Casting - How to get consistant results

Hi all,
I’ve been casting with Castable resin since it came out. The results are still not 100%, but they are close, with results that are consistent enough to incorporate into my everyday production.
After trying the plasticast and special burn out cycles, which didn’t help at all, I turned my attention to curing - it seems that the resin is just not fully cured no longer how long I leave it in the UV chamber.
So, now I am back to regular investment, although I kept the burnout cycle because longer is ALWAYS better, no matter what you are casting. But the real game changer is how I cure the resin - I use a MICROWAVE OVEN.
The pattern goes in a bowl full of water, and in the microwave for 20 minutes. Depending on the power of your oven, you may need to refill the water during this process. Make sure the pattern is always fully submerged in water (if the water evaporates your pattern will be ruined). I started with 10 minutes, then 15, now I am up to 20. If I have time after that, I put it in the UV chamber, but I’ve gone without with fine results.
My castings still show some surface imperfections and so I will continue to pursue this avenue of improving curing…perhaps with more microwave time, perhaps with different liquid. It would be great if a material scientist (like someone at Formlabs!) could explore the process of curing their resin and concentrate on finding a solution to obtain a FULL AND COMPLETE CURE. I believe this would make Castable Resin truly castable!

I’m having difficulty understanding the mechanism by which the microwave is curing parts, other than possibly heat. First, I’ve never cooked anything for 20 minutes in a microwave in my entire life. I’m imagining that the micowave is consuming a boatload of energy in this process. Since heat may be the operative process here, have you tried just doing this on the stove?

Also, what about just putting the part in direct sunlight for 20 minutes? That’s free :smile:

I am the originator of the idea to microwave cure from a different forum. I came up with the Idea as I understand how microwaves work, I also have bought and experimented with Form 1 casting resin and many others trying to get any/ all of them to cast properly.
A microwave cures from the interior of the object to the exterior. Doing it in water or various liquids stops the material from being directly exposed to air while curing. For some materials, it is more important then with others. I have tried baby oil which works on some materials and causes issues with others. What works for my system is water. 5 minutes on. cool down. 5 minutes again,… cool down and a final 5 minutes… totaling 15 minutes…then i UV cure for as many hours as possible using twin 36 watt UV curing boxes and a rotary table to make sure the part gets cured as much as possible.
I use Plasticast investment. I also do many other operations to try an guarantee that the casting comes out.
You can mix boric acid at 1% to 2% to make the investment stronger. It also sets up faster, so be careful. That can be used when you notice the investment is breaking down… If it is not the investment breaking down then I use a vacuum cleaner with a steel nozzle to Vacuum the left over material in the cavity. The vacuum seems to help. After Vacuum, I put it back in the oven to recover.
With 47 years doing high volume production, I have a large number of casting tricks that I start to use when Problems arise.
The problem with having to try different things is that you have to have more of the same part. Luckily I can make my own.
I am attaching a picture of how I set up the tree for vacuum … you will be able to understand a bit better how it works.

you might want to check your stated assumptions here:

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Hi Chris,
What you have is the technical explanation. If you talk to various people who sell them, they tell you that it cooks food and other substances from the inside out… Passing through the outer layer to the center etc…
What ever the explanation is , on many prototyping materials, it does a good job of speeding up the curing process. I have a lot of people who have tried this when other methods have failed. Microwave in water alone does not finish the process… But it helps a lot on tough to cure designs. The more the item is cured, the better the casting.
Some other materials can be oven cured. All I am pointing to is that when things don’t work out using the standard methods of curing and burnout, There are other methods to try.

I have tried the standard method recommended with the Form 1 castable and had some success with small ladies rings, but larger pieces with deep engraved letters were a failure. Hence , the experiments. If the standard burnout process worked for everything, then there should be no failures. Adding the Vacuum vents as I described above helps a lot… I also used a clean filter on the vacuum and guess what… I did collect ash! And got good castings.
My oven controllers are very high end , self calibrating controllers that are periodically checked for accuracy, So the ash is not coming from pour burn out.

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