casting parts at home

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pishta

pishta

I know I'm right....
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sounds crazy, right? I finally landed a classic cassette player model I've been chasing for 6 years and I find that 1 nylon gear and a nylon idler tire 'rim' is cracked and is unavailable. I saw a guy cast a gear in AL using the lost wax method: a silicone mold is made to make a relief of the glued part, then he cut away the gear carefully and filled the mold void with wax to get a perfect wax replica of the gear. He then placed it in a plaster casting and let it dry. He then dug out a drain hole to the wax and put it back in the kiln inverted to let the wax melt out. What was left was a perfect gear shaped void ready to fill with AL (in my case lead as it melts at a much lower temp and sets slower, avoiding casting flaws). His gear was about 4" across. mine is .250! The nylon gear is pressed onto a shaft that opens the crack (between teeth) and jams the other gear when it comes to the fault. with any luck Ill be able to replicate this gear in lead and have my cassette player up and running. Anyone ever cast resin or other material? 3D printer would be F'n awesome but Im not sure if it could be precise enough for a .250 gear? Id be happy to reimburse anyone that could 3D print it for me. I could CADD some plans if needed.
 
Make multiple molds.
Lead may work, but brass or aluminum would be better.not much harder to melt.
 
Might want to youtube hobbing gears.
Something that maybe can be done by an old school machinist.

if i had nothing but time on my hands thats what i would attempt.
 
3dhubs.com. You create the cad and upload, then people will give you bids. They tack on fees but you could get some workable parts, basically make 25 or so for the same price of 1.
 
Might want to check you local library or community college. Our local library has a 3D printer the community can use. We made aluminum castings in junior high using some kind of oil sand. The aluminum was melted in a little natural gas furnace not much bigger the burner on a stove top.
 
+1 for 3d printing.
Stratsys, quick parts, or any number of smaller outfits can do it.
CF filled nylon 12 works well. I've made replacement parts including fixing a headlight switch for a Ferrari using it.
Any unfilled material will abrade rather quickly. Give an allowance of .005" per side for surface irregularity. Parts can be modeled or printed to-size, but will need to wear in.

Casting aluminum can be tricky. Easier to use zamak or similar casting alloys. Better flow and fewer issues with oxides. Can be melted over a space heater like lead too.
 
C521B44B-C1B2-411C-BFAE-577D35037CE6.jpeg

I used Alumilite resin and mold making silicone to cast a 3 inch gear. I reused the original gear’s metal hub in the mold. It had a lot of air bubbles in it because I didn’t follow the instruction to put it in a pressure pot to force out the air, but it was still plenty strong.
 
@pishta , you may want to check out eBay, I have purchased one of these kits to pretty much repair what you are doing. Found a plastic gear that worked perfect for me.
Plastic Gears Kits Pulley Spindle Shaft Worm Bevel Gear Sleeve DIY for Toy Robot

gears.jpg
 
Dicer, It needs to be a very precise gear size to fit on shaft OD and mesh with other gear. Yeah its gonna need to be cast or printed. My kids school has a printer too. Maybe his tech teacher can whip one up for me. Still going to try and cast in lead. Ill post results or ashes of garage.
 
Tinkercad render to autodesk viewer. I added full radius caps off mesh area for strength as the old one cracked between teeth
Not sure what the little arm does but its on there. Diameter of gear is .280"

gear.jpg
 
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