Epic Casting Fail

A 1:1 mix of Red and Cherry, yielding a lost wax capable resin tuned for 30 - 70 micron slice thickness
lswatson
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Epic Casting Fail

Post#1 » Fri Apr 01, 2016 9:39 am

I cast this flask of silver this morning and 6 out of 7 parts are incomplete. Never had that happen before.
All are 1:1 Mix prints.
Yesterday, 4 parts failed in a similar manner in a flask of bronze. This was a flask of MadeSolid and 1:1 Mix models.
No porosity. Just incomplete parts. I've been casting these models since August with no problem.
These are sun cured for hours and hours, plus UV finger nail box for extended periods of time.
My guess is the melter temperature needs to be set higher. I have it at 1050 C (It's Italian, so no F temp setting).
So maybe I should raise that to 1070-1080 C?
Any insights would be appreciated.
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Robert Howle
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Re: Epic Casting Fail

Post#2 » Fri Apr 01, 2016 11:15 am

Just looks like incomplete flow. HIgher flask temp is safer than overheated metal.

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Re: Epic Casting Fail

Post#3 » Fri Apr 01, 2016 12:21 pm

definitely a casting temperature issue... could be Oven related as the controllers for Jewelry are not self calibrating and could be off by as much as 100 oF or more. for the oven, get some burn out cones to check your ovens accuracy.

The same is true of the Italian melter, although their Electronics are definitely a bit better....
My guess is to increase your oven Temperature by 50 to 100 degrees.

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Re: Epic Casting Fail

Post#4 » Fri Apr 01, 2016 12:58 pm

To me it looks like your temp is good ( couldn't hurt to bump it up slightly) It really just looks like a " Flow" Issue, you definately have enough metal ( good size button) it looks like the Sprues are very thin and all that metal has to reach the very end of every model. I think a thin 3mm sprue towards the top of the models would allow it to fill up with material no problem.

Hope this helps.
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lswatson
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Re: Epic Casting Fail

Post#5 » Fri Apr 01, 2016 1:31 pm

Thanks, gents.
Glad its a temp thing. Now to figure out if its the furnace or melter.
I can pour tomorrow before the furnace gets down to 960 F. If that doesn't do it, the next pour will be with
higher metal temp.
The button is very slightly convex by the way and one friend told me that means melt temp is high.

lswatson
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Re: Epic Casting Fail

Post#6 » Fri Apr 01, 2016 2:23 pm

By the way this cast was made with fresh casting grain and a brand new crucible.
Just to eliminate possible other variable.
Pouring a flask of bronze in the morning.

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akgold
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Re: Epic Casting Fail

Post#7 » Fri Apr 01, 2016 2:30 pm

So what is the square in the middle for?

That is what is taking up your flow if it wasn't there and all your sprues were in the center rather than around the main item they would have filled just fine.
the sprues look the same as what you have used before or have they changed in diameter and placement?

mover them to the center of the spruebase and it will fill.
I'm so far behind I think I'm First !!

lswatson
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Re: Epic Casting Fail

Post#8 » Fri Apr 01, 2016 2:57 pm

Hey Tim,
No square. The central sprue is the usual cylindrical purple wax main sprue I've used since August.
No layout or sprue changes at all.
I've cast hundreds of these models since August in silver and bronze.
Two of the last three flasks had incomplete areas in the parts. 95% to 98% complete is failure on these models.
Hopefully some temp adjustments will even things out. I have tons of stuff to make and ship.
And a trunk show in a week, I found out about yesterday.

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akgold
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Re: Epic Casting Fail

Post#9 » Fri Apr 01, 2016 8:08 pm

Larry,
so if you reduce the length of your center sprue it will concentrate more force to the other areas. the void the sprue is causing is reducing the volume of metal to the areas that need it.
Usually when we use a center sprue the items attached go up to a point allowed by the can's top.
the center main sprue is cut just above the last feeder sprue
in this case half your metal is filling the large void far above the the last sprued item causing back flow or back flow porosity and/or back flow pressure preventing metal from pressurizing the feeders below it adequately to fill the voids of the actual items below. think ebb and tide action vs reaction.

just something to think about next time.
I'm so far behind I think I'm First !!

lswatson
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Re: Epic Casting Fail

Post#10 » Sat Apr 02, 2016 5:07 am

Ok, now I understand.
Never thought about that.
So I should make the center sprue as short as possible, and cut it just past my last sprue.
I'll try that tomorrow.
This morning I'm going to pour into a hotter flask.
Thanks for the explanation, Tim.

lswatson
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Re: Epic Casting Fail

Post#11 » Sat Apr 02, 2016 9:04 am

Here is another angle, Tim.
So you're saying I should trim the main sprue down to the last model on the tree.
I'll try that tomorrow.
I don't normally layout my trees this way. Most of the time I pack in little models here and there.
This was a flask for a special order.
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Robert Howle
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Re: Epic Casting Fail

Post#12 » Sat Apr 02, 2016 9:40 am

Larry I agree, u don't need all that main sprue going past where the last model is attached. Def can be part of the problem.

Robert Howle
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lswatson
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Re: Epic Casting Fail

Post#13 » Sat Apr 02, 2016 10:25 am

Thank you, Robert.
Good to know.
I can lose that bad habit pretty easily.

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Re: Epic Casting Fail

Post#14 » Sat Apr 02, 2016 11:47 am

Yes, Robert and Tim are correct. The extra tree wastes metal and adds no benefit to casting. The Vacuum vent, the way you have it helps the wax tree melt out quickly as it opens up a channel for the air to come in as the wax melts out.As a side effect, that might help suck out the debris from the resin a tiny bit as your pieces all drain in the correct direction

Vacuum vents work best if directly attached to the top of the pieces or to areas that have no drainage.

That being said, you should try casting without a Vacuum vent to see if you get any difference.You might not need it due to the shape and size of your designs.

My observation:
Your designs are much easier to evacuate as they are long and everything points/ drains to the base. That explains why you have no problems casting some of the other resins and why you have very little residue if any.

When you look at other designs that do not drain / burn away easily due to long sections going across from one side to the other or heavy complex items with engraving or raised lettering and areas that act as a "trap" for the resin ...thats where the Vacuum vent really helps. Put the vent near or on one of those areas and it is a big help.

In the case of a section not being able to drain correctly, thats where the very high burn out can help 1400 oF and higher as some people are doing.

I guess that was more then 2 cents :lol:
:lol:

lswatson
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Re: Epic Casting Fail

Post#15 » Sat Apr 02, 2016 12:43 pm

Thank you, Daniel. I'm all ears.
I turn all my flasks with the sprue hole up now. It saves my right wrist when grasping and the parts come out the same.
When I did the two bronze flasks and had some incomplete prints, it was the flask that had been turn with sprue hold down that had the problem. The one with sprue hole up, worked fine.
A few times the vent has not filled all the way to the top of the flask. Those sometimes have poorish prints.
When the vent fills there are virtually no problems. So I like the vent.
One time I forgot to turn the vacuum on before I poured. So I turned it on after. I think I discovered an easy way to get desirably poor castings. Desirable for patina as they look pretty rough. Archaeological, almost.
Trying to kick out orders and prep for a two day show next weekend.

lswatson
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Re: Epic Casting Fail

Post#16 » Sun Apr 03, 2016 9:39 am

Adjusted the central sprue as per Tim and the resulting castings are perfect. No change in temp. settings on the furnace or melter.
Ten in the 4 x 4 flask. All prints were B9 1:1 Mix. Sprue hole up during burnout.
Many thanks.
I'll be watching that from now on.
L
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panastation
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Re: Epic Casting Fail

Post#17 » Sun Apr 03, 2016 12:37 pm

Thats alot of metal scrap u will have to do 60/40% new material.
for the vent i think this forum topic will help u.
https://www.asiga.com/forums/viewtopic.php?id=257
since the vent sprue is not gona do much in that place.

lswatson
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Re: Epic Casting Fail

Post#18 » Sun Apr 03, 2016 1:37 pm

Interesting. Thank you.
This entire cast was a previous button and center sprue.
Sometimes I do 100% grain, sometimes 100% recycle (2-3 times), sometimes a mix.
I have a target weight range I like to pour, so I just get that any way I can.
After the third or fourth melt, I send the buttons and center sprues to the refiner and trade for grain.
I get about 90% credit when I send around 20 ozs. or so.

My market doesn't buy by weight and the margins allow for this workflow.
I won't sell to anybody that puts my work on a scale for valuation.

lswatson
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Re: Epic Casting Fail

Post#19 » Mon Apr 25, 2016 5:40 am

Discovered I was having a problem with my furnace. One element died, which wouldn't allow it to heat up properly. I believe it died slowly, so the furnace has been under performing for some time. Maybe weeks.

What I learned is that elements can be checked with an ohm meter (or multi meter) to insure they are close to what they need to be. Your mfg can tell you what is optimum or the range that works well. I'll be checking mine every couple of weeks to make sure everything is heating properly and will keep a spare element on hand.
With misdiagnosis and shipping errors, I was unable to cast for two weeks. Not good.

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