Re-casting Unobtainable Parts

[Potmetalman]

Hello Everyone. I thought you'll might like to see this 1941 Cadillac Convertible vent window that I just created? The guy had been looking around for a 2 or 3 years LT side and finally decided to call in make the request. 
So what we did was digitally copied RT side, flipped it and made a matching LT side. The polished one is the newly created frame.
Hope ya'll find it interesting. :) 

Thanks.

[keiser31]

Request sent.

[Potmetalman]

Hey Brother. 

 

Sure I can make ya a set, but I need at least one side, in order to make a complete set. If you've got one that's in rough shape, I can use that as well.

 

Thanks for reaching out.

 

James Ruther - The Pot Metal Man

[1939_Buick]

Do you make allowances for shrinkage of the cast material?

[Potmetalman]

48 minutes ago, 1939_Buick said:

Do you make allowances for shrinkage of the cast material?

Yes, but it depends on the part and materials that are used? For instance, I do a prototype casting first to check dimensions. If it shrinks i scale it up a bit and do another casting until it comes around. Usually with the parts I do, the shrinkage is roughly 3% and I build that into the model prior to prototype casting. 70% of the time it's on the money.

 

Thanks

[Gary_Ash]

What is your process to get from the 3D scan to the cast part?  Do you use a “lost wax” type of process from a 3D printer pattern or something else?

[Potmetalman]

Hey Gary.

 

I do 3D print and import into Autocad for reverse engineering to clean up the pattern to prepare it for printing.

Edited August 5, 2023 by Potmetalman (see edit history)

[Potmetalman]

1 minute ago, Potmetalman said:

Hey Gary.

 

I do 3D print and import into Autocad for reverse engineering to clean up the pattern to prepare it for printing.

...With lost wax, theres no way to scale for shrinkage. 

 

[Gary_Ash]

James, you may have misunderstood my question.  When I referred to a "lost wax" type of process, I really meant "lost PLA".  I've been successful in having investment cast bronze parts made by creating a model in CAD at 100% size, then 3D printing a PLA pattern at 102% size (for shrinkage allowance).  The PLA goes into the plaster investment and is melted out and burned out during the firing of the investment, just like wax.  This saves the processes of making a silicone rubber mold and a wax replica.  Have you tried this?

 

Here is a sample pattern in black PLA and some bronze water pump impellers made by the lost PLA process.  Other types of 3D printing filaments may not work as well.  I've tended to use clear PLA more recently to be sure there is no residue in the investment after burnout - any remaining clear PLA will burn to CO₂ gas and water vapor.  I haven't needed any Zamac parts but will keep you in mind if I do.  Your work is impressive! 

[pmhowe]

1 hour ago, Gary_Ash said:

Your work is impressive!

So is yours!

[JV Puleo]

As the person that machined those bronze impellers I can testify that Gary's castings were really impressive. I've machined a lot of sand castings and the difference between them is remarkable. When centered in the lathe I was able to get those rough castings to run with only .005 runout.

 

I'll add that the sand castings I've worked with are also extremely good which says a lot for the accuracy of the lost PLA process.

Edited August 5, 2023 by JV Puleo (see edit history)

[edinmass]

Garys castings came out great……..but that’s because he has an engineers eye for details. Unless you have a willing and helpful foundry things can go south fast. Fact is today every part of the process need a close eye to get acceptable finished results. Way, way too many people in the process can have a good enough or I don’t give a shit attitude……..and the results magnify into poorly fitting parts. I NEVER assume ANY repop part I buy will fit………and frankly I’m astounded on what people sell and think are acceptable parts. 

Edited August 5, 2023 by edinmass (see edit history)

[TTR]

1 hour ago, edinmass said:

…and frankly I’m astounded on what people sell and think are acceptable parts. 

Same here, but more so on the fact that there are people actually buying/paying for them.

 

[dodge28]

I never thought there are members of this club are so talented. The Australians are pretty good but are in the process of retiring. Glad there is someone in USA are able to take up the slack 

[JV Puleo]

5 hours ago, edinmass said:

…and frankly I’m astounded on what people sell and think are acceptable parts. 

I've wondered about that myself...all second hand because I haven't had reason to buy reproduction parts but judging from the horror stories I read here it seems they are wrong more often than they are right, so much so that if they are right someone wants to comment on it. I really find it hard to imagine going to the effort of making something and having it not fit. Or is  it that the majority of the buyers don't even realize that the parts  aren't right.

[JV Puleo]

2 hours ago, dodge28 said:

I never thought there are members of this club are so talented. The Australians are pretty good but are in the process of retiring. Glad there is someone in USA are able to take up the slack 

The talent is out there but you won't find it in what were the conventional places. I know some very talented people but most of them are hobbyists rather than professionals or professionals  (like Gary) who are willing to share their expertise with fellow enthusiasts. I'd bet there are some in Australia...but you have to find them. They aren't going to be advertising on the internet.

Edited August 5, 2023 by JV Puleo (see edit history)

[edinmass]

Here are still talented craftsmen in the agricultural heartland of the US, but they are pretty much gone on the coasts. 

[Guest]

What are the capacities of your foundry for lost wax silicone bronze hopefully 300+, cost per pound and location?

[Jim Skelly]

15 hours ago, JV Puleo said:

I've wondered about that myself...all second hand because I haven't had reason to buy reproduction parts but judging from the horror stories I read here it seems they are wrong more often than they are right, so much so that if they are right someone wants to comment on it. I really find it hard to imagine going to the effort of making something and having it not fit. Or is  it that the majority of the buyers don't even realize that the parts  aren't right.

For those of us who have cars built in the 1970s with flexible plastic filler panels between the sheet metal and front/rear bumpers, the aftermarket parts are generally very poor fitting.  I've read many complaints and have seen many cars with reproduction parts that just don't fit properly.  People buy them because it's that or nothing after the original parts disintegrated.  Most of these cars are not in high demand, so manufacturers are not willing to invest what is necessary to make accurate parts.

[Potmetalman]

On 8/5/2023 at 7:44 AM, Gary_Ash said:

James, you may have misunderstood my question.  When I referred to a "lost wax" type of process, I really meant "lost PLA".  I've been successful in having investment cast bronze parts made by creating a model in CAD at 100% size, then 3D printing a PLA pattern at 102% size (for shrinkage allowance).  The PLA goes into the plaster investment and is melted out and burned out during the firing of the investment, just like wax.  This saves the processes of making a silicone rubber mold and a wax replica.  Have you tried this?

 

Here is a sample pattern in black PLA and some bronze water pump impellers made by the lost PLA process.  Other types of 3D printing filaments may not work as well.  I've tended to use clear PLA more recently to be sure there is no residue in the investment after burnout - any remaining clear PLA will burn to CO₂ gas and water vapor.  I haven't needed any Zamac parts but will keep you in mind if I do.  Your work is impressive! 

Yes Sir. That's almost the same process but I've found that I get better results with castable resin and Ceramic Shell over sold mold vacuum casting. Depending on your printing equipment, with resin printing you can get down to .025 layer thickness so thin that there's not layer patterns. Down side is, it takes longer to print, but you get far better castings...

[californiamilleghia]

On 8/5/2023 at 11:09 AM, edinmass said:

………and frankly I’m astounded on what people sell and think are acceptable parts. 

The problem is also that the companies that commission  parts to be made , then   accept  these bad parts because they want something to sell , 

 

It must be hard to have a shop where you are buying from dozens of suppliers and quality all over the board.