Question on casting knee and elbow joints

[Taterbot]

I having some problems with the material I am using to cast the knee, shoulder and elbow joints. I am using Smooth-On 327 and they keep breaking after a few uses. I realize that I am not using the right material to cast it. What material should I use that will give some flexibility and solve this problem. I have Task 16 that I use for helmets and hats but that is way to flexible. Any help or knowledge would be greatly appreciated.

 

[Vortious]

I use a mixture of Task 3, and 45 D. By using varying amounts of each of the materials you can go from soft, and really flexible like capes (just 45 D), to good, and solid, but not as brittle as Task 3 by it self is. You just have to play around w/ the mixtures. I've found that a 2 D to 1 T3 gives a nice flexibility like MU arms, and legs, the 1/2, and 1/2 (my main go to lately for arms, legs, and weapons) is fairly hard as long as there isn't too much dye added (so if you want it to be really hard just use 1 color), and the 2 T3 to 1 D is very stiff good for joint pegs (though the 1/2, and 1/2 is just as good for pegs, and Tbars). The 1/2, and 1/2 is what I use to make the Angel wings, Ares accessories, and even the entire Beast kit so that it'll be all one color. Then there's my clear mixture, but that one is staying under wraps for now.

So my question to you is how hard is the 327, and how soft is the Task 16? I've only ever use Task 3, and 45 D.

 

[Taterbot]

I use a mixture of Task 3, and 45 D. By using varying amounts of each of the materials you can go from soft, and really flexible like capes (just 45 D), to good, and solid, but not as brittle as Task 3 by it self is. You just have to play around w/ the mixtures. I've found that a 2 D to 1 T3 gives a nice flexibility like MU arms, and legs, the 1/2, and 1/2 (my main go to lately for arms, legs, and weapons) is fairly hard as long as there isn't too much dye added (so if you want it to be really hard just use 1 color), and the 2 T3 to 1 D is very stiff good for joint pegs (though the 1/2, and 1/2 is just as good for pegs, and Tbars). The 1/2, and 1/2 is what I use to make the Angel wings, Ares accessories, and even the entire Beast kit so that it'll be all one color. Then there's my clear mixture, but that one is staying under wraps for now.

So my question to you is how hard is the 327, and how soft is the Task 16? I've only ever use Task 3, and 45 D.

Thanks for the reply and info Vortious. I will be ordering some of that and give it a try.

327 is pretty hard stuff. Not much in the line of being flexible. Task 16 is extremely flexible and is really great for helmets and mask. But it will tear easy if the piece is too thin. Downside to the Task 16 is that it is thick when mixed. I use a syringe to inject into the envelope molds.

 

[DarkWynter]

What pressure are you using with the 327? 327 is not as hard as task 3, but it should be more than sufficient for shoulder/knee joints.

 

[Vortious]

What pressure are you using with the 327? 327 is not as hard as task 3, but it should be more than sufficient for shoulder/knee joints.

If it is just slightly softer than Task 3 then you shouldn't have any problems with it. Try pressurizing your pot to 30 psi for about 3hrs.

 

[Tofujesse]

Sorry I can't help out on this but I only use a few different resins. I do have a few questions myself if you guys don't mind. Always looking to learn new stuff.

What pressure are you using with the 327? 327 is not as hard as task 3, but it should be more than sufficient for shoulder/knee joints.

How does the amount of pressure affect anything?

If it is just slightly softer than Task 3 then you shouldn't have any problems with it. Try pressurizing your pot to 30 psi for about 3hrs.

Why pressure it so long?

 

[Taterbot]

What pressure are you using with the 327? 327 is not as hard as task 3, but it should be more than sufficient for shoulder/knee joints.

Im using 45-50 psi.

If it is just slightly softer than Task 3 then you shouldn't have any problems with it. Try pressurizing your pot to 30 psi for about 3hrs.

I will give this a try.

Thanks guys!

 

[Vortious]

Sorry I can't help out on this but I only use a few different resins. I do have a few questions myself if you guys don't mind. Always looking to learn new stuff.




How does the amount of pressure affect anything?



Why pressure it so long?

To answer your first question the amount of pressure is two fold one it forces the air out, and 2 it helps to galvanize the material. If you don't have the pressure high enough then your parts will be a bit softer, but if you have it too high they can be even more brittle.

To answer the second I leave my parts under pressure until they are fully cured, and ready to be demolded. This goes hand in hand with the galvanization I mentioned about the amount of pressure. If you don't leave the parts under pressure long enough they may end up being too soft as well. I've had parts come out that should have been very solid (1/2 45D, & 1/2 Task 3), but because I took them out too soon they were more flexible like my 2 parts 45D to 1 part task 3 mixture.

I'll be honest though I myself am still learning even with a year, and a half under my belt. That's one of the fun things about this hobby/ business there is always something new to learn.

 

[Tofujesse]

Hit me in a pm....Thongs are things I've never heard of.

To answer your first question the amount of pressure is two fold one it forces the air out, and 2 it helps to galvanize the material. If you don't have the pressure high enough then your parts will be a bit softer, but if you have it too high they can be even more brittle.

To answer the second I leave my parts under pressure until they are fully cured, and ready to be demolded. This goes hand in hand with the galvanization I mentioned about the amount of pressure. If you don't leave the parts under pressure long enough they may end up being too soft as well. I've had parts come out that should have been very solid (1/2 45D, & 1/2 Task 3), but because I took them out too soon they were more flexible like my 2 parts 45D to 1 part task 3 mixture.

I'll be honest though I myself am still learning even with a year, and a half under my belt. That's one of the fun things about this hobby/ business there is always something new to learn.

 

[DarkWynter]

Sorry I can't help out on this but I only use a few different resins. I do have a few questions myself if you guys don't mind. Always looking to learn new stuff.




How does the amount of pressure affect anything?



Why pressure it so long?

Pressure effects density. The higher you pressurize the liquid resin as it cures, the denser it will come out as a solid. The specs on most resins from Smooth-on (shore hardness, density, and tensile strength) are quoted from curing under a pressure of 60 psi. during the entire cure time.

327 has a cure time of 3 hours, thus the 3 hour time frame Vortious suggested for keeping it pressurized.

The explanation Vortious gave is also true of injection mold machines as well. They force heated plastic into the molds at far greater pressures. The bigger machines can be measured in tons of pressure. The plastic comes out far more dense (and thus stronger).

Some resins also want to foam as they cure and will not cure into a solid without the pressure. You can always experiment with a given resin to see how pressure effects it by simply filling three cups to a standard line. you only need a small amount for the test, a quarter of an inch is fine. Cure one under pressure the entire cure time, cure one under pressure only halfway throughout the process, and do not pressurize the third.

In this experiment you will find 327 expands above the line if not pressurized as it cures and will never fully harden. It is almost a foam on the surface. The cup taken out of pressure halfway will expand slightly above the line and not be as dense as the specs given. Depending on how early you remove it, it will also be slightly "puffy". It could still be used for some applications, but not small joints that need maximum hardness. The cup pressurized the entire time will be the only one that reached the density and shore hardness given on the technical specs, and the only one that stays or shrinks below the fill line slightly.

Not all resins will foam during curing, so some can cure without expanding. However, even they will be more dense (thus stronger) if cured in a pressurized environment.

 

[Tofujesse]

Got it, didn't realize it took 3 hours to cure. That's a long time. As for the amount of pressure affects density, I have never heard that. I know pressure crushes the air molecules in turn making a more dense part. Never heard more pressure equals more density....interesting.


Ok so here's a little input hope it helps. If you want your resin harder and this goes for any resin....post cure it at 125 degrees in ita mold for 3-4 hours and it will turn out harder. I find that for what we do I personally need to turn out parts fast, so it's 15/20 min demold time for me.

Pressure effects density. The higher you pressurize the liquid resin as it cures, the denser it will come out as a solid. The specs on most resins from Smooth-on (shore hardness, density, and tensile strength) are quoted from curing under a pressure of 60 psi. during the entire cure time.

327 has a cure time of 3 hours, thus the 3 hour time frame Vortious suggested for keeping it pressurized.

The explanation Vortious gave is also true of injection mold machines as well. They force heated plastic into the molds at far greater pressures. The bigger machines can be measured in tons of pressure. The plastic comes out far more dense (and thus stronger).

Some resins also want to foam as they cure and will not cure into a solid without the pressure. You can always experiment with a given resin to see how pressure effects it by simply filling three cups to a standard line. you only need a small amount for the test, a quarter of an inch is fine. Cure one under pressure the entire cure time, cure one under pressure only halfway throughout the process, and do not pressurize the third.

In this experiment you will find 327 expands above the line if not pressurized as it cures and will never fully harden. It is almost a foam on the surface. The cup taken out of pressure halfway will expand slightly above the line and not be as dense as the specs given. Depending on how early you remove it, it will also be slightly "puffy". It could still be used for some applications, but not small joints that need maximum hardness. The cup pressurized the entire time will be the only one that reached the density and shore hardness given on the technical specs, and the only one that stays or shrinks below the fill line slightly.

Not all resins will foam during curing, so some can cure without expanding. However, even they will be more dense (thus stronger) if cured in a pressurized environment.

 

[Falcone]

....

Thongs are things I've never heard of.

 

[Tofujesse]

....

I didn't even catch that.