First sand casting

[stragenmitsuko]

Today I poured my very first sandcasting .

Been casting alum for a couple of years now , mostly I simply fill all kinds of tin cans to cast rounds and squares wich can then be used on the lathe and mill .

So I decided to take it one step further , make a pattern and give it a go .
Turned out quite acceptable for a first try .
The part is half a carriage for a moving gantry cnc router I'm building .
The other half was also cast , but I don't have pictures .


Furnace , greensand , flasks and offcourse the pattern ..... it's all homemade .
Greensand was made from construction white sand , powdered bentonite and water . The bentonite was like flower , very fine and dry . I found it at a garden center .

The surplus of molten metal was poured in a couple of tincans .
I use a lot of these round "stock" for all kinds of things .

Pat

 

[stragenmitsuko]

Couple of more pictures of what it should look like when finished .

The two bores will get 4 lineair bearings wich will slide on two supported rails on a fully supported frame . More a design exercise then a practical machine .

These two "prototypes" were carved out out of a large block I cast in a square paintcan .
Took a lot of metal to remove , the entire shop was full of chips .
And when I finally got there , I goofed up with the two bores .
On both parts . :wall:

So start over again from scratch , hence the sand casting to avoid removing all that metal again .
Now let's see if I can getthose bores right this time .

The steppers are rotating nut types .
A fixed leadscrew has several advantages , and the steppers already have an integrated inti backlash nut .
Well worth giving it a try

 

[Herbiev]

Nice work. Especially for a first casting.

 

[xlchainsaw]

Nice work. Especially for a first casting.

i was thinking the same[emoji1]

 

[vederstein]

I'm envious. I hope set up an aluminum foundry some day, perhaps this year or next.

 

[stragenmitsuko]

Thx for all the nice comments guys , I'll post some pictures of the furnace I made from a propane tank .

I don't have anyone round here to teach me or to guide me .
So all I've learned sofar comes from the interenet .

There's a guy called myfordboy on youtube showing 50+ video's on patternmaking , moulding , casting .... Very informative , I highly recomend looking at his channel if you want to learn how to do this .

Mrpete222 also has some real nice step by step video's on the subject

And offcourse there are several others .

 

[robbay]

That first picture, if it is "as cast", is superb. You must have de-gassed the aluminium and removed dross in the ladle well to produce that surface quality, especially from greensand. The casting is well above commercial castings.

 

[swood1]

I guess a large part of this is having a good pattern to cast. I for one would be interested in seeing some photos of your furnace. I did read something recently in Practical Classics (UK), where a guy was making aluminium casts for car parts. I shall re-read this article.

Out of interest what was your pattern made from?

Steve

 

[mohavegun]

EXCELLENT first castings, good job!

 

[AdvenJack]

STRAGENMITSUKO - I'm sure that you are very satisfied with your result, as it looks fantastic.
I've just started watching MYFORDBOY on You Tube, and I agree that his videos are extremely informative!
Keep on building your skills and allowing us to see the progress!

 

[MRA]

You did well to get the pattern out - I know the draught angle is allegedly small enough, but I often end up with bits of sand stuck to the pattern, especially on deep sections like that. Good stuff!

 

[Stone]

Very nice casting, impressive.
What was the source of aluminium you used?

 

[stragenmitsuko]

Oh I seem to have missed the replies to this thread .
Sorry .

The first picture is the pattern , not the casting .
It was spray painted silverish but it's wood underneath .
Pattern was made from some bit's n pieces mdf glued together .
The source for alum iirc was a bent alloy wheel from a car .

Here's a picture of my furnace .
I put it on a lawnmower frame , makes it easy to move it .
And it's always nice when visitors ask what on earth is that


And another casting I did a couple of month's ago .

 

[Arild]

Hi All,

I've been casting aluminium for two years now, and got some experience. I also used Bentonite clay and sand to start with - its good for larger parts. But if you need to make small and highly detailed cast, you should use "red sand". Red sand has excelent holding, and will not fall appart. Parts shown is for my "pre-project" V2 engine. It uses the same valve, sylinders etc for the V8 Ferrari, that I'm building now.
Excuse my poor spelling, but I'm Norwegian!

 

[robbay]

Hello,
As a chemist in a foundry supply company "Foseco" the biggest in the world, I gained a lot of experience in core and mould binder systems for sand castings, refractory mould and core coatings, casting defects from all causes (important to know because if a defect occurs a foundryman will usually blame the binder system since his melting or metal treatment cannot be at fault {sarcasm}. Finally, for my sins, ending up as CEO of a large worldwide steel foundry group. So I have a lot of experience in foundry moulding, core making and coating practice for sand castings, mostly ferrous but with some aluminium.
If anyone has any queries in these areas I would be glad to contribute and if I don't know I won't go on myth and ********, a lot of both are prevalent in the industry. Melting practice, die casting and metallurgy are not my areas.
Rob

 

[Arild]

Hello,
As a chemist in a foundry supply company "Foseco" the biggest in the world, I gained a lot of experience in core and mould binder systems for sand castings, refractory mould and core coatings, casting defects from all causes (important to know because if a defect occurs a foundryman will usually blame the binder system since his melting or metal treatment cannot be at fault {sarcasm}. Finally, for my sins, ending up as CEO of a large worldwide steel foundry group. So I have a lot of experience in foundry moulding, core making and coating practice for sand castings, mostly ferrous but with some aluminium.
If anyone has any queries in these areas I would be glad to contribute and if I don't know I won't go on myth and ********, a lot of both are prevalent in the industry. Melting practice, die casting and metallurgy are not my areas.
Rob

Hi Rob!
I would like to make core/hard sand, but find it very difficult to get natrium silicate here in Norway (unless ask for several 100 liters). Do I also need special sand?
I've tried to make core out of "plaster of Paris", but even completely dry, the molten aluminium bounce off (I guess because plaster don't breath).
Any suggestion to make core sand?
Oh, Foseco also got sales in Oslo!!, But I guess they also only sell in large quantity...

BR,
Arild

 

[robbay]

Hello Arild,
Foseco Sweden are based in Ed not far from the Norwegian border and they would probably give samples of Sodium Silicate. A common name for S.Sil. is Water Glass, pharmacies used to stock it. You could also try begging samples from a jobbing foundry.
I like S.Sil. systems for the low toxicity, low odour. I don't like it for its thermal breakdown that makes shakeout or knockout more difficult.

The following descriptions will ignore binder systems impractical for home use such as Hotbox, Shell Sand (Croning), amine gas with iso-cyanate oils or resin systems. My experience is commercial/ industrial and practices that would not occur there due to high labour content, may be employed at home, where time is less relevant and part of the fun. For non commercial hard sand practices, core and mould systems are interchangeable.

Sand:
Modern jobbing (means one off castings) core making or moulding practice needs clean, washed and dried silica sand free of alkaline traces (seashell fragments), or clay, both of which lower thermal refractory properties and may interfere with binder systems . River sand is best since it has rounded grains that give low surface area enabling less binder for any given strength. The temptation is to go for fine small grain sand for finer as cast surface finish but this can give low mould or core permeability and needs more of any binder so is harder to compact. A good compromise is an average "Grain Fineness Number" of between 45 and 60, this means an average grain size of between one forty fifth to one sixtieth of an inch, I don't know if this is expressed in mm in Europe.
Coarser sand will need a refractory coating to prevent metal penetrating core or mould, these may be aqueous suspensions of graphite for aluminium or iron castings ( I won't describe steel casting practice since melting steel at home is beyond most people), the coatings are applied with a paint brush and dried with a low flame. Even rubbing on dry graphite to a finished core or mould is better than bare sand. Traditional "greensand" moulding practice has carbon from coal dust and clay from bentonite so generally doesn't need coating, just high compaction or ramming as it's called in industry.

Binders:
1. Sodium Silicate.

Self Setting.
Using a catalyst that is a low or non toxic ester mixture such as, Glycerol or Ethylene Glycol tri/di acetate, sodium silicate may be cold set. The catalysts are available from foundry suppliers (Foseco trade name is Carset) or the chemical industry. Again ask for samples or go to a jobbing aluminium or iron foundry and plead for help. "Triacitin" is slow curing, "Diacitin" is fast setting, so for home use Triacitin is best with set times of say about 2hrs at 20 degrees centigrade. The sand is mixed in a Hobart or large food mixer with about 3.5% by weight of the correct sodium silicate for about 3 minutes (Sod. Sil varies in soda ash to silica ratio used in manufacture). The catalyst is then added at 15% based on silicate weight and mixed for a further 3 minutes. The sand mixture is then added to core box or mould pattern and well compacted, rammed with a stick, especially into corners. The mix will then set hard. Stripping the mould or core is best done before total rigidity after "rapping" (hitting the sides) of the corebox. The finished shape is then allowed to fully harden.

CO2 Gas Cured.
The silicate sand mix is rammed into the corebox, vented with a small diameter rod and CO2 gas from a cylinder passed through it with a small diameter tube inserted or with a top board, edges sealed with rubber strip. The gas needs to penetrate to all areas and vents in the corebox may be needed for some shapes.

Core boxes or patterns need smooth surfaces, correct taper (draft) and a release agent like talc (baby powder) or wax to enable stripping the core or mould half.

Having written a small essay I won't describe cold set resin systems but these are hard sand process with high strength and good thermal breakdown properties compared to Sodium Silicate.

Good luck in sourcing.

Rob

 

[ThomasSK]

Hi Rob!
I would like to make core/hard sand, but find it very difficult to get natrium silicate here in Norway (unless ask for several 100 liters). Do I also need special sand?

PM me and I'll give you a small bottle I have here. Since we are more or less in the same town, it shouldn't be a problem.

Thomas.

 

[stragenmitsuko]

Another casting I did yesterday .

This will become a bowl to make a waste oil centrifuge .
The size of the bowl is abt the largest my lathe can handle .

The pattern , made of pieces of mdf , cut at a 22.5° angle and glued
together to make a circle .
Primed with latex or emulsion paint , and a high gloss top coat from a spray can .

Pattern draft is 2° .

 

[stragenmitsuko]

The mould
bentonite / water / whitesand , the ususal home recipe .

Was a bit of a struggle to remove the pattern , but it came out quite nicely .

If I would do this again, I'de probably use a core instead of a pattern with draft on both sides .
The sand sticking out in the first jpg was reinforced with abt 20 wood screws . This held the sand together while pulling the upper half of the flask .