Casting Techniques and Components Quiz

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Questions and Answers

What is the purpose of a wax pattern?

To hold the investment material

To form the mold (correct)

To provide structural support

To cool the molten metal

What is a sprue channel?

A channel or hole through which molten metal will be cast into the mold.

What materials can a sprue former be made of?

Plastic

Metal

Wax

All of the above (correct)

What is the function of a sprue base?

A pedestal on which the sprue former is positioned and held in place during the investment procedure. Signup and view all the answers

What is a casting ring?

An enclosure that contains fluid investment and holds everything in its proper place. Signup and view all the answers

What should a ring liner provide when using a solid metal casting ring?

A cushion allowing for the lateral expansion of investment. Signup and view all the answers

What does investment do in the casting process?

Surrounds the pattern and forms a refractory mold. Signup and view all the answers

The direct sprue method is most frequently used for _____________ crowns or copings.

single Signup and view all the answers

What should the length of the sprue be for direct spruing?

Long enough to position the wax patterns outside the heat center. Signup and view all the answers

Where should reservoir balls be located during direct spruing?

In the heat zone of the ring. Signup and view all the answers

The length of the sprue former will depending on the size of the pattern and the type and size of the __ ring.

vary; wax; casting Signup and view all the answers

What is indirect spruing commonly used for?

To cast multiple single units or units joined together. Signup and view all the answers

The sprue channels for indirect spruing lead directly from the crucible former to the pattern.

False Signup and view all the answers

Indirect spruing involves being attached with a _ _ instead of a single straight sprue former.

running bar Signup and view all the answers

What is the diameter of the runner bar (reservoir bar)?

4-6 gauge. Signup and view all the answers

What is the purpose of ingate sprues?

To supply alloy to each of the wax patterns. Signup and view all the answers

What are down sprues also referred to as?

Primary sprues. Signup and view all the answers

What should the pattern placement be in indirect spruing?

Placed off the runner bar just outside the heat center. Signup and view all the answers

What should you consider when selecting sprue gauges?

Select based on the volume of alloy needed to supply the pattern to be cast. Signup and view all the answers

Manufacturers include sprue gauge _____- for their alloys but technicians need to know the and _ of patterns to be cast in order to select the correct gauge size.

recommendations; thickness; number Signup and view all the answers

What can happen if wax patterns are placed too close to the runner bar?

They may not undergo orderly solidification. Signup and view all the answers

Attach the wax pattern so that the alloy is toward the ____ sections, such as the margins.

toward; thinner Signup and view all the answers

Position the wax pattern so the margins of the patterns face the _ of the casting ring.

trailing edge Signup and view all the answers

Place a wax on the crucible former trailing edge, to serve as a _____ reference once the patterns have been invested.

dot; orientation Signup and view all the answers

What forces does a wax dot take full advantage of once the patterns have been invested?

Centrifugal and gravitational forces. Signup and view all the answers

Study Notes

Wax Pattern

Formed for creating molds; wax is melted away and replaced by molten metal.

Sprue Channel

Channel for molten metal to enter the mold and allows wax to escape during burnout.

Sprue Former (Sprue Pin)

Forms the sprue channel and can be made of plastic, metal, or wax; varies in length (recommended 1/4 to 3/8 inch); should attach to the bulkiest part of the wax pattern.

Sprue Base

Pedestal that holds the sprue former in place; directs molten metal into the sprue channel; can be made from rubber, resin, or metal.

Casting Ring

Encloses fluid investment and maintains proper alignment; materials include steel, rubber, paper, or plastic.

Ring Liner

Cushioning for solid metal casting rings; must be at least 1 mm thick to accommodate lateral expansion of investment.

Investment

Surrounds the wax pattern to create a refractory mold.

Direct Spruing

Uses a direct sprue former to allow molten metal to flow straight to the mold; attached to the thickest part of the wax pattern and connected to the sprue base; can include a sprue ball or vent.

Direct Sprue Application

Most commonly used for single crowns or copings; potential for suck back porosity can occur, but using a sprue ball or vent can mitigate this risk.

Sprue Length for Direct Spruing

Should be sufficiently long to place the wax patterns outside the heat center.

Location of Reservoir Balls

Should be in the heat zone of the ring to prevent premature solidification of molten metal.

Variation of Sprue Former Length

Dependent on the size of the wax pattern and the type/size of the casting ring.

Indirect Spruing

Typically used for casting multiple single units or connected units like splints or fixed partial dentures.

Contrast with Direct Spruing

Indirect spruing does not have sprue channels running directly from the crucible former to the patterns.

Indirect Spruing Configuration

Patterns are connected to a running bar instead of a direct sprue former.

Runner Bar (Reservoir Bar)

Diameter of 4-6 gauge; extends horizontally from ingate sprues; supports multiple patterns and prevents early solidification of metal.

Ingate Sprues (Feeder Sprues)

Diameter of 8-10 gauge; approximately 1/4 inch long; provide alloy to each wax pattern.

Down Sprues (Primary Sprues)

Diameter of 8 gauge; connect the crucible former to the runner bar; staggered placement relative to ingate sprues.

Effective Indirect Spruing

Patterns should be near but not in the heat center; reduces turbulence, promoting smooth alloy flow into mold cavities.

Sprue Gauges

Selection based on the volume of alloy needed; larger gauge numbers indicate smaller diameters.

Manufacturer Recommendations

Sprue gauge considerations depend on the thickness and quantity of the patterns to be cast.

Wax Pattern Positioning

Patterns too close to the runner bar risk incomplete solidification, leading to casting defects.

Alloy Orientation

Attach wax patterns so that the alloy flows toward thinner sections, improving filling efficiency.

Pattern Margin Orientation

Position wax patterns with margins facing the trailing edge of the casting ring for optimal mold filling.

Wax Dot Orientation

Place a wax dot on the crucible former's trailing edge as an orientation reference, utilizing centrifugal and gravitational forces effectively during casting.

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Description

Test your knowledge on various casting techniques and components used in metal casting. This quiz covers essential terms such as wax patterns, sprue channels, and investment materials. Ideal for students and professionals in metalworking and foundry practices.