Shot blasting is a post-production finishing service for investment castings which is processed through the rapid impacting on the surface of investment castings with a defined amount of abrasive material. This results in a faster and more efficient process when compared to filing for flash removal that remained on investment castings. By using very specific types and amounts of shot material, CFS foundry can shot blast parts of all sizes and shapes. For example, tiny steel shot is utilized to produce a very polished and smooth surface. Larger shot sizes can aggressively remove heavy flash.
Main fuction of shot blasting is also used for removing burrs, scale and rust that may interfere with the integrity, appearance or definition of investment castings. Shot blasting can also prepare the surface of investment castings for coating by removing surface contaminants and provide a surface profile for increased coating adhesion.
Shot Blasting is different than Shot Peening which is used to induce compressive stresses on a part’s surface for increased fatigue life, increasing strength or preventing fretting of castings.
Shot blasting after heat treatment is performed to remove any oxidation or scale that has formed on the casting during prior heat treating processes. During heat treating of investment castings, oxidation can form during annealing, normalizing, hardening, or tempering operations depending on the particular process parameters. Shot blasting treatments easily remove this surface oxidation, which makes additional operations like machining easier to perform.
Tips for achieving a successfully shot blasted floor
1. Remove chewing gum, sticky adhesives or other soft materials from the floor that will prevent the surface from being evenly shot blasted.
2. If a floor is soaked with grease or oil, clean it first with an industrial detergent. If not cleaned first, the heat generated during the shot blasting process will bring the oil to the surface.
3. Make sure the surface of investment castings is dry. A shot blaster will not work properly on a wet floor.
4. Shot blast a small test area first to ensure that the desired result is achieved.
5. Plan the travel route for your shot blaster so that you achieve a consistent pattern over the entire surface.
6. Use the smallest steel shot size possible that still provides the desired results. Smaller shot provides better coverage and higher production.
7. Monitor the level of the shot in the hopper. Keeping the hopper full will help achieve a more consistent blast pattern.
8. Vary the travel speed of the machine as needed to address areas of softer or harder concrete.
In Summary
Shot blasting is the necessary posting treatment method after investment casting. Equipped with numerous shot blasting machines in house, we can do this kind of service directly in our investment casting foundry. Of course, we can also supply other surface treatment services on investment castings, such as painting, powder coating, zinc plating, ect. But not all the surface treatments are finished in our factory, some are from outsourced surface treatment companies.
