Trouble in Casting Paradise

[samatheang]

Seem like you are very frustrated. Here is my opinion and maybe something new for you to try if you haven't tried it yet. I don't think you should cure the investment for more than six hours according to the R&R instruction below. I just do 5 hours or 5 hours and a half at most.

"To achieve appropriate green strength, allow the investment to sit undisturbed (bench cure) for 2-6
hours.
Note: if bench cure will exceed 6 hours, maintain moisture by rewetting, covering with a wet cloth
and sealing in a plastic bag. This will reduce potential cracking of molds due to uneven drying."

Also, it is better to start with 212F for two hours and 350F for another two hours to help cure the investment. After that I just go as fast as possible straight to 1400F and hold for three hours and down to 1000F for one hour and cast. I have 99% success rate including thick ring, engraving with milgrain, etc. using that burning schedule from someone on 3dcadjewelry.com.

Hope that helps.

[rkundla]

R&R's recommendations for wax burn out of plasticast are 300, 700 and 1350 degrees.

Is the primary goal of the 300°F period to dry the flask of moisture, drain the wax as quick as possible or both are important?

The 700°F phase was part of the chemical process of getting the investment to reach its maximum expansion before you slammed on the gas to hit 1350°F for the actual decomposition of the carbon leftovers.

Heh, it is all voodoo to me. As long as it works, I shouldn't care too much about how it works.

[Archerm]

I have done lots of experimenting with the different investments. The Plasticast can take a faster ramp up if it bench sets longer. That is why I let it sit between 6-12 hours in the oven Before I cast. Normally that is over night. Now the Satincast is way more sensitive. I am anxious to try the Prestige investment as soon as I get low on the Plasticast. I have cast on average 1-2 times a week with the Plasticast since I started casting the emerald prints and haven't had any failures or break down like above. I almost feel there is something else going on with the process. I would like to get one of your prints or the file of this and try to cast it and see how it comes out.

[rsaldivar]

seems to me that the problem is that the investment keeps reaction to the resin where all the fine detail is , so yes cure the heck out of it , heat and uv , however , and I hate to say this because its yet another purches , when it comes to detail like lettering , you might need platinum investment , I use the RP investment from Stuller , it is Rock hard and a bear to remove because of it , but for jobs like these , so the investment wont break or react , maybe this might be the way to go
Also one reason I use the RP is because of cost , it cost about the same per weight , but it allows you to buy less weight so less money to try ? about 67.00 https://www.stuller.com/products/21-706 ... SiteSearch

thick pieces require , In my opinion , longer hold at 1400 , more resin to dissipate
sorry man , we've all been there , hope this helps

[Diaro]

I am new in this forum. I use Solidscape printers for 12 years now and I cast for about 10 years now with continue research for better plasters and resins for modern printers. I am close invalved with Indutherm Germany about casting and we have contact with Indutherm resellers and their knowledge all over the world.

I see in the pictures that the coin is engraved in the 3D file, with very fine lines. There are rules in casting. Even with the very best plasters and the easiest wax, it is hard to cast these text paterns. The rule is aprox. this: minimum whith 0,25mm and max depth = the minimum whith. So, when the line is smaller than 0.25mm, you will get risks. When the depth on that point is more than 0,25mm, you will probably fail in casting. What I see happening in resins, is that they expand a bit before they burn. If the opening is small, the expantion will crack the plaster. And also, when the burnout is perfect, the liquid metal will destroy the finest plaster parts. The result is that the small broken plaster-parts end up in the edges of the model and after cleaning they leave small open spots. Like poreusity. Combined with some left ashes from the resin, you get this result.

My advice:
Be sure, the Font-lines are wide enough for casting. Check if the depth is not deeper than the smallest line.
Use the right plaster. I am testing a new plaster from Turkey now, and we see incredible results with B9 resin and also from other brands. burnout possible up to 1550F/850C. I will update this soon with Formtec and Solus prints.
Cure long enough ( as you already know and do)
Sometimes it will help to blow with compressed air ( low pressure) into the flask, before casting. This will help a bit, to remove ashes from the plaster inside.

I read about Platincast or kinds of. These plasters will "eat" the resins. In these cases, you need Procad or simular "dipping" liquid, to protect the resin model against the chemicals in these plasters.

[Dstonic]

Casting engraved letter like those has been a night mare for me. I use B9 Green and use plasticast and still have issues. What is happening when your metal slams into the mold, it is braking off the little letter sticking down. The deeper the letter the worse the problem. I have even gone as far as tapering the letters which is a real PITA. I have just gotten in some Prestige Optima investment and looking forward to trying it. If you figures something out I would be interested in hearing how you did it. I have tried everything I can think of.

Hi I new to the forum and just read your comment, have you tested the Optima? I thought of buying it for my first castings. Curious to the results such as mixing ratio, vacuuming, curing time befor oven burn out as well your burn cycling. I know these are lots of questions but sure would help me understand more. Thanks .. David

[jdwages]

So far I love the optima investment. I am getting the best casting I have ever gotten casting resin, reminds me of casting injection waxes. I followed all the instructions that optima suggest except I don't preheat the oven and only cure before burnout around 1.5 hours. I am going to experiment with some engraved charms soon.

[MobiusJewelryDesign]

Hi All! Sorry I have been away for so long.....been very very busy! I took another crack at this piece and this is what I got. I think that Diaro is right that the letting is just too thin....I tried like hell to make it work but in the end there are limits. I am casting in green now, I notice that the green tends to be a bit more tempermental in printing than yellow. You need more supports otherwise you tend to have spots that don't come out.....I used yellow for a while there because of this, but didn't like the fact that yellow likes to warp my film. Anywhooo....Here are some pictures for more deductions. I will cast and post again soon.

[MobiusJewelryDesign]

One more thing! I really appreciate all the love and support I get here! From the bottom of my heart, Thank you Thank you Thank you!!

[wawatobi]

Another 2 cents. I get consistently better results when I include 2 hr. at 250 F. before ramping full to 800. I don't know why it works but I am guessing that this strengthens the investment.