The International Hobby Metal Casting ezine.
Brought To You By:
Col Croucher, administrator of: www.myhomefoundry.com
Australia.
Number: 81. August 2010.
How's the year been for you so far? Are your projects flowing along as planned, or are they lagging behind. Sometimes even the best-laid plans run off the rails, but what ever happens, don't give up and just forget about your projects, they are important to you and your own sense of achievement.
In our particular region of Southern Australia we are seeing the first real signs of the coming spring, it is a wonderful time of the year to witness the new growth on everything, the few degrees of temperature change must be like a secret trigger to the plants to get the sap flowing, perhaps we humans also see this as something that spurs us on to new thoughts & aims & new projects to begin, or to complete existing ones, and lets face it, after a long - cold - wet winter the first tentative signs of spring has to be good for the soul.
There have been many new people becoming involved in metal casting. Did you know that all types of crafts worldwide are going through a huge resurgence?
Does this resurgence indicate to you that many thousands of people are perhaps growing very tired of having Bland New, yes, you read that right.... bland new junk products & items dished up to them in stores around the globe... and no prizes for guessing where most of the junk is coming from.
Take note when you go into your favourite bed or furniture retail store... take a close look at what they sell to you as “wrought iron” bed ends? Study the way the "wrought" iron is formed and finished... and the average Joe customer quite willingly accepts this crap metal work as the standard quality offering. It makes me mad, & I bet you get mad too when you see these poor quality metal products on offer at the price they ask.
Look, I know it has been going on for many years now, and the accepted standards of the people seem to have shifted, but I think it is time to reject what is offered... what do you think?
On the other hand, there are people making huge profits from importing junk items into your country for peanuts, and then reselling those same items for big mark-ups... eg, import an item for $1.50 and resell it for $25.00 or $30.00 bucks and no one blinks an eye... a done deal. To be quite frank, I cringe when I go into some shops... how can they sell that rubbish.
And that is one big reason why it is so rewarding to be able to learn many different metal craft skills and then use the stuff you see in the shops as an idea springboard, but use the ideas to put your own stamp of skilled quality into the item and feel mighty proud when friends & visitors pay you the best compliments for your workmanship.... and feel better still when they ask you to make one for them.... and that's probably how several micro businesses have been born... maybe you are about to embark on a special journey soon. Have a think about it.
Col.
Sprues - Gates - Runners - Risers. How Important Are They?
Do you understand the importance of them? Often, the time spent designing the gates runners & risers for a given pattern could nearly take as much time as designing/making the pattern.
The speed in which molten metal flows into the sand mould will have a very large bearing on the final outcome of the final casting quality... carry out a well controlled pour & chances are you'll get a good casting.... allow the metal to gush in at a hundred miles an hour and the casting will be ruined.
So it is wise to sit down & read a good book on the subject and take in what is being explained, then apply that knowledge to your work, and the chances are that you will discover that your casting reject rate will drastically fall, and you wont be feeling down when you wonder why your metal casting is not as successful as you would like it to be.
To be sure though, you can get away with very basic gating and runners on small items, I have had success on "one of" items using very simple hand cut ingates and it works, but if you want consistent quality when reproducing small qty batches of a given product and you need repeatable quality, then you will want to learn all you can about gates, runners & risers.
Below, we have some pictures of cast iron engine blocks, these pictures are a good example of very good gating runner & riser design, study them closely, there is a lot of learning to be had here, the principles shown here are much the same as what is shown & described in the The Design Of Gates & Risers, the ebook available with our ebook package. (Hint; had to throw in a commercial)
The castings below are all cast iron, or grey iron as some would say, and I'm not suggesting for a minute that you might want to cast your own engine blocks... (Although there are hobby casters who have succeeded at this to but it is tricky to do).
It is also interesting to understand how and why a certain ingate method was used to deliver the molten metal to the mould cavity. Bottom feeding provides one of the better feeding methods... the molten metal being under considerable hydrostatic feed pressure, bottom feeding tends to be much less turbulent than top feeding methods provide.
If you trawl through back issues of the ezine, you will find a blower housing project (Qty of twelve were cast) we employed a similar bottom feeding method, and I have to say it is a great way to feed a metal casting. But not all castings can or need to be fed this way.
Hobby Foundry Knowledge Toolkit.
Grab The:
Pattern Making ebook.
Or.
Decorative Metal Work ebook.
The deep pouring
sprue, note the height, the choke and the bottom feeding system.
Another view of the
sprue & bottom feeding system.
View from the bottom, note the
chokes (narrow setions) employed.
The mighty down
sprue, a big pouring cup on top, narrow neck (first choke) wide feeding
basin, and narrow ingate choke feeding into tapered runner and ingates.
The
other end of the casting, showing the riser, the feeding runner on the
top & bottom of the engine block, making sure that the mold fills
evenly as possible, and to provide plenty of feed metal while cooling.
==
Building A Hobby Crucible Furnace.
Efficient melting of metal in the hobby foundry requires a simple, but well Designed, easy to operate melting furnace. A well-designed furnace does not necessarily mean it will be expensive to build, or that it is complicated to construct and operate.
If you're just beginning your metal casting journey, there will be a multitude of questions that will need to be answered; and if you follow some simple methods, your learning curve will be dramatically reduced.
A well-built furnace will take you another step along the path to being able to maintain an important piece of equipment for your hobby foundry set up. Without an efficient furnace your hobby metal casting experience could well be one of total frustration & disappointment.
It is possible to build a furnace from scrap materials found around the workshop.
This is not to say that it will look trashy, or poorly made, the point being made here is that you do not need to build everything from new materials. The only material you will need to buy is the special high temperature resistant refractory to line the furnace walls with, plus a few brass connectors from the local plumber for the gas feed line and some brass rod to custom-make your own special gas jet for the burner. The rest you can quite easily make yourself if you have metal working skills.
One of the biggest problems the hobby foundry worker has to overcome, is to acquire the knowledge to build a high-energy output burner, the subject of burners can raise many arguments amongst hobby foundry workers, and there is a straightforward solution to building an efficient burner, by following simple instructions any practical person can fabricate an efficient burner that will quickly melt metals such as aluminium and bronze without effort. The process to build a high output furnace burner is really quite simple, but there are a few small parts that need to be machined on a lathe.
If you don't have the luxury of a lathe in your workshop, perhaps a friend can help you out. Although, many hobby metal workers do own a metal lathe these days; it is almost a “must have” for the average home engineer in this ever- popular DIY era. You may also require a MIG or electric ARC welder (Max 180 Amp) to fabricate the furnace.
Be very careful with your gas pipe & joint connections, although there are no great line pressures involved with the gas feed to the burner, but any small leak could lead to the possibility of a dangerous explosion.
Propane gas expands between sixty and one hundred times once exposed to air. So be aware, but gas is the most efficient fuel you can use to fire a crucible furnace, but it can also be an extremely dangerous material.
You need to follow any building instructions carefully and not be tempted to take any shortcuts as they may lead to personal injury.
If you are a resourceful, practical person, you could build your own crucible furnace for less than $100.00US, this is a mere fraction of the cost of a commercial unit, and should be equally as efficient, and provide many years of reliable melting service.
Like many things in life, you can learn from established proven methods, or you can spend many months floundering around, not knowing what to do. But you can dramatically reduce you're journey to metal casting success; learn from more than fourteen years of metal casting success.
)))000(((
And here's to your future success... take a little time to learn the knowledge... apply it in a way that fits best with what you are doing... then move forward from there, you wont learn it in a week, but from those first small steps, success will be yours.
Col.