Ceramic Shell Casting Steel

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sunworksco

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I am wanting to learn the best method of having a pair of steel bicycle pedal arms cast, using ceramic shell investment casting method. I can have 3-D printed arms made into models that burn out for the lost wax casting process. What percentage of upsizing the 3-D printed model should be given?
I would like to find someone that can cast the arm, as well.
Thanks!


Here are the measurements:
• 9/16” bottom bracket x 1/2” pedal threads
• 7/8” profile width on bottom bracket end of arm
• 7-3/8” overall length of arm
• 25/64 smaller diameter of tapered arm
• 33/64 larger diameter of tapered arm
 

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abby

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It would be helpful if you said where you are located, not much use me giving you a contact in the UK if you are elsewhere.
It is very unlikely that a commercial foundry will risk burn-out on a printed plastic pattern.
Ceramic shell is very brittle and cannot withstand much expansion of the pattern without cracking , wax melts very rapidly so no expansion , don't know about RP plastics.
For shrinkage I allow 3% , this is for a wax pattern produced from a silicone rubber mould.
Dan.
 

sunworksco

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I’m in Alameda, California
I’m not sure which method is best.
To have the arm 3-D scanned is around $150.00USD. To have it 3-D printed is an unknown.
All I know is that I need a steel arm reproduced.
 

Cogsy

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If you have the arm to scan it could be silicon moulded, then cast in wax for lost wax casting. To have it 3D printed it is going to need to be modelled (or scanned) which is going to cost as well.
 

Jasonb

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Taking a mould off the crank won't allow for shrinkage of the wax or the metal. From your photo it is not a very complex part so should be easy enough to draw and machining allowances will be easy to add at that stage, infact it is quite a simple part to machine from solid which would only cost your time.

Best to ask the foundry what shrinkage allowance they require. If you could get it printed in wax then try Boulder River who do the lost wax shell steel casting for Morris and Marvin, they may also be able to advise on where to get the waxes done.

 

stevehuckss396

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Its a fairly simple part to machine. Have someone machine up a pair and then send them off to the sand blaster to make them look like a casting.
 

rlukens

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Dumb question: why cast?
 

sunworksco

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It doesn’t matter how it’s made, as long as the arms are strong and can be nickel plated.
 

sunworksco

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It would be nice to find a reputable machinist to make it for me, that is in the USA.
 

maury

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sunworksco, there are many art foundries around.They make jewelry using investment casting. If you can't find one, I can get you the name of a few here in the great state of Texas. All you will need is a phone call and a USPS flat rate box.Almost all art foundries cast stainless steel, and the part you need should not be too large for them. When you find a foundry, get information on the alloy and look it up to find the shrinkage if you are worried about it. It will probably be around 1.2%.

maury
 

sunworksco

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Maury,
Thanks!
Please post the foundry names.
I need to find someone to make the wax model, now.
 

maury

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Send me a PM, I don't think it's a good idea to post third party information.
maury
 

Lotus-14

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Looking at the photo, it looks like a very simple part.
Why not make a drawing from the part, and have it machined, assuming you cannot do it yourself.
You do not need to supply a CAD or 3D CAD file to get the part made by a machine shop.
If you go to the bother of making a pattern, no matter what method of casting you choose, you might as well just machine it. I am assuming you are not in production, even then a CNC machine center would make these parts much faster than a specialty steel casting foundry. You will still need to machine the bores. Also with most steel castings, you will still need to heat treat the parts, which is one more layer of cost.
I hope this helps.
 

MRA

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The last thing I made like this (a kick-start for a diesel motorcycle - takes a bit of torque :) ) I made the bushes at each end and welded them to a shaft made from a big drop-forged ring spanner. The spanner had a broken ring on one end, which along with the fact I'd fallen over it on the shed floor for years before finding a use for it, made the whole thing unreasonably satisfying...
 

sunworksco

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The arm needs to match the existing arm.
A machine shop in Berkeley, California, wanted several hundred dollars!
 

Jasonb

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Probably still less that cost of producing waxes, casting and then machining the castings
 

sunworksco

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I can have 4 arms ceramic investment cast for around the same amount. Machining is very minimal on investment casting
 

Barnbikes

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What brand is the bicycle?
Can't believe somebody does not have an original you can buy.
 
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