Choice of steel and welding rod composition for high-wear medical parts

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I am attempting to make a pair of leg braces for myself to correct foot drop.  The main structure of these braces consists (so far) of a 1x1/4" bar of mild steel that runs down the back of my leg starting at the upper-calf and curves around my heel to under my foot.  I'm 3d printing the portion that actually comes into contact with my foot and leg, and those pieces will attach to the structural steel portion with machine screws.  Long story  short, I have to integrate a hinge onto the bar roughly at the position behind my achilles tendon.  That hinge is going to need to be hard-wearing.  I've made some prototypes using only mild steel, but I have serious doubts about how long I can expect those to last under heavy use.  The hinges will support my well-fed 225lb frame, and I walk about 5-10 miles per day.  I don't know much about different steel types though, so I'm left to guess what might be a good choice.  I've been  looking at W1 stock since it's reasonably cheap and apparently easy to harden once worked.  I don't know if that's an appropriate type, however.  Any thoughts on that?  I've been using a SMAW welder with 6011 and 6013 electrodes because that's just what they have at the hardware store.  I'm open to ordering something more appropriate if necessary. Use of stainless shouldn't be necessary.  I'm going to be painting the steel with some pretty serious self-etching paint.  Can anybody toss me some advice on this?Last edited by JayWatt; 4 Weeks Ago at 12:12 PM.
Reply:id at least get some stainless, i i had to wear it.    i had a prosthetic company call me once to fix a hinge on a ladys leg.    i used 308 tig.    u can buy some 3/32 308 for ur stick machinev if u go stainless
Reply:

Originally Posted by JayWatt

I am attempting to make a pair of leg braces for myself to correct foot drop.  The main structure of these braces consists (so far) of a 1x1/4" bar of mild steel that runs down the back of my leg starting at the upper-calf and curves around my heel to under my foot.  I'm 3d printing the portion that actually comes into contact with my foot and leg, and those pieces will attach to the structural steel portion with machine screws.  Long story  short, I have to integrate a hinge onto the bar roughly at the position behind my achilles tendon.  That hinge is going to need to be hard-wearing.  I've made some prototypes using only mild steel, but I have serious doubts about how long I can expect those to last under heavy use.  The hinges will support my well-fed 225lb frame, and I walk about 5-10 miles per day.  I don't know much about different steel types though, so I'm left to guess what might be a good choice.  I've been  looking at W1 stock since it's reasonably cheap and apparently easy to harden once worked.  I don't know if that's an appropriate type, however.  Any thoughts on that?  I've been using a SMAW welder with 6011 and 6013 electrodes because that's just what they have at the hardware store.  I'm open to ordering something more appropriate if necessary. Use of stainless shouldn't be necessary.  I'm going to be painting the steel with some pretty serious self-etching paint.  Can anybody toss me some advice on this?
Reply:Hi and welcome!That sounds like an interesting project, for sure.  Can you post a picture or two of the prototypes?  I'm not an expert on alloy/tool steels but I've played around with them enough to know they aren't always straight forward.  Welding on them can easily cause them to lose their hardness, then you have to redo the heat treat which can cause them to change dimensions, etc.Check out my bench vise website:  http://mivise.comMiller Syncrowave 250DXMillermatic 350P with XR AlumaProMiller Regency 200 with 22A feeder and Spoolmatic 3Hobart Champion EliteEverlast PowerTig 210EXT
Reply:Thanks for the replies.   I've considered stainless but I'm concerned about my ability to work with it properly since I'm more-or-less a novice at metalworking.  It's also more expensive, so mistakes could be very costly.  That may be something I try after I get a little more skill under my belt though.I live in Tennessee, USA.  I'll get a few pictures when I get back to the house this evening so you can get a better idea what I'm talking about.  Bear in mind that I'm a novice at welding.  I'm getting better, but it's a work in progress.  I'm just working off of tutorials online since I've never had any kind of formal training.  My condition is called Charcot Marie Tooth disease.  It causes muscle weakness below the elbows and knees.  I don't get much in the way of exercise per se, but I have to walk a lot out on the plant floor where I work. (Whirlpool USA) I've been using prescribed carbon fiber braces for a few years now, but they keep cracking on me from heavy use.  They cost about $3000 per pair, so it's getting to be expensive.  I figure if I can build something then I can be the one to maintain and repair it if necessary.  This is one of two designs.  The other is 100% 3D printed.  I'm running some tests with some more advanced materials such as carbon fiber nylon to see how well it will hold up.  I had to upgrade the printer to even try that type of plastic.  Standard 3D printing materials such as PLA, ABS and PETG just don't have the strength to hold up.  The cyclical load causes stress cracks to pop up after a day or two.
Reply:Any chance you can incorporate a small bearing/s of some sort? They'd prolly last longer than bushings..............Mike
Reply:This is what I've got.  I plan to put more time into the finished pieces.  I'd love to have these use some kind of bearing, but I'm not sure how I could easily integrate one here without bulking up the hinge too much.  I have a cheap drill press, files, grinders, etc.  I did the cuts with a hack saw and cleaned it up with a file.  I welded blocks onto the back to act as stops and attached pieces of automotive belt.  I'll be happy if I get 6 months out of these.  I don't expect them to last forever.  I just need them to get me to a point that I can have something a little more elegant ready to go.




Reply:If you can haul this around I aint lippin off.  I am not sure about elegant but lighter might be a feature or add wheels to drag it along.   You will be well grounded,,, but that might be osha concern?Last edited by Sberry; 4 Weeks Ago at 06:50 PM.www.urkafarms.com
Reply:It's not as bad as you might think.  Not much different than a pair of chonky work boots to be honest.  I just walk around on the factory floor a lot.  No hiking through the forest or whatnot.  That thing provides so much support though that it feels like I could jump out of an airplane, land on my heels and my feet would still be at 90 degrees.  That's comforting when you've tripped over your own feet and faceplanted a few times in public.
Reply:There are weldable hinges available. Might be worth looking into?  Otherwise I second the people saying at least a bushing if not a bearing for this.  You could get pre-hardened, ground rod for your hinge pin in your current design, but again bushings at least would help a lot with wear.A great place to start looking for ideas is the Mcmaster-Carr catalog online.  Start looking through theirs sections on bearings and bushings (and rods and materials) and you will learn a lot plus see what is available out there.  www.Mcmaster.comI also agree on weight.  I'd think aluminum would be great for parts of it, and save the steel for the parts that really need it. Would require bolting over welding of course unless you can weld alum, or anytime you go from Alum to steel.Good luck.-DaveXMT304 with: 22A Feeder, or HF251 Hi Freq DC TIG air cooled
Reply:not to derail this thread but my pediatrist has and can make out of plastic for my drop foot.  mine from injury and from stroke.  it fits inside your shoe or boot, what i wear.  i also crushed that ankel and its about 2 times as big as other one.  they also have them at orthopedic footwear places.  if interested, try looking for a dr. comfort dealer near you.  my boots  or shoes are diabetic shoes so thats who would handle them.lincoln 125spdayton 250 ac/dcmiller 211 w/spool gunahp  200 sx tiglotos ltp5000dkubota b3200 FEL BHof course duramax diesel
Reply:If you have a file you printed from, perhaps you can send to somebody who has the capability to print an appropriate material.  I suspect somebody has one(printer for metal or carbon fiber) in their garage. You could just work on the design...?
Reply:I have a pair of those!! (The one I have are probably a man's size ~8 or 9,, she is 6 feet tall, womens size ~10??)My daughter played basketball, starting at age 9.5 years.By the time she was 14 YO,, she could turn her foot 90 degrees to her leg, with zero pain.The braces IIRC,, somehow Velcro strapped to the lower calf, there is a hinge right at the ankle,, then a foot part that inserts into the shoe.A doctor custom made them for her,, without them, she would be out of a basketball game within 1 quarter,, she would have a twisted ankleWith them, she never injured an ankle again.She wore them for basketball, and volleyball, for the remainder of her athletic career.They cost,,, sit down  ,, are you ready,,,,,,,?? $10,000,, and I had to pay 100%. zero insurance coverage.(I had been quoted $5,000,, but, they did not detail that the $5,000 price was E A C H !!)She ended up getting a full ride athletic scholarship to The College of William & Mary,, so, I consider the ankle supports to have been a good investment,, which paid back MANY times over.If I can find them, I will take photos, showing the hinges,, I am VERY familiar with the hinges,I had to rebuild the hinge parts at least a half dozen times,, I used LOTS of Loctite Red!!

The repairs were always needed the day of a game,, so no time to schedule a DR visit for repairs,, dad had to step up!!


Reply:Well, it turns out that I'm not going to be making this particular pair.  I learned how to sculpt objects in Blender (3d modelling software) and it has turned out to be WAY easier than I initially expected it to be.  I already have a design more-or-less ready to go.  I just need...hinges, for the ankles.  So I'm going to apply what I've learned here to make them.  I have the ability to print carbon fiber nylon, so that's what I'm going to be making the bulk of them out of.  I've been getting braces from the doctor, but they are crazy expensive, and I've broken a few pair since I'm a little hard on them.  I think it'd be cool to release the design to the public so that anyone could theoretically have a pair for about $100.  I managed to snag a few photos of the hinge on a demo pair of braces last time I was at the orthotist, so I think I'm going to try to make these.  I've also included a photo of a similar brace (AFO) to the one I've knocked out in Blender.

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