Airflow in burnout

[dcpattni]

My oven gets air flow from a vent on top and with a small chip in the front of door panel. I have put my flasks down and when casting the cherry I did vacuum the flask. The green burns out much cleaner. No ash to worry about. I do regular wax and green resin burn out at the same time with same burn out settings as I did for wax only. Using regular Satincast investment.

hi,

do u mean same burnout you are using for B9 emerald resin which you do for normal wax injector burnout?

and instead of pouring metal you first flip(up side down) for vacuum ash then you flip and pour metal??? correct me if i'm wrong as i'm going to start casting first time.

[Jewelermdt]

Yes I do. My top temp is 1350 degrees held for 3 hours. I look at the button area and see how clean it is. If there is some residue I will vacuum it out. Only take 3 seconds, then back in oven to return to casting temp.

[dcpattni]

@ Jewelermdt

you will see B9 burnout cycle below link
viewtopic.php?f=9&t=32&p=3454#p3454

check an attached

as never did casting will be first time for normal wax & castable wax will do.

any other advice plz tell me i.m learning.

why oven manufacturer say like this when i show them b9 burnout abt 28*F ramp:-

Yes. 28*F in nature is equal -2,22*C but we speak about temperature incremetn and it is always larger than zero when furnace is heating.
I also never seen burnout furnaces with speed heating more than 10*C/min.

[rkundla]

A ramp rate of 28°F per minute is 1680° per hour! That is really fast. That translates to 15.5°C per minute. (28 * 5 / 9)

You don't subtract 32 when computing the rate of change, think y = mx + b, we only want the m part.

Many burnout schedules for wax will show a ramp rate of 540°F/hour which is 9°F (5°C) per minute.

If you can do 10°C per minute, then that is 18°C per minute which is 1080°F per hour, which is decent. I use 1000°F ramp rates for my burn out with B9 resins.

[Grasshopper]

Hi,
I am just getting set up to cast myself, so I am choosing all the equipment now. I am a novice caster and 3D printer, outsourced casting up to now. I am about to buy a burn out furnace that has additional air circulation. I was advised that some investments give off sulphuric acid fumes that are eating thermo-couples at the rate 5 in a year! That can be countered with stainless steel sheath and walls. The model I am considering is the Neytech with a modded thermo-couple.

http://www.espchemicals.com/9493985-Ney ... P6151.aspx
See downloads section Brochure.

But it has to be shipped from USA to France. Pricey. I'd really appreciate any advice on locally available furnaces that have a proven ability to cleanly burn out the common castable resins.

Is the air supply venting a must have?

When using Plasticast, have you had any problems with sulphuric acid corrosion in your furnace? Counter and safety measures?

I was advised to bubble gases through Calcium Hydroxide or Potassium Hydroxide to neutralise the fumes.

All advice on any any aspect of setting up shop very welcome.

G

[rkundla]

I am not aware of any sulfuric acid fumes being output as a result of the burnout process when using standard commercial investment material. I am curious to know who made this statement and can say specifically what investment that gives off such a hazardous fume.

Burnout benefits from additional oxygen available to help in the complete combustion of the resin print and reduces the amount of ash. Depending on the model of furnace or kiln, it will either provide that air via venturi like the Neycraft you mention, or you can drill holes into the kiln or pump air into the cavity using heat resistant tubing. The more combustion air, the less likely a failure due to incomplete burnout.

[Grasshopper]

I was speaking to Dentsply USA about their Neycraft furnaces when I was told by a guy in the repairs section that he was fitting the 5th thermocouple to a customers furnace in 2016 due to acid attack.

He did not know exactly what the customer was burning out. So I checked the story with a chemical supplier that also sells Neycraft and the guy there confirmed what you say; neither the common investments nor the resins seem likely to create sulphuric acid fumes. I have ordered a Neycraft from here.
http://www.espchemicals.com/9493985-Ney ... P6151.aspx

[rkundla]

That furnace should be able to provide plenty of combustion air. Just make sure you vent the exhaust out of your workspace - resin burnout is stinky.