Review Of Centrifugal Casting Methods; Types, Process…
As you remember from the sand casting methods, gravitational forces are the influential forces to fill up the mold cavities with molten metal. But sometimes, another kinds of force sources are used with different physical principles. One of the example of these casting methods is the centrifugal casting. As you understand from its name that in centrifugal casting, centrifugal forces are influential rather than gravitational forces. So, in the design of centrifugal casting process, process parameters are related to the amount of centrifugal forces. In here, we mention about the types and mechanisms of centrifugal casting methods.
The types of centrifugal casting methods are;
- True centrifugal casting process,
- Semicentrifugal casting process and,
- Centrifuge casting process.
What Is True Centrifugal Casting Process?
In the production of large tubular parts from metals such as large tubes, bushings, pipes etc. In true centrifugal casting process, a large round, hexagonal or orthogonal hollow molds are used. These molds are rotated around their center axis, then molten metal is poured inside this rotating hollow mold. Rotation produces a centrifugal force, and this centrifugal force sticks the molten metal on the inner section of mold. So, molten metal takes the shape of the round hollow mold. After the solidification of molten metal inside the mold, hollow tubular metal part is obtained.
True centrifugal casting method is applied in both horizontal and vertical positions. But the most common application direction is the horizontal one.
In horizontal true centrifugal casting process, required rotational speed can be calculated via this calculator;
Required Rotational Speeed In Horizontal True Centrifugal Casting
As you see above, we prepared a very basic calculator that you can calculate the required rotational speed in centrifugal casting method. Just enter the required parameters that you have inside the blanks, then click on ‘Calculate!’ button to get results. If you want to do an another calculation, click on ‘Reset’ button to do calculation again.
In here, ‘GF’ is the G-factor of centrifugal casting method to be applied. It is basically calculated centrifugal force divided by weigth. GF actually an empirical value and if it is very low, the molten metal inside the mold cavity will not remain sticked to the walls of mold, and it will ‘rain’ inside the mold.
In general applications of true centrifugal casting methods, GF is generally considered between 60-80, and the GF values betweeen this range give good results.
‘D’ is the inner diameter of the mold which gives also the outer diameter of produced part. The unit is ‘m’ and the obtained rotational speed is ‘rev/min’.
We gave the formula of this calculator also to check your results by hand;
In vertical true centrifugal casting processes, the diameter of the produced part at upper side will be lower then the bottom side diameter, because of the gravitational force. With the additional machining processes, this diameter difference can be eliminated.
For the vertical true centrifugal casting method, you can use this calculator;
Vertical True Centrifugal Casting Method Rotational Speed Calculator
As you see above, there are different parameters that you need to enter inside as inputs to get required rotational speed. In here, ‘L’ is the vertical length of tube and ‘Rt’ and ‘Rb’ are the inner radius values of produced part at top and bottom respectively. All the units of these inputs must be meter to obtain result as rev/min.
Here the equatio for rotational speed of vertical true centrifugal casting process that you can check your results;
A one defect that needed to be considered with tru centrifugal casting methods is; the density of produced hollow parts’ outer regions are bigger than the inner regions. So some defects may occur inside the produced parts to be eliminated extra machining processes.
What Is Semicentrifugal Casting?
This is a type of centrifugal casting method that wheels, pulleys and parts like them are produced. In this method, mold is generally produced with sand. And like in sand casting method, a riser system is used. Round but solid objects are produced with the casting of metal inside the rotating mold around its axis. The molten metal goes and fills the outer sections of mold cavity.
Because of the use of sand in mold making, semicentrifugal metal casting can be said as expandable casting method.
With the effect of centrifugal force, the metal quality at the inner side of mold will be low. So, this inner side is used as riser system to feed the outer sides of the mold. At the outer sides, the density of metal will be higher compared inner sides, so the quality of the produced part will be higher.
After the solidification of cast metal part, riser is cut with machining processes.
The G-Factors that are generally used in semicentrifugal casting methods around 15.
What Is Centrifuge Metal Casting Process?
This a very similar centrifugal casting process with semicentrifugal casting processes. Sand mold is used and the other contraption for centrifuge casting is nearly similar with semicentrifugal casting process.
But in here, the produced parts are not have radial symmetry as the parts that are produced with other centrifugal casting processes. Separate parts are placed far away from the axis of rotation, inside the sand. And these separate parts are combined with gating and sprue systems with center feeding section of mold.
Conclusion
These are the general information that may be very useful for you in the designing of centrifugal casting processes to your parts.
Mechanical Base do not accept any responsibility of the calculations that are made by users in calculators. A good engineer must check the calculations with hand calculations.
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