Problem with sucessfull casting

[Christian K.]

Good evening!


Since 2 weeks we try to cast a ring with this profile:

In this groove are also adjustments for the diamonds.
When we cast the ring it rip out these adjustments away, and on the surface are small holes (plasticast rests)

Perhaps there are too great tensions when burnt out, that damage the investment material.

Only this ring make us this problem.. we cast everything without problems.

We use de Emerald green Resin.

Our burnout is:


Ramp up to 430C° hold for 3hours
up to 800C° hold for 4 hours.
down to casting temperature.

Have anyone an Idea how to cast this ring successful?

best regards!

[Jewelermdt]

If you are leaving a very thin edge you may have breaking of the investment. How are you spruing the ring. I would have 3 to 4 feeds to the inside of ring.

spru.JPG (32.51KiB)Viewed 27444 times

[Christian K.]

Thanks a lot.

Had the same idea yesterday.. but what if the investmant break because of the expansion?

we will give it a try on wednesday i hope.. thank you !!!
best regards !

[Dstonic]

Opti Cast investment....100:38 ratio...flask set time 5+ hrs....burn cycle is ramp 9999 to 1400 degrees 4.5 hrs then ramp down 675 degrees per hr to 850 degrees casting temp.

The B9 did better than Protowizard..... thinking the proto could not handle this ramp cycle? My investment is too old?

Three times straight having the recessed area of letters filling in with gold. My other concern is that the surface on the rings are terrible too.

I'm leaning on investment issue either by my mixing.... or the investment breaking down?
Would appreciate help and professional criticism

[Messerbr]

Idk about that proto resin, but for the B9 emerald a formula that has been giving us great results is:

1- Cure UV 405nm 2 hours
2- Microwave cure resin in water for 3 minutes. Let water cool for 15-20 minutes. Do this 3 times total.
3- Invest. We have been using Plasticast but just recently switched to Prestige Optima. Let flask set for 8hours.
4- Burnout Cycle: (degrees in Fahrenheit)
Ramp 800 to 800. Hold 3 hours
Ramp 1000 to 1450. Hold 2 hours.
Ramp 1000 to Casting temp. Hold 1 hour.
-Cast-

The key is making sure the resin is fully cured no matter what when I forget whether I have done 3 or 2 microwave cycles...I run it one more time just to be safe.

[Jewelermdt]

That fast of ramp most likely cause the Proto wax to boil and cause investment breakdown. The spur you have inside of the ring of the resin model, is that wax or resin. If wax it needs a way to melt out before the resin burns out. You would need to run it to the button. You might try turning the ring sideways. Also coat the lettering area with investment while you vacuum your mixing bowl. It should thicken up a little. Sometime the surface tension of the resin and investment won't allow it to flow around the lettering.

[Christian K.]

@Dstonic:

We have found a very good way for such Rings!

First of all - perfect curing!
cure the pieces half an hour bevor the microwave cycles!
3 times 3 minutes at 750W in the microwave in destilled water.

We have a small pastic bowl we put in the microwave - after the microwave we put this bowl with water and the models for 3 hours in the UV oven ( selfmade .Led stripes in color can ).

After the curing in the uv we put the models in the oven at 120-150 °C - i would recommend 1 hour at 130°C.
Then the models are ready to wax them up.
You have to much wax channels to the piece.

try it this way. and you will see it will work much better ( photo added. )

after investing the models let them rest at least for 4-5 hours.

burnout for emerald (with plasticast 38/100):

4°C/min - to 100 °C - hold it for 1h30min.
4°C/min - to 170C - hold it for 1h30min.
9°C/min - to 430 °C hold for 3h. ( very important)
9°C/min to 800°C - hold for 3-5 hours.
back to casting temperature ( 500 C°) - we cast with a indutherm MC15+.


the first to steps are very important.
Plasticast will hardens, that expansion won't cause damage the investment.
What we also do ( although everyone say: oh no- why you do that, you don't need it.. the investment will become too hard.. blabla.... ) is adding 2% of boric acid to the destilled water. Just 100 gram in a 5 litre bottle.
and YES it get a little bit harder, but we had never problems to get the models out without sandblaster. If you put the flask in the water 1 minuter after casting you will never have problems. some hammerplows arround the flask and the investment comes out.

we cast 100-200 grams a week - so we saw the difference between "with or without boric acid" - the investment do not break down and get much harder. - so you can go much higher ( 800 degrees for plasticast without boric acid would cause problems sometime.

the oven treatment is recommended for lettering / thin investment part etc. for normal Rings etc you don't need to put them in the oven ( because they will shringk a little bit)

some pictures of the last casting ( silver )

These models were only cured in the microwave and in the oven NO UV curing. ( The LED strip was dead after one year of use )

[Christian K.]

AND - if you want - send me the Stl of the ring and i will try our burnout - i love challenges

[Dstonic]

[quote="Jewelermdt"]That fast of ramp most likely cause the Proto wax to boil and cause investment breakdown. The spur you have inside of the ring of the resin model, is that wax or resin. If wax it needs a way to melt out before the resin burns out. You would need to run it to the button. You might try turning the ring sideways. Also coat the lettering area with investment while you vacuum your mixing bowl. It should thicken up a little. Sometime the surface tension of the resin and investment won't allow it to flow around the lettering.[/quo

The spur is Proto wax, it is from my rotary cut. Coating the lettering is something I had not thought of and is a very good idea.

[AndrewWest]

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