Casting Help

[Travis_UT]

I have made an example plate that I plan on showing at the FEGA show this year. I had a few people ask about castings so I thought I would take a shot at making them and it's been a little frustrating. This is my first time making a casting and the results are less than desirable. I used Smooth On OOMOO 30 silicon to make the mold. I put it in a vacuum chamber and was able to pull -25 inHg, the mold came out with no bubbles but the perfectly smooth areas on the plate are not perfectly smooth on the casting. The Part A (pink liquid) silicone rubber compound was very thick, not sure if this is normal or not. I was able to get part A and part B mixed well and seemed to be going okay. I poured the resin (Smooth Cast 320) at 40 psi, ambient pressure and -29 inHg and all the results are about the same with regard to the smooth areas mainly the sky. Any advice from you experienced guys would really help. Am I using the wrong products or am I doing something wrong in the process? I have attached a few pictures to hopefully show what I am talking about.
Travis

 

[monk]

check the tips section. there may be some info listed there

 

[Guido.]

Hi Travis UT

Great engraving work on plaque,well done.
I have done some minor casting work ,my only feeling is that may be not enough down pressure from back of plate or rubber mold, as rubber mold setting (strange as other fine details look fine)

can flat sections be polished down a little without affecting finer engraved sections? to improve.?

Regards Guido.

 

[wowilson]

I make my castings with Smooth-Sil 945 for the mold and Smooth-Cast 321 for the resin. I don't get vacuum pots involved, only the pressure pot. I make my mold at 30 lbs and I make my castings at 30 lbs. I have never had any problems with this product. I don't know if our relative altitudes have any bearing on this or not. I suspect not. It is possible that your pouring technique trapped some bubbles. Be sure to begin your pour off of the piece and don't move from that spot until you're done pouring. There is also surface tension that can be dealt with with the lightest amount of talcum powder. I'd try the pouring first technique first.

 

[Travis_UT]

I make my castings with Smooth-Sil 945 for the mold and Smooth-Cast 321 for the resin. I don't get vacuum pots involved, only the pressure pot. I make my mold at 30 lbs and I make my castings at 30 lbs. I have never had any problems with this product. I don't know if our relative altitudes have any bearing on this or not. I suspect not. It is possible that your pouring technique trapped some bubbles. Be sure to begin your pour off of the piece and don't move from that spot until you're done pouring. There is also surface tension that can be dealt with with the lightest amount of talcum powder. I'd try the pouring first technique first.

Wade, are you saying you start pouring the resin to the side of the mold?

 

[tdelewis]

I have never done castings but would like to know more about making them. Are there any videos that demonstrate the process?