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GreenTwin

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The "proper" protection is gold coated but these are expensive. More so for me because I have to pay $$$$$ for shipping.
I use a faceshield that fits onto a hardhat.
I have clear and tinted face shields.
I wear tinted glasses under the faceshield to protect from the IR radiation.

It is a good idea to wear some thin leather or something under the hardhat, and extending over the shirt/leather jacket collar, to protect the neck.

The plastic faceshields will melt easily if you lean over a bit to look into the lid opening.
I use a refrigerator shelf in front of the face shield when I have to look into the furnace.
I also have a metal mesh face shield, and it works well, but does not fit onto a hardhat.

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GreenTwin

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I can't see how radiator scrap could make good iron for engine parts.
My plan is to use cast iron engine blocks because the metal properties and quality of the iron would be optimised for long engine life.
I use electrical motor end bells, but I believe that engine block gray iron would also work (one of those things I disagree with MIFCO on).

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GreenTwin

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It has been about 20 years since John Campbell published his first book on casting, yet I rarely see examples of his guidance being applied.
Here is an example of casting the John Campbell way. Only worth watching the firs half.
I have John Campbell's book, which contains the 10 rules for good castings.
There are John Campbell believers/followers, and John Campbell's detractors.
However you feel about Campbell, I feel his 10 rules are important to making consistently high quality castings.

One summary of the 10 rules is here:

and another link here: (click on the NEXT link on the lower left side to go to the next rule)

As with all things foundry, I use a hybrid of rules.

1. Many use a pour basin; I do not; I pour right down the sprue, while keeping the sprue as short as possible.
Sometimes I use a ring of steel sitting on top of the mold, but it is not what I consider a pour basin, but rather a spill container.
I don't try to keep the ring of steel full, but rather focus on keeping the sprue full.
I keep the lip of the crucible as close to the sprue opening as possible, sometimes resting the lip of the crucible on the top of the mold (you can do this with bound sand).

Pours are not linear, and you have to be able to quickly adjust the pour rate during the pour.
Typically the flow is fast as you are filling the runners, and then slows as the gates begin to regulate the metal flow.
I often see folks spill metal all over the side of the flask when the runner(s) get full, but that can be anticipated and minimized; you don't have to spill any metal while pouring a mold.

2. I keep the sprue and runner about the same size (sometimes I oversize the runners), and try to make a smooth transition from vertical sprue to horizontal runner(s).

3. I use a spin basin at the end of each runner, with the runner entering the spin basin on the tangent.
My spin basins open to the top of the mold. The spin basin(s) stop the bounce wave that occurs with dead end runners. The bounce can eject metal through the gates in a sudden spray, which is undesirable.

4. I use gates at the top of the runner(s), with both the gates and runner(s) typically located in the drag or bottom half of the mold.

5. I initially pour quickly to fill the sprue, and then be sure to keep the sprue full at all times during the pour.
If you pause slightly during a pour and interrupt the pour, you will probably have a cold joint in the casting where the fill was interrupted and then restarted.

6. I don't use tapered runners.

7. The mold does not begin to fill until the entire runner system is full, and any impurities in the mold such as loose sand are swept into the spin cavity, along with theoretically any floating slag, and air-entrained metal caused by the turbulence of filling the sprue.

8. The gates control the flow into the mold cavity, and the gates tend to scrap any slag from the metal flowing down the runner (another reason to put the gates at the top of the runners).
The gates should be sized to allow a complete mold fill at pour temperature with the sprue/runner/gate size you select.
The gates should be sized to reduce the metal velocity to obtain a fill that is free of turbulence.
I often fill the mold cavity upwards, and use the gates at the bottom of the mold cavity (one of John's rules I think, don't waterfall into the mold cavity).
Molds will fill upward. With bound sand, you need small vent holes at the high points in the cope, else you will trap air.
And cores should have vents in them/through them, with the ends of the core vented out the top of the mold.

9. I use smooth curves and transitions in the runners. No sharp corners.
I often oversize the runners a bit to get a really hot flow of metal running down the mold before metal begins to fill the mold cavity.
Some folks do not use runners at all, but rather feed directly into the mold cavity from the sprue. I think this is asking for problems.

10. High velocity and turbulence are two things to avoid when metal casting.

11. I use risers in strategic locations when I feel like there may be shrinkage in the part.
Keeping the ferrosilicon to a bare minimum keeps shrinkage to a bare minimum.

12. I keep the iron castings in the mold overnight, until they cool naturally.
Pulling iron castings out of the mold when they are hot can make the metal very difficult to machine.

13. Another of John's rules concerns keeping the thickness of the part even if possible (old castings generally have a consistent thickness).
If the casting has thick and thin sections, then the thin sections will solidify first, and then draw from the thick sections, which can cause hot tears.

14. Sharp corners should be avoided in castings/patterns.
Sharp corners often set up high stress points, which can turn into cracks/points of failure.

The methods above work well for me, and after I adopted them (after reading John's book) have provided very consistent and high quality iron castings that are easily machinable.

Everyone has their own sprue/runner/gate/riser layout favorite methods, and there is no one exact method that works universally.
If you come up with your own system, and it consistently produces high quality castings, then it really does not matter too much what that system is.
Generally speaking though, I think if you are producing high quality castings, chances are you are following many if not all of the 10 rules, and perhaps a few of your own.

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GreenTwin

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That guarantees it is unobtanium for me. I doubt there is a distributor within a few thousand miles.
If I did not have access to high grade refractory, I would look for hard fire bricks, and stack them in a circle.
Hard fire bricks actually work with iron temperatures, and they are used around the world to line wood stoves, pizza ovens, etc., so perhaps more obtainable.

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dazz

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If I did not have access to high grade refractory, I would look for hard fire bricks, and stack them in a circle.
Hard fire bricks actually work with iron temperatures, and they are used around the world to line wood stoves, pizza ovens, etc., so perhaps more obtainable.
I can get castable refractory for the hot face and lower temp soft insulating bricks or fibre for backing.
I have not seen plastic refractory but only a slim chance of finding it.
I can't get ceramic mold coating.

Catalogues only make me envious.
 

dazz

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I wear tinted glasses under the faceshield to protect from the IR radiation.
It is a good idea to wear some thin leather or something under the hardhat, and extending over the shirt/leather jacket collar, to protect the neck.
I also have a metal mesh face shield, and it works well, but does not fit onto a hardhat.
Steel mesh visors and helmets like the one shown are widely used in the forestry industry. The neck protecting cloth in the picture will definitely not be heat resistant, but easy to change to something that is.
The ear protection might not be needed for a home furnace, but they are removable. If left on, they would provide some level of protection to the side of the head.
The black plastic might melt but application of some heat reflecting adhesive tape would add protection from infra-red heat.

I think a helmet/steel mesh combination looks like the best option for a home foundry.
 

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dazz

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I have John Campbell's book, which contains the 10 rules for good castings.
There are John Campbell believers/followers, and John Campbell's detractors.
However you feel about Campbell, I feel his 10 rules are important to making consistently high quality castings.

One summary of the 10 rules is here:

and another link here: (click on the NEXT link on the lower left side to go to the next rule)
A good read.

As with all things foundry, I use a hybrid of rules.

1. Many use a pour basin; I do not; I pour right down the sprue, while keeping the sprue as short as possible.
. . .

14. Sharp corners should be avoided in castings/patterns.
Am I reading the GreenTwin 14 Golden Rules?? ;)
 

GreenTwin

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Am I reading the GreenTwin 14 Golden Rules?
Some/most of these are John Campbell's rules.
The ferrosilicon is by trial and error, and watching what happens with other's shrinkage vs ferrosilicon level, as is the premature removal of the casting from the mold.

There is a guy named Bob Puhakka who is John Campbell's protege, and he runs a foundry in Canada.
Bob has made a few videos discussing how to make good aluminum castings. Bob's videos tend to come and go, but he does show evidence of making very high grade aluminum castings using John Campbell's methods.
I have learned a lot about John's methods by observing how Bob Puhakka applies them in a commercial foundry setting.

.
 

dazz

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Hi

Here is a photo showing commercially made keyed refractory bricks. The difference to mine is that I would mold specific shapes to form a furnace.
These are also a lot thicker than I was planning, but these will be for mens sized furnaces. Not a little DIY backyard casting furnace.
At least I know the concept is proven.

keyed fire brick.png
 

dazz

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Hi
Attached is an image of a Ceramic Foam Filter, for use in casting iron, aluminium and other metals.
These are made in China but I have seen them advertised elsewhere for 3x the price.
 

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GreenTwin

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These are also a lot thicker than I was planning, but these will be for mens sized furnaces. Not a little DIY backyard casting furnace.
At least I know the concept is proven.
The industrial refractory business is very big.
I can't name all the industries that use it, but I suspect refineries, steel mills, etc.
I have seen photos of enormous rooms/chambers that are completely lined with refractory.

There are all sorts of precast refractory shapes available, as shown in the photo below.
I got the bright idea I would make a furnace lining from some of the curved shapes below, and got a quote on them, and WOW, the price!
It would be much cheaper to just line the furnace with gold than those precast refractory units.

I was able to purchase some 2,600 F insulating fire bricks for a reasonable price.

And the MIFCO furnaces use sections of refractory blocks in a modular fashion.

r20190528_152856.jpg
 

GreenTwin

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I used ceramic filters for several aluminum pours, and tried it with cast iron also.

The aluminum pours were successful with the filters.

The cast iron pours were not successful, but this was when I was still trying to learn how to melt gray iron, and I don't think my pour temperatures were high enough for use with a filter.
Now I use spin traps with iron, and no filter.

If you skim correctly, and use spin traps, slag inclusions are not a problem, and so a filter is not necessary.

rIMG_2770.jpg



rIMG_3007.jpg
 

dazz

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How much fuel is burned to do a melt??
If I used a 20litre Jerry can with diesel, would that be enough for a melt??
Would I need 2x Jerry cans?
 

GreenTwin

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Looks like 20 litre is about 5.3 gallons (we are in gallon land here).
I burn about 2.6 gal/hr (9.8 liters/hr) for my furnace dimensions, and an iron melt using a #10 crucible generally takes 1 hour (+ -), assuming you know how to tune your burner, which is simple, just adjust the combustion air for a few inches of flame out the lid opening.

I have seen people melt iron using a 5 gallon container, no problem, and I am sure it can be done if your burner is running at 2.6 gal/hr.
I think my smaller fuel tank is about 10 gallons, but for me it is more a matter of not wanting to have to refill it every time.

When I first started melting iron, I was not sure what the correct fuel flow should be, and so I would panic and open the fuel valve too much.
Too much fuel will drain your tank quickly, and will actually operate the furnace cooler than 2.6 gal/hr.

A given furnace will only pass so much air through it, and so the idea is to find the fuel flow rate that burns 100% of the fuel INSIDE of the furnace, or most of it inside the furnace at any rate.
Big flames out the lid are a total waste of fuel, but are impressive at night, if you are into the impressive sort of thing (some are).

.
 

awake

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If you skim correctly, and use spin traps, slag inclusions are not a problem, and so a filter is not necessary.
You mentioned spin traps before, and I am curious about what that is. Is this a particular shape you give to the sprue or basin or ??

Thanks so much for your posts - very informative!!
 

GreenTwin

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Gating and risering is an art, and not an art that many people agree upon.
My approach has been to find a method that works, and stick with it, while generally adhering to John Campbell's 10 rules for good castings.

Traditionally the layout used for the passageways into the mold cavity consisted of a pour basin (where you pour the metal initially into; located on the top of the mold), a tapered sprue, which conveys the metal from the pour basin vertically down to a horizontal runner or runners, which are often located at the junction between the upper mold (the cope) and the lower mold (the drag).

The runner(s) are usually V-shaped, probably so you can remove the runner form from the sand; I have used non-V-shaped runners and they work also.
Metal runs horizontally down the runner(s) to one or more gates.
The gate is the horizontal passage from the runner into the mold cavity.

The gates are generally rectangular, and generally narrow and thin.
Gates serve several purposes; they slow down the metal velocity, skim the slag off the top of the metal flowing down the gate (if you put your gates at the top of the runner), and allow the casting to be easily cut off from the sprue/runner/gate assembly after casting.

Much of the discussion I have seen by the folks who are making high grade castings in commercial foundries with virtually zero defects and zero rejection rates centers around metal velocity as it flows into the mold cavity.
High metal velocity is bad, since it churns air, sand, slag, etc. into the molten metal, and thus often causes defects in the casting.

Below are a couple of software simulations used for both fill and solidification.
One of John Campbell's rules is to not let a thinner section of the casting cool first and then draw metal from across the mold cavity from a thicker section, else you will get hot tears.



 

GreenTwin

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Another of John Campbell's rules is to avoid waterfalling, which churns air and debris into the casting.

To avoid waterfalling, I don't use a pour basin.
A pour basin seems to be what you want to avoid as far as splashing and entraining air and sand into the mold cavity.
I pour directly down the sprue, keeping the crucible lip as close to the top of the sprue as possible, and often the lip of the crucible touches the top of the mold.

At the bottom of the sprue, there needs to be a curved transition into the runner(s).
Traditionally a basin was used at the bottom of the sprue, but it has been found that this entrains air and debris into the metal.

The metal (for my layouts) travels down the horizontal runners (in the bottom part of the V-channel) to the spin trap located at the end of each runner.
The spin trap is nothing but a vertical hole in the cope sand, perhaps 1" or 1.5" diameter, that extends to the top of the mold cavity.
Without a spin trap, the metal will hit the end of the runner and bounce back, causing a jet stream of metal into the mold cavity, with ensuing air/slag/sand entrainment and casting defects.

The runner enters the bottom of the spin trap at a tangent, ie: the runner enters one side of the vertical hole, so that the metal spins as it begins to rise in the trap, and thus there is no bounce back and no sudden change in pressure when filling the mold.

The air, slag and debris caused by the initial filling of the sprue flows down the runner and into the spin trap.
By the time the runner is fully filled, and the level in the runner reaches the gates, the debris and entrained air have been swept past the gates and into the spin trap(s).

The gates then begin to fill the mold, and I often put the mold cavity in the cope, or as much as possible in the cope, to avoid waterfalling from the gate down into the mold cavity. The mold cavity basically fills from the bottom upwards, which gives a smooth even fill with a velocity that is controlled by the gate size.

The sprue has to be kept full during the pour, else you will send a large amount of air down the runner system, which will generally give a defective casting. An interrupted pour can also cause a cold joint in the casting, where the metal stopped flowing, began to solidify, and then started to flow again.

The fill has to be fast enough to completely fill the mold before any part of the casting begins to solidify, but slow enough to prevent a churning action.
You don't want the metal to have so much velocity that it acts like waves breaking on a shoreline.
If the metal is rolling like waves, and splashing/bouncing around, you will have defects in the casting.

I don't try to restrict the metal velocity with the sprue or runners, but rather use the gates to control the velocity.

The runner/spin trap method uses more metal than a system that does not use these, and so the crucible may have to be larger for a given pour.
There are many examples of people just filling a mold by feeding the sprue directly into the mold cavity, but there are also numerous examples of defective castings too.
People use shortcut and quick methods to make castings, and for simple work, and especially non-structural parts such as artwork, you can often get away with that.
There is always that person who violates all of the 10 rules for good castings, and gets seemingly perfect castings, but I think what really happens is that there are defects within castings made that way, and the defects may show up when you begin to machine the parts (inclusions, slag, hot tears, voids).
I have read many times that people purchase castings, begin to machine them, and then discover problems that makes the parts unusable, or the part fractures under stress.
I have no desire to try and find out what I can get away with, but rather I use a method that so far has produced 100% perfect castings inside and out.
Often people don't have time to lay out an effective sprue/runner/riser/trap/gate system, but they always have time to recast the part (often numerous times) when the casting turns out defective.

My motto: Do it once; do it right the first time.

For engine parts in gray iron like I make, and with resin-bound sand, it is tedious to mix and make up the mold, and so I want the castings to be defect-free on the first attempt.
So far, using resin-bound sand, and using my new furnace, I have never had to re-pour a cast iron part, and have not had any defects in the iron castings.

So the spin trap is just a vertical straight hole that goes from the end of each horizontal runner up through the cope and out the top of the mold.
The trap is offset from the centerline of the runner, so that the metal enters the trap on a tangent, and spins as it rises upwards.

For those who have machined their spin traps, they report that the top 1" or so of the trap metal is not usable due to slag, sand inclusions, voids, etc. which sort of reinforces the idea behind using the spin trap, ie: to sweep entrained air, sand, slag, etc. past the mold cavity, and not feed trash into the mold cavity.

I have not actually tried to machine a spin trap casting, but I believe they work, and I believe they prevent the splash-back into the mold cavity effect.

As I said before, show me a perfect casting, and section the casting (cut it down the center) to make sure it is void/inclusion free, and then I will consider a different sprue/runner/gate/trap layout; otherwise I use the method that works for me every time.
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dazz

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I used ceramic filters for several aluminum pours, and tried it with cast iron also.

The aluminum pours were successful with the filters.

The cast iron pours were not successful, but this was when I was still trying to learn how to melt gray iron, and I don't think my pour temperatures were high enough for use with a filter.
Now I use spin traps with iron, and no filter.

If you skim correctly, and use spin traps, slag inclusions are not a problem, and so a filter is not necessary.

View attachment 127770
My plan is to not try filters until after the inevitable casting failures. I need to get good enough to the point where I might see an improvement in casting quality using filters. That is likely to take a long time after a lot of failures.
 

GreenTwin

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For me it took a few steps.
I had to figure out pattern making (pretty easy), draft angle (relatively easy), and shrinkage (I use about 0.015 for iron).

Then I had to figure out how to set the correct fuel and air flow on the burner.

Next was learning how to handle the slag on top of iron.

Discovering ferrosilicon for machinability, and figuring out the exact amount to add.

Sprue, runners, gates, risers, etc. are pretty forgiving; I see all sorts of types that work pretty well (generally).

Sand conditioning (mulling/mixing).
Creating the molds (build some flasks first).

It is a multi-step learning process.
Master one step at a time, and you will probably be pouring good castings rather quickly.
I have seen one individual get it worked out in a month, with assistance/advice from a professional foundry.

It took me about six years to figure it all out to the point where I could match commercial iron foundry quality.

If you avoid all the trial and error, and blunders that I made, you can be making quality castings very quickly.

I know of one individual who was at a brass/bronze level, and the transition to iron for him was pretty easy.
He had a few defects in his first iron pour attempt, and had it all figured out on his second iron pour.

If you can get feedback from individuals who have poured a lot of iron (I received quite a bit of feedback from various folks), it makes things much easier.

.
 
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dazz

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I requested John Campbell's book for my birthday in Sept. It arrived yesterday from Amazon, but I can't read it until I receive my "surprise" birthday present.

I don't know anyone that pours hot metal, and the nearest professional foundry is 2 hours drive. I want to do some horribly complicated engine castings so I expect to be doing a lot of trial and a lot more error.
 

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