Any ideas as to what is causing this 14kW

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printcast
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Any ideas as to what is causing this 14kW

Postby printcast » Mon Jan 01, 2018 5:24 pm

I don't cast a lot of gold but when I do this is often the result. The shanks generally turn out smooth but light metal areas are completely pitted.

It looks to be like maybe gas bubbles? Possibly incomplete metal fill maybe due to ash? Maybe metal starvation. Not really sure but I do not think it's investment break down.

Not being an burnout issue due to the investment not being an issue the whole process wont be posed but the program holds at 1400 for 3 1/2hr then cast temp at 1200f for 1hr. Metal was 1900f. Quenched when sprue button turned from red to grey.

This was what should have been well over cured Emerald.
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rkundla
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Re: Any ideas as to what is causing this 14kW

Postby rkundla » Mon Jan 01, 2018 11:18 pm

From the photo, is it a positive defect or a negative defect? Positive defect would be a investment failure, while a negative defect can be lots of things, many of which you mention.

The prongs look fine but the gallery wire looks pitted. Probably a temperature/gas/metal flow problem. If it was ash, your prongs would be pitted as well. That's my guess anyway...
printcast
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Re: Any ideas as to what is causing this 14kW

Postby printcast » Tue Jan 02, 2018 3:19 am

Those prongs were actually sanded on a bit to see how deep the pits went.

I am casting another tomorrow. This time there is a light coat of melted wax of all those areas that pitted. That was done to thicken those up slightly and give space for expansion (but the investment seemed fine).

If anyone can offer flask and metal temps to try, I'll try it. This seems to be gas from something being overheated.
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Jewelermdt
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Re: Any ideas as to what is causing this 14kW

Postby Jewelermdt » Tue Jan 02, 2018 3:36 am

I run a wax wire to my heads from the button to the head. Helps get air to those thin spots and aid in metal to this area.
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M-Williams
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Re: Any ideas as to what is causing this 14kW

Postby M-Williams » Tue Jan 02, 2018 6:34 pm

This is simply a failed casting. You must go back to the basics. A good curing, 36 to 100 ratio( Plasticast works well for us) We do 1375 for 3H before we step down cycle to casting temperature ( we use a programmable oven).
Hope this will help. Marc
printcast
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Re: Any ideas as to what is causing this 14kW

Postby printcast » Wed Jan 03, 2018 6:07 pm

I reached out to a very experienced B9 resin caster who informed me that he thinks this issue is remaining resin ash. He said he sees this sort of thing fairly regular but with a laser welder is able to repair these things. He also said that he sometimes makes a wax sprue vent from the highest points to a spot on the rubber base away from the button so that he can vacuum residue through and out.


Something to think about.
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M-Williams
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Re: Any ideas as to what is causing this 14kW

Postby M-Williams » Wed Jan 03, 2018 8:41 pm

I would say if the print is fully cured, with the right Burnout Cycle.There is really no need to add any wax vent.
lklutts
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Re: Any ideas as to what is causing this 14kW

Postby lklutts » Tue Jan 09, 2018 1:57 am

I find your cast temp of 1200 to be really hot.900 works for me aND I let it sit for a couple hours at cast to make sure it is cool enough
rsaldivar
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Re: Any ideas as to what is causing this 14kW

Postby rsaldivar » Tue Jan 09, 2018 5:15 pm

not cured properly or long enough regardless of what resin you used , thats a reaction form under curing

what resin ?
printcast
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Re: Any ideas as to what is causing this 14kW

Postby printcast » Sun Feb 11, 2018 8:47 pm

rsaldivar - That is emerald. What I did with that ring was to add a very light coat of wax. Fortunately the design was organic so adding that bit of wax only added to the organic look. What is happening with these resins is that in tight areas it leaves residue that simply can not clear out. I think it has more to do with oxygen not getting into those areas. MAYBE a longer burnout. I do have a fish tank pump pushing air in as well as a few holes in my kiln.

Iklutts - you might be right as well.

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