Control OD Variation in Plastic Tubing Extrusion

Plastic tubing extrusion involves melting polymer resin and pushing it through a die to form a continuous tube. Internal air pressure is introduced to support the tube's bore and size the outside diameter. Regulating that internal air pressure with precision — typically in the ultra-low range of 0–5 psi or below — is essential to controlling wall thickness and OD consistency.

Key extrusion parameters include melt temperature, screw speed, line speed, die geometry, cooling water temperature, haul-off speed, and internal air pressure. Internal air pressure is one of the most sensitive parameters: small changes directly affect OD and wall uniformity. MicroAir regulators address this by maintaining pressure set points with ±0.1% full-scale accuracy and responding in under 0.1 seconds.

MicroAir units cover ultra-low pressure ranges starting at 0–2" or 0–3" of water column up to 0–5 psi. Range change service is available, and each channel in multi-channel units can be configured to a different range to suit the specific lumen or tubing geometry being extruded.

Yes. MicroAir II models accept Air Up / Air Down contact closure inputs from OD diameter gauges or external controllers. MicroAir IV models accept a 0–10 volt analog input, enabling direct PLC integration for closed-loop diameter control, bump-and-taper switching, and automated profile changes without manual intervention.

Each lumen in a multi-lumen tube requires its own independently controlled air channel. OLC offers dual-channel (2-lumen), 3-channel, and 4-channel MicroAir units. Each channel can have a different pressure range, its own display, and its own output option, making it straightforward to control complex multi-lumen catheter or medical tubing profiles.

MicroAir IV units respond in less than 0.1 second — typically around 20 milliseconds for a 50% full-scale step change. This high-speed response is achieved via a precision voice-coil linear motor with viscostatic damping and is essential for bump-and-taper tubing applications where the pressure set point must switch rapidly between two programmed levels.