Trouble in Casting Paradise

[rkundla]

While I would end up making something like that with wax rods, that looks pretty good! I'll be waiting anxiously for the result.

[Archerm]

I would have done the sprues with sprue wax as they would melt away way faster and allow air to enter the cavity for burnout of the resin. Let us know how it comes out as I am curious.

[MobiusJewelryDesign]

It didn't come out again. I used a 38/100 ratio with Plasticast, Mark's recommended prep and burnout schedule. The only difference is that I used yellow resin. This piece is a tough cookie. I had better luck spruing it the other way. What I don't understand is why are there voids in the model that the gold didn't fill on the side. Is it ash, or broken off investment. Totally perplexed. I might have to relent and do a RTV mold of it. ::Sigh::

[MobiusJewelryDesign]

...Perhaps doing it this way but with wax rods would have helped. I guess I'll try that out, but look at the clean up that I would have to do if indeed it turned out. I am going to give it a rest for now and to see if I can come up with a better way. The amount of resources, time, and effort I've put into this has been a bit much, but I never give up. TO BE CONTINUED!

[rkundla]

What I don't understand is why are there voids in the model that the gold didn't fill on the side. Is it ash, or broken off investment.

You figure that the investment that is eroding off of the lettering has to end up somewhere. Even where the sprues were located you can see the erosion in the letters by each one. The cracks are something else, perhaps metal temperature or furnace related?

One thing I found worth the test is to replace the resin print with a wax print and use the exact same method to cast it to see if it looks better or is different. That gives you a very good data point on whether or not your process is flawed for the easiest of materials. If you find cracks or other problems, then you know you need to focus on your process and get that squared away before you deal with the resin itself.

[Jewelermdt]

I would have those feeders flipped. Your metal has to rise up to get filled in. This traps air/gas into the lettering and can cause this. Even with vacuum casting. I'm casting a pendant with lettering also and having the same issue. Mine is more investment issues. Metal temperature is very important on getting it to flow into that area of the pendant.

[MobiusJewelryDesign]

@rkundla - I believe you are absolutely correct. The resin is burning out no problem, but the little bits of investment that are breaking off and swimming around in the gold are causing the large craters in my cast. Another thing that I think it might be a problem is that the lettering in my charm is too deep (.4mm) which gives the gold more surface area to push and break. I believe Mark mention a good point. I should have made the sprues in wax rather than the resin, so the vaporized resin gas has more space to escape. Which ties into what jewelermdt said.

@jewelermdt - You also make a good point. The air or gas does need to go somewhere and by spruing it this way as well as making them in resin leaves little room for the air to escape. I sprued it this way instead of the other way thinking that it would be easier on the lettering, nope wrong!

What I am doing this time is shortening the letter depth, making the sprues in wax, and spruing it upright again. I'll post my results soon. Fingers crossed.

[MobiusJewelryDesign]

This is another attempt....I believe it came out a lot better than previous times. I'm getting there folks! This is what my procedure.

Resin prep
5+ Hour cure time in nail box
Microwaved piece in distilled water 3 x 3min cycles

Invest
38/100 ratio Plasticast
Cured investment for 6+ hours

Burn out
Ramp 1000/hr to 800
Hold 3 hours
Ramp full to 1450
Hold for 2 hours
Drop to casting temp held for several hours - Burn out overnite casted in the morning.

On the next one, I am going to widen the thin parts of the lettering a bit....shorten them just a tad more then do everything else the same. If anyone else has anymore suggestions, I welcome them.

[rkundla]

This is another attempt....I believe it came out a lot better than previous times. I'm getting there folks! This is what my procedure.

Did you ever try painting the investment directly into the lettering to see if that helped improve the quality? I am curious how much that really helps.

The font and the depth are two big factors on how well it holds up. I can't really adjust the font characteristics within RhinoGold, so I have to stick with fonts that don't have too much fine detail that can break away during casting. If money was no object, I'd invest in a laser engraver, but that will have to be a fantasy for a very long time.

[Jewelermdt]

I find painting the lettering a big help. Just tonight I invested a pendant with lettering. I first dipped it into the investment mix. When I pulled it out bubbles came out of the letting on most. Some did not and on those letters the investment did not fill in the letter. That's why I rub the investment into the lettering. If you don't do this then it may happen even though you vacuum the flask or not fill into letter fully. Thus a filled in letter when you cast.