How is a hypotube made

Laser Cut Hypotubes (LCHT) have revolutionized how catheters are manufactured while also pushing the fold on what is achievable with a catheter. Compared to traditional braid or coil systems, LCHT lend catheter shafts increased tensile strength, kink resistance, column strength, and more, all of which allow for catheters to reach more challenging anatomies. So what is it about LCHT that causes it to outperform traditional reinforcement methods? The answer is two-fold. Firstly is the precision and customizability of the laser cut pattern, which can impart the stainless steel hypotube with predictable flexibility at any given point along the shaft. This wouldn't be possible of course without the hypotube itself, which brings us to the second root cause for LCHT's high performance in catheters: the hypotube.

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Why hypotubes?

For a long time humanity has made use of hollow tubes, their first medical uses dating all the way back to Roman and Greek times when Physician, Surgeon, and Philosopher Galen made use of simple piston syringes to deliver ointments to the body. Hypotubes, or medical grade needle tubing quickly became a standard for modern medicine due to their uniform inner diameter, outer diameter, wall thickness and unbeatable strength. Thus hypotubes made for an easy choice as a material for catheters for delivery and extraction of fluids to and from the body. Advancements in laser cutting allowed engineers to create flexible hypotubes, giving way to today's new innovative devices. Though laser cutting hypotubes is an advanced manufacturing process, the creation of hypotubes themselves is equally as impressive. Let's take a look at how precision medical grade tubing is manufactured, and how this process creates tubes with unbeatable mechanical properties.

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How are hyptoubes manufactured?

The process of manufacturing a hypotube starts with large sheets of thin stainless steel which is cut into a series of uniform strips in a process called slitting. Our approved vendors follow strict processes and guidelines to ensure repeatable results with exact tolerances and clean edges. These thin strips of stainless steel are then coiled in long lengths before they are formed into their final tubes. During the forming process, the stainless steel strips are progressively bent from their original flat shape to a circular profile by a series of precisely positioned rollers. At the end of these rollers, once the stainless steel has reached a circular profile, a continuous welder joins the material at the seam, creating a true seamless tube.

Now the hypotube is starting to look more like one would expect: a tube. The next steps are plugging and sinking where a floating plug is placed in the inside of the tube. The size of the plug will determine the inner diameter of the final tube. With the plug placed inside the tube, it is then pulled though a diamond die with a precisely sized hole that determines the outer diameter of the final tube. This process is called cold working, where the shape of the stainless steel is manipulated without the use of heat, and it is an important part of what makes hypotubes an excellent choice for catheter reinforcement. Cold working increases the tensile strength of the hypotube though an increase of dislocations in the crystalline structure of the metal, which is a critical performance characteristic for catheters. Cold working also results in a smoother surface finish, higher dimensional accuracy, and increased corrosion resistance all of which are important material considerations for catheter engineers. 

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The hypotube now has highly accurate and consistent dimentions along the entire length of the tube and can now be annealed (heat treated) to achieve even more custom material properties. Annealing can relieve stress in the tube and allow for further reductions if necessary. One such method for further reductions is centerless grinding, where the hypotube is placed between two abrasive grinding wheels to remove some portion of the outer diameter to achieve a higher OD to wall thickness ratio.

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At this point the tube has reached all of it's final dimensions besides the length. The hypotubes are now cut to length through one of several processes depending on the desired end-finish. Some tubes are sheared which results in a crimped end, others are laser cut for a clean, burr free cut. Other cutting methods are also available, and the preferred method depends on the end application of the hypotube.

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Secondary processing

Parts are then cleaned through ultrasonic electrolysis or laser finishings before they are carefully inspected for their physical properties and surface finish. Different inspection sampling plans are available depending on the customer's quality needs.

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The completed hypotubes are then sent to Symmetry Laser where we preform the high precision laser cutting which turns the already impressive hypotubes into advanced flexible reinforcement for innovative medical devices. After we cut our customer's tubes, we also take great care to de-burr, clean, and inspect finished parts to our customer's exact needs.

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