Pressure Pot vs Degassing

[asok]

I have read about both ways of getting air out of a cast. I am just not which is better for my application so, I would like suggestions on which is better for what I am trying to make.

Hopefully in the next month I am going to start making some parts the will have alway have air hole no matter how I make the mold or pour the resin. So, any suggestions on which is better to remove the air from the part? There will be pour area that I will be remove so, I do not worry about if it bubbles up or not.

 

[exoray]

If you are talking about trapped air in the mold, then my suggestion is to vacuum the filled mold once you pour in the resin in hopes that it will expand the trapped air large enough to allow most of it to burp out... Remove the vacuum and top off the mold as it will certainly have boiled over and need more resin... Then put it under pressure and let it all cure under pressure in hopes to squeeze any existing trapped air to a minimum...

Another option to consider if you know where the problem areas are is this...

Take the mold and brush on a gel like layer of resin in the problem areas, let cure... Then carefully close the mold up and pour the rest... As long as you don't disturb the gel coat too much or dislodge it you should be able to get a near seemless casting...

 

[speedracer]

If you are talking about trapped air in the mold, then my suggestion is to vacuum the filled mold once you pour in the resin in hopes that it will expand the trapped air large enough to allow most of it to burp out... Remove the vacuum and top off the mold as it will certainly have boiled over and need more resin... Then put it under pressure and let it all cure under pressure in hopes to squeeze any existing trapped air to a minimum...

Another option to consider if you know where the problem areas are is this...

Take the mold and brush on a gel like layer of resin in the problem areas, let cure... Then carefully close the mold up and pour the rest... As long as you don't disturb the gel coat too much or dislodge it you should be able to get a near seemless casting...

The brushing is excellent advice..=)..takes a lot more work than pouring but you should have a great piece...well worth all the work..

 

[Great_Bizarro]

Vibrating helps bring bubbles to the surface too.

 

[LeMarchand]

Another thing that helps when air gets trapped in undercuts is to close off the pouring hole(s) and sprues (with a plastic bag or latex gloves for instance) when it is fille up with resin and rotate the mold in all kinds of directions to release the air in the pockets