So I just realized that I haven’t posted any pics of the polishing process (say that five times fast). I’ll update you a bit.
Since finishing the frame a few months ago I got online and researched sanding and polishing aluminum. There’s a TON to learn when you prep for anodizing. I opted to go the cheap and easy route.
Hahahah, but seriously folks. I had you there, didn’t I?
Instead of using the TechShop buffing wheels that may have been corrupted with steel (a deadly combination when you’re anodizing aluminum), I bought several different brand new buffing wheels. I also got two different types of aluminum polish (Mother’s Aluminum polish and Mother’s Billet polish). But before I even got to that point I had to sand.
And sand. And sand.
Here are two pics of a part when it’s ready for sanding;
You can see the milling marks, scratches, dings, crud, and ink from the plant. The aluminum feels rough and the edges are sharp. Yes, it’s a completed part but it’s still a visual mess.
The vertical rods (3/4″ solid aluminum) are about the same:
Yuck. The aluminum gets beaten up and scratched during the milling, forming, and tapping process, and it doesn’t start in a very good condition when you buy it anyway.
So I bought a set (which ended up being two sets) of wet/dry aluminum sandpaper. I also got a cheap pneumatic sander. Using the sander I hit the aluminum with 400 grit w/d sandpaper until I removed all of the basic scratches. If I had to do it again I’d have probably started at 200 grit. 400 took forever to remove the scratches. This is metal, after all. I’d work on a little 6×6 section for probably ten minutes before the big dings had been replaced by 400 grit sanding marks.
Next, I repeated the process with 800 grit, then 1000, then 1500, then 2000, then finished off with a 3000 grit wet/dry pad. For all 38 pieces of the frame. Total time spent sanding was about 20 hours over several weeks. It was also a mess with wet dirty aluminum “sawdust” flying everywhere. Even wearing an air mask, shop apron, gloves, and goggle/faceshield, I still ended up coming home looking like a coal miner.
For the aluminum rods I had to first use a hard wheel to remove the worst of the scratches:
(Thanks to Sean for filming)
Once I had the parts sanded up to 3000 grit I installed a Sisal buffing wheel onto the new grinder/polisher/sander at TS. It’s a great tool! Big enough to do a project like this.
I’m simulating this pic with a non-spinning wheel:
I then put white polish on the sisal wheel and made a pass over each part to start to bring out the shine. Once all 38 parts were done I installed a soft cotton polishing wheel, put red jeweler’s rouge on it (the kind that you use on fine silver and gold), then started over and polished each piece until they sparkled. But I wasn’t done yet!
I then put the pieces into my storage box that I’d made at TechShop on the laser cutter (the box is in the “Because-I-Can” category). Then, one by one, I took each piece out and put a coating of Mother’s aluminum polish on them, followed by a final coat of Mother’s Billet Polish. These last two use a chemical reaction to get any surface oxidation off and give it a final, final polish.
If you’re keeping track, all of the above means that each coat gets ten different passes of progressively higher grits. The first grit, 400, is usually my final grit when I’m woodworking. For R2, that was the starting grit. By the end of the process I’ve polished the 6061 aircraft aluminum up to a chrome-like shine.
After a total of over 600 hours of work, here is the final result. Aluminum ain’t supposed to look like this, folks:
Finally, I brought the parts home and wiped them down with a soft rag to get any little bit of polish remaining off of them before I took them to the anodizers.
The anodizing company is doing the job for an extremely inexpensive rate. When the plant manager saw that it was an R2 frame he was really excited about it. The normal charge from another company is $500 but he’s doing it for $70 (basically cost, I think). I told him that all of his employees would get their names etched into the frame as thanks. Might even buy them pizza when I pick it up. It’s a really screamingly great price for a job like this. They even agreed to mask and plug any questionable holes that might interfere with the process. They’re going above and beyond since it’s a nice change from the generic metal unidentifiable parts that they usually do.
Why go to all that work to polish up to such a ridiculous shine if the parts are only going to be anodized black, you ask? Well, the final color will be black, but the final finish takes on the finish of whatever the unanodized surface looks like. If it’s bead-blasted then the finish is matte. A brushed aluminum finish will give you a brushed anodized look. And a stupidly-polished aluminum will look something like this:
So thats where the project stands right now! I have to admit that I’m a little nervous knowing that the box of parts is sitting in the anodizing warehouse. I’ll be glad when I get it back.