Aluminum Bronze surface treatment

[MotorMan12]

We are buying a sand cast Aluminum Bronze (C 954) housing. Due to the external geometry it cannot be milled. Since it is sand cast, my concern is that it will not look very good. I am sure we are not the first to have this "problem": What are the options/methods available to surface treat the housing externally to make it look good?

 

[cloa]

Surface texture would depend on the particular sandcasting process used- what are you seeking?

http://en.wikipedia.org/wiki/Sand_casting

 

[unclesyd]

A couple of options to improve the surface finish appearance.

The first and easiest would be to blast the part with glass beads or a media that will improve the finish. Will improve the profile only slightly. This can easily be done in house.

Depending on the configuration of the part you may be able to use a vibratory finisher, polisher, tumbler. This will actually improve the surface profile. If you don't have a finisher there are plenty of job shops to do the work.

Another that you might want to inquire about is electropolishing the part. This will improve the profile while polishing the metal. This is normally for a value added part and you will have to look around to find someone that can and will do the work.

http://www.delstar.com/electropolishing/metals-that-can-be-electropolished.html

I would get with the foundry to see if they can improve the as cast surface by use of a mold wash, sand composition change, etc. If this is going to be a production item I would look at the possibility of changing the whole casting process to get an acceptable finish as cast.

 

[btrueblood]

In addition to the process used, we've found that a lot of the cosmetic appearance of castings is in the care and expertise of those preparing the molds. Find a shop that can do clean, pretty castings and pay them what they are worth. Hint: you need to visit them, and look at the stuff they make.

In addition, a well designed pattern and core set will help a lot in getting clean castings, and to do so repeatably. Pattern-making shops earn their money. Find one early in the design process, so they can help you get what you want.