Uncured Resin inside the Ring

[pr19939]

Hey,
Happy New Year to you all. Over the new year weekend, I tried printing a ring. Two things happened.

1. One of the edges did not come out properly. It looked like it was burnt. I could see a blackish tint on that part.

2. After a week, when I broke apart the ring, I found uncured resin on the thickest part of the ring. I had cured the ring for 30 minutes under a 50W UV Light and it has been a week since I had created the model.

I would like to understand what could be the cause and how to rectify.

Edge formed correctly

Malformed Edge

Uncured Resin

Thanks
Venky

[akgold]

I would check your model slice by slice to see if it shows areas causing hollow spots.
I looks like it was a hollow space that could have only been created by the software not exposing that area and as the ring rises
the hollow area will retain resin in it from the up down process of the build table.

[panastation]

emerald and yellow need msm bump and they print well. lets say for example that you were printing at 1.1 msm raise it to like 1.35 1.4ish..

[Robert Howle]

Is that ring hollow under the stone plate, and what orientation was used while printing (vetical, etc.)

How about a screen capture of the layout with supports.

Robert Howle

[Robert Howle]

Looks like trapped resin in the model that was not even partially cured during the print (not part of a projected layer).

Is the ring a hollow shank model?

Robert Howle

[pr19939]

All,
I went back and checked the STL and Job Preview. The ring is indeed a hollow shank model. The steps on the side is covered with a under-plate. And on further breaking, I found uncured resin on both sides where there is a hollow space. During direct casting, the hollow space was completely filled with the plaster and the final cast model had a lot of plaster in it. This brings me to the next question, is it possible to print hollow shank models and direct cast them. I had outsourced the casting to a third party who always chooses the shortest time to cast objects. So, I think he did not give enough time for the plaster to cure before pouring the metal. Is this a correct assumption?

Thanks
Venky

[Robert Howle]

I would put a base on the ring as pictured below. Use heavier supports like pictured. I would print it in two pieces (top plate separately. Yes u can print hollow items. Just make sure all the liquid resin is removed before curing. Wall thickness is very important in hollow rings in order to get good castings.

You are using way more supports than are needed. Send me the file and I will do a layout with supports. Rather have the stl so I can separate the top plate, or send the ring in two pieces.

howlere@gmail.com

Robert Howle

[pr19939]

Hi Robert,
Here is the zip file containing the Layout and STL. Thanks for your help.

https://drive.google.com/open?id=0B9-FY ... y12UDZzVlE

Thanks
Venky

[Robert Howle]

This Mesh is a mess in my opinion. I really need the .3dm if a Matrix model. So many coplanar "parts", this is not needed. I would be afraid that even though it "test" as a valid stl, that printing and slicing is going to be problematic.

Colored all the diff pieces just to show u what I am talking about.

Robert Howle

[akgold]

Robert is correct this is a hot mess

here is why it was leaking resin as I mentioned about this before
it is hollow

you need to fix this area I circled plus all of the problems Robert mentioned.


Plus all those tiny supports in the middle and outside of the ring need to be at least .8 like the other thick ones you have.
What vers. of Matrix are you using to make this model ?
If you have M8 you should be able to "heal" this using the mesh tool.
I understand that you using the B9 resins but isn't this also printing on another printer than B9?

[Robert Howle]

Like AK says, if u "repair" this model and still want a hollow shoulder, u will have to CAD it differently.

I really dont' think the original was intended to be hollow in the shank. It's hollow only because of the way it was modeled.

I have seen rings like this from many years back when the "Rolex" looking links were cast in a different color (two tone ring).

The only way to print this is in 3 to four pieces, or just make it solid and print it if it's going to be one color. The little bit of metal that will be saved will surely be "eaten up" by the labor to assemble and finish.

Robert

[pr19939]

Hi Robert and AkGold,
Thanks all for your feedback. I will definitely take this up with my CAD designer. I will get you the .3dm file tomorrow as it is a Sunday here and we are closed. We are using Matrix 5 as of now and will be upgrading to the latest version next month. I presume the hollow space was left to bring the ring to customer specific weight requirement. One question here, what would be the multiplication factor for Emerald Resin Model weight to 22 Karat Gold weight?

I had given this ring to be printed in an EnvisionTec Perfactory machine. The difference is that, envision tec models are not direct castable. So, we will generate a wax model from the EnvisionTec model using a silicone die. The hollow parts in the model has been rectified during the silicone die creation as it generates the mould only using the outer layers. Hollow issues come into play only in direct casting. I will keep you posted on the progress.

Thanks a million.
Venky

[Robert Howle]

As to the conversion factor for the Emerald, use the weight of a solid model x .9 to get the equivalent wax weight (Specific gravity of 1), then multiply by the SG of the metal to be used.

Have included a chart of metal SG I have been using for over 30 yrs., trust it. It is true that varing the different metals available for alloying gold to different Karats will cause the SG to vary a small amount. In the case of 22k you could use coins that are 22k or mix your own alloy with fine gold and use the following to determine the SG of the alloy.

Assuming 22k = 91.67% fine gold and the alloy is 5.33% copper. The resulting SG of that mix will be 17.7 to 17.8 (so the equivalent wax weight X the SG would be the amount of metal used to cast (not counting sprues and button).

Hope this helps.

Robert Howle

PS: A hollow print that is castable will not matter in direct casting as the investment only molds to the surface, therefore hollow prints or waxes should cast the same. I agree that a wax may be better for production work. I will print u good B9 resin print that u can used to mold for $35.00 (if i do 3-4 the price would be $25.00 each) + postage, if u need it. In most cases I ship the day following the order, in some cases the same day, just depends on my printing schedule at the time.

Robert Howle

[pr19939]

Hi Robert,
Thanks for your detailed reply. It is very useful. I am not sure if I had mentioned already. I am half way around the globe, in India. Most of my customers come with a very short deadline. I will definitely seek your services if need arises.

Thanks
Venkatesh S

[Robert Howle]

Sorry, I only ship domestic, no international.

My best,
Robert

[rkundla]

PS: A hollow print that is castable will not matter in direct casting as the investment only molds to the surface, therefore hollow prints or waxes should cast the same.

But wouldn't the caveat be that if you have enclosed hollow spaces, the total weight of the model will be off and your calculation of metal required be too little?

Odds are you have overkill for the button, so it may not make a difference.

[akgold]

PS: A hollow print that is castable will not matter in direct casting as the investment only molds to the surface, therefore hollow prints or waxes should cast the same.

But wouldn't the caveat be that if you have enclosed hollow spaces, the total weight of the model will be off and your calculation of metal required be too little?

Odds are you have overkill for the button, so it may not make a difference.

Honestly, if you calculate your weights of metal to cast to the point of having NO button left after casting then yes it could be a factor.

Technically you are correct if that is your point, but in reality in this ring or any other ring that would be intentionally left hallow even if the hallow area is not filled with investment during the vacuum process, which could easily happen and cause worse results of free unsupported investment flowing into the rest of the casting, that amount of added weight would be insignificant to account for individually.
Now if you had 10 of these rings that cast solid considering what Robert has stated and is true, you might have a miscalculation that could reduce the button weight to maybe half it's size.

But most people cast using enough metal that any discrepancy in the calculated weight of a ring would be compensated by the button.
In the case of the ring that is being discussed here on this forum the amount of "hallow" area is only going to result in tenths of grams.