Media Blasting

[turbosax2]

Thanks for the info


Anybody else with experience, feel free to chime in.

 

[Defiant]

Carbon dioxide ice crystal media.

 

[OddNotion]

This is an ongoing project of mine as well. Years ago my automechanics teacher in high school had a small media blaster from harbor freight similar to what you can see here:
Astro Pneumatic ASTSBC1 - Google Product Search

We had it hooked up to shop air (no problem with water in the lines or low pressure there) and also bolted a flange to which you could attach a shop-vac hose. Without the shop vac, glass beads would blow out of every possible place. Having some negative pressure is essential in these things. The more CFM you ventilation system makes, the better.
Eventually the teacher bought a REAL shop media blaster and gave me the old H.F. unit. The gloves had holes in them, he kept the flange and shop-vac, and the top/window wouldn't sit right. I tried to make a new window but the stock one and my new one were so thin it just wouldn't seal. I gave up on it and it sat outside for years.

Last summer I bought this clamshell type:
Astro Pneumatic sand blast - Google Product Search

What a joke! From the first blast, beads were blowing out of the seal all over me. Both cabinets had absolute jokes for seals. While this one was rubber instead of foam, the blown Polyethylene shell had no rigidity and the sealing surface was warped. This pathetic strip of rubber around the edge was maybe 3/32" thick. I used massive amounts of Silicone on it to try to make a seal, but it would always find a new hole and blow beads.

I will post horror pics later.

So if your cabinet isn't sealed up like the Space Shuttle, with some sort of negative pressure system, expect to lose most of your beads all over the garage, house, neighbor's car (yep), and your clothes.

It seems like the one turbosax2 is considering has some advantages:
1. It's metal- this will help keep the shape of any sealing surface.....
2. The window isn't one of the doors- Lexan and acrylic don't like to have hinges or holes drilled in them.....

However, I see a lot of problems:
1. It's way too small. They don't tell you that you can't spray back TOWARD yourself and your arms and the gun take up a lot of space. The gun does not like to move around much either. I couldn't do all of my oil pan in the clamshell one, and neither will you in this one. You will quickly see how you can't fit parts that you'd really like to in there.
2. Two doors are neither necessary, nor desireable. At least caulk one of them shut.
3. Those two tiny ass clamps are not going to seal that thing, plus the door has 5 corners which don't seal well.
4. You will need a light but the ones that come in these cheap blasters always go bad from the beads.
5. It's not very deep (vertically) so you will constantly be lifting the grate and pushing the beads into piles on top of the pick-up tube.
6. The gun is a full sized blasting gun. It just doesn't fit in a tiny cabinet. Poor enigneering. The air and pickup hose will either kink, or be too stiff to shoot anything that isn't in the back-left corner, and not much bigger than a throttle body.

Mr. Peepers has the best solution by far.

While tolerating the beads all over me and everything , I was able to make some parts on my 180K mile eclipse look good with the clamshell blaster.


Note that the T-stat housing and PS pump were blasted, sprayed with brake cleaner, then painted with "Alumi-blast" paint from a can. The driver side engine mount was blasted, washed, then mounted



Sorry for the long post, this may have been better as a tech article, and may yet become one.

 

[white_dsm]

I might consider buying one of these, it will clean up a lot of parts in my engine bay which will help with my sale.


I hear of the saying, you get what you pay for, but if anyone finds a cheaper sand blasting setup than the harbor freight than post up a link!

 

[OddNotion]

Do not forget that you have to add the price of blasting media. It's best to get it from a parts store locally to avoid shipping.

A 50lb bucket of "medium grit" glass beads weighs, oddly enough, about 50lbs. Input 50 lbs into any shipping computer...........

I also recommend the fine grit glass beads. The medium-fine wasn't quite as fine as I was used to. Aluminum looks really good with a fine glass bead.

The parts place may not understand what you are asking for. If you say something like "it's similar to sand blasting" they might get the idea, but be prepared for the old "hold on- (muffled)hey jeff, do you know what "glass beads" are? do we have that?(unmuffled)......Sorry sir, we don't carry that. Try Advance auto"

My 50lb bucket was about 80 bucks from a local shop that has a lot of auto-body supplies along with everything else under the sun.

Auto body supply houses are a good place to start..............

 

[turbosax2]

Thanks for the help ejc83. You certainly convinced me that the Harbor Freight one is a waste of money. So I guess building my own is the way to go. My friends dad is good with wood, so maybe he can help me out.


Mr. Peepers - Do you have any blueprints for your cabinet? Or at least can you point out some of the major design aspects? Also, what gun are you using?


ejc83 - How do you like the look Aluma blast compared to bare aluminum blasted with fine grit glass beads? Do you have any close up pictures of the motor mount? How well does the Aluma blast hold up over time?

 

[TiradoCC]

eBay Motors: TP TOOLS SKAT BLAST 770 Sand Blaster Sandblast Cabinet (item 360034554546 end time Mar-28-08 17:18:59 PDT)

That is a decent sized blast cabinet, should take care of most parts that you guys need to blast.
When I first started powdercoating and blasting, Aluminum Oxide worked great for me.

If you really plan on using the cabinet often, I highly recommend buying one with a vacuum system.

 

[OddNotion]

ejc83 - How do you like the look Aluma blast compared to bare aluminum blasted with fine grit glass beads? Do you have any close up pictures of the motor mount? How well does the Aluma blast hold up over time?

I think it looks really good. At the GMU DSM meet people were asking how I got my PS pump and Tstat housing to look like "that"

I will take some pics of my stuff after having driven it all winter, so you can see how it holds up. I noticed that wiping it with a harsh solvent WILL hurt the finish.

It looks very close to blasted aluminum. Surface prep is key though. I bead blasted mine first which gives a good "tooth" for the paint to adhere to.

My medium grit glass beads didn't make it look as shiny as I wanted, so I tried the paint.

The motor mount was left bare because I didn't want to have to tape off the rubber or deal with the holes and irregular surface during painting. Blasting the rubber had no effect on it, and I just put a bunch of Tire Shine on it to keep it pretty and supple.

The medium grit bead actually made the mount look better in my opinion. It's not something I really want blinged out. It just looks new. My friend was like "THAT'S JUST PLAIN ALUMINUM!?"

I ardently encourage you to build your own cabinet. Mr. Peepers could probably fit an engine block in his! Make sure you build the bottom nice and deep so the beads stay on top of the pick-up.

I am a CAD drafter, but I don't have time lately to draw any plans. Someday soon maybe.

 

[OddNotion]

If you really plan on using the cabinet often, I highly recommend buying one with a vacuum system.

He is exactly right- we had this old, old shopvac in my Automechanics class that was super quiet. I'm looking at a small portable shopvac type thing at home depot for around 30 bucks.

You need some kind of filter though or else you will just suck all the beads out while they're swirling around the cabinet.

I'm using my stock NT Spyder airbox. I traced the MAF opening on the side of my old cabinet and then cut it out with a dremel. After that I bolted the airbox up with the stock airfilter. It's pretty big for this purpose!

To keep the media from just accumulating in the bottom of the airbox I bought a big window-unit air conditioner pre-filter from HomeRepo. I cut that into several mats and just laid them behind the airfilter and latched the whole thing shut. I have to mount a shopvac on there somehow. The hole is almost small enough for a 2.5" hose i think.

Pics to come....

 

[Mr Peepers]

I actually made it so I could fit an engine block in it. Hell, I can fit in it I'll try to get some dimensions tonight- ~3' tall, 3.5' wide, just under 3.5' deep.

I don't have any blueprints, just some dimensions I probably threw away.

IIRC, I made a skeleton box out of 2x2s and got it as squared up the best I could. I was really really anal about that for sealing down the road(boost leaks).

Every seam and joint was sanded flat.

For the bottom of the box skeleton I cut a 45* angle into some 2x4's so I could mount the bottom "funnel" easily. I covered all that with 1/4" and 3/8" wood sheets.

The thicker 3/8" was used in the front, back, and door for rigidity and to keep sand from eating through. I haven't had a problem with it anyway.

For the funnel I used some math(magic) to figure out how to make a rectangular box come together at a 45* angle. I painted it white in an attempt to make the sand slide better. The bottom was cut open and a block with foam was screwed to it if you ever need to drain the sand. A tube siphons the sand so you don't need to mess with it too much.

Hot glue(hey, it was the "high strength stuff") was used in every crevice and corner once it was together. I found some foam stripping and stuck it around the door opening and wedged the 1'x2' glass window between the stuff for a good seal.

The glass was just from an old window and holds up pretty well, I don't think it's the safest thing though.

The door was reinforced with 2x2's and hinged to compress the foam as it's closed.

For the light, I found a glass jar and threw a 100 watt halogen bulb into it, then stapled some sheet aluminum on the walls next to the light for reflection.

The grate was a piece of steel mesh(there's a name for it) with angle iron and flat stock welded to it.

The gloves Lovingly sewn by my grandma from an old pair of jeans and work gloves. Work great but the gloves I used were cheap and are now splitting at the finger seams(sand hurts!).

A shop vac is connected to remove any dust. I used one of the old attachments to shield it from directly sucking up any sand and barely find any in the vacuum. The filter needs to be shaken out every hour or so. It gets old. The cabinet is sealed pretty damn well and will make the gloves stick straight out once the vacuum is turned on.

The gun was an old craftsman one that I don't think you can buy any more. My dad had it laying around probably since the 80's.

The stand was made from more 2x2's. After figuring out how tall it would be for a standing one(and messing up some measurements) I made it a sit-down one.

Some more pics:

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I've used a couple other sandblasters before this, and I tried to fix everything I didn't like about them. I used the brightest light I could find, the biggest window, and the largest capacity I've seen. I can't stand working blindly.

Being able to sit down is a huge plus as well.

 

[OddNotion]

IIRC, I made a skeleton box out of 2x2s and got it as squared up the best I could. I was really really anal about that for sealing down the road(boost leaks).

, boost leaks........

It's cool that your grandma made those gloves. You need some rubber ones though. They won't eat away as quickly.

Seems like everything else you did is spot on. I'd get some lexan from Home Depot or Lowes for the window though. Imagine if it fell with your arms in the guillotine........

 

[Mr Peepers]

, boost leaks........

It's cool that your grandma made those gloves. You need some rubber ones though. They won't eat away as quickly.

Seems like everything else you did is spot on. I'd get some lexan from Home Depot or Lowes for the window though. Imagine if it fell with your arms in the guillotine........

I have some rubber ones, they're just uncomfortable and don't fit my large hands. I couldn't find actual sandblasting gloves for the life of me. I could have gotten some online but they didn't fit my budget and I didn't want to wait a couple days at that point

-the guillotine. I've used lexan extensively for other things, I just don't know if it would hold up to sand as well as glass. Have you tried them both? I know lexan at least wouldn't shatter if a part hit it.

 

[OddNotion]

The trick is using the acetate (or whatever) sheets that you get with the $10 Chinese bead blasters that are supposed to protect the window. They have an adhesive line around the edge.

Problem with those is, the micro pieces of dust work their way between the sheet and the window so you get even more obstruction. I've yet to try it, but rest assured I will use electrical tape to outline the edge of the plastic sheet to really seal it up. If you don't, you will have to polish the window (assuming it's plastic) to get the view back.

That's probably easier than risking chopping your arms off to change the sharp glass.

I don't know what the sheets are made of, but you can buy them from Harbor Freight or another media blasting company.

 

[turbosax2]

Mr. Peepers -

1. How big is your window?

2. Is there an easy way to empty the media out of the bottom? I was thinking about putting a hole in the bottom center of the funnel (possibly with a screen too to filter the media), then running a pipe from there to a bucket where the media can collect. This way I can quickly switch between different types of media just by moving the feed and return hoses to a different bucket. Thoughts on this? Also, the funnel portion could be made of something more smooth than wood so none of the media gets caught up.

3. Is your steel mesh floor supported by anything but the wood on the perimeter?

4. How / where do you hook up the shop vac? Is it the black thing on the door?


ej83 -

Let me know if you get around to drawing up some plans!

 

[OddNotion]

I wouldn't worry about a screen ON the device because most of the dirt that gets removed is near the same size as the media itself. You really wouldn't sift anyhting out except the odd nut or other small part you dropped into the funnel while blasting. Maneuvering little parts is hard.

You will want a hole in the bottom, without question. Let gravity do the emptying work. The larger industrial ones have a little flap/door on the bottom of the funnel that is parallel with the floor. When it swings open, there is no way any media can stay inside. That could be hard to make though.

My small plastic one has a round plug that pokes from the INSIDE. The media can be heavy and could push a plug OUT.

Seems to me that some large diameter ball valve with a lever would be good to mount. You should be able to close it and I'm sure there are lots of flanges that would bolt up to the wood.
pvc ball valve 2" - Google Product Search

Medium Density Fiberboard would be good to build the cabinet with. It has some structure to it and is easy to cut (with power tools). Use wood glue and screws (pre-drill your holes) to hold it together.

 

[Mr Peepers]

Mr. Peepers -

1. How big is your window?

About 1 foot tall and 2 feet wide.

2. Is there an easy way to empty the media out of the bottom? I was thinking about putting a hole in the bottom center of the funnel (possibly with a screen too to filter the media), then running a pipe from there to a bucket where the media can collect. This way I can quickly switch between different types of media just by moving the feed and return hoses to a different bucket. Thoughts on this? Also, the funnel portion could be made of something more smooth than wood so none of the media gets caught up.

I cut the bottom out and screwed a plank of wood in its place, with some foam in between to keep any sand from leaking out. When I get near the end of a project, I tend to start taking shortcuts. It works, but could be better.

I cut a hole near the bottom and siphoned the sand directly from the bottom of the funnel. A lot of dust would come out the bottom if it drained into a bucket, but I like the idea of being able to quickly switch medias. It may get tricky with a vacuum attached as well.

The only time I've considered needing a mesh screen was when I was removing loose paint that came off in chips. It would clog once in a while and I'd need to blow air down the sand tube. Eventually it broke the chips down into smaller pieces, and/or got sucked into the vacuum.

I haven't had any problems with media getting caught on the sides, a 45* angle seems to work well, and easy(er) to build.

3. Is your steel mesh floor supported by anything but the wood on the perimeter?

Nope, I welded supports underneath and thats about it.

Enough to hold me, 170 lbs or so. I bounced around in there for good measure.

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The grate is 1/8" thick. I'd suggest going to a sheet metal shop and ask for scraps, I got that for probably $5.

4. How / where do you hook up the shop vac? Is it the black thing on the door?

I used one of the triangle-like attachments as a shield to keep sand from getting directly sucked into the vacuum. It's located on the door near the back. I barely find any sand in the bottom of the shop vac, but the filter quickly fills with dust.

EDIT: For you, ejc83.

 

[OddNotion]

the image of Mr. Peepers in his unitard, bouncing around inside his blaster, shredding an apple......

 

[turbosax2]

I just found out one of my friends friends has a medium sized blast cabinet. He said I can use it whenever if I provide my own media. So I guess I don't need to build my own for now - but once I get my own place I'm definitely building one!

I think I'm going to go with the coal slag for paint removal / general purpose and fine glass beads for a nicer finish.

 

[OddNotion]

Can't argue with that.......

Another trick I learned is using some rust dissolving jelly to get rid of the rough work. A heavily rusted item takes forever to bead blast, especially if there is pitting. You can get the jelly at most auto places. I think mine was made by Permatex in a short, fat spray bottle. More of a liquid than a jelly, but it stuck to my engine block without dripping, then I just rinsed it with water. It's nasty stuff though, so rinse it well.

The parts of my block that were rust were just a gray kind of color. I then painted with high temp black, still looks sweet. All this with the engine in the car!

 

[absolute_DSM]

^Does that actually eat at the rust or just cover it?

 

[OddNotion]

No, it is actually a chemical reaction that makes the rust either wash away, or turn into something else. It is sometimes called "Naval Jelly" (not like that stuff you find in your belly button) and it has a nasty smell.

Read about the science here:
Phosphoric acid - Wikipedia, the free encyclopedia

Rest assured, after scrubbing all the nasty stuff off, the bare, grey metal was Iron, and took the paint well. It still holds strong after a winter of driving.

 

[turbosax2]

I'm going to blast my throttle body and transmission. Anybody have advice for preventing damage to them and protecting the insides so media doesn't get in the transmission?

 

[Defiant]

Duct tape, and a sharp eye. Use the thickest tape you can find, double-layer it, and use lower blasting pressure. Be careful to not get under the edge of the tape. The adhesive and the thickness provide an absorbing layer that lets most of the media bounce off.
However, a throttle body will do better in a bucket of carburetor cleaner. Look for a dip tank.

 

[Mr Peepers]

Duct tape, and a sharp eye. Use the thickest tape you can find, double-layer it, and use lower blasting pressure. Be careful to not get under the edge of the tape. The adhesive and the thickness provide an absorbing layer that lets most of the media bounce off.
However, a throttle body will do better in a bucket of carburetor cleaner. Look for a dip tank.

Real Media Blasters go by skill alone.

 

[AndrewD5418]

You wanna blast some stuff for me peepers?