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, other kinds of force sources are used with different physical principles. One of the examples of these casting methods is 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 the centrifugal casting process, process parameters are related to the number of centrifugal forces. Here, we mention the types and mechanisms of centrifugal casting methods.
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The types of centrifugal casting methods are;
- The 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 the true centrifugal casting process, large round, hexagonal or orthogonal hollow molds are used. These molds are rotated around their central 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 the mold. So, molten metal takes the shape of a round hollow mold. After the solidification of molten metal inside the mold, the hollow tubular metal part is obtained.
The true centrifugal casting method is applied in both horizontal and vertical positions. But the most common application direction is the horizontal one.
In the horizontal true centrifugal casting process, the 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 the centrifugal casting method. Just enter the required parameters that you have inside the blanks, then click on the ‘Calculate!’ button to get results. If you want to do another calculation, click on the ‘Reset’ button to do the calculation again.
Here, ‘GF’ is the G-factor of the centrifugal casting method to be applied. It is calculated as centrifugal force divided by weight. GF is an empirical value and if it is very low, the molten metal inside the mold cavity will not remain stuck to the walls of a 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 between this range give good results.
‘D’ is the inner diameter of the mold which gives also the outer diameter of the 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 on the upper side will be lower than 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 the required rotational speed. In here, ‘L’ is the vertical length of the tube, and ‘Rt’ and ‘Rb’ are the inner radius values of produced part at the top and bottom respectively. All the units of these inputs must be meters to obtain the result as rev/min.
Here is the equation for rotational speed of vertical true centrifugal casting process that you can check your results;
One defect that needed to be considered with true 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 the 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 the mold cavity.
Because of the use of sand in mold making, semi centrifugal metal casting can be said as an expandable casting method.
With the effect of centrifugal force, the metal quality at the inner side of the mold will be below. So, this inner side is used as a riser system to feed the outer sides of the mold. On 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 the cast metal part, the riser is cut with machining processes.
The G-Factors that are generally used in semi centrifugal casting methods are around 15.
What Is Centrifuge Metal Casting Process?
This is a very similar centrifugal casting process to semi centrifugal casting processes. The sand mold is used and the other contraption for centrifuge casting is nearly similar to the semi centrifugal casting process.
But in here, the produced parts do 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 the center feeding section of the mold.
Conclusion
These are the general information that may be very useful for you in the designing of centrifugal casting processes for your parts.
Mechanicalland does not accept any responsibility for the calculations that are made by users in calculators. A good engineer must check the calculations with hand calculations.
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