Pouring cup or pouring down the downsprue?

Hello HT1,

The pattern I have has great detail and it will transfer to the sand. If you take a look at my posted pictures, you can see the wax patters, I made from the exact same SLA printer pattern I am using with the sand casting. I know the petrobond holds the detail, because I can see it in the rammed sand. I posted a picture of this too. I can get good detail but the resulting part has pinholes. Caused by air trapped in the pour down a tall pour sprue and or the higher charge temperature being used.

My original post was about what you bring up, pressure head (I used a bean can to extend my pour spruce rather than making a deeper Cope.) Or should you use a pouring basin, as some other casters recommend, to ovoid the molten aluminum washing over, splashing through your fine detail mold and not holding the detail?

1) your pattern : Does the pattern have as much detail as you require??? Yes.
or
2) your mold : is the detail transferring from the pattern to the sand , ram up the mold and look at it NO REALLY LOOK get a flashlight and a magnifying glass if you need to! Yes.

the metal having pin holes is entirely a separate issue

(I am trying to solve this issue too because they are related as you state, below. Temp of the pour verses pin holes in the final casting. High temp, good detail, Bad pinholes. Lower temp 1350 F say, little or no pinholes, bad details. Thanks. Jgaertner

now just for aluminum because of it's high surface tension, you get more detail if the temperature is higher, but you get a better overall surface finish if the temperature is lower in the pouring range , but with that big clunky part you need to be low in the pouring range or you will get other issues

as always you pick up more detail if the head pressure is higher , that's half the reason for putting the detail in the drag , so you might consider a taller cope , but I dont think it is necessary

 

Hello Kelly, I measure the orifice and it 0.042" or #58 wire drill . The burner tube has an ID of 0.819" standard cast iron pipe.

I do not know the LP pressure. I do not have a gauge on my 60 Lbs tank. The tank is full, right now. I can install one from stock on hand. Does the gauge go after the tank and before the regulator or after the regulator. Dumb question, but I am sure it makes a big difference. What range would people suggest for the gauge? I keep a whole variety on hand.

Jgaertner

 

Hello Kelley, Thanks for confirming that regrading the orifice and burner tube. I put a 0-60 PSI down stream of the red regulator. Had the parts on hand. Will see what can learn as far as regulating the flame?

 

Your pattern has good detail that transfers as shown by the investment pic in post #10 but I'm not seeing a pic of any petrobond impression? The only pic of petrobond is in post #1? - and I'm also of the opinion that that batch of sand looks quite course.
Also, you mention using 'facing sand' with the petrobond? It has been a few years for me but I never used any facing sand with petrobond. Sieving out the chunks from used is all I ever did. If you are using a dry fine grained sand as facing sand, or greensand , then this could also be a source of your detail problems.

What model Avro is getting restored?

 

Hello Smoking Shoe. The facing sand is PetroBond #130. It is finer than the backing PertoBond I use. I then just fill the rest of the cope and drag with regular PetroBond. It all gets mixed together when I break the mold open. No attempt to save the facing sand. I run everything through a riddle, after it has cooled. I have never used green sand for casting.

I am restoring the last Avro 504k in the world. I have my axle covers already made. These new ones are for some in museums that do not have the authentic axle covers.
www.BlueSwallowAircraft.com or www.Avro504.org for more details.

Thanks, Jgaertner

 

130 is not a fine petrobond sand at ALL, its actually course, petrobond original and II call for 120-180 sand, I have seen up to 220 available

here is the original info
https://www.slideshare.net/FoundryJoe/petro-bond-foundry-sand-brochure

additionally you need a hard ram to transfer the detail,

the gating system in the first picture is awful and could be your gas issue, though definitely take the advice of the furnace experts here they wont lead you astray

V/r HT1

P.S remember, you could have several issues not just one

 

Hello Ht1, Can you please explain your comments so I can learn what I may be doing wrong? What do you mean by "Hard Ram"? I am ramming my sand molds by hand. I do not have a jolt rammer or air powered rammer. You said the gating I showed was "Awful". OK, please explain what would make it better? That is why I am posting on this forum. To hopefully learn how to improve my casting. I have read all of Stephen Chastain's books on casting and felt I was following his recommendations as best as I could. Thanks. Jgaertner

 

Here is a good start:
Olfoundryman
This will get you started down an informative rabbit hole.
Some guys just have a way of getting at the basics and making things simple. Jeff Hanson is one if you are just starting out as an engineering student.
There should be a list of these excellent teachers?

 

hard ram refers to how tightly you pack the sand it's measured at the surface with a precision instument https://sandtesting.com/product/mold-hardness-tester-digital/
or by experience, in petrobond your looking for an 80 this is quite firm, you would still be able to depress the sand with your finger, but it would be difficult , this is something you have to learn by experience

you need to do a little research on gating system design, you basically just poured metal down a riser which is always a poor practice

V/r HT1

 

"hard ram refers to how tightly you pack the sand it's measured at the surface with a precision instument"

While I really like putting numbers on various factors in the foundry, it is really not a practical thing to do for way to many of the variables we deal with. HT1 is suggesting a way that would allow him, in Florida, to measure just how hard he rams his PB and John several hundred miles away in VA could actually objectively compare how hard they each have rammed up a mold. They would not have to resort to using necessarily vague and ill-defined terms like hard ram. But buying the device linked is not likely in the cards for almost anyone on this site. (Does ANYONE own a sand hardness tester like the one linked above?)

I have been wracking my brain to think of a cheap universally available testing method. Here it is: The Golf Ball Drop Test. I know HT1 lives in the golfing mecca of the world so he can likely get his hands on one. And most likely John can get one too. Maybe next time HT1 rams up a mold nice and "hard" he could drop a golf ball from a few measured heights and measure the diameter of the indentation. Then John and anyone else interested now or in the future would have something to objectively compare.

Based on my not-so-calibrated thumb, I do know that the top rammed surface of a mold will be much greater than the hardness of the mold cavity surface. I often ram deep molds in two "lifts" for that reason. So measureing the top rammed surface hardness will not fully tell the tale. Some destructive testing of the mold cavity, say parting line, hardness will also be needed. I'll see if I can find a golf ball around here before I ram green sand this morning.

Denis

Added: If someone find it difficult to measure the indent diameter, just count the numbers of bumps left by the dimples in the ball. 5 bumps= very hard. 10 bumps=medium. 30 bumps=soft. ;-)

 

Hello Denis, Thanks for your comments. I had to build an ASTM qualified impact tester for a DOD lab I use to work at. One of our MANY projects was inventing a new deck blast mitigation material for the US Navy. I believe that impact tester cost my company $10,000 to build. But your simple idea of dropping a golf ball is a good one. Smokingshoe suggested watching Olfoundryman on YouTube, which I have been doing for several weeks now, as time allows. His set up is a great deal larger than anything I can afford or need. But he certainly has a lot of experience and insight, to share.

My #1 goal right now is to get better control over the combustion in my LPG furnace. I spoke to Steve at 101Foundry.com, who makes these LPG furnaces, and he said he had not had a problem with the burner being too rich or too lean. But I am getting a yellow flame, through out, so a possible controllable air blower is next on my list to experiment with. If this solves my burner problem, then hopefully I will see fewer hydrogen bubbles in my pours.

Goal #2 will be to prepare better pour sprue and gate my molds to reduce splashing and getting air trapped in the charge. Oldfoundryman was using a pouring cup in some of his videos but later I see him filling his molds with a yellow pouring tube. This seems very similar to how Myfordboy does his pours with the metal can above the cope, to provide a height of aluminum to help fill the cavity and allow for shrinkage. In Chastain's Vol 2, he shows using a pouring basin, resting on the top of the rammed mold and a tapered sprue that goes into a dross cup at the bottom before the charge is sent to the cavity via a runner (pg.77)

There has to be as many ways to make a sand mold as their are subjects to cast (well, almost). Jgaertner

 

Thanks Kelly, I have a NA burner. Pin hole is pretty much right on the money, as stated before in this thread. I have not had any chance to test the burner outside with the LPG pressure gauge I just installed on the burner mechanism because the humidity, in Virginia right now, is like 88%. So I know, from previous experience, there is no point in trying any casting. I have to wait until a cold front comes through and the humidity drops to around 50%. Then I will be able to see what pressure I have at the burner and whether I can adjust the combustion with a forced air source, I have yet to put together. Cast only when mother nature allows and try and tune my furnace burner... Jgaertner

 

ok going all the way back to my apprenticeship we where taught to ram pertrobond as hard as we could with out making the flask lift, so if you are pushing sand out of the bottom of the flask you are ramming too hard,
with a proper hand rammer, and using 3.5 inch tall flask sections (dimensional lumber) I put down facing tuck it in with my finger tips, then fill the flask more then full, then aggressively peen the the sand as hard as I can holding the flask down with one hand on 12X12 flasks that is fine, any larger of flasks, I clamp the flask down to the bottom board or matchplate, this will about half fill the flask, then you fill it again, and peen it, then use the Butt to finish it off flat, you might have to add a little sand in the corners to fill them, this is not the hardest you can ram sand, but it is close, if I have a troublesome pattern, I will try a softer ram, sometimes you can get a pattern out of a slightly softer ram when a hard ram will take sand with it, especially in high details, like lettering ( the triangle in "A" being the absolute worst)

if you have a pneumatic rammer, I would use about the same technique UNLESS the pattern had a tall section, then you need to mark that so you dont hit it with your rammer, and you may need to make multiple passes with the rammer, short and skinny irregular patterns, are difficult to work with and require a degree of finesse that has to be learned by experience

V/r HT1

P.S. your second and any additional rams say you are using 8 inch deep flasks can be softer then the first , the sand directly in contact with the pattern is the only area where sand Hardness is critical UNLESS your pattern is VERY heavy , like billet in brass or Cast Fe , so dont ill yourself trying to get the backing sand crazy hard its a waste of energy

 

Hello HT1, Thanks for sharing these details. Jgaertner

 

Kelly wrote:

In the 90kbtu range, that burner is plenty for the furnace he offers. I'd be surprised if it could not be suitably tuned. Might just be a matter of getting better acquainted with you set up.

I agree, I will try running my existing burner paying close attention to the gauge pressure and see whether I can get a leaner flame? Only try a blower if necessary.
Something else I realizes is that I recently switch from using those 20 Lbs LPG tanks that you can exchange for all new 40 Lbs tanks I bought. May be a difference there. with the avialable pressure at the regulator due to the larger volume of liquid propane.
Jgaertner

 

John, maybe this will help.
I tune my burner by sight and sound.
First, absolutely no flame out the vent.
Then you want a blue flame, no yellow.
Put the lid on and listen to the sound, play with the gas pressure Until it reaches the highest, crispest sound. Then lower the pressure a half pound.