Aluminium surface finishing, glass bead blasting?

[cameraman32]

I've been taking aluminum parts i've been making to my local anodizing guy, and saw some parts from another customer there. The surface looked great, kind of a smooth matt, and i was told that they used a bead blaster on the parts before being anodized.

I've been looking into blasting cabinets but know nothing about it, I have a big knowledge gap in this area. Is glass bead blasting what I want? Can someone give me some tips on what someone needs to get to do some glass bead blasting? I'm wondering what kind of equipment to get I've found some inexpensive tabletop blast cabinets with guns included at harborfreight, but do I also need some sort of hopper? How does the glass media get into the gun's airstream? Can you re-use the media?

Any advice would be appreciated. Thanks!

Stewart

[in2steam]

I cannot answer if its what you want that is almost as subjective as asking what color it needs to be when its done.


As far bead blasting, part size is important that determines what you need to buy. The Harbor freight cabinets are at best OK, you will based on my own fupar want a light if you get cabinet bigger then 12"x12". You will also need to get an air compressor of several horsepower, I would say that 3HP is bare min. the least you should get, the bigger the piece the more HP you will need. The media itstelf is also a choice, you can use multiple different types, for alum you might want to use walnut shells or plastic bead. Bead blasting is incredibly messy, the HF cabinets leak terribly so you will need to seal it up the best you can, also its best done outside, otherwise vent to the outside.

The media itself is sucked up through a tube and ejected into the airstream it works just like a paint sprayer does. The nozzles do wear out and will need to be replaced. I purchased the the cabinet last year for $100 and got a cheap compressor(2HP for $)90 because my use was only about 2 square inches. In the end I should have gotten a much larger compressor, both tank and horsepower. Its 2 HP and I can only go for about 10 seconds before I loose most of my pressure even with the compressor running. The nozzle and suciton tube are not the best, you actually can buy the guns at HF to repalce the ones that come with it, those look like they would work better as they have a hopper on the gun. The media can be reused in most cases but it does break down after time. The silcon media esp nasty when it breaks down, it leaves a thin white film which is not good for you all over. The cabinet has a hopper in my case, but you can get ones that don't have them I reccomend you get a free standing unit if you are planning on doing this in volume for the cleanup aspect, also you will need some silcone to seal it up after you purchase it. If you have a compressor already you may want to invest in some tanks for reserve capicity esp if its smaller in size as you use a lot of free air doing blasting.

Any other questions?

chris

[cameraman32]

Hey Chris, thanks so much for the detailed explanation, you've definately helped me figure some things out.

I'm sure the harbor freight ones are cheapo, but can't beat the price. I think i'll get a desk top unit since my parts are so small, and put it on a roller cart to take it outside to use. A friend will let me borrow his 5hp, 20 gallon compressor, that should have capacity to run it.

Thanks,
Stewart

[steve323]

I used a glass bead blaster in a previous job. It would drain the air tank really quickly even with a huge tank. Expect to run intermittently even with a 5hp compressor.

Wear a good dust mask even if you are outside. You don't want to breathe any of the dust.

Glass beads leave a nice finish on soft aluminum. It can warp thin pieces by pounding many tiny dimples on one side. I was blasting a project case made from 0.050" thick aluminum. I had to blast the inside to straighten it back out.

[RICHARD ZASTROW]

As for reusing the media, I would think you can till it "wears out". I assume this will be used only for aluminum. If you blast iron or steel, the media will be poluted with ferrous debris which will impinge into other material. If you blast aluminum after steel with the same media, then your aluminum will rust.
It happened to me on stainless steel.

[cameraman32]

Thanks for the tips, I won't mix metals, only aluminum. I got a $99 kit from Harbor Freight, it does drain the air tank fast, but the results are stunning. It is almost like spray painting on the finish, looks great. I definately need to replace the seals, it leaks quite a bit.

Thanks!
stewart

[in2steam]

Steward one thing I have not tried yet, but rigged was an extra line of air from a manifold were I hook up the gun. This runs through a valve, to a line which I put inside the enclousre, I hooked it to 1/2 pipe which I drilled a series of smaller holes around #25. I want to turn that on to help clear the air before I open the cabinet. I do mostly cast iron, so its rather nasty and messy, I can't see either after a few seconds, thats why I wish I had bought the light. I should note I vent this to the outside, so the idea is to push the dsut outside before I open the door.

chris

[chad123]

Just a little something to think about.. I have been doing the same thing for a project i am working on.
After the bead blast things look awesome, after anodize they still look awesome. The problem is it is very easy to scuff the part. Now the anodize is usually harder that whatever is scuffing it and it can be wiped off but bead blasted and anodized parts look dirty easy, especially with dark colors.

I still am looking for a good way to deburr and hide tool marks that doesn't take forever and still leaves a nice finish..

.02c

Chad

[ImanCarrot]

I bead blast ally parts using a high pressure water jet and powder mix. The whole thing is enclosed in a sealed cabinet with heavy duty plastic gloves to allow handling of the part and gun (like a chemical cabinet thingy).

The finish comes out very nice, but if you want a real nice finish.. then diamond turn it hehe... here's one I made earlier: