First Time Casting

Discuss casting techniques
OpedHead
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Joined: Wed Sep 14, 2016 2:27 am
Location: Melbourne, Australia

First Time Casting

Postby OpedHead » Sat Dec 05, 2020 9:51 am

Hey guys, sorry for the noob questions, I bought a second-hand vacuum casting setup during lockdown (per cast vacuum caster, kiln, furnace etc), it’s my first time casting, never been taught, in my apprenticeship my boss used casting houses and I don’t know anyone else who does their own casting, nor 3D printing here (Melbourne, Australia) You guys in the US and Europe seem to be much more advanced jewellers than us Aussies with these sorts of things.

I have tried 4 casts and they have all been pretty terrible.
First flask blew out the bottom when pouring (I think I didn’t have enough plaster over the model), the second had parts which the metal didn’t fully congeal so I upped the metal temp the next turn.
Third was white gold one (pictured), fourth was red/white looking ring (pictured)
There were no casting books in stock here in Australia so I read the Stuller guide and checklists for investing/casting, watched every youtube video I could find, and I’ve read a lot of posts in this casting section of the forum (most after trying I admit) and I’m guessing my major problem is either investment breakdown or maybe ash problems, but I’m not sure and was hoping someone could nudge me in the right direction.
Cast-1.jpg
9ct Yellow Gold casting (4th cast)
Cast-2.jpg
9ct Yellow Gold casting (4th cast)
Cast-WG.jpg
18ct White Gold cast using clients gold


These are the main details:

Investment: Goldstar Omega+, mixed at 40:100 ratio using kitchen mixer, vacuumed, invested in flask, vacuumed, left for 90mins before going into a cold kiln.
(Omega+ was the only investment powder in stock here designed for casting resins)
Resin: Easycast HD Brown. Models were perfect
Flask size: 85mm x 100mm height perforated
Burnout: Exactly as instructed by Goldstar Omega+ (below)
Omega Goldstar.jpg


I mix the investment with a kitchen mixer in a rubber bowl, vacuum, pour into flask, vacuum flask, sit for 90mins then into cold kiln and start program.

The red/white looking ring with heart shaped setting was actually newly alloyed 9ct yellow gold 37.5% pure gold granules, 31.25% copper, 31.25% silver out of the acid, and the other was 18ct white gold using clients old gold.
(Red I believe is from ferrous metals but no idea what makes parts go white/silver plate)

I don’t think it’s vacuum, as both sides of the machine reach full vacuum in 5-10 seconds, and after I turn the pump off after a cast, it holds vacuum for long time unless I lever the flask out of the machine.

I don’t think it’s curing, as my casting house gets flawless results in silver, gold and platinum on my current curing routine. I also get pretty shitty results when I’ve given them an under cured part which makes me think they don’t do any further curing on their end. (pictured below)
My curing: Direct Australian sun on rotating platform for at least a few hours - usually the whole day, or if it’s heavy overcast, under strong hydro grow lights for at least 6+ hours. (I will now add 5 x 5min microwave water boil technique)
Casting-House.jpg
Silver casts from my casting house


My guesses:

The setup came with an old Italian smelting furnace, which died after once use lol, so I’ve been using a torch – which I could be pouring the metal in too hot causing investment breakdown?
Is there a trick to getting the right temperature with a torch while I wait for a new furnace to arrive in the mail?

Could it be ash or airflow? I’ve noticed a lot of people here vacuum their flasks, flip them or find ways to add more airflow in their kiln (wish I read that first).
I just have a duct from the top plug hole going straight outside, and I have been sitting the flasks on a cake warmer on a pizza tray, which I noticed has slumped under the heat
Should I remove the front plug off the door for more airflow?

Spruing? I’ve never done it before but I did make sure the joins were smooth to assist flow. I used the large sprue for the first 3 and sort of carved the top like an arrow it so it flowed into the ring width.
I have noticed some people here use multiple sprues rather than just the one main one, but then a lot of you don’t – both with great results so I’m not sure how critical this is.
I only used one as my casting house only ever uses one, with great results, plus I read some things about creating turbulence if you don’t do the multiples correctly

Any tips to troubleshoot would be much appreciated :D
OpedHead
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Posts: 41
Joined: Wed Sep 14, 2016 2:27 am
Location: Melbourne, Australia

Re: First Time Casting

Postby OpedHead » Sat Dec 05, 2020 9:54 am

This is the kiln and how I had placed the flask(s)
Kiln.jpg
Burnout.jpg


The ring which didn't form, sprued
Spruing.jpg


Casting machine I'm using
Vacuum-Caster.jpg
Mikkopee
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Joined: Mon Feb 13, 2017 1:18 pm

Re: First Time Casting

Postby Mikkopee » Mon Dec 07, 2020 6:36 pm

Is it possible to try cast B9 Emerald so we can rule things out?
Kokos
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Re: First Time Casting

Postby Kokos » Mon Dec 07, 2020 7:05 pm

Your problem looks like ash. Possibly bad curing or bad burnout. I think burnout is the most likely.

First you need to make sure your oven reaches the Temp. that you have set. Sometimes, especially when the coils get older, wont reach the set Temp.
So maybe you have set the oven to 750C top but if it only reaches 700 that can cause problems.
There are special kiln cones to verify your oven.
Something like this: https://www.theceramicshop.com/store/ca ... 113/Cones/

Also I would suggest printing a batch off the same ring or both the ring you tried in Red and White gold. Then cure them all and send 1 of each to a casting company to cast in silver.
Then you also cast the rings in silver using your method. Then you can rule out bad curing methods.

Suggestions:
- Check temperature oven with cones.
- Don't use the investment burnout curve, use the Resin burnout curve. Investment curve goes to 250C as first step, Resin one only to 150C.
- Use longer time before you put the flasks in the oven. Try waiting 3 hours or more. And see what happens.
- You can add some borax to your investment and water when mixing. This will make your investment stronger.
-Try casting in silver first. It is cheaper and easier than white or red gold. But I dont think your metal temp is the problem.
- Only change 1 thing at a time so you know what is the solution to your problem. Should you run into it again in the future then its an easy fix and you dont have to try 10 things.

First things I would do is order some cones. And change Burnout curve to the Resin recommended curve.
You need to know your oven temps are good. Otherwise it is shooting in the dark, then you can change al you want but if the temps are not right then you're getting nowhere.

Keep us updated. And good luck!

Mikkopee also has a good suggestion. If you can use a different resin to burnout and cast. Then you can also rule out your resin or curing.
rsaldivar
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Posts: 325
Joined: Tue Jun 30, 2015 8:51 pm

Re: First Time Casting

Postby rsaldivar » Mon Dec 07, 2020 11:09 pm

fill flak all the way
longer bench sit times (4 hours)
metal is way too hot ,(for Silv,Yell gold) melt metal with the torch to where the metal liquefies but dont hit the metal directly with the flam , make it melt by making it hot around the perimeter of the metal, hot enough to melt the gold , ONCE THE METAL LIQUIDFES THE METAL IS READY TO POUR , (THATS THE RIGHT TEMP)
OpedHead
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Joined: Wed Sep 14, 2016 2:27 am
Location: Melbourne, Australia

Re: First Time Casting

Postby OpedHead » Tue Dec 08, 2020 1:22 am

Mikkopee wrote:Is it possible to try cast B9 Emerald so we can rule things out?


Certainly, I have some old B9 prints laying around I can cure and cast.

I should mention I used B9 Emerald to begin with, then after about two years tried EasyCast HD (brown) and love it.

The castings from my casting house very slightly improved as well, though that could've been from better printing. The pic of the successful casts above are cast from the EasyCast resin

Either way I'll test it incase it works better with MY casting :D
OpedHead
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Posts: 41
Joined: Wed Sep 14, 2016 2:27 am
Location: Melbourne, Australia

Re: First Time Casting

Postby OpedHead » Tue Dec 08, 2020 3:10 am

Kokos wrote:Your problem looks like ash. Possibly bad curing or bad burnout. I think burnout is the most likely.

First you need to make sure your oven reaches the Temp. that you have set. Sometimes, especially when the coils get older, wont reach the set Temp.
So maybe you have set the oven to 750C top but if it only reaches 700 that can cause problems.
There are special kiln cones to verify your oven.
Something like this: https://www.theceramicshop.com/store/ca ... 113/Cones/

Also I would suggest printing a batch off the same ring or both the ring you tried in Red and White gold. Then cure them all and send 1 of each to a casting company to cast in silver.
Then you also cast the rings in silver using your method. Then you can rule out bad curing methods.

Suggestions:
- Check temperature oven with cones.
- Don't use the investment burnout curve, use the Resin burnout curve. Investment curve goes to 250C as first step, Resin one only to 150C.
- Use longer time before you put the flasks in the oven. Try waiting 3 hours or more. And see what happens.
- You can add some borax to your investment and water when mixing. This will make your investment stronger.
-Try casting in silver first. It is cheaper and easier than white or red gold. But I dont think your metal temp is the problem.
- Only change 1 thing at a time so you know what is the solution to your problem. Should you run into it again in the future then its an easy fix and you dont have to try 10 things.

First things I would do is order some cones. And change Burnout curve to the Resin recommended curve.
You need to know your oven temps are good. Otherwise it is shooting in the dark, then you can change al you want but if the temps are not right then you're getting nowhere.

Keep us updated. And good luck!

Mikkopee also has a good suggestion. If you can use a different resin to burnout and cast. Then you can also rule out your resin or curing.


Thanks for your response and tips Kokos, I'm taking them straight on board.

-I've ordered some oven cones and have changed the burnout schedule to the resin.

-I invested two flasks and let them sit overnight, rather than the 90mins I had previously done.
I also have Pro HT high temp Platinum Casting invesment which has phosphate in it. So I put on a flask with that investment as well to see a comparison in results (though the investment powder is twice the price)

-I took the door plug off for more airflow

*This could be the main problem*
I ended up reading almost every single thread in this casting forum and read that I should be burning out the flasks button up.... I had previously burned them out button down (woops)
One thing I am unsure about is if you start them button down to let the wax sprues melt out (for the 150c soak) then flip them to button up for the high temp ramp - or - just put them in button up for the whole cycle?
Because I'm burning out through day hours I will do the manual flip this time.

-I will also try a quick compressed air blast and vaccuum during the final temp soak to remove ash.

Regarding the curing test, I have done that with 3 different casting companies, including one that further cures prints you give them with the envision tec flash curing machine. I have also given an intentionally non-full cured resin to a particular caster to see if they do their own curing without mentioning to customers, but it seems they don't, as the undercured item came out worse than the cured item I gave them (see pic below)
- I did however add 5 x 3min microwave water boils to the curing on one of the pieces, so I'll report if there is any quality differences.
Cured-not-Cured.jpg


Thanks again for the suggestions, I will post the results these changes made
OpedHead
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Joined: Wed Sep 14, 2016 2:27 am
Location: Melbourne, Australia

Re: First Time Casting

Postby OpedHead » Tue Dec 08, 2020 3:15 am

rsaldivar wrote:fill flak all the way
longer bench sit times (4 hours)
metal is way too hot ,(for Silv,Yell gold) melt metal with the torch to where the metal liquefies but dont hit the metal directly with the flam , make it melt by making it hot around the perimeter of the metal, hot enough to melt the gold , ONCE THE METAL LIQUIDFES THE METAL IS READY TO POUR , (THATS THE RIGHT TEMP)


Thanks, I'll fill them right to the top now on, and yes I'll defnitely let them sit at least 4 hours too.

Thankyou so much for the melt temp guide, I was hitting the metal full on all the way into the flask. I'll melt the metal like you said
OpedHead
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Joined: Wed Sep 14, 2016 2:27 am
Location: Melbourne, Australia

Re: First Time Casting

Postby OpedHead » Tue Dec 08, 2020 3:21 am

Thought I would add - I found this helpful troubleshooter and other info off the Siam Casting Website.
http://www.siamcasting.com/casting_problems.html

And here is the info I found on the Stuller site which has some good info
https://www.stuller.com/benchjeweler/re ... rat-golds/

Casting Problem Troubleshooter.pdf
(165.65 KiB) Downloaded 71 times


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rkundla
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Joined: Sat Jan 09, 2016 6:01 am

Re: First Time Casting

Postby rkundla » Mon Dec 14, 2020 10:37 pm

OpedHead wrote:I ended up reading almost every single thread in this casting forum and read that I should be burning out the flasks button up.... I had previously burned them out button down (woops)
One thing I am unsure about is if you start them button down to let the wax sprues melt out (for the 150c soak) then flip them to button up for the high temp ramp - or - just put them in button up for the whole cycle?


I've cast small flasks both ways and have not been able to definitively say that either way is better than the other. I prefer to start button-down to collect the melted sprue wax, then remove it from the oven before raising the temperature. This keeps my oven cleaner longer since I have one with the muffle versus firebrick.

Now I have been steam dewaxing my small flasks using one of those Insta Pot rice cooker appliances. Now I can cast without dealing with that hot wax drip tray. :D

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