HOME FAQs BOOKS JOBS: Help Wanted Suggestions you are here: Hotline/Forum => Letter 7020
Lowering the average surface roughness of hardcoated aluminum casting
+
I am interested in means of lowering the average surface roughness of a hardcoated aluminum casting without losing hardness / wear resistance. Target roughness is less than 10 um Ra on a 50 um thick hardcoat.
Kirk Cooper- Troy, Ohio, USA
+
Your questions concerns both hardness and surface finish. I have a partial answer for you. If you want to improve hardness as well as surface finish, your best method is probably a mass finishing system using steel or SS ball media. This is similar to shot peening, which improves surface hardness, but without the dimpling effect. The only problem is, I am not sure you can achieve that much surface improvement as you want or need using this process. You might want to consider a 2 step operation using a new dry organic media shape first.
|
AF Kenton Huntingdon Valley, Pennsylvania |
+
What is the surface finish before hardcoating? If you can improve the surface before hardcoating, this will probably make your target surface easier to reach afterwards. A good finishing media that you might also consider is a very hard and dense ceramic (140 lb/cu ft). There are some available that have light abrasives for cut and polish. This type of media used in conjunction with a fine powdered abrasive could work very well.
Arnold Walker- Independence, Kentucky
+
Depending upon the initial Ra of the raw part, there are numerous ceramic, plastic, and synthetic medias capable of reducing your finish below a 10 Ra. I suggest you send parts to a process lab that has the necessary surface reading equipment to run samples with the different types of media and take the Ra readings for you.
Eric M Hurley- Hamilton, Ohio
++++++
Kirk,
Typically hard coat anodize will raise the surface finish of anodize
2 ¼ to 3 times the starting RA. First you need to begin with a very low RA. I have developed a process that will only increase the RA by
1 ¼ times. With a very low starting RA, this process and some of the other suggestions listed you should not have a problem reaching your requirement.
- Centerville, GA, USA