Media Blasting Advice
If you're thinking about setting up a small-scale media blasting outfit, let me offer you some free advice: there's a good chance it's going take more than you think.
Last month, I mentioned that I already have a small media blasting setup built around an Eastwood bench top blast cabinet. After using that setup for months, I learned a few practical things about media blasting equipment.
First off, let me explain why it was that I chose the equipment that I did. Outside of money, the biggest influence on my choices was space. The Old Classics and Performance Garage was beyond tiny. I couldn't even move around the car unless I was sideways. The only space I had to fit a blast cabinet was half a bench — the other half was taken up by a small bench top parts washer. The space was so confined that if it weren't for the fact that it was so frustrating to work in and nearly eliminated any pretense of productivity, it would have been comical. The equipment also needed to be able to do two things: be mobile so that it could be setup and broken down every time it was used, and the cabinet needed to be light enough that it could be easily transported should I need to put it in deep storage. The second biggest influence was the electrical system in the garage: it was 110V and had a very, very weak circuit — and I didn't have the ability to do anything about it. The third most influential factor was the kinds of items I would be cleaning: small parts that ranged from nuts and bolts to oil pans. The fourth influence was the results I was looking for: no marring of the substrate — that is, neither profile (roughness of the cleaned substrate) nor shape (distortion) — while being able to reclaim and reuse the media as much as possible.
After some research I came to understand my basic equipment needs: A bench top blast cabinet, a mobile air compressor capable of running on 110V power, a dust collector, plastic media, and odds and ends like personal safety equipment, and media blasting accessories to make the job easier.
The major items I chose were as follows:
- Eastwood Bench Top Blast Cabinet — Plastic: I chose this model because of its size and weight. The only thing about this cabinet that stood out as an obvious flaw was that it could only handle media as aggressive as glass bead — however, because I was going to use plastic media, it was perfect for me. Another negative was that it used a 14 CFM @ 90 PSI gun — we'll get to this issue in a minute. Eastwood no longer sells this cabinet.
- Craftsman 2 HP, 33 Gallon, Vertical Portable Air Compressor: This was the biggest, baddest mobile air compressor on the market I could find at the time (somewhere around 10+ years ago). It could run on 110V power and it had an output of 6.4 CFM @ 90 PSI. While horsepower and tank size are an easy way to market an air compressor, for the purpose of gauging the effectiveness of an air compressor for use with a media blasting outfit, the number you're concerned with is the CFM or cubic feet per minute rating. Also, take note of the pressure needed — it matters. If the compressor meets your needs for pressure, be certain it can build that pressure at the pressure the gun requires. In this case, the CFM requirement for the gun in the cabinet I have needs to be produced at 90 PSI as stated above. Another useful number is the duty cycle — because, if it can't handle running as much as you'll need it to, it'll wear out — again, I'll get to this issue in a minute. This air compressor is no longer available.
- Eastwood 90 CFM Dual Filtration Dust Collection System: Basically, this thing is a tall, 53 1/2", stationary vacuum cleaner with a bag in it to collect media. Eastwood still sells this unit.
- Skat Plus Plastic Abrasive: Plastic blasting media (PMB) in a 30-40 grit size. It can be used for a while before it turns to powder. However, as mentioned in Media Blasting & Metal Preparation, PMB is known to remove paint and other coatings less aggressively than virtually any other media — including soda. I haven't used soda, so I can't tell you how well it works in comparison, but, Soda is a one-time use media that requires a special setup, so there you go. This product is still available from TP Tools.
Here's how this setup worked for me: I was using it to clean up mostly painted parts from the LX in pretty good shape with little to no corrosion that I needed to repaint or powder coat. If there was rust, I used a non-destructive chemical rust remover like Rusteco to remove it — so neither the corrosion on these parts nor the fact that PMB doesn't do a very good job removing it was a concern for me.
The biggest issue I ran into was with the air compressor. First of all, I had to shut off everything throughout the house that was on that circuit or it would blow. In fact, it still blew — just not as easily. Second, I could only get a few minutes at a time to blast before pressure in the tank got too low and the compressor had to take a few more minutes to repressurize it. So, progress was both choppy and slow. Holy crap, I gave that thing a workout and the compressor's motor started to lose its oomph after a month or two. That's what happens when you don't have enough CFM to run the equipment you're using and if Matt Joseph is correct in Media Blasting & Metal Preparation, he says it's necessary to have an air compressor that exceeds the requirements of the media blasting setup you're using — even double the required output. What I can tell you from my various experiences, is that media blasting is strenuously demanding on the air compressor — and the one I bought was rated 7.6 CFM below the requirement of the gun in the cabinet and consequently I exceeded the air compressor's 50%-75% duty cycle recommendation an awful lot in order to get anything done.
The cabinet had a couple of flaws — which may be why Eastwood no longer sells it. First of all, obviously if you want to run anything more aggressive than glass bead, you're SOL, but, more importantly, it didn't seal well and the seal on the plexiglass window would breakdown pretty quickly — even when only using PMB. After just a day of use, the LX was covered in a fine dust (click on photo above) and media was everywhere throughout the Old Classics and Performance Garage — not to mention caked on my face, in my hair, and inside my clothes. Mind you, I was using a cabinet, I wasn't free blasting. Yes, I wore a respirator, eye and ear protection. However, this cabinet is lightweight and easy to store, so bonus, there. Also, on the positive side, because I was using PMB I never needed to replace a nozzle on the gun, and although I had to replace both the seal around the window and the protective shield on it — repeatedly — nothing else ever wore out.
The air compressor's need to constantly recharge the tank wasn't the only thing that kept things slow. The gun just didn't have much spread, so, combine that with the slow-cutting PMB and the pauses in blasting, and it took forever to get anything done. I think it took me two days of blasting to remove the coating on the LX's brand-new oil pan. In case you were wondering, it was scratched and I wanted it powder coated to match the finish of the original oil pan on the car.
Now, I haven't used or tested any of this equipment, so I can't tell you if it would really work, but, if I had to do it over again, here are the changes I would make:
- Eastwood B20 Bench Top Blast Cabinet: It's about the same size as the plastic unit I own, but it's made of steel, the lid looks more robust and hopefully seals better, and the gun in the cabinet only requires 7 CFM of air to run at 90 PSI — at least, that's what I can see and read on the Eastwood website.
- Eastwood Elite QST-30/60 Scroll Air Compressor: This compressor is mobile, but its horizontal instead of vertical and has a much larger footprint. The tank is 30-gallon, but it has a quieter, 4 HP scroll-style compressor motor that pumps out 12.7 CFM of air at 90 PSI. Although not double, this one has a rating significantly higher than the gun in the cabinet — which should hopefully help it keep up with the demands of blasting. And trust me, running a regular air compressor near you — even with ear protection — you'll appreciate a quieter compressor.
- Eastwood 90 CFM Dual Filtration Dust Collection System: No change here. A blasting cabinet needs to be cleared so you can see, plus it removes a lot of the pulverized media so it doesn't get mixed back into the good media and reduce its effectiveness.
- Skat Plus Plastic Abrasive: No change here — although slower than other media, it's reusable and it doesn't mar the substrate of metals. I would start with this media to clean paint and other coatings.
- Glass Bead Blast Media: This is a peening media (see Media Blasting & Metal Preparation for more detail on that), so it doesn't cut, but it also doesn't heat the substrate the same, so less chance of warping sheet metal parts — like the valve covers on the El Camino — while still being effective for rust removal. Also, although slower for cleaning rust from steel, if it's the correct grit, it will work great for cleaning aluminum castings as well (I just have to keep it away from machined surfaces and out of passages and other internal casting areas) — so I wouldn't have to keep a third media around for the little blasting I would do with this setup. This is what I would follow the PMB with after I knew what kind of rust was on the part. See the note further down for using media blasting on both steel and aluminum. You can grab this media from Eastwood or TP Tools.
- Other Changes: I wouldn't media blast in a garage attached to a house, again — nor would I prefer to media blast in an area I use to work on cars or parts, especially if I used a harmful abrasive like glass bead or worse, because it can get inside parts like engines and transmissions and destroy them when they're running. I'd also need a dedicated 220V circuit for the new compressor. Next, more space — even though the old outfit fit in the space I used it in, it was way too tight to function well. For the sake of productivity, even a small, mobile setup like the one designed here needs a little space for movement — and to layout both pre-blasted and finished parts. Also, extra space for storage of equipment — ideally, this setup would have enough space in the shop that it wouldn't need to be taken down. Oh, and the Eastwood Elite QST-30/60 Scroll Air Compressor is considerably larger than the Craftsman unit I had, so, more space isn't just a luxury, it's a necessity.
- Aluminum Note: if you're planning to blast both steel/iron and aluminum parts, you need to consider two separate cabinets or run the likely risk of cross contamination and the unstoppable electrolytic corrosion you'll get when you embed particles of either metal into the other — this corrosion won't stop if you cover it with primer and paint and will lift what you've applied.
I can tell you that over 10 years ago, the cheap setup I bought ran me about $800 + supplies and media, and as of this writing, the new setup would be somewhere around $2,400 + supplies and media — and both these setups are enthusiast-grade, not industrial grade — so media blasting isn't a cheap investment. Or rather, doing it cheaply is still expensive if you plan to do it effectively. The price just goes up from expensive to more expensive, to a lot more expensive. But, as Matt Joseph notes, it's simply the best all-around method for cleaning metal. Whether you choose to go the media blasting route is up to you, but — from my research and based on my experience — for many situations, you won't find a better process for stripping parts.