Coating Hypotubes, Part I
Today, Dave DiBiasio, Vice President of Sales and Marketing, and Dick Buxton, Director of Process and Application Engineering for Precision Coating’s (PCCI)— the leading authority on coating, medical instruments, both interventional and surgical, as well as robotic platforms in the world—are talking about hypotubes. They are answering many of the common questions customers and prospects ask.
Question: Are there any special considerations when coating hypotubes versus standard guidewires?
Answer: Hypotubes are very fragile; they will kink, bend, and damage very easily. When you ship hypotubes to us, the protection of them while coming to us is highly important. They usually are shipped in a hard tube, straight in length.
Question: That brings up the next consideration. Is it difficult to fixture and handle hypotubes versus the standard wires?
Answer: Yes, very much so. Core wires are much easier—they have some structural stability. The hypotube being very thin walled, it’s very easy to bend or kink. The fixturing of it is a little difficult—different than the regular core wire, but tape or mechanical fixturing is available.
Question: So, is it correct to say that the smaller the diameter of the of the hypotube, the more difficult it is?
Answer: Yes. The smallest hypotube that we currently handle is about 10-thousands. That is small. But we do work with larger diameters, and we do work with longer lengths—up to about 110 inches in length.
Question: How do you fixture these tubes? How do you attach them to the fixtures?
Answer: There are two different methods. In the 10-thousands diameter, it’s very highly unlikely that you’ll be able to get a tooling wire inside that hypotube—so those are usually taped onto a fixture. In using tape, and given the length of the hypotube, we need at least three inches of area that would be uncoated on each end to support that length of hypotube.
On shorter hypotubes, we can work with a little less of a whole point. The other method is mechanical, where we actually have the ability to put a mandrel inside; we can put that under a mechanical fixture and coat the whole length of the hypotube.
But when you get down to that 10-thousands, it’s difficult to use the mechanical fixture; it’s like trying to push a string in a straw. You’re just not going to get that fine wire in a 10-thousandth hypotube.
Question: Speaking of a tooling wire or a mandrel—in some cases, can that mandrel be built into the fixture?
Answer: It depends on the length of the hypotube we’re trying to coat and its ability to support itself in the length. There are some ways we can incorporate that tool or support mechanism in the fixture; but again, it has a lot to do with each customer’s particular needs.
Question: I get this question often, as obviously there are costs associated with the mandrels: can you reuse the mandrels?
Answer: We always prefer a new mandrel. With the smaller diameter mandrels, it’s difficult to reuse, and hopefully the cost associated with that is not going overcome the project. But in the larger diameter mandrels, they can be reused. Preferably they are clean, not bent, and full length—so we don’t have an assortment of lengths of mandrels coming to us.
Question: Can you reuse a mandrel, perhaps, three times?
Answer: Again, it all depends on how well they’re preserved in their use.
Question: Cleanliness for hypotubes and mandrels is very important, both for the tooling and for the tool itself. Talk to us about that.
Answer: In fact, there’s no way that we can check the cleanliness of the ID of the hypotube, so it needs to be clean before it gets to us. Then, the other is the mandrel itself. Hopefully it’s clean before for certain. There’s nothing worse than finding out you have a dirty mandrel in a clean hypotube. It kind of defeats the purpose.
Question: Yes. You mentioned the insertion of that mandrel and that everything has to be clean. Sometimes we actually receive the units with the mandrel inserted by the customer. And then sometimes we do that work ourselves. It’s very important for you, as the customer, if you’re going to do that work on the front side, to ensure that everything is very clean—mandrel and the hypotube.
Coating Hypotubes, Part II
Click on part two of our video discussion about hypotube coatings to further explore more questions customers ask us about hypotubes.
Question: What diameter and length can you coat hypotubes?
Answer: We can coat any diameter or from 10-thousands to 80-thousands, and lengths from 25 millimeters up to 110 inches.
Question: What’s the recommended coating for hypotubes?
Answer: Given where they are used, a solvent coating is almost always used.
Question: Are there specific properties associated with solvents that lend themselves well to the hypotubes?
Answer: It has good adhesion characteristics, given the surface texture or profile of the hypotube being highly polished; solvent is definitely the preferred coating.
Question: Which means it has good bondability?
Answer: Correct. And it has good lubricity too, as well, making it a good universal coating.
Question: Is there a minimum tolerance for holding a hypotube in the fixture?
Answer: It really depends on how the hypotube comes to us. Some hypotubes in the 10-thousandth diameter will come to us straight-up hypotube, no tooling inside. In those particular cases, we need 3 inches on each end, given the length to be somewhere around 110 inches; in the larger diameters, you could probably put a tooling wire in, and it would almost be beneficial to have one. We can coat the full length. In that case, you can coat the entire hypotube with a tooling mandrel in it.
Question: Can you mask the tubes?
Answer: Yes, we can. We can mask the ends of the hypotubes, and we can also mask some areas in the medial section.
Question: So, you can put marker bands, if needed?
Question: And the last—and dreaded—question is: can the ID of a hypotube be coated?
Answer: That’s a special application, and it’s one that would have to be discussed with the customer to understand the real need for the coating—how it would be measured, and the length of the tube. There’s a lot that would have to be reviewed.
We’re happy to share these insights with you and hope they help you prepare for your next high-performance coating project. If you have any other questions, please check out more information on our website, or give us a call at any of our three locations: Hudson, Massachusetts, Coyol Free Zone & Business Park in Alajuela, Costa Rica, and Woonsocket Rhode Island.
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