Precise stable air pressure is a critical component in the extrusion of small plastic tubes....
On Line Controls has achieved the milestone of 40 years in the extrusion tubing equipment business selling a niche product is a feat we have accomplished by being the best in the business. On Line Controls is recognised globally as the leader in high-precision ultra-low air pressure regulation.
The simplicity of our regulators and the small but important part we play in the free extrusion of plastic tubing leads many to think that we are not essential. In fact, most articles about tubing extrusion only make a small reference to air pressure usually calling it “using free internal-air tube processing”, “internal air”, “positive pressure” “internal air pressure”,” in-line air pressure”, or “support air control”.
Our air pressure regulators and controllers are used by some of the most well-known and niche medical tubing manufacturers to make some of the world’s smallest and complex tubes with the tightest tolerances. The precision is needed to be capable of precisely controlling even the slightest pressure variations when making complex medical tubing. For many years the industry would choose between making medical tubing with vacuum or air regulation but as the tubing has changed, with different types of plastics properties and with smaller OD, ID and Wall, many now require the use of both vacuum (used to minimise water drool at the tank entrance) and air to hold the dimensions. Single-lumen, multi-lumen, medical, catheters, bump, taper, co-extrusions, profile, balloon, multi-layer, automotive, co-extrusion, custom extrusion, micro-tubing, and new thinner walls tubes are just some of the products that require a MicroAir unit during the extrusion process.
“Less air is best as air is compressible,” says Bob Bessemer of Novatec. Over the years we have seen our customers ordering lower and lower ranges of air pressure. Many now using air pressure below 1” of water (0.036 psi). Each MicroAir unit has a customised range chosen by the customer.
Changes to our MicroAir, ultra-low air pressure regulators and controllers over the last 40 years have included adding a model MicroAir II which can be controlled by contact closures with up/down signals usually from an OD Gauge; and the MicroAir IV designed initially with high speed switching for bump and taper tubing (now also used for 0-10 volt input control from PLC or other controller). The MicroAir III was a 1980’s version that was retired when the MicroAir IV came out. Digital Display and output options of voltage or current for closed-loop control were added to the MicroAir II and MicroAir IV models in the 1990s. Also added to the line was a remote control unit for the MicroAir II with 100’ cable to control the unit from the end of line; and more recently a stand with rollers. Multilumen tubing can require our 2, 3 or 4 channel units to supply air to each lumen.
Kay DeWolfe, President of On Line Controls says, “The most important changes to our MicroAir units have been internal. While the outside stainless-steel box and the controls have not changed, smaller tighter tolerance’s on the internal parts have made for higher the precision, stability, and reliability.” Built to last 10 – 20 years, MicroAir units are rarely returned for repair but should be replaced after 15 years as the internal parts will start to wear down and lose accuracy.
Our name “On Line Controls, Inc.” while sounding like it has something to do with computers, was actually founded in 1980 before the internet was started. It stands for equipment used on an extrusion line to control the internal air pressure (MicroAir) and also On Line Controls was the first manufacturer of ultrasonic Wall thickness measurement equipment (known as the UltraGage). Now, this technology is used on almost every extrusion line and has become a necessity when extruding tubing and pipe. The UltraGage line was sold off in 2007 when the former owner, who was one of the original design engineers of the ultrasonic wall thickness technology and software retired.
The MicroAir, ultra low air pressure regulators and controller models; and motorised potentiometers which were used to control speed on an extrusion line, are the main products now. President DeWolfe says, “On Line Controls continues to improve the precision and accuracy of our products”.
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