1. Casting process (continued)
Module 4b

2. Principle of the process Defects/quality control
Casting
Principle of the process
Structure
Process modeling
Defects/quality control
Design and DFM
Process variation
Process design: how to determine the process parameters so that the desired product can be manufactured and defects are eliminated as much as possible
Module 4a

3. Decision making on these issues
Design of a casting process is to determine:
pattern, mold, sprue, gating system, mold cavity, riser, parting line
pour temperature
Decision making on these issues
Process goal: Mold cavity is completely filled without defect
Process constraints: casting material, casting geometry, cost, time, quality
Module 4a

4. Process design – additional riser
To control the shrinkage cavity to the riser
Module 4b

5. Process design – location of riser
Directional Solidification – Forced Solidification
Riser
(V/A) > (V/A)1
TST > TST1 1 2
External and Internal Chills
Module 4b

6. Process design – parting line or plane
Design for locating parting line – determine parting line or surface
Parting line or parting surface is the interface that separates the cope and drag halves of a mold, flask, or pattern and also the halves of a core in some core-making processes.

7. Parting line or parting surface is the interface that separates the cope and drag halves of a mold, flask, or pattern and also the halves of a core in some core-making processes.

8. Process design – parting line or plane
Design for locating the parting line or surface
Pulling direction

9. Process design – parting line or plane
Design for locating parting line and surface
Pulling direction

10. Process design – parting line or plane
Design for locating parting line and surface
Bad parting line
Best parting line

11. Process design
The main constraint requirement for determining the parting line is: the pattern can be drawn out from the mold to leave a cavity. Besides, the selection of parting line can affect
Cores (as little as possible)
Draft (as little as possible)
The core and draft cause material waste and extra steps in the casting process, which means cost increase and should be avoided if possible.
(a)
(b)
(b) is better as there is no need of core and no need of draft; but (a) needs core and draft.
Module 4b

12. Process design – parting line or plane
Parting line or surface determination
Parting line (correct)
Design features, such as round, may also put restriction to the location of parting line in the above cases
Module 4b

13. Principle of the process
Casting
Principle of the process
Structure
Process modeling
Defects
Design and DFM
Process variation
Module 4b

14. Design and DFM
Original design
Modified design
Module 4b

15. Design and DFM
Design for Controlling the process
Module 4b

16. Design and DFM
Intersection of two sections causes: hot spots (gap) and stress concentration
shrinkage
Hot spots
Module 4b

17. Design and DFM
Fillet
Holes
Module 4b

18. Design and DFM Avoid hot spots
Cross section area of B-B is too larger than cross section area of A-A. As such, in the area of B-B, there may be insufficient fluids (or there presents hot spot).
Avoid hot spots A B C
A-A
B-B
C-C
Module 4b

19. Design and DFM Pattern shrinkage allowance
Large casting, special rule: 1% - 5%
Solution to Cavity caused due to Shrinkage
Module 4b

20. Summary Mold with cavity How Pattern is made How Mold is made
Basic elements in the Casting Process
Mold with cavity
How Pattern is made
Mold Materials
How Mold is made
Module 4b

21. Summary
One mold multiple casting
Permanent casting
Casting
One casting one mold
Expandable casting
So far the expandable sand casting has been discussed. It is a generic casting process.
How pattern and mold are created is added onto the generic process so as to create a variety of casting processes.
How to make mold drives the invention of new casting processes.
Module 4b