Fix Tubing Diameter Variation on Your Extrusion Line

Tolerances vary by material and application, but medical and catheter tubing routinely requires OD tolerances of ±0.001" to ±0.003". Achieving these tolerances demands ultra-stable internal air pressure. On Line Controls' MicroAir regulators maintain accuracy to ±0.1% of full scale and can regulate pressures below 1 inch of water, enabling consistent diameter control well within tight medical-grade specifications.

Diameter variation is most commonly caused by unstable internal air pressure during free extrusion. Fluctuating factory air supply, inconsistent flow rates, or imprecise manual regulators create pressure spikes and drops that directly change the tubing bore. MicroAir regulators eliminate this by maintaining hysteresis-free, constant pressure regardless of varying downstream flow rates.

MicroAir I units use a manual 30-turn knob for set-point control — ideal for stable, single-diameter runs. MicroAir II adds contact closure inputs (Air Up / Air Down) to accept signals from an OD gauge or external controller for automatic closed-loop diameter correction. MicroAir IV accepts a 0–10V analog or PLC input and delivers sub-100ms high-speed response, making it suitable for bump and taper tubing production.

Yes. MicroAir IV models accept a 0–10V analog input compatible with PLCs and other control devices. MicroAir II models accept contact closure (Air Up / Air Down) signals from OD gauges or line controllers. Both interfaces allow closed-loop diameter control, with the MicroAir IV offering the highest speed response — typically under 20 milliseconds — for dynamic process control.

Each lumen in a multi-lumen tube requires its own independently controlled air pressure channel. On Line Controls offers dual-channel and 3- to 4-channel MicroAir units in a single stainless steel enclosure. Each channel can be configured with a different pressure range and its own digital display, allowing precise, independent diameter control for every lumen simultaneously.

MicroAir regulators are available in ultra-low ranges starting from 0–2 inches of water, with options up to 0–5 psi. Most plastic tubing extrusion applications fall within the 0–3 inches of water to 0–3 psi range. A range change service is also available if your process requirements change after purchase, and units ship configured to your specified range.