casting technology'.ppt
DESCRIPTION
Casting TechnologyTRANSCRIPT
![Page 1: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/1.jpg)
م�ن عق�د�ة� لل� و�اح�ان�ي {27}ل�س�
ق�و�ل�ي �ف�ق�هوا {28}ي
ح�من� �الر الله� � م �س� ب
�� ح�يم � الر
ا العظيم صدق
![Page 2: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/2.jpg)
Casting Technology
The purpose of the casting procedure is to provide exact metallic duplicate of missing tooth (or teeth) structure with
maximum possible accuracy in all dimensions, For →
InlaysOnlays
Crowns & Bridges
![Page 3: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/3.jpg)
Direct restoration
![Page 4: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/4.jpg)
Indirect restoration
InlayOnlay
![Page 5: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/5.jpg)
Gold bridge
![Page 6: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/6.jpg)
Reduced tooth
![Page 7: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/7.jpg)
Impression
Cast / Die
![Page 8: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/8.jpg)
![Page 9: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/9.jpg)
Gold Crown
![Page 10: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/10.jpg)
Steps of casting procedures
Wax pattern constructionSpruingInvestingWax eliminationCastingFinishingPolishing
![Page 11: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/11.jpg)
I- Wax pattern construction
Direct technique
Indirect technique
Indirect direct technique
![Page 12: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/12.jpg)
II- Spruing
Create a channel to allow the molten wax to escape from the mold.
Enable the molten alloy to flow into the mold which was previously occupied by the wax pattern.
Role of a sprue:
The wax pattern is attached to a sprue
for proper handling without distortion
![Page 13: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/13.jpg)
Sprue materials
Waxes
melt at the same rate as the wax pattern thus allowing easy escape of the molten wax
Plastics
MetalsHollow
Or
solid
![Page 14: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/14.jpg)
Attachment and Direction: Sprue should be attached to the
thickest part of the wax pattern
with a 45º C angle to the proximal wall
This orientation avoids:
* Turbulent flow of the molten metal
→ air bubbles leading to
# porosity
![Page 15: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/15.jpg)
Diameter (Thickness):
Equal or slightly Thicker than the thickest part of the wax pattern →
* improves flow of alloy into the mold • provides reservoir during solidification.
Reservoir: piece of wax attached 1 mm. Away from the wax pattern it is the last part to solidify,allows continuous feeding of molten alloy to compensate solidification shrinkage and to avoid shrinkage porosity
![Page 16: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/16.jpg)
Number of spruesmay be single, double or multipleThere may be a main sprue with accessory sprues.
Single Double Multiple
![Page 17: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/17.jpg)
Length of sprueShould keep the wax pattern
about 6-8 mm from the end of the casting ring
Short sprue → prevent escape of air leading to
back pressure porosity.Long sprue → fracture of the investment, as mold will not withstand the impact force of the entering molten alloy.
![Page 18: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/18.jpg)
Preparation of the casting ring
![Page 19: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/19.jpg)
Crucible former: usually made of rubber, which constitutes the base of the casting ring during investing.
![Page 20: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/20.jpg)
Casting ring and liner: Casting ring may be metallic, or rubber ring.
Selection depends on: choice of casting alloy and investment material.
Casting ring lined using asbestos,
then wet the liner.
Functions of liner:
1) Creates space to allow for investment expansion.
2) Allow setting of investment material under water to give hygroscopic expansion.
3) Facilitate removal of investment from the casting ring after casting.
![Page 21: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/21.jpg)
Types of ring
Metallic Rubber Split
![Page 22: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/22.jpg)
![Page 23: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/23.jpg)
III- Investing
Surfactant
![Page 24: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/24.jpg)
Investing the wax pattern:Wax pattern must be invested immediately to avoid distortion of wax pattern,
which may be due to release of internal stresses
Wax is a hydrophobic material → Improper wetting of wax pat. →
irregular surface of the metallic cast. Minimized by applying
surfactants (surface acting agents)
on the wax surface → * increases surface energy of the wax * decrease contact angle between and
investment material.
![Page 25: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/25.jpg)
Methods of investing the wax pattern: Hand investing procedure and vacuum ***Vacuum mixing of investment
is highly recommended to obtain casting with minimal surface defect.
Investing wax pattern may be
done by regular mix investment technique OR by double mix investment technique → * improve adaptability of the investment material to the surface of wax pattern * avoid distortion of wax
# After the ring is filled to the rim, # allow the investment to set for about one hour # remove the crucible former and the metallic sprue
![Page 26: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/26.jpg)
Investing technique
Hand mixing Vaccum
![Page 27: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/27.jpg)
IV- Wax elimination
![Page 28: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/28.jpg)
Wax elimination: Heating the investment must be done
to achieve the following:1) All traces of the wax are vaporized: bring
the furnace to 200º C and hold this temperature
for 30 minutes . Most of the wax will be eliminated by this
time.2 )Increase the temperature gradually to the
final burnout temperature (about 650º C), this is accompanied by thermal expansion of the investment.
The mold temperature is now ready for casting.
![Page 29: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/29.jpg)
V- CastingA) Melting the alloy
Using flame Using electric furnace
![Page 30: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/30.jpg)
B) Casting:A casting machine requires * a heat source to melt the alloy. * casting force, so the casting will be completed.
Methods of melting alloys:* flame: Melting gold alloys is done by a blow pipe flame while melting base
metals is done by oxyacetylene flame.
* electric furnace.Methods of Casting: (driving the alloy into the mold)* Air pressure casting machine Compressed air* Centrifugal casting machine.* Both centrifugal and gas pressure
![Page 31: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/31.jpg)
Casting machines
Air pressure casting machine Centrifugal casting machine
![Page 32: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/32.jpg)
Solidification of the alloy is done under pressure, then
Allow for cooling and
when the color of the molten alloy has changed
from red to black color,
the ring should be quenched in water.
Devesting , Finishing and polishing of the casting are subsequently performed.
![Page 33: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/33.jpg)
VI- Divesting and finishing
![Page 34: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/34.jpg)
VI- Polishing
![Page 35: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/35.jpg)
Casting Defects
![Page 36: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/36.jpg)
I) Distorted casting: Due to distortion of the wax pattern.
** Improper handling of the wax pattern and/or its
** Delayed investing.
II) Dimensional inaccurate casting: Small or large casting may be due to :
a. Improper type of investment material.
b. Improper temperature.
![Page 37: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/37.jpg)
III) Surface roughness of the casting: due to:
*** Air bubbles on the surface of wax pattern during the investment procedure
* Improper use of wetting agent
* Improper vacuum investing
![Page 38: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/38.jpg)
VI) Porosity:
1) Shrinkage spot porosity:
at the point of attachment to the sprue, it is due to using a
thin sprue,
which leads to incomplete feeding of the molten alloy during solidification.
2) Back pressure porosity: It is due to using
***short sprue. The distance between the wax pattern and the end of the ring is more than 6 mm;
***Non porous investmentair will not escape from the mold and creates back
pressure during flow of molten alloy into the mold.
![Page 39: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/39.jpg)
V) Incomplete casting and rounded margin:
Due to resistance of the flow of molten alloy into the mold:
*Using short sprue.
*Insufficient venting of the Investment.
*Insufficient casting pressure.
*Under heating of the alloy causing premature solidification.
*Incomplete wax elimination.
![Page 40: Casting technology'.ppt](https://reader031.vdocument.in/reader031/viewer/2022013103/55cf9dbd550346d033aefb54/html5/thumbnails/40.jpg)