I having slight success in casting, but not perfect

[jefree]

At work I use the Solus to grow resins and then the DWS UV curing unit for 3 hours. Then I take the cured resins home and I use the vacuum oven presented by Binnion in his paper on casting photopolymers. It's a very cheap unit I got from Ebay for $100, in fact that's what it originally sold for in 1952, the year I was born! Anyway, the seal is still good and I use a vacuum that doesn't mind running a long time, it's a Welch 1402 I also got on Ebay for $300. It's got a fairly large bore and the motor rotates at 525 rpm, so it's slow but develops a high vacuum eventually.

For the burnout I use my 25 year old Satellite oven with the autofire express controller. The method I use is get rid of the sprues at 300 for an hour, ramp up to 800 at the top speed for 3 hours, the ramp at medium speed to 1600 for 6 hours. I use 1600 because at 1400 too much ash was left, but I haven't figured out why yet. I then lower the oven to 800 and cast.

I cast an old Envisiontec wax I grew with PIC 100 green and it cast perfectly, but a little ash was left with the B9R green. I wonder if the Pic 100 must have continued to cure for 6 months? I also wonder if the opacity of the B9R green inhibits the cure?

I also wonder why the water method works for some people. I tried it and it failed to work for me. Eventually I will figure it out. The answer must be multi processes which produce the perfect casting usually. I notice that the best casting house, Zero Porosity, has several failures every day, just the last piece I got from them failed the first print.

[Jewelermdt]

I use 1000 degrees at the end. If it takes a while for your vacuum reach the peak then your flask is way to cool by the time you pour. I get peak vacuum in a 5 to 10 sec. I assume you are using a hard investment, cause at 1600 most investments will break down and crack.

[jefree]

I called R&R about their plasticast investment and they told me that it is good up to 1700 degrees F, wouldn't try it before I found out. I cast and get no flashing.

I use a spin caster, maybe I should switch to vacuum casting? Do you notice any difference?

The place I used to work swore by vacuum casting, they used a very weird routine. They used Triumph investment and would heat the flask to 1700 and drop to 1350 to vacuum cast, had to use the high of a temp with Triumph. I told them I can cast with a centrifuge just as well (40 years experience) but they wouldn't believe me. They used a machine made in Italy, not unlike the Rio resistance casting machine, I forget now what it was called.

[Jewelermdt]

I have used vacuum casting since I started (18ys), so could not tell you if it would be any different. I would think your flask would cool down a lot using 800 degrees buy the time you loaded it in caster then melted your metal. I'm talking about using small flask 2 by 2.5. That is what I use mostly, and they cool quick.

[MobiusJewelryDesign]

@jewelermdt - I have both systems. Vacuum and centrifugal....I have been using the latter for resin and I have only vacuum casted with wax and solidscape. My question is....do you have perfect casts most of the time, by perfect I mean like smooth surface quality so as not to have to fill voids and hammer out porosity at all....or does it come out with minor defects because it is what it is. I hear a lot of about perfect casts, but what's perfect to some is not to others. Please don't be offended by my question, I have read just about everything you wrote on this forum and respect your opinion...I am only gauging what can and can't be expected and wondering whether I should change systems. I would appreciate the input.

[Jewelermdt]

Most of my cast come out great. Some with voids and porosity. Most of the voids and porosity I believe is in the way a model is spured and supported. I also find using customers gold cause some of this problem. I won't reuse white gold. I prefer using the Argen comp. "Vanilla" white gold grain. Meets Euro standards for nickel.

Here is some I did last week. These are cleaned in ultrasonic only. First one is 14k Vanilla white gold, other two silver.

[MobiusJewelryDesign]

Very nice! Love the designs! These are some pics of a casting that I did this morning. If you notice, there is some porosity on the surface and a few voids. I can fix most of them, but there is one that is By the 14k stamp I made in side the ring....that one will be a bit of a challenge. I appreciate the pictures and the insight!

[MobiusJewelryDesign]

Pictures

[Archerm]

MobiusJewelryDesign Those are looking much better. A tip. Make your prongs rounded on the tops. This will eliminate that sharp corner which can cause issues.

[MobiusJewelryDesign]

@archem - Thank you! I'll do that for future models. I still have a few places with pits and voids to tend with...

I just bought the optima investment and they have recommend burnout top at 1500 for 7 hours.....I am pretty sure I could cast just about any plastic material at those temps and still get a perfect cast. The start out temp is 1112! Geez! My fortune teller told me that she sees a brand new oven in my near future...::sigh:: Cost of doing business? I am putting stuff in the oven tonight. One of which is the dreaded letter coin piece ::fearful gasp:: along with other pieces. I will post pics after casting. Wish me luck.