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MG MGA - Blast Cabinet
|I am currently spending hours scraping a lot of my engine external painted parts back to bare metal for repainting. Have any of you made yourselves blast cabinets for this sort of job? |
I have a good compressor, so I reckoned I could usefully use a cabinet such as the one from Frost depicted here: http://www.frost.co.uk/item_Detail.asp?productID=8066&frostProductName=DIY%20Blast%20Cabinet%20Kit&catID=16&frostCat=Cleaning&frostSubCat=&subCatID=
|Get one bought Steve, you can't make one for that price..|
|Robert (Bob) Midget Turbo|
|I made one of those a few years ago and found I hardly ever used it. It is now used mainly as a cupboard. The biggest problem is that the appetite for air is enormous and my compressor just couldn't cope. The compressor is a SIP one with a 3hp motor and is rated at I think 12cfm. The other big problem is the lack of a system to clear the air. Within seconds of starting the whole cabinet fills with dust and you can't see what you are doing so unless you want to keep stopping every few seconds you really need some sort of extraction system and that is not included - all there is is a vent with a filter. Although the finish produced was good it is very slow process getting there. Parts also have to be thoroughly degreased first or the blast media is not effective. |
I find a wire brush on an angle grinder much quicker and for engine parts just as good.
|I got a big second hand cabinet on eBay a couple of years ago for about fifty quid. It has dust extraction and a turn table inside. I have a high capacity compressor and a lot of space. It's noisy and dusty so you really need a dedicated room. |
I used to take parts down to a local shot blasting place before that. It didn't cost much to have stuff blasted and primed.
If you don't use the cabinet that much it's money, time (to build) and space. If you do use it more, then that plywood is no use and you need extraction.
My advice would be to find your local shot blasting place!
|I built mine out of plywood for about $75 Canadian, everything. Best thing I ever made. I have a Campbell-Hausfeld 20 gal tank compressor, about 6 cfm. Works fine with a C-H gun. The dust is extracted via a port to the Shop-Vac. This is essential. I will post more when I get out the camera. I find it a very satisfying operation to clean up bits that are impossible otherwise. Window is simply a sheet of 6 mil clear PVC which I change as it gets blasted opaque. Also there is a lamp inside. Gloves are old leather work gloves and these are attached to sleeves from old jeans legs.|
|I built mine years ago using plans from:|
It was a build using parts scrounged where I could. The tempered glass is from a wall shelf. The arms were made from an old leater jacket sewn to a pair of used electric power workers safety gloves. I lined the inside of the glass with a disposable clear vinyl to protect the glass. I coated the inside with latex caulk to minimize the abrasion damage to the walls.
I run a 2HP 110volt Sears compressor (15-20 years old). It will not keep up with the demand but does a good job for small items. One trick is to use the smallest orifice you can find to minimize the air usage. I have gotten a lot of use from it. Nice to have it sitting in the garage for a quick cleaning of parts. A Lamp is important as is a port for a vacuum and fresh air intake. Baffle the intake to prevent the sand from escaping.
I also built a pressure blaster from an old water heater. It does a much quicker job but is awfully messy.
|The glass is not necessary. 6 mil PVC is OK on its own.|
See pics - self explanatory I think. Dimensions to suit yourself.
|One at a time I guess|
|As somebody else mentioned, the secret is the compressor, in USA cabinets are good choices starting around $150 Dollars, incluiding glass window, gun, etc., available in Ebay also. The limitation is the size of the parts required to be sandblasted. Bigger cabinets are more expensive.|
Depending the application But the best of my findings I do believe is the vaccum sand blaster, see this video: http://www.ehow.com/video_2200670_sand-blaster-vacuum-car-restoration.html
I picked up a bench top blast cabinet on ebay for $75. Running a 2hp compressor, so the run times are limited to 30 -45 seconds, but works well on anything that will fit in the cabinet as long as you take your time. As several have mentioned dust control is a must. I ran some 1Ē plastic pipe from the cabinet into a sealed, empty 2.5 gallon plastic bucket, then cut a hole for the vacuum connection. A few other notes worth mentioning:
The Plexiglas will become fogged over time. Clear plastic protectors are available or just replace the Plexiglas.
Wear a good dust mask and eye protection.
When putting together the cheap commercial units use plenty of extra silicon sealant in all of the joints and seams.
Pay attention to moisture in the compressed air. I donít have a really good dryer on my compressor so have to stop from time to time to dry out the separator and air lines.
Using 80 grit glass bead. The dark abrasives seem to make it harder to see what you are doing.
Pickup a small wire basket for the small parts.
|I currently own one of the TP blast cabinets, and have extensively used it and another of their cabinets that my dad owned. For the effort you will spend building a decent one, IMO it is better to just buy one of theirs, pre-built. And as mentioned, the things that will make it a viable tool are not generally the cabinet itself, First, you have to have a compressor that can keep up with it, or it will just be an exercise in frustration. Second, a good vacuum, or if you can afford it, one of their dust collectors. I'm currently using a shop vac, but the continuous use is eventually going to kill it, and at that time I plan to purchase one of the TP vacuum units that is made for longer periods of use.|
The other important thing is what abrasive to use. Most people use glass beads, but in my experience they are way slow, and not very aggressive, plus they dull quickly. The very best abrasive I have used is silicon carbide, which is fast cutting and lasts a long time, although it is probably too aggressive for use on aluminum. My stepmom uses it a lot in her glass etching business. I can't get it easily right now, so I use aluminum oxide, which is the next best thing, and I can buy it locally. When using either of these abrasives, you will go through nozzles quickly, so invest in a carbide nozzle, which will last a long, long time. Even using glass beads the carbide nozzle is a huge upgrade, and actually costs far less over its lifetime than constantly replacing ceramic nozzles.
Also, I wouldn't bother with one of the cheaper units sold by the discount places. TP makes good stuff, and they stand behind it with parts support that you probably won't get from harbor Freight, et al.
|Steve, Many of our ideas seem to co-incide. I have had one of those very inexpensive blast cabinets for many years and it is quite useful but, as someone has said, it is really air delivery that is the key. My compressor is only about 8cfm and the system is quite useful but really only for smallish items (and saves driving around, waiting for things to be done, etc). The cabinet quickly fills up with dust (again as mentioned) but I have got around that by using a small (very inexpensive) domestic exhaust fan with some 2 or 3 inch dia tubing well above the cabinet (so as not to suck out the abrasive) which then exhausts outside. There is quite a bit of fiddling around but I know that you are resourceful enough to get there and it is worth it in the end because the system can be made to work on small items.|
|I have had a TIP 780 unit for 15yrs and their vac34 system. One of the best things I've ever done.I use a 6hp Sears compressor with medium nozzles and even it has to work to keep up.In the past I too used wire wheels but it does not really clean down into any pitting.I had to buy a abrasive reclamer since at times I use the carbid abrasive and that vac system really really pulls, and you'll waste abrasive if you don't have one.I also use the carbid nozzles like Del does. Check out tptools.com alot of good there.|
|All good stuff and very helpful. Ready assembled would appear the easiest way to go.|
The following link is to one of our UK high street suppliers. I this the sort of thing I could consider? http://www.machinemart.co.uk/shop/product/details/heavy-duty-blast-cabinet/path/parts-washers-blast-cabinets
|The one in the ad looks similar to mine. I note that they recommend 10cfm and that is not surprising, although lesser delivery is still OK provided that you wait each time for the receiver to build up. I also had trouble running out of abrasive (in the centre where the nozzle draws from) and modified the chute to avoid this. In the end quite a handy device but for larger jobs (which don't fit into the cabinet anyway) I still get the professionals involved. The latter use huge electric motor/compressor combinations, something like 20 hp motors, etc (no wonder we struggle!).|
|Steve, is it big enough? Can you get a wheel in it for instance, also can you manipulate it when inside and get at everywhere? I don't see a reservoir for the sand at the bottom, how does it pick up?|
I have just been to look at it. It does have a hopper base and drain hole. Not big enough for a wheel, but to be honest I was not looking for that size cabinet. More a case of the smaller parts such as tappets covers, rocker box, timing chain cover etc.
That all said, the chap in the shop said I would be wasting my time unless I had a compressor with at least a 3hp motor and very large storage tank. I think mine will not be capable.
|Steve, if you purchase a cabinet like the one shown, the corners will probably not be well sealed and you will have dust all over the place. As John mentioned above, use a sealant over the cabinet joints, where the sides are folded over and screwed together. Also, I don't see a port for a vacuum, also a must IMO for this work.|
There is a vacuum port to the left of and below the light. It is covered by a rectangular filter. It does not show in the photo, I grant you that.
|sTEVE, i JUST HAVE A SO CALLED "4hp" COMPRESSOR. bUT THEY LIE IT WILL RUN 115v AND 15a OR 220v AND 8 A, really only 6-7 cfm at 100 psi. But I can run it continuously, pressure drops to about 50 and it is good enough. Get the gun about 1" off the work.|
|The info in my previous post re professional gritblasters was by memory. In case I had exaggerated I spoke to my friend who has such a facility. He tells that his compressors are 200cfm and that the electric motors are 50hp!|
|There is a pro shop near me called Media Tech. The guy has a 75-HP compressor sitting on a 300 gallon air tank, and he thinks it isn't big enough. $7/hr for electricity to run it.|
|It all depends on how long you want to spend on a job. As I said, a 6 cfm is good enough for small jobs, even up to a wheel. If you are charging $50 /hr commercially it is different|
|I have this compressor, and it has no problem keeping up with my small blast cabinet, or my pressure sandblaster:|
When I'm using either blaster, the compressor runs frequently, but not continuously. Tank pressure never drops much below the 150psig or so that activates the pressure switch. I usually set the regulator to 80psi or so. I also run a fairly large water trap, which I consider to be a must-have item if you are going to be doing much blasting. The pressure sandblaster can be adjusted to tolerate some moisture, but any water getting into the cabinet's siphon blaster can shut it down fast.
Another point to keep in mind when you are looking at a cabinet, is that what will physically fit inside, and what can effectively be blasted are two entirely different things. I can just barely put a wheel from my pickup truck inside my blast cabinet, but it would be nearly impossible, not to mention time consuming, to try blasting the whole thing that way. It's good for small parts, but really not much else.
On the other end, there are some really large cabinets available, but you run into another limitation because every one of them uses a siphon gun, which really limits the speed and effectiveness of the blast process. At some point, even though that car fender, motorcycle frame, or other large part may physically fit inside your cabinet, you're better off just suiting up and doing it outdoors using a pressure blaster. Also, larger cabinets necessarily have a shallower angle to the reclamation chute, so the bigger the cabinet gets, the worse media recovery will be. On my dad's old huge blast cabinet, we actually installed a "shaker" motor on the outside of the chute, that ran whenever the cabinet was being used, that added vibration to aid in the flow of media down to the pickup tube.
|Nice compressor, Del, but a funny ad. I would never consider buying an air compressor without knowing the air delivery specifications. Would you like to enlighten us? Got a spec plate on that unit?|
|Husky page says it's a 12.6 cfm|
I've built several of them (too big to bother moving long distance when relocating)and have used them to death. I modified my last one lately by hinging the glass door which makes it easier to load and easier to wipe the dust off the inside of the glass when blasting a lot of parts. I hooked up a vacuum cleaner to a port I installed in an upper corner and drilled a smaller intake hole on the opposite side of the box. No dust to speak of. If you can smell the dust its too much. Good luck.
|Dragged this back from the archives.|
I had a long conversation with the staff in Machine Mart, but finally went ahead and bought a cabinet, even though they advised me that my compressor is inadequate for the task.
I did a test on an old and rusty horn. I am delighted with the result and find the cabinet okay for the small tasks have lined up.
Once I move south and, if I have any funds left, I will probably acquire a larger compressor.
|A good answer to the compressor problem is just more tanks. You can hook as many as you like together to increase air capacity, helps a lot in getting things done, and the small compressor can catch up later. You can get tanks from dead compressors, junkyards, dead trucks etc, and you can put them in the attic or outside - out of your way. Tanks in series give you progressively drier air too if you remember to drain them once in a while, but in parallel they just add storage. In parallel you only need a single air hose with a quick coupler to plug into a manifold block for each tank. I plug my carry around air tank in to the compressor system, so it's always full when I need it, and it adds to my storage. A system I use sometimes has two 80gal tanks and you can do several blasting sessions of as long as you can stand before the compressor comes on.|
Another trick is multiple compressors. Set the main one at whatever ON pressure you want, and the secondary to a somewhat lower pressure. Then, when the primary can't keep up, the secondary kicks in. You can use a small compressor for day to day air, and only have the big one kick in when needed. Saves electricity and wear on the expensive unit, and if you have wheels on the little one you can use it as a portable. And when one dies in the middle of a job, you are not airless!
A breath of fresh air to my thought process.
This thread was discussed between 22/11/2009 and 10/02/2010
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