provided, as well as glass produced thereby. The method includes heating the mouth of the hollow precursor; introducing a mandrel along a first direction into the mouth while the hollow precursor is rotating; and pressing shaping rollers along a second direction on an outside of the mouth while the hollow precursor is rotating with the mandrel in the mouth. The first and second directions are perpendicular to one another. The method can include moving the mandrel along second and/or third directions together or separate from expanding the mandrel along the second and third directions.

A method for shaping the mouth of a hollow precursor made of glass is provided, as well as glass produced thereby. The method includes heating the mouth of the hollow precursor; introducing a mandrel along a first direction into the mouth while the hollow precursor is rotating; and pressing shaping rollers along a second direction on an outside of the mouth while the hollow precursor is rotating with the mandrel in the mouth. The first and second directions are perpendicular to one another. The method can include moving the mandrel along second and/or third directions together or separate from expanding the mandrel along the second and third directions.

Methods for providing feedback control of converters for converting glass tubes to glass articles include a model predictive control framework. The methods include operating the converter, providing target values for attributes of the glass articles or glass tubes, measuring the attributes for the glass articles and glass tubes, conditioning the measurement data to remove outlier data points and calculating statistics representative of the measured attributes, and determine updated settings for one or more process parameters from the previous settings, the statistical properties, and the target values, where the updated settings are those that minimize an objective control function for the converter. The methods further include adjusting the process parameters to the updated settings. The model predictive control framework enables feedback control of the converter that compensates for disturbances that act on the process.

Methods for providing feedback control of converters for converting glass tubes to glass articles include a model predictive control framework. The methods include operating the converter, providing target values for attributes of the glass articles or glass tubes, measuring the attributes for the glass articles and glass tubes, conditioning the measurement data to remove outlier data points and calculating statistics representative of the measured attributes, and determine updated settings for one or more process parameters from the previous settings, the statistical properties, and the target values, where the updated settings are those that minimize an objective control function for the converter. The methods further include adjusting the process parameters to the updated settings. The model predictive control framework enables feedback control of the converter that compensates for disturbances that act on the process.