Back to Ganoksin | FAQ | Contact

Possible to sand cast rings?


#1

Please excuse my ignorance, but I am trying to visualize this in my
head…is it possible to sand cast rings? I have found a few
examples on line of rings which folks profess to be sand or Delft
clay cast. By looking at the frames of those two systems, it seems
both would present a different method. What I can’t figure out is
how one would maintain the void in the center of the shank. I can
picture that method (I think) with the Delft frame, but then I don’t
know that one would get a good “flow” to form the shank. Any
help/advice, or feelings about the two methods in general (sand vs
Delft clay results) are appreciated.

Holly


#2

I hope this helps:
http://www.ganoksin.com/gnkurl/1q1


#3
Any help/advice, or feelings about the two methods in general (sand
vs Delft clay results) are appreciated. 

Holly, Delft “clay” and sand casting are the same. Delft clay is a
marketing name for a fine grain commercially produced oil bonded
casting sand. There are other sands also used, with various binders
including just water sometimes, for various types of sand casting.
Sand casting can be surprisingly complex, more so than many rings.
Consider that the complex shape of an engine block for an automobile
engine is typically produced by sand casting as a single piece, with
all it’s internal voids, holes that become cylinders, oil and lube
chambers, water coolant areas, and more. All these voids are made the
same way that one might produce the hollow hole through the shank of
a ring. The method is called a “core”. For a ring, you’d make an
initial mold of the exterior of the ring in two halves. However,
during molding, you’d have a bar of something, wood, metal, whatever,
inserted tightly into the shank opening, and extending a bit out
each side. This resulting mold now does not contain anything to
produce the center shank hole. However, now you take that bar from
the ring, and produce a duplicate of it. A common way to do it would
be to take a tube of similar inside diameter to the bar, and pack it
with sand. pushed out, you now have a bar of sand identical to the
bar you put through the ring shank. Because the bar extended past the
shank of the ring, there are depressions in the main mold on each
side of the shank, and you can place this core (the bar of sand)
into those depressions. Then you close the mold, and the internal
cavity of the mold now will produce the whole ring. Cores can be more
complex than this, too. For example, if that bar, the core, is made
with an upper projecting bump of desired shape, then the ring you
cast can have a hollowed out space under the top, or that can be a
whole seperate small core that produces a hole where a stone will be
set. And so it goes. The molds can be multi part, and that allows
much versatility. However, making molds with cores can get much more
complex than the usual things Delft clay was designed for. Simple
rings, like plain bands, can be made without cores, just by modling
them with the parting line down the center. If the inside of the
shank is slightly tapered to each side, like a comfort fit band, then
you’re making a single mold with two halves, no cores, tht will cast
your “donut” shaped ring.

Fully filling the mold cavity when sand casting is simply a matter
of having the metal hot enough. The sand is porous enough that air
easily escapes, and with Delft, the oil based binder burns, creating
a very nice reducing atmosphere, to minimize metal oxidation. That
porous structure of the sand mold also tends to make it a good
insulator, which has less of a chilling effect on the metal, so even
casting with a room temperature mold usually works quite well.

Hope that helps
Peter Rowe


#4

Holly - I have Delft cast rings and a couple other things. Rio has a
kit that comes with a helpful Dvd and it’s reasonably priced. Give
it a try. Can’t say that it would be worth doing for production or
having something to ‘sell’ after you are done. It takes practice
like anything else and I had a 50/50 fail rate… but it was worth
learning. It’s the air vents and sprue that get ya! but I did have
some success. I can just make a ring faster as opposed to Delft
sand/clay casting it. Have fun - give it a try :wink:

joy kruse


#5

I’ve used the Delft system to cast several different rings. It works
very well but, in common with all with “sand-type” casting, it’s
pretty much impossible to incorporate undercuts. Take a look at one
of the Delft Casting tutorials such as

Regards, Gary Wooding


#6
Please excuse my ignorance, but I am trying to visualize this in
my head....is it possible to sand cast rings? 

It just takes a bit of pre planning. You need a wood mandrel about 2
inches long, and as big as the inside of the ring; and another
that’s the same size, but split lengthwise, and a tube that the round
mandrel fits into, tightly, and is the same length as the mandrel.

Pack half the flask with the half mandrel. Remove the half mandrel
from the sand. Thread your ring model onto the round mandrel and push
the assembly into the half round impression until you seat the dowel
in the old impression.

Pack the other half of the flask, and pull the model and mandrel. Cut
your gates and vents in the sand mold.

Pack sand into your tubing, then use the mandrel to force the sand
core out, and carefully put the sand core in the place of the
mandrel, then close your cope and drag back up. Pour.

It’s the same trick for making things like gears and other hollow
parts.

“Delft clay” is really just very fine sand with an oil binder. I use
if for things that I know I’m not going to do a lot of reshaping on.
I use a coarser oil-bonded sand for rough parts. Functionally, they
work the same. You just typically have to be better about venting
with the clay.

Ron Charlotte – Gainesville, FL


#7

Holly- Back in he Jurassic period I worked in a really old school
trade shop where we sand cast. I’d avoid it if I were you. The
surfaces are very crude and require a lot of filing. Much better to
carve a wax and cast from that.

Have fun and make lots of jewelry.
Jo Haemer
www.timothywgreen.com


#8

I have used the Delft clay system with great success. You are
depending on the weight of metal in the sprue to act as the force
behind the molten metal which has to fill the mould by gravity.
Don’t expect to cast fine 3 stone claw rings by this method I found
it good for sculptural forms and the odd signet ring. I used to keep
a lump of silver specifically for the “Force” and just added the
weight required for the object. Another factor are the vent holes to
allow air and gasses to leave the mould and not hinder the incoming
molten metal. Sand casting is the same, finely divided sand mixed
with oil to make a clay like consistency. I used to use cuttle bone
for casting, and old technique dating back to Egyptian times. Lovely
for making the impressions of an object. I have drawings of the
process which I can post on the webb page

Regards
Hamish


#9
Delft clay is a marketing name for a fine grain commercially
produced oil bonded casting sand. 

Yeah, but Delft is far better than standard casting sand, and priced
higher too :wink: CIA


#10

I had thought about posting this last week. It’s good to put it out
there for all the tinkerers around here. Lindsay’s Technical Books
is a great place to get reprints of old books, largely about metals,
machining and foundry. And new ones, too, many of which are written
by major tinkerers - how to built your own milling machine. I have
the US Navy Foundry Manual on the following page, and it’s really
great for understanding sand casting and what it involves. And
more… http://www.ganoksin.com/gnkurl/1q7

And the home page: http://www.ganoksin.com/gnkurl/1q8

Yes, it’s folksy and funky, but the books are cool.


#11

The way I overcame the problem was to get two square pieces of
aluminium just larger than the outside diameter of the round flask.
Now you know where the two pieces of the flask join together. Well I
cut a hole about 25 mm round through the joint, so that each half of
the joint of the flask had 1/2 of the hole cut out of it. The Flask
would be set up on its side, hole would be placed at the top and the
two squares of aluminium gently clamped covering each end of the
flask. The flask held with the ‘new’ pouring hole at the top and
held there by the two squares.

After separating the flask place the two non-joint ends, one on each
square and fill the flask with the inside overlapping flange,
compressing and levelling the sand as usual.

Now take your ring and embed it on its side up to half its thickness
into the sand with the heavier section away from the hole in the flask
where the sprue will be. The tricky bit is making the sprue nicely,
either solder a sprue onto your ring or carefully embed a wire which
should be greater than the cross section of the shank of the ring you
want to cast. or you can embed a suitable bit of wire so that it
protrudes from the centre of the hole. Be careful as there will be
loose sand where the wire touches the ring.

Join the two halves of the flask, making sure the hole is perfectly
round and that there is no sand in the overlap joint. Sprinkle with
talcum powder, dont inhale. Then carefully compress the sand around
your embedded ring and sprue, cover with the second square of
aluminium.

The sprue wire should be protruding from the centre of the hole. It
is important that you part the flask vertically without twisting as
any circular movement will destroy your efforts. A two person job.
Practise first with an empty flask, perhaps emery the outside edge of
the inner section of the overlap first. Now part the flask and remove
the ring and sprue and cut a deep funnel, pat the sand to compress it,
making sure there is no loose sand in the ring or sprue. Join the
flask, VERTICALLY so the hole is perfectly round though a small
amount of circular adjustment before the flask is closed completely
is possible. Keep the end squares in position and gently clamp so the
sprue funnel is vertical. Melt your silver and pour so the funnel is
full but must not touch the aluminium. Hope this all clear, best of
luck.

By the way, only cast things that it would be more difficult to make
repeatedly.

David Cruickshank
jewellerydavidcruickshank.com.au


#12
I have used the Delft clay system with great success. 

Me too, and it’s excellent for lost foam. CIA


#13

Please excuse my ignorance, but I am trying to visualize this in my
head…is it possible to sand cast rings? I have found a few
examples on line of rings which folks profess to be sand or Delft
clay cast. By looking at the frames of those two systems, it seems
both would present a different method. What I can’t figure out is
how one would maintain the void in the center of the shank.

As I think you understand, the Delft clay does this for you. It
comes with a set of aluminium rings that let you form and align two
clay impressions of whatever you want to cast - one on the top and
one on the bottom. You first of all fill the bottom ring with clay
then press the ring pattern into the clay horizontally, then add
talc, then press more clay on top.

You then remove the top layer, then remove the pattern. What you
have left is two pieces of clay which, when realigned and pressed
together, leave a void in the shape of a ring. There’s clay in the
center of the shank, so no chance of silver getting there. You then
need to prepare your sprue and risers - holes for silver to go in and
air to get out as you fill the mould.

I can picture that method (I think) with the Delft frame, but then I
don’t know that one would get a good “flow” to form the shank. Any
help/advice, or feelings about the two methods in general (sand vs
Delft clay results) are appreciated.

Other people have posted links to instructions on how to use Delft
clay. Making rings can be slightly trickier than most other things,
because of the risk of getting an air bubble caught along the shank
with no way for it to escape. But you want to minimise the number of
risers to reduce the amount of finishing work needed afterwards.

I managed to get good castings with only two holes - a sprue and a
riser on opposite sides of the ring. Before you pour, place a bit of
tile about 5-10 mm thick under the riser end of the Delft clay rings
so that they are tilted with the riser slightly higher than the
feeder. This way, when you pour the silver it forms first of all a
’C’ shape with the feeder in the leftmost part (center) of the 'C’
then meets up to form an ‘O’ with the riser on the right-most part of
the ‘O’.

The biggest problem I have had is with grains of sand crumbling free
into the mould and causing cavities in the finished castings. It’s a
fairly labour intensive technique too - but very good for
experimenting and making small numbers of pieces.

I have some pictures of rings I made, complete with sprue and riser.
I found I needed a fairly large sprue, perhaps because I was only
using propane and couldn’t get the melt quite as hot as I would like.

I got better at it since then, but still need to do a lot of
finishing on the back of the rims. If you were thinking of using
silver, I found Argentium worked better than Sterling.

Kit


#14

Holly,

There are better buys on sand-casting kits than Rio, at least the
last time I looked.

FDJtool.com has this kit:
http://www.ganoksin.com/gnkurl/1qa

If you already have some items, you can just buy what you need
instead of the kit.


#15

Lindsay Publishing produces books that are an excellent starting
point, you find it easier to acquire after you have read
them.

There is a fairly large problem with the book, in that they are
produced for the American market, and any other country has to re-do
the calculations, and source raw materials from your local market.

I’ve got quite a few of the books, but I’ve never made anything
straight from them.

Regards Charles A.


#16

Hi Kit,

Maintaining the void is dependent on the sand casting method you
use.

Vents too large, well that’s a simple thing to fix, make more
smaller profile vents.

If you use a removable model, you need the sand to be the right
consistency. If the model is really complex then you may need more
than a 2 part mould.

If you choose to use an architectural foam model, there are two ways
to handle this. If you are using loose sand, all you need is a hole
to pour the metal, there is no need for vents. If you use a
traditional sand or Delft clay, then you need vents.

You just have to pour fast.

Regards Charles A.

P.S. If you have more questions, and I can’t answer them, I can ask
the old timers on a couple of foundry lists.


#17

Any help/advice, or feelings about the two methods in general

Not really directed at the quote, and no doubt somebody will post
some sort of rebuttal, but it should be said I guess. Sand casting
is still used in industry - somebody mentioned engine blocks, that’s
one place. And I’ve known people who did it all the time for various
things. Sure… But for the effort of doing core casts and
crossing your fingers on a gravity pour and all of that…
Investment casting, whichever method you prefer, is 100 times easier
and gives 1000% better results. And you can cast ANYTHING… Even
if you have to pay for it from Racecar or somebody. Just to say…


#18
Sand casting is still used in industry - somebody mentioned engine
blocks, that's one place. And I've known people who did it all the
time for various things. Sure......... But 

Well these days engine blocks are done in lost foam, no cores are
necessary.

My point of view is what do you want to achieve and how fast do you
want to achieve it?

With investment casting, you have to wait for the plaster to set,
and you have to wait 12-24 hours for the plaster to finish the burn
out cycle. If you’ve screwed up you find out after you devest the
casting. If you’re successful, then you will be presented with a nice
black piece. If you aren’t successful then you have to start again.
Also if you were short sighted, and only used an original wax model,
then you have to make a new wax model. The smart person makes a cold
cure rubber mould :wink: Dead smooth surfaces can be achieved.

With traditional sand casting, you start with a hard model, pack the
sand around it, remove the model (the more complex the model the
more mould pieces… imagine casting a cup and saucer with a spoon in
it), pour in your metal. The packing takes a little time, but far
less than investment casting. If you bugger up the mould, you can
start again rapidly. Usually a grainy surface, but this is dependent
on the size of the grains of sand. You can get close to investment in
surface fineness, but you’ll never match it.

Then, of course, there’s lost foam casting, this takes even less
time to do than traditional sand casting, and has an added advantage.
No seams.

Now to the disadvantages.

Investment casting… takes a looooooong time, the model is
destroyed in the casting process. The plaster powder can kill you, so
breathing protection is mandatory.

Traditional sand casting… doesn’t take a long time for the
casting, but depending on the complexity of the mould, there may be a
lot of time spent cleaning up mould lines.

Lost foam casting… the amount of time it takes to do lost foam is
ludicrously short. The real disadvantage is that the model is
destroyed, and polystyrene models cannot be easily moulded, you need
special machines set up for it. The models are one-offs (I’m
investigating a way to used polystyrene beads and a burnable binder,
but haven’t been successful).

Casting sand can be plain sand no additives, sand and water, sand
and oil, cement and oil, sand and chemical binders, Delft clay. There
are a few others that I’m working on that include baby oil and other
industrial/art casting powders.

Pretty much anything shape that can be cast in plaster, can be cast
in sand, and vice versa.

Of course the above is when you do it yourself, when you pay someone
else to do it, who cares how it’s done, as long as you’re the happy
customer :wink:

Regards Charles A.


#19

I have just started making ring blanks with the larger delft clay
tubes.

I find it very successful compared to using an ingot mold. (95
Percent of my wire ignot mold pours freeze prematurely)

but back to the sand cast ring blank…

Yes, I have a little bit of porosity but only on one side of the
blank and only where the sprue button is created. I can sand most or
all of it away every time.

When you press in your model, you may have to adjust it by sticking
the model back in and pressing things flat after you cut your funnel.
Alos, Sounds like to me you are having problems with the pour. Is
your metal hot enough? Also, and I think this is the most
important… are you making enough or well made air vents/lines? The
air has to escape for your molten metal to fill the void before
freezing. Here is a ring blank I just made yesterday. I think with
practice, I could eliminate all porosity. Notice I made 8 air
vents/lines. Most I ever made and this was the best pour I ever made.
This is a full size ring blank to make a size 12 and it’s 3 mm thick.

http://www.ganoksin.com/gnkurl/1qt