High precision extrusion of glass tubes

Abstract

Precision glass tubes for analytical instrumentation often require tight tolerances in their inner and outer diameter, which makes them cumbersome to fabricate. The extrusion method is a potential method for the fabrication of precision glass tubes, however, the effects of die swell and taper which occur during the extrusion process can distort the final product. This work aims to determine the tolerances that can be achieved for glass tubes fabricated using the extrusion method by comparing the extent of the die swell and tapering on tubes extruded under a variety of extrusion parameters. Lead‐silicate glass tubes of 6.5 mm outer diameter and 0.50 mm inner diameter were fabricated with a taper of <1% for the outer diameter and <5% for the inner diameter over 200 mm lengths. This target geometry was achieved using a volume flow rate of 4.7 mm3/s, a glass viscosity of 107.2 Pa.s and a die geometry that accommodated a 8%‐10% offset due to die swell. This result indicates the extrusion method is a viable method for producing glass tubes with tight tolerances for applications in analytical instrumentation.

Phosphate glass-based microstructured optical fibers with hole and core for biomedical applications

“…Also, a 15 and 1% reduction in ID/Pin and OD/Die ratio for the (4.5 mm -10 mm) die. These results align with Kalnins et al with noticeable improvements [46]. To assemble the preform, the strategy employed for the stack-and-draw is illustrated in the schematics of Figure 1.…”

“…Since the glass is hanging under its weight at higher speeds for a shorter time and at lower temperatures, the glass is in a more viscous state during the period it is hanging from the lower part of the die channel. Subsequently, increasing speed and reducing the temperature during extrusion leads to the higher force needed for extrusion [46].…”

Toward the fabrication of extruded microstructured bioresorbable phosphate glass optical fibers

“…Although the swelling effect cannot be removed at all but simply limited by reducing the friction at the glass/die interface, it does not significantly influence the flow inside the die but causes a dimensional growth of the features of the glass preform. If precise tube dimensions are required, the amount of these distortions can be taken into account as detailed by Kalnins et al 62 In our case, both the temperature control, which influences the glass viscosity, and the weight of the extrudate due to the relatively low glass density (compared to other glass systems), 63 as well as the preform dimensions, led to homogenous and controllable distortions in the extruded products.…”