Back to Ganoksin | FAQ | Contact

Spruing techinques


#1

Dear All,

The sprue is the major contribution in the jewelry gold casting.

I want to know about, How to decide the Sprue in silver master?

Any techniques or System is available to find out the correct Sprue
Location and size against the Silver master in all kind of category.

Please give your valuable suggestion as above.

Regards,
C. Karmekanandan
Ped


#2

I’m really not sure exactly what question you are asking. The
fundamental principles of sprueing are:

  1. Arrange your pattern of spruues to ensure that the molten metal
    flows away from the button through the tree to every part of the
    pattern without any significant reverse flows

2 Ensure that your sprues are sufficiently thick so that metal
remains molten in them until the patterns are completely filled. I
usually use 2.5mm sprues for the main sprues and sometimes 1.5 mm
supplementary ones.

  1. Sprue to the heaviest parts of your pattern and is a position that
    makes it easy to grind, file and sand off the attachment point when
    finishing. Depending on the shape and size of the pattern multiple
    and supplementary sprues may be required. For instance when I am
    casting a 40 gram bangle in 925 silver I use a radial pattern of up
    to 7 sprues back to the button. I can send a photograph on request.

  2. Ensure that the attachment points of sprues to the pattern and
    branches in sprue pattern are filleted so that there are no sharp
    points where investment can break off when the metal flows

  3. Have a sufficient reservoir of molten metal (5-15 grams depending
    on the overall weight of the casting) in the button to ensure that
    shrinkage can be accommodated.

May the casting goddess look upon your efforts with favour.

Jennifer Gow


#3

Dear Karmenkanandan,

This is a brief write up on designing sprues. Please come offline if
you need any further assistance.

Gating system refers to all passage ways through which the molten
metal passes to enter the mold cavity.

BASICS OF GATING:

The flow of metal in to a mould is very much affected by the type of
gating system employed, for example the design of a system having
several ingates will influence the distribution of the flow between
the ingates. A good design will have even distribution between the
ingates both initially and during the subsequent period in which the
mold is being filled.

THE GATING SYSTEM IS COMPOSED OF:

Tree button or pouring basin
Sprue button
Main sprue (or) Runner
Feed sprue (or) gate
Pattern (or) pieces
Tree top

RUNNER (OR) MAIN SPRUE:

The main runner which also acts as a feeder is usually truncated
cone in shape. A runner originates at the main sprue and has several
feed sprues to multiple pattern or multiple points on a single
pattern. Runners generally fill to the end and then back pressure
starts the metal to flow in to the sprues. The runners form hot spots
in the mould which create torsional stresses with consequent possible
distortion of the casting. Much of the above applies when gravity
casting methods are employed. The most significant point; however is
that owing to the slower velocity of the metal, it is usual to
increases the size of runners, gates and feeders over those normally
employed for pressure casting techniques.

TREE BUTTON (OR) POURING CUP:

The size of the gate depends upon the rate of solidification. The
gate basin or button to act as a reservoir or store for molten metal.
It prevents turbulence

FUNCTIONS OF GATING SYSTEM:

GATING SYSTEM SHOULD:

Fill the mold cavity completely before freezing

Introduce the liquid metal into the mold cavity with low velocity
and little turbulence

To promote temperature gradients favorable for proper directional
solidification

Consume least metal

PURPOSE OF THE SPRUE:

To permit the wax to escape during the burnout.

To provide a passage for the molten metal to reach the pattern
cavity.

To provide a reservoir of molten metal for the casting, as they
shrink upon solidifying there must be more metal fed into the space
left.

To properly position the wax pattern so that it receives the molten
metal in the smoothest & most efficient way.

MAIN POINTS TO BE CONSIDERED FOR SPRUE ARE :

It should provide sufficient space for the molten metal to flow into
the mould so that all cavities are filled completely.

Main feed should be the last segment of the casting aggregate to
solidify.

Sprue should have smooth radius & taper so as to avoid turbulence,
when liquid metal enters.

The sprue should have a parabolic taper generally a straight taper
is constructed.

The sprue entrance should be generously filleted.

Taper sprue helps establishing proper flow characteristics rapidly.

IMPORTANT FACTORS AFFECTING THE MOLTEN METAL:

Type and size of sprue
Type and size of runner
Type of main sprue
Type of feed sprue
Calculating the volume of metal & the properties of metal.

Thermodynamics of the system (Flask temperature, pouring temperature,
& rate of solidification) Designing Sprues.

CAD is extensively used for carrying out the designing of sprues
once the CAD files are ready. In many complicated designs we print
the designs along with the model being printed. CAD has made the
process of designing spures easier.

If you need any further assistance please come offline or get in
touch.

Umesh. G.Chavan
Mumbai


#4

Generally speaking the sprue should be attached to the thickest
widest part of the ring or object. Feeder sprues can be attached to
run to the thinner more delicate parts of the object if necessary.

All connections should be smooth and free flowing to the object.
This lessons turbulence in the metal when cast…

Regards,

Russ Hyder
The Jewelry CAD Institute


#5

Dear Jennifer Gow,

Thanks lot giving the Sprue details.

Could you send some sample pictures about sprue?..

Regards,
C. Karmekanandan

[Edit]

Attachment removed:

How can I share files and pictures with the list?
http://www.ganoksin.com/gnkurl/ftp

Or… send the files to the attention of service@ganoksin.com and
we will upload them for you…

[/Edit]

How can I share files and pictures with the list?

https://www.ganoksin.com/gnkurl/ftp

Or… send the files to the attention of service@ganoksin.com and
we will upload them for you…