Curing question

B9 Core Series - Ideas and Discussions
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RobertW
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Curing question

Post#1 » Thu Dec 21, 2017 2:54 pm

Inadequate curing causes... what?
I cure all models for 8 hours minimum before giving them to our caster. Emerald resin. Our caster is having casting issues with large (but lightweight) items (pendants) and heavy gents rings. It looks to me like some debris remained in the cavity causing the surface to be pitted or look nibbled on. I believe a sprue vent from the top of the piece to the base of the flask (away from the button) and vacuuming it before casting will solve the problem. But that's extra work for him. He believes that the problem is models aren't being cured enough. So I'd like to tell him specifically which casting defects are the direct result of inadequate curing.

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akgold
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Re: Curing question

Post#2 » Thu Dec 21, 2017 4:45 pm

What temp is his peak burnout and how long is it being held at the top end?

I vacuum all of my cans no matter what plus you can model them with a vent sprue for him.
I don't like to use resin for my vents or anything other than the model itself, I like to think the wax melting first allows any ash to come out quicker. It just adds to the chance of additional ash as far as I am concerned using the resin for sprues and vents.
I'm so far behind I think I'm First !!

danfurlano
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Re: Curing question

Post#3 » Thu Dec 21, 2017 5:05 pm

I would send your prints to one of the people that frequent this form. I use Metalcaster and have never had any issues. I am sure Robert Howle will do high quality work also. There may be others but these are two that I personally know of.

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RobertW
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Re: Curing question

Post#4 » Thu Dec 21, 2017 5:28 pm

akgold wrote:What temp is his peak burnout and how long is it being held at the top end?

I vacuum all of my cans no matter what plus you can model them with a vent sprue for him.
I don't like to use resin for my vents or anything other than the model itself, I like to think the wax melting first allows any ash to come out quicker. It just adds to the chance of additional ash as far as I am concerned using the resin for sprues and vents.


The peak temp is 1420F held for 3 hours.... which should be fine. He says he vacuumed the (snow white) cans. A red/cherry resin ring model in the same flask came out perfect but it was a pretty standard ring. The failed emerald resin model is an open 45 x 17 x 1mm, lightweight pendant frame for an asymmetrical piece of jade. It was probably fully cured in an hour but I let it cure for more than 8 hrs.
But back to my original question... can you fill in the blank?

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RobertW
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Re: Curing question

Post#5 » Thu Dec 21, 2017 5:30 pm

danfurlano wrote:I would send your prints to one of the people that frequent this form. I use Metalcaster and have never had any issues. I am sure Robert Howle will do high quality work also. There may be others but these are two that I personally know of.

Not an option.
But I'm hoping one of them can answer the question!

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Metalcaster
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Re: Curing question

Post#6 » Fri Dec 22, 2017 3:57 pm

If I could see the casting and it's problems, I could probably explain whats happening...
Can be caused by many things... Inadequate Sprue, Sprued in wrong area for casting of that style... Need a picture.

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RobertW
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Re: Curing question

Post#7 » Sat Dec 23, 2017 11:54 am

I truly appreciate the attempts to help troubleshoot a casting problem but this is a curing question. I'd like to know the effect(s) caused by inadequate curing.

Assuming the model was under-cured but it was sprued and envested correctly and the flask sat undisturbed for 3 hours before burnout:
Will it cause the envestment to break down resulting in a loss of detail?
Will it prevent the complete incineration of the model?
Will some kind of residue remain in the cavity that prevents debris from escaping?
Will it stain the envestment?
Will it discolor the casting?
Will it cause porosity, pitting, cracking, brittleness, or incomplete fills?
I currently don't think any of these are curing issues, but I'm not certain.

It seems to me the main benefit of curing is the ability to cleanly file, sand, and rubber wheel the resin to remove print lines, supports, etc.

There seems to be a general consensus here that a cured model casts better than an under-cured model. Why?

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Metalcaster
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Re: Curing question

Post#8 » Sat Dec 23, 2017 3:39 pm

Well, Here are the answers I come up with...
Question:Assuming the model was under-cured but it was sprued and envested correctly and the flask sat undisturbed for 3 hours before burnout:
Will it cause the envestment to break down resulting in a loss of detail?

Investment is not what is breaking down... in most Cases, it will be caused by left over debris. External defects are plaster related which can be over come.
Q)Will it prevent the complete incineration of the model?
Usually,Yes
Will some kind of residue remain in the cavity that prevents debris from escaping? Sometimes,yes
Will it stain the envestment? Sometimes
Will it discolor the casting?
Some discoloration that will usually pickle off
Will it cause porosity, pitting, cracking, brittleness, or incomplete fills?
Yes, It will … the effects are similar to Porosity, But it is due to left over debris
I currently don't think any of these are curing issues, but I'm not certain.

I have been up to 1600 for 10 hrs with Various investments on Items, I thought were fully cured and had left over debris in the casting. NOT outer surface issues, all internal. Repeated process with Longer cure time and added Vacuum rods to the pieces. Vacuumed using flat vacuum casting table with silicone seals, custom made attachments and collected debris,then cast into flask at temperature required and had perfect castings.Not all items require Vacuum rods to cast properly… some do.
I cast a secondary flask with Matching cured 2 pieces on the tree and no vacuum … 1 piece was perfect.. 1 had a small amount of debris.
[/u]


It seems to me the main benefit of curing is the ability to cleanly file, sand, and rubber wheel the resin to remove print lines, supports, etc.

There seems to be a general consensus here that a cured model casts better than an under-cured model. Why?
Because it is part of the casting problem. If you don’t cure at all, which I would love to eliminate! you get lousy castings
If you are successfully casting with under curing, I would like to know what your process is

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Robert Howle
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Re: Curing question

Post#9 » Sun Dec 24, 2017 5:16 am

Cast this 20 gram ring with regular curing for heavy piece (4 sessions of 6 min each in the model cure). Then after some slight cleanup (sanding and file work) back in for 6 min. This is to cure any uncured material after sanding. Mike has stated that complete surface cure is all that is needed to avoid any interaction with the investment. 10k scrap yellow gold (chains, ring parts, etc.) in my broken arm casting machine using acty and oxygen torch. Regular SatinCast and tap water, slightly thick on mix (adjusted by eye while mixing by hand in a bowl) bench set time only 1 hr. Then into room temp oven and start, 325 F 2 hrs, 750 F 2 hrs, 1450 F 2 hrs, down to casting at 850 F after 2 hrs, Cast! I do ramp speed at 999 F per hr., up and down on temps.

This had a heavy sprue (4.25 mm) at the base of the shank, a three "pronged" sprue (2.5 mm dia), on the inside (each shoulder and one to the upper bezel area)

On this heavy stuff I do believe that the 300 to 325 soak in the oven for 1 to 2 hrs will get u complete internal curing. This takes the question of incomplete cure out of the equation. It then boils down to burnout and proper spruing. In the case of the B9 resins (only ones I have experience with) the spruing has much to do with eliminating all the resin residue just as high end temp and oxygen availability.

Cast this stuff almost daily. Like metalcaster and others, it takes a little mod of your spruing and burnout, but other than that I have no idea what your caster is doing without standing there and watching what they do or don't do.

Since other casting houses and small shops are having success, then looks like u need to get another caster or get them to do the work and figure out what they need to change.

This cast first try and the raised text here is only .35 to .4 mm in width in most places. B9 emerald green, printed on the Core 530.

The ring is 21.5 mm across the top and and finger size 13-1/2. Done from line drawing supplied by the client for a ring he lost many yrs ago.

Structioneers ring.jpg


Structioneers panel 2.jpg


Robert Howle
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RobertW
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Re: Curing question

Post#10 » Wed Dec 27, 2017 4:43 pm

Thank you for the replies! It sounds to me like inadequate curing and inadequate burnout have the same symptoms... and inadequate sprueing may also play a role. I like Robert's suggestion about the 325F soak to remove 'incomplete cure' from the equation. All of Metalcaster's input is very helpful.
I have 35 years experience casting gold and silver. Centrifugal and vacuum.Wax. Been working with resin since 2014... but I'm NOT the caster here. I'm the CAD/CAM designer/technician. Our caster has lots of experience doing quality bench work but maybe 3 years experience in casting... he started casting wax and it went pretty well and then resin came along and he has really struggled with it. To wit: this particular pendant had to be cast 3 times, and the 3rd time wasn't perfect but it was salvageable with the laser. Pendant is 46 x 16 x 1.3mm (plus prongs). The pictures are of the 2nd attempt. I saw it on the tree and it was at a 45 angle in the middle of the tree, but it was facing DOWN with the (2) secondary sprues above the pendant. The fact that the 4 skinny prongs are completely filled is testament to the Indutherm Casting machine... not sprueing technique. The 3rd attempt was sprued rightside up with 1 primary, 4 secondary sprues and the vacuum tube. I believe it would have come out perfect with 6 secondary sprues. Peak temp 1450F for 3 hours. Opinions?
R1095 700x700.jpg
pend front.jpg
pend front.jpg (180 KiB) Viewed 2090 times
pend back.jpg
pend back.jpg (263.61 KiB) Viewed 2090 times

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Metalcaster
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Re: Curing question

Post#11 » Thu Dec 28, 2017 2:31 pm

If correctly cured and burned out, I would cast that with 1 sprue only... as a safety, I would add a vacuum rod to guarantee that the cavity is perfectly clean.
I started casting resins many years before I had any printing machinery... as far back as 1987. Started casting in 1964 and burned out anything I could find and test... Have not stopped experimenting since :-)
Nice looking design.

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RobertW
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Re: Curing question

Post#12 » Thu Dec 28, 2017 3:55 pm

Metalcaster wrote:If correctly cured and burned out, I would cast that with 1 sprue only... as a safety, I would add a vacuum rod to guarantee that the cavity is perfectly clean.


One sprue? Did you notice the model is 46mm long but only 1.3mm thick?

The caster thinks the oven's internal fan is failing so we have ordered a new one and I'll install it when it gets here. Oven is an old Neycraft Vulcan 3-550 (220 volt). What fun.

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Metalcaster
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Re: Curing question

Post#13 » Tue Jan 02, 2018 6:11 pm

Yes, I would do that with 1 sprue and a vacuum rod attached at the very top.Then Vacuum the flask before casting
Over sprueing can also cause problems and it's a lot harder to remove all of them.

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