Looking for advice about casting fundamentals

CatamountRob

CatamountRob

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Any tips on casting from a boat CRob?
Did I ever tell you about the time I hooked my math teacher through the earlobe while we were fly fishing? Probably not. It was a royal coachman and looked pretty good there.
 
kimba

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Hi Abe
Just been looking through this thread again.
Glad all seems to be going well.
Without throwing a spanner in the works , I don’t agree to keeping the resovoirs separate.
As long as the total weight is bigger than the total weight of the crowns .
Also you DO NOT want a button after casting. Just have the resovoir complete with a little of the spruce left. A large button will cool quickly as the casting arm spins and suck alloy away from the resovoir and crown.
Also when casting large span bridges if you have a button it can contract the sprues slightly leading to ill fitting castings.
Hope I’m not confusing the issue just trying to help
 
HonestAbe

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I appreciate all advice given and I'm trying different things out.

I'm also a welder and I don't know if this principle applies to casting, but there are multiple ways in welding to achieve good/acceptable results. Like if I picked up another welder's machine and tried to weld with it I might have trouble with their settings. My process here is to gather everyone's best practices, experiment a little, and find what works best for me.

I think my biggest weakness here is that I'm not the one doing the metal finishing, so I have to rely on feedback from that. What I really want to do is get to the point where I'm making the least work for them possible. If I can keep getting farther ahead of schedule I might be able to get some time to learn the finishing side of things but as I'm sure you all know, it's hard when things are busy and you're being pulled in 10 directions at once.
 
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Michael @ Beyer Dental la

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I would google around for info on casting with different fuel sources. Many years ago, when I was still new to this world, we were using acetylene(!!!!) to cast with. It was dirty and we were having miscasts. I started googling and found a father son duo who had a great article about casting with different fuels and found out real quick that acetylene should not be used :). We changed over to propane and oxygen. Natural gas should be fine also.

Spruing is the other big concern. Making sure you have big enough reservoir is key. Also keep in mind how your molten metal is flowing. I try to limit the mount of directional changes the flow has to make before it gets to the margins.
Work on spruing. I have bee using acetylene for over 30 years and no problem. Thick castings require bigger spruing.
 
HonestAbe

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Any thoughts on when to replace O2 bottle? I'm at 500 psi left in the tank atm but was noticing some odd things adjusting my flame yesterday. Like I got it dialed in to where I wanted it but it was way more finicky and sensitive (tiny turn of knob, sudden big change in flame kind of thing).
 
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Willard

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Maybe be a problem with your regulator
500 psi I wouldn’t consider low
 
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karlanm

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Quick tip. Find the density of your metal in g/cm3, weight crown and sprue, and then multiply by density and then 1.3. Too much metal causes porosity issues and too little is heartbreaking
 
HonestAbe

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Overall things have been doing well, did end up with a little pit of porosity on one crown near the sprue connection and right on a contact which sucked but I'm not certain why it happened.

What is the industry standard for how much weight gets added to the bill to account for the kerf?
 
HonestAbe

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Still getting porosity sometimes at the sprue location and I'm not sure why. I can't tell if it's adjacent to where the sprue is or directly where it meats the pattern. My gut is telling me it's something to do with the way I'm attatching the sprue (too broad perhaps? will get some closeup pics of next ones I do) but others here are insisting it's because my button wasn't big enough.
 
CatamountRob

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Try a bigger reservoir, not a bigger button. You don’t want more than 1/4” of investment over the top of your pattern.
 
JKraver

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Why don't you just mill the gold at strategy milling or argen?
 
HonestAbe

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Why don't you just mill the gold at strategy milling or argen?
Tried Argen recently and the results were really good. I'm trying to keep my hand in it for rushes but otherwise they seem worth it. The time I save is better applied to more CAD design and from what I understand the finishing is way quicker (as in hardly any needed).

They've had a few hiccups now and again with minor delays but the 2 day turnaround seems pretty consistent.
 
JKraver

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Tried Argen recently and the results were really good. I'm trying to keep my hand in it for rushes but otherwise they seem worth it. The time I save is better applied to more CAD design and from what I understand the finishing is way quicker (as in hardly any needed).

They've had a few hiccups now and again with minor delays but the 2 day turnaround seems pretty consistent.
Milled gold is the only way to go these days IMO. I see like one every two years. I am amazed you see enough to have a protocol for it.
 
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D and D

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So I'm relatively new to casting (only a few years experience) and realizing that I've been getting by alright but when things don't go well (miscast, porosity, investment problems) I don't have a strong foundation in the fundementals to troubleshoot what's going on. I don't really have anyone that can look over my shoulder and point out what I'm doing wrong. I get the sense that I'm doing most things correctly but there's so many variables that sometimes a combination of things adds up to me messing something up. The areas I perceive I'm weakest at are:

Getting my torch set correctly for different alloys
Optimal sprue technique

I'm just wondering if anyone has some resource they can point me at to read up or watch where I will hopefully notice things I am doing sub optimally. Most of what I cast are full gold crowns, with the occasional pfm, custom abutment, or post.

EDIT: I suppose I could also start documenting stuff with photos so we can laugh the next time I mess something up and hopefully figure it out, but for now I'm mostly just looking to read and study something to see if anything jumps out at me.
Try contacting talladium. They have been very helpful over the years with casting issues.
 
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MarkDT

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So I'm relatively new to casting (only a few years experience) and realizing that I've been getting by alright but when things don't go well (miscast, porosity, investment problems) I don't have a strong foundation in the fundementals to troubleshoot what's going on. I don't really have anyone that can look over my shoulder and point out what I'm doing wrong. I get the sense that I'm doing most things correctly but there's so many variables that sometimes a combination of things adds up to me messing something up. The areas I perceive I'm weakest at are:

Getting my torch set correctly for different alloys
Optimal sprue technique

I'm just wondering if anyone has some resource they can point me at to read up or watch where I will hopefully notice things I am doing sub optimally. Most of what I cast are full gold crowns, with the occasional pfm, custom abutment, or post.

EDIT: I suppose I could also start documenting stuff with photos so we can laugh the next time I mess something up and hopefully figure it out, but for now I'm mostly just looking to read and study something to see if anything jumps out at me.
Where is your pattern placement within the ring? as that can effect the out come of your casting, also are you venting your wax patterns with say 18 or 20 gouge wax. And depending on the size of the ring and metal to be thrown that also can effect your out come a reservoir on the sprue can help to feed thicker patterns. On large round house bars for over denture I would have to take the ring up in stages x amount per minute hold at 400 for an hour move up to 800 after x amount of time and then 1200 and then 1600 or so depending what I am casting. Preheat the crucible as well as it makes for a smoother and less radical heat exchange before casting
 
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MarkDT

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Like this. You want everything above the red line full of alloy and as little as possible below it. I usually use round rings for full gold but mostly as a matter of habit.
View attachment 39388
I seemed to have better luck with round rings I think that it has to do with even heat distribution the ovals just not as consistent unless of course it is a bridge and then well oval it usually was.
 
Affinity

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The OP was a bot that only came around during the pandemic, this thread was posted to make him appear human.
 
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