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Carbon fibre as an orthotic material

Discussion in 'Biomechanics, Sports and Foot orthoses' started by PodAus, Mar 15, 2006.

  1. PodAus

    PodAus Active Member

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    <ADMIN NOTE> This thread has been split off from the thread on Middle distance spikes and orthoses </>
    Real Carbon fibre is very easily ground with no greater health risks than grinding any other orthotic materials (actually much less risk than traditional orthotic plastics). Normal dust extraction as with EVA, polyprop, etc. -- I'm sure you're not keen to inhale any materials into your lungs (even if you're a smoker..?)

    Carbon Fibre is safe to use, and superior to other semi-flex/semi-rigid/rigid orthotic materials
    Last edited by a moderator: Mar 15, 2006
  2. gangrene

    gangrene Member

    To sidetrack a little, when do one normally use a carbon fibre orthotics?
    Any specific conditions that one can relate to?
  3. It comes down to what Bill Olsen described as the thickness to weight ratio. Basically, you can create a much stiffer orthotic with a much thinner and lighter shell by using carbon fibre. So to answer your question: any condition, but when weight and maybe strength of the device is key.
  4. PF 3

    PF 3 Active Member

    Are you still limited to the amount of arch height you can mould them too? I found in my limited experimentation a few years ago that there was only so much bend it could take when pressing it to a positive cast before it creased or just wouldn't confrom at all.
  5. PodAus

    PodAus Active Member

    This Carbon Fibre based orthotic material is continuing to be developed - it can now be used in forming a wide range of devices MUCH thinner and MUCH more durable than other orthotic materials. Footwear accomodation and comfort are major benefits. Why use a heavier, less durable material, which is difficult to accomodate in footwear??
  6. William Fowler

    William Fowler Active Member

    Because it can't be heat adjusted; costs more; and can't be used in the more modern automated orthotic manufacturing processes.
    Last edited: Mar 17, 2006
  7. PodAus

    PodAus Active Member

    doesn't cost more depending upon who's selling it to you - heat adjusting is an average method of orthotic modification, and should not determine the orthotic material selection - can be used in modern automated orthotic production, although maybe not with template milling
  8. Jamie

    Jamie Active Member

    Just to point out that there are different "make ups" of Carbon Fibres used in Orthotic Treatment. The most commonly used in Orthotic Insoles are Composties. XT Sprint and the Langer Product (not sure of Brand name) are laminated layers of a Composite of Carbon Fibre and Homopolymer Polypropylene. These would be Thermoplastic and when heated the resins holding the layers together would release allowing the layers to move over each other and mould. In the past the heel cup has been restricted to 20-25mm but with new resins and if you cut any excess material off round the heel before you heat it will prevent the creasing up at the heel curve. The TL materials are a Carbon Epoxy mix which are one layer so more care needs to be taken when moulding but would be slightly thinner.

    The Prosthetics boys for Sole Plates or Sockets will use Dry fibre laminates with Resins, which is Thermoset and needs to be protected against with Heavy duty PPE when working with it. In Scandinavia Dry Fibre Laminates are used for Orthotic Insoles and I have seen the resins mixed inside a bag.

    Not sure if that helps the discussion but I thought you might be intereseted.


  9. Ian Linane

    Ian Linane Well-Known Member


    I went through a period of making carbon Fibre devices a few years ago. I used the wet uplay technique, that cold cured, and certainly made some very pleasant looking beasts and have had them used by both runners and walkers alike. The technique took CFibre cloth and layered it up building strength just where you wanted it. Some have used strips of carbon as reinforcement when doing this but to my mind it left a bulky line to the area supported. I was able make it in such a way that you could have a device that appeared uniformly thick but in some places was 4mm and other places 2mm with variations on a theme all on the same device. Once made you could certainly twist the material longitudinaly and provided the arch was not to high get a modicom of flex on it.

    Manufacturing wise it was hugely time consumming and fidley and vacuming the resin over the carbon layers brought the odd expletive. I still keep one for posterity.

    Certainly, once made, you could always grind it further but you could not have heated it

    Today I tend to use the carbon composits and been very satisfied with them. I guess the key is using the materials of choice for a given situation is what the rule should be.

    (perhaps the sado thing I once did was make a tiny orthotic carbon fibre key ring. Great but when you sat on it Bloomin hurt!!!

    Mind you when a teenager I once had a pink Kaftan!!! aaaah, to much information.

  10. PF 3

    PF 3 Active Member

    I can't buy into the weight issue. It obviously is lighter, but how many times have you had a pt complaining about the weight of an orthotic. If this were an issue, surely you would be weighing different f/w options as well. I guess the advantages it seems to give are only slight and perhaps not worth the extra cost? I hear they can crack as well.

    I will try get my guy to get his hands on some and give it another shot with the new composite stuff on my feet. Whats the average increase in cost?
  11. I remember when the first composite orthoses came out. I have experimented with them on and off but have never liked the rearfoot posts (compared to my orthoses that use a polypropylene post fused onto a polypropylene plate) or the inability to grind plantar fascial grooves into them (I grind many plantar fascia grooves into orthoses). In addition, my breakage rate for polyproplyene is about 1 out of 10,000. I would be interested in the breakage rate for graphite and composites. From what I have seen, most of them show signs of fatigue fractures after 5 years of use and, by the time a mandatory topcover and/or rearfoot is added to these graphite/composite orthoses, my polypropylene orthoses are thinner and take up less room in the shoe.

    So why would I want to use graphite orthoses for my patients?? What can it do better than polypropylene??
  12. PodAus

    PodAus Active Member

    Remember the research which shows prescribing habits directly associated with when and where the Pod studied (habitual, therefore)...although weight is a factor, particularly for athletes and sports-specific footwear (taekwondo training shoes / track spikes / cycling shoes), it certainly is not the primary reason to use carbon composite devices (CCD's).

    One of the most important factors concerning any orthotic prescription is footwear accomodation. CCD's address the bulk issue which often restricts orthotic use. Often covers are not required nor desirable (bulk), posts may be incorporated, or additional (EVA) if required at all, and plantar fascial grooves may be incorporated during the moulding process.

    Everyone assumes composites cost more... it shouldn't, so your lab might be charging more because it's 'high-tech'.

    I use CCD's as it satisfies all of my prescribing requirements and Patient's love it (thinner,lighter, durable, high-tech, etc.).

    Why would I use Polyprop - because that's the material I learnt to use at Uni 10 years ago??
  13. Craig Payne

    Craig Payne Moderator

    Kevin -- does this thread remind you of those verbal duels that Bill Olsen and Chris Smith used to get into at a couple of Weed Seminars?
  14. I grind polypropylene to 1 mm thick at the heel contact point....are CCDs thinner?

    I doubt that CCDs are more durable than polypropylene....I have only had one spontaneously break in 20 years....have made more than 10,000 pairs of polypropylene orthoses over the past 20 years....CCDs don't even come close to polypropylene in terms of durability.

    What happens if the plantar fascia becomes irritated with a CCD orthosis and you didn't put in a plantar fascial accommodation into the positive cast? Does the patient have to pay for the second orthosis you must make, do you absorb the cost, or do you tell the patient to not worry about their arch pain because it will get better over time?

    Also, how do you modify the orthosis to make the orthosis more comfortable if the patient has plantar fascial irritation if you don't have a new orthosis remade?

    How durable are the rearfoot posts that attach to CCD orthosis? What are they made of? How much do they add to the thickness of the heel contact point of the CCD orthosis? How often do they delaminate from the CCD shell?
    In the polypropylene orthoses made by my lab, the orthosis rearfoot post is fused to the shell and they do not delaminate. They can be ground to 1 mm (or thinner) thickness at the heel contact point without any increase risk of orthosis breakage or delamination of rearfoot post.

    And finally, I never was trained to use polypropylene at CCPM. In fact, polypropylene was discouraged as an orthosis material at CCPM. I was taught that Rohadur was the only acceptable and durable orthosis material and that polypropylene flattened within a year of usage. Interesting how times change.
  15. Stop that Craig!! I was having a little fun in my old age! Need a good argument every now and then to keep my blood pressure from sinking too low!

    Oh yeah, those were some good arguments we used to have at the Weed Seminars. Do you remember when I told Bill Orien to stop being such a "pushy moderator" and let Tom McPoil have a chance to speak up. Or the time I told Bill Orien that "gravity doesn't always cause pronation"?

    You think those meetings were fun, you should have attended some of the Root Lab Seminars and seen Mert Root's face turn red when I told him back in 1984 that heel bisections were unreliable and that even the biomechanics clinicians at CCPM couldn't agree on heel bisections!! Talk about me getting a tongue lashing......I guess I'll never change....if I do become nonconfrontational, Craig, just go ahead and bury me. :eek:
  16. Craig Payne

    Craig Payne Moderator

    It was probably all that running alone :D

    For those unaware ..... Bill Olsen was involved with the TL composite materials and Chris Smith from Northwest Labs had also developed their own composites .... made for good listening and viewing.
  18. A block of polypropylene is heated with the polypropylene shell separately in the oven and then they are pressed together in the vacuum press. Actually, this a very tricky business, that I have never done myself, and which took the lab a few years to perfect. This "welding" process produces a seamless polypropylene to polypropylene rearfoot post. It looks like the orthosis is all made out of one block of polyproylene with no demarcation evident between rearfoot post and shell.

    The orthoses I currently wear are a pair of polypropylene orthoses with polypropylene rearfoot posts that were made in May 1989. I have worn these orthoses on a daily basis at work and at home for nearly 17 years and they still fit the positive casts like they were pressed yesterday. Pretty amazing stuff that polypropylene....no matter what others say about it.
  19. javier

    javier Senior Member

    It can be done also by direct milling from a block of polypropylene.

    Polypropylene's performance depends on different variables:

    - Heating temperature
    - Vacuum process
    - Intrinsic properties (homopolymer or copolymer polypropylene)
    - Thickness
    - Patient weight and activity

    It seems that choice of orthotic materials is a common topic of discussion among podiatrists worldwide. But, nobody can give accurate data about one material superiority to other. Orthotic achievement depends on other matters. Material choice depends on the podiatrist preferences.
  20. How deep of a heel cup can be made by direct milling of a polypropylene block? It seems that most direct milling processes can go to about a 14 mm heel cup height but can't go to a 18 mm heel cup height nicely due to the verticality of the heel cup at that heel cup height. I'm sure technology will improve this with time.

  21. Kevin,
    18-20mm heights are very achievable when millling orthoses (with as you suggest, the right technology) and when even when incorporating a large lateral flange on a device I have milled up to 30mm.

    Phillip Hartshorne
  22. Dantastic

    Dantastic Active Member

    Its great that they have lasted so long and kept the same shape, but if you were to take positive casts today would they still fit? I mean, would the foot not change over such a long period of time? :confused:
  23. The foot may or may not change over time, depending on the individual. So far, they still work well for me, which is all I care about. If they weren't working well for me, I would have new casts made.
  24. Very impressive. Are the costs of the orthoses comparable considering the investment in equipment required?

  25. Kevin,
    The cost of a pair of orthoses is $95 (Australian dollars) + coverings, ie for a vinyl shell length cover add $2. With your US dollar being a little stonger than the Aussie dollar at the moment it would cost you about US$65-70.

    There maybe a bit of an extra cost to ship to and from the USA, but I imagine that those costs/time would quickly be absorbed from the USA to Australia route when you purchase a 3D scanner.

    I know CP hasn't stopped thinking about the scanner with its time savings and overall cost savings, since he had to compete with me on the trade display next to me at New Zealand last year. :D

    I look forward to your first quote not from the Precision Intricast Newsletter but from the Virtual Orthotics Newsletter!

    Phillip Hartshorne
  26. Atlas

    Atlas Well-Known Member

    How on earth does one grind carbon fibre without the gunk being left on a once-useful abrasive paper?

    Should I use a lower speed? Should I do a majority of the cutting with a band saw? Should I wet grind????
  27. PodAus

    PodAus Active Member

    Increase the grit/grain of the sandpaper to 60. The courser the grain, the easier to grind.
  28. Atlas

    Atlas Well-Known Member

  29. CPedTechie

    CPedTechie Member

    My two cents worth of experience with carbon fiber: At our lab we had a few clinicians request the XT Sprint, but the demand has diminished over time. I think the idea of using a "high tech" lightweight composite was appealing and used as a selling point for a few athletic patients. This appeal didn't last long when a few 1.5mm shells came back within a month after cracking at the MLA near the heel blocks (55-65D EVA)

    On a positive note, it grinds and finishes quite nicely, but be careful working with it. I have a tendency to pinch and run my fingers across the end of a shell to remove burrs and excess material. Doing this with the carbon fiber composites will slice your fingers open worse than a nasty paper cut!

    We keep our S500 vacuums clean and well maintained so inhaling carcinogens was never really a concern.

    I agree with Kevin that polypro has a lot of attributes that makes it better to work with and adjust. It's easier to mold, adjust and more cost effective at this time.
  30. rob_orthotic lab

    rob_orthotic lab Welcome New Poster

    Yes carbon fiber may be lightweight and thinner than polypro but does have a tendencey to crack. In my opinion, polypro is a much better product to work with and adjust also.

    My two cents also,

  31. Graham

    Graham RIP

    If carbon fiber cracks perhaps the prescription is incorrect exerting compensatory pressures on the device due to the "inappropriate" effect of the orthoses on the foot. I wonder if Polypro, being a bit more flexible, doesn't show these pressures, but are they still there?

    I have used X-T sprint in my sagittal devices for the past 12 years. None have cracked to date. I have recently switched to Performance Rx - a nylon based material on the recommendation of my LAB.
  32. PodAus

    PodAus Active Member

    I haven't had one crack in 14 yrs... (XT material)
  33. I've used XT a fair bit. I switched back to poly.

    Not because it was a bad material, it did the job, I just didn't like it much.

    Yes its lighter, but who comes back with probs because their orthotics are 20 grams too heavy?!

    No it doesn't crack, but thats rarely a problem for me anyway.

    I found poly easier to work with, easier to grind, easier to mould and easier to adhere stuff too.

    But I've recently switched (mostly) to High molecular weight poly (mandrillian) and not looked back. Its a shade stiffer per unit thickness, has a MUCH wider working temperature bracket, and finishes better (for me at least). I guess its tougher as well but as I say, I rarely had problems with poly.

    At the end of the day though, I've seen an effective orthotic made from humble poron and regen, and I've seen orthotics made with the most expensive materials fail badly. Whatever works.
  34. PodAus

    PodAus Active Member

    yep, definitely agreed...

    what suits is what's best

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