Trying lost wax casting

[ghart3]

Years ago started on making a 4 cylinder T-head engine called Simplex. Didn't get all the castings. Main ones missing were the 4 con rods. Wanting to do lost wax casting thought it would be a good place to start. This is my second try, first try didn't allow for shrinkage in the rubber mold and in the metal plus couple other things I did wrong. Mostly finished a new model of the rod that is 6 percent bigger then hopefully the finished size will be. Shrinkage of 3 to 4 percent for the rubber and about 1 and half percent for the metal.

The model is made up of 11 pieces silver brazed together. Didn't get all the seams silver soldered so hope to redo tomorrow without destroying it. Then hopefully vulcanize rubber mold of the model tomorrow. From the rubber mold wax patterns will be made.

 

[Maryak]

ghart3,

Very very nice :bow:

Is lost wax the same as investment casting ???

Best Regards
Bob

 

[Kludge]

What metal will you be using for the rods themselves? I'm nowhere near the level to do this (All mine's low temp metal and a little pewter) so I'll be following this closely.

BEst regards,

Kludge

 

[jack404]

Bob

yes "investment" and lost wax are similar

spin is also the same except it has a spun bottle otherwise the same process

nice work ghart3

yes shrinkage guaging is my biggest PITA too

i cast the lock plates and brass butt for my rifles

but have steel alloy molds made for these items, but brass will shink 11% - 17% depending on comp. steel 7%-1%

lead i dunno but its about = to steel ( i do a lot of sinkers )

i do the "try again 'till it fits method " for making fitted items but am getting good at guessing nowdays

the good thing about casting is if it dont work, back in the pot.. ;D and if your lucky you can guess and actually leave it big enough to work without 1/2" of machining needed.

he can use what he wants Kludg,e 1020 mild steel, 2011 T6 ALU , Ph2 bronze, ( i'm only starting on alu casting and have only done sinker molds so far) but my modified wok burner furnace can do way more than i can i think but the limits of casting are set by you, the process only gets hard with specialist stuff.

Kludge in US vernackular i'm not fast, casting and its finishes and how fine you can cast dont matter ,

even i have made good steel castings and it has that "esoteric" type feel about it. its a great craft

i like the bit in the movie about the worlds fastest indian motorcycle

thats exactly how home casting is and should be done

( 1 part chevy, 2 part ford and a little lime to clear the s##T out and make it slag up good ) , good movie

cheers

jack

 

[Kludge]

he can use what he wants Kludge

Well, yeah. I figured as much. I was interested in what he actually is going to use.

Aside from high school, my experience is with lower temperature metals and latex molds, and I doubt crown pewter et al would be of much use in this hobby. I don't know, maybe they would but I'm thinking that's not what he'll be pouring.

In the meantime, I'm still watching and learning and plotting my overthrow of the world one Twinkie at a time.

Best regards,

Kludge

 

[John S]

What temperature will the rubber mould take, or rather what material will it take ?

JS.

 

[Tin Falcon]

Lost wax 101

pattern made from metal.

Mold made from pattern either poured silicone rubber
or natutal rubuuer shhets pressed with heat and vulcanized.
Mold cut from pattern and indexes installed or cut in
wax poured into rubber mold
Rubber mold peeled away
wax sprues gates attached to wax pattern
Wax pattern(S) dipped in ceramic or brushed with investment then placed in flask and investment poured around. Vacuum sometimes used to pull out air bubbles.
Flask(s) placed in oven to cure investment and melt/burn out wax.
Molten metal then poured in hot investment mold.
Usually with a centrifugal casting setup of some kind.
When cool investment mold is broken away from part and part is finished.
So the wax copy of the part and the investment mold are both lost in this process. The rubber mold can be used over and over.
This process is comparatively expensive process but poduces high quality parts often needing little finishing other than where the gates and sprues attache to the part. It is typically used to make jewelry but is also used to make gun parts and steel is poured into molds.
Tin

 

[ghart3]

Kludge, the metal will be some kind of mystery bronze from my junk pile. It was some kind of bronze used for electrical contacts in a very large bridge crane. When melting it didn't give off bunch of white smoke from zinc burning off. So, I call it bronze.



John the vulcanizing temperature of the rubber is a little over 300 deg. F. The book says the model must take a minimum of 460 deg. F. for the vulcanizing. Wish I knew if could get by using soft solder. Only, seem to recall that it is not recommended. Sure would be nice for fixing flaws and building up fillets.



Ti, good explanation of the process. Have built both centrifugal caster and vacuum method of drawing the metal in. The vacuum method works better for larger sizes. Sand casting works better for even larger castings. These rods are too big for my broken arm spin caster, so will be using vacuum.


Kf2qd, RTV (Room Temperature Vulcanizing) is one method of doing it. I will be using a heated vulcanizing press, mainly because a friend gave me one that I was able to fix up.

 

[John S]

What temperature will the rubber mould take, or rather what material will it take ?

JS.

Reply's to own post [ first sign of madness ? ]

Note to self:-

"What part of lost WAX did you not understand thickie ?"

Now sulking in corner with damp copy of Exchange and Mart over head......................

.

 

[shred]

Good summary TF. Strictly speaking a metal mold to make the wax masters in isn't required; you can build the wax up just from shapes, but unless you're doing one-offs, you don't want to do that. You can also buy wax masters for a vast number of standard jewelry shapes-- blob on a little extra wax, cast away and it's 'one of a kind, hand-made'

The key (for those that haven't BTDT) is you burn/melt out all of the wax before dumping hot metal into the mold (as opposed to lost-foam where the foam is burnt out by the metal)

We always used to drop the hot flask with the cooled-enough-to-not-move metal into a big water tank. The still very hot plaster investment mostly removes itself that way, but it does splash a lot

 

[bigal2749]

Lost wax 101

pattern made from metal.

Mold made from pattern either poured silicone rubber
or natutal rubuuer shhets pressed with heat and vulcanized.
Mold cut from pattern and indexes installed or cut in
wax poured into rubber mold
Rubber mold peeled away
wax sprues gates attached to wax pattern
Wax pattern(S) dipped in ceramic or brushed with investment then placed in flask and investment poured around. Vacuum sometimes used to pull out air bubbles.
Flask(s) placed in oven to cure investment and melt/burn out wax.
Molten metal then poured in hot investment mold.
Usually with a centrifugal casting setup of some kind.
When cool investment mold is broken away from part and part is finished.
So the wax copy of the part and the investment mold are both lost in this process. The rubber mold can be used over and over.
This process is comparatively expensive process but poduces high quality parts often needing little finishing other than where the gates and sprues attache to the part. It is typically used to make jewelry but is also used to make gun parts and steel is poured into molds.
Tin

Also used extensively in dentistry for gold crowns, other metal copings for bases of procelain fused to metal crowns, and casting frameworks for partial dentures.

When I was in dental school making jewelry paid for my rent and groceries

 

[ghart3]

Work some today. Silver brazed missed seams on rod. Cleaned up some and put in metal frame and packed with rubber. Had to use all the scraps had and barely had enough.

Frame packed ready to be vulcanized.

Vulcanizing. 307 deg. F. for 75 minutes. Frame has 1/8” holes in sides so excess pressure can be relieved by forcing some rubber out.

Rubber mold split and rod model ready to get out. Notches in rubber is for indexing the two sides, so sides match up when put back like they came apart.

The brass turned all dark, guessing from sulfur in the rubber. Was hoping to make a wax pattern but air compressor quit working. If not too cold might work on compressor tomorrow, hoping it is just start capacitors.

 

[Kludge]

Kludge, the metal will be some kind of mystery bronze from my junk pile. It was some kind of bronze used for electrical contacts in a very large bridge crane. When melting it didn't give off bunch of white smoke from zinc burning off. So, I call it bronze.

Cool, thanks. The closest I got was a few bismuth mixes to get the idea then crown pewter for decorations for wooden pens since I got tired of the kit junk. The next step was supposed to be gold & silver but I never quite got there; lifus interruptus. (And, yes, I know that's not real Latin.)

Eventually, I'd like to get to brass but that won't be for a long time so I'm using this as pure education.

BEst regards and thank you,

Kludge

 

[Kludge]

Lost wax 101

Many much thanks, Tin. This helps a lot.

Best regards,

Kludge

 

[kustomkb]

Thank you all for sharing your info about "lost wax"

I am eager to learn,

Jack,

( 1 part chevy, 2 part ford and a little lime to clear the s##T out and make it slag up good ) , good movie

cheers

jack

Great movie!

What about the part about Chevy's having a touch of Titanium in the pistons?

Movies love throwing around words like Titanium, Lasers, and now fuel cells, Etc.

All good fun, sorry to clog up the real info, reading with anticipation,

Kevin.

 

[T70MkIII]

I used to melt a little aluminium in a 'flowerpot' foundry when I attempted to build a Gingery lathe a few years back, until kids and renovations - in no particular order - got in the way. I don't know about titanium, but I sure did find a lot of magnesium in some of the old alloy car pieces I picked up from the scrap metal merchant - it made a lovely shade of "too bright to look at".

Which leads me to a slight thread hijack: do any of you melt down your aluminium swarf etc into ingots for re-use in non-critical components? This sounds like a good cost saving idea to me.

 

[Metal Mickey]

Really interesting psot, will store away for the future. Don't pictures say a thousand (or is it 9765?) words!

 

[rleete]

I haven't yet, but I have been saving it with that in mind.

 

[Bluechip]

Hi Folks

If you have a grope around on this site

http://tiranti.co.uk/subdivision_product_list.asp?Subcategory=63&Subdivision=

There is some info on RTV moulds & Low Temp casting alloys.

Never done it myself, but might give an idea or two .

I've had other stuff from them in the past, good firm to deal with, helpful.

Was nothing to do with metal casting tho'.

Dave

The link's a bit screwy .. click 'Casting' on the LH Side takes you to Alloys etc.

A lot of Cold Casting Resin Stuff .. confusing to old varmints such as meself

 

[shred]

Which leads me to a slight thread hijack: do any of you melt down your aluminium swarf etc into ingots for re-use in non-critical components? This sounds like a good cost saving idea to me.

I've thought of it, but there are couple issues-- 6061 isn't a great casting alloy and swarf has such high surface-area to volume that almost all of it ends up as dross and not metal. I'm sure it can be done with the right process-- recyclers buy tons of the stuff, but I don't know the details of what process they use to return it to ingots.