An extrusion device for producing an object having a cavity, in particular a tube or a container, includes a material feed that opens into an extrusion nozzle, and a support gas feed that opens into a blow-in opening for introducing support gas into the interior of the resulting object, wherein the support gas feed has at least one valve for regulating the support gas, characterized in that at least one valve for regulating the support gas is a proportional valve which can be regulated by a controller.

A process for forming a film for dynamically vulcanized alloy comprising at least one elastomer dispersed within a thermoplastic resin domain wherein the film is characterized by low shrinkage rates after completion of the formation of the extruded film. The film has a shrinkage rate, measured at not earlier than 96 hours after formation of the film, of less than 1.5% relative to the film width as measured just after film formation. During formation of the film, the extruded film is subjected to a cooling rate of less than 97 C. per second and the frost line of the extruded film is greater than 135 mm.

Silicone tube structures are formed having a particular dimensional accuracy. In one embodiment, a silicone tube structure can include an extruded hollow body having an inner bore. The extruded hollow body can have an inner diameter, an outer diameter, and a length of at least approximately 20 m. The extruded hollow body can also have a dimensional accuracy that is measured by the standard deviation of the inner diameter being no greater than approximately 0.8% of an average inner diameter of the extruded hollow body over the length. In an embodiment, the silicone tube structure can be cut to form a number of silicone tubes.

A method for determining the position of a frost line of a tubular film of thermoplastic material during its manufacture, includes: detecting a temperature profile of the tubular film along a first measuring track along the axis of production; determining a first provisional position of the frost line along the first measuring track at which an absolute value of a temperature gradient of the temperature profile in the production direction falls below a first predetermined value; detecting a diameter profile of the tubular film along a second measuring track along the axis of production; determining a second provisional position of the frost line along the second measuring line at which an absolute value of a diameter gradient of the diameter profile in the production direction falls below a second predetermined value; and checking the plausibility of the first provisional position and the second provisional position based on a distance therebetween.

A method is disclosed for determining at least one geometric parameter of an object comprising a molten component. The method includes determining a relationship between a refractive index of the object and a shrinkage occurring during a solidification of the object. The refractive index and at least one geometric parameter of the object comprising the molten component is determined using a measuring apparatus. At least one geometric parameter of the solidified object from the refractive index and the at least one geometric parameter of the object comprising the molten component is determined using the measuring apparatus and taking into account the determined relationship between the refractive index of the object and the shrinkage occurring during the solidification of the object.

A device for determining the temperature of a tubular strand conveyed out of an extrusion device includes at least one temperature sensor configured to measure a first temperature of an outside of the tubular strand at a first position of the tubular strand. An evaluation apparatus further included and configured to compare the first temperature with a second temperature of the outside of the tubular strand at a second position of the tubular strand and determine at least one of a temperature within the tubular strand or a temperature on the inside of the tubular strand at a position of the tubular strand based on the comparison of the first and second temperature.

The invention relates to a blown film system for producing a film tube made of plastics material, comprising: an annular nozzle, out of which a plastic melt having a closed cross-section can be brought; a take-up device, by means of which the plastic melt can be drawn up from the direction of the annular nozzle so as to form the film tube; an air-provision device, which is downstream of the annular nozzle when viewed in the transport direction of the film tube and by means of which an amount of air can be provided; and a calibration device, which is downstream of the annular nozzle when viewed in the transport direction of the film tube and surrounds the film tube and by means of which the outer circumference of the film tube can be delimited. At least one detector is contained that has a plurality of detection elements, by means of which electromagnetic radiation emitted or reflected at various points of the film tube can be detected, such that at least one planar region and/or contoured region of the film tube can be detected with regard to characteristic properties, wherein the detector comprises at least 32 detection elements.