Carbon fibre as a foot orthotic material

Well, no ofence, but if you replaced 2 in a week, I thought you might need one. It was not "in how to make an orthosis" , it was in how much to melt the CF. Maybe now you "comprehend" more.

With reference to polyprop,

It doesn't. Read my posts above. Different people have different opinions, this is how we are. You have yours , me along with some of your customers have other. Your customers know what they want , they just don't know why. And I was trying to explain in my post "why". I don't care how many of you use PP or CF or whatever is . I said it before , you can do whatever you like.

 

Try to avoid the one based on Acrylic. That one cracks sometime. It is lighter though.

 

I have used both very successfully. Polypro is a safer first pair as you can more easily reduce its thickness with grinding or polishing etc. However, once you know what you will do in the future, especially if the first polypro pair is good, carbon fiber device are as strong or stronger with less volume and weight. Very good for dress shoes and various racing/low profile footgear... Soccer boots, skates, sprint shoes and so on.
Freeman

 

Mahone,

My comprehension is fine. Perhaps you should re read what you wrote to see why your advice was incomprehensible

I don't personally make devices any more. The two failures to which I refer were made by 2 well respected labs. I know how to melt carbon fibre. I should hope that they do too.

That being said, I had 2 carbon fibre devices made by 2 different labs that failed within 1 week. In 10 years of having polyprop devices manufactured by different labs, I have had 2 failures.

Still a no brainer.

Allow me the opportunity to offer you some advice

By all means, have your opinion, but don't come on to a forum where some of the best names in the business offer sound, experience based advice and make statements that are ill educated.

You might come out of it looking like you have little credibility

Robin

 

Well maybe you can try to think this way : -If unfortunately an orthotic cracks in the shoe, the patient is not happy , but takes it off.
-If an orthotic modify its shape in time little by little, the patient doesn't notice it, and is happy for a while, but that orthotic is a lie, because is not doing anymore what is suppose to.
If you don't like CF , feel free don't use it, there are other materials. But I believe polypro is not good for patients, because bottoms out and doesn't serve the purpose it was made for and what was paid for.
I thought this is an open forum.
What I said above is technically right, if you don't agree with me it does not mean that my "statements are ill educated" .This is just your "agressive" way to talk. So what you do is trying to shut down anyone who does not have your opinion.
Again, I thought is an open forum and I made reference in my posts only to materials, not to people posting here.

 

Mahone both poly and Cf have their place. Material failure is uncommon period; carbon fiber rarely cracks and poly does hold its shape for years typically. They are both excellent materials and suit different purposes, the point made was that CF is a new age material and for some their preference is a standard (poly) that has served patients well.

The response that you received was because your denunciation was very severe. I'm fond of saying that if Slick Willy, Bill Clinton had just said "yes that young intern gave me oral sex" and admitted he was wrong, the whole thing would have gone away.

Food for thought..

 

David, I already did that few posts above :

"It looks like I've touched a sensitive chord regarding polypro.
Although the replies to my comment are fairly true "somehow".
I didn't mean to upset anyone, I just express the feeling I had reading the posts. I did not advise anyone what to use or what to not, everyone does it accordingly with its own customers."

 

I actually have very little experience with carbon graphite devices, but among the plastics I have worked with:

Polypropylene is generally the most accepted in our industry, at least for cadcam based products. It does, however, stress relieve as it's cut, which can sometimes affect tolerances. As to the differences between thermoformed and machined, It's also likely that there's tempering of the material similar to what occurs in metals when they're heated and cooled.

HDPE has poor machining characteristics but is similar in strength to polypro. Of all of the plastics I've worked with, this material tends to stick to the cutting tool the most. Conversely, finish grinding easily results in a polished finish. Thermoforming characteristics are unknown.

UHMW is tougher than polypro and less flexible but has poor finish grinding quality.


ABS has better machining and thermoforming characteristics but has yet to be used significantly in terms of manufacturing of foot orthoses.

Delrin (AKA acetal) is probably the nearest comparison to carbon graphite and also has better machining characteristics than Polyproplene. It is also more than twice as expensive. Additionally, and unlike polypropylene, it does not stress relieve when cut and can be cut with greater accuracy. Many of the laboratories I work with use this material as an alternative to carbon graphite. It is more than twice as strong as polyproplene, has excellent machining characteristics, and like HDPE, grinds easily to a polished finish.

 

The polypropylene orthotics that I made for myself a decade ago is virtually indestructable. The hundreds of pairs of Carboplast graphite orthotics that I have fabricated also holds up wonderfully. Initially, some of my Carboplast came back broken. I didn't realize that the shell had to be cut diagonally, not parallel or perpendicular to the grain of threads.:bash:

When using my 20 grit tungsten carbide wheel along with 20 grit Norzon zirconia abrasives, graphite or polypropylene poses no problem while grinding it.

If you ever had to adjust Carboplast via heat, it proves far superior over polypropylene. Although Carboplast is made of polypropylene, the graphite layers promotes even, consistent molding. Whereas, polypropylene will contract and expand in various spots, due to the fluctuation of temperatures in some areas of the orthotics, causing it to distort and warp.

If there is a chance that you will have to adjust the orthotic shell, stick with graphite/polypropylene. Polypropylene should not be adjusted with heat.

 

Most Carbon composite sheet materials used in foot orthosis manufacture use Polypropylene as their primary bonding matrix together with Acrylic. The addition of Graphite is there as a polymer flow lubricant to help the forming process and adds little to the overall strength of the finished product. Polypropylene is long chain Hydrocarbon polymer that will soften at around 190 degrees C, Carbon composites will soften at a slightly higher temperature due to the insulating characteristics of the carbon. Carbon becomes fluid at around 4000 degrees C so over cooking it is highly unlikely.
One thing to remember when using Carbon, when your patient wished to dispose of their orthosis or have them replaced, they'll be around for a very very very long time. They don't biodegrade because there's nothing for them to degrade into .... they're Carbon ... an element.
Polypropylene will eventually decay back into hydrocarbon .... oil

 

In my 15 years of fabricating devices I've found that the material selection is first dictated by the patient's pathologic need and secondly must be matched to the intended use. Third is comfort. Fourth is price. Fifth is time. Sixth is color. I have a novel method of creating a CF orthotic that, while expensive, performs remarkably well and lasts virtually forever. It is my top-of-the-line device and I sell more of these than any other style because they satisfy all the above conditions and are infinitely adjustable to accommodate pathologic changes and patient desires. CF is the only material that allows me the freedom to manipulate stiffness by changing dimensional shape without altering the inherent elastic modulus, making deformation under load more intuitively predictable than other shell material.

 

But, I'll use a football and a pair of Crocs to give my patient relief if I have to. And I have! I strive to match the device to the materials that are indigenous to the patient's home country. CF is often not selected simply because it is unavailable in certain areas of the world. I've used coke bottle plastic, banana leaves, palm bark, and even a soccer ball top cover! So please be open to all materials and learn to use them. CF may have some unique properties but it is not better or worse, simply different.

 

:boxing:My 450hp '72 Chevelle SS454 says you should pick another analogy, friend :butcher:

 

Aloha,

This is a great thead.

Here is a very educational link.

http://www.acmanet.org/bsa/index.cfm

It is the latest merit badge for the US Boy Scouts on Advanced Compostites (broader and better term than just CF).

Unfortunately less than a thousand Scouts have recieved the badge because the scout leaders are unfamilular with the technology, materials and manufacturing processes, perhaps that is the same for us?

If you had to play US Open Champion Andy Murray would you use a tennis racket made of wood, metal, graphite, advanced composites or polypropolene??

What material offers the best puncture protection?
What material offers the highest Young's modulus?

What would/could/should your shoes be made of ??

A Hui Hou,
Steve


Don't get Weft behind its Warp Speed ahead with Kingetics' Advanced Composites...TM