Blast cabinet liner

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BadDog
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Blast cabinet liner

Post by BadDog » Thu May 30, 2019 3:23 pm

This topic started on another thread that I didn't want to take it further off topic, so I'm taking it here to continue.

Original thread for reference

Most relevant commentary from that thread.
Harold_V wrote:
Wed May 29, 2019 1:05 am
Yeah, soft materials are a great barrier for blasting. Fact is, it's soft rubber that is used in masking tomb stones so they can be "engraved" (sand blasted). It's readily available in rolls, with a self adhesive backing. Apply the rubber, then remove the portion you want to engrave. Hard rock is very quickly cut that way.

I used that same rubber (1/16" thick) to line the interior of my blast cabinet (to prevent creating holes). It's just now starting to fail, but only because it's gotten hard. It's been more than 25 years. It was never perforated in use, so it's extremely resistant to abrasion.

Traces of grease on objects to be blasted slow down the process something fierce, and it's never a good idea to introduce any to your blasting media. That's why I suggested degreasing before blasting. I try to keep my media free from oils so they flow properly.

H
BadDog wrote:
Wed May 29, 2019 4:04 pm
Me too. I've got a rather large cabinet, big enough to put a few 16" truck wheels in. Either from the big door on one end, or the front side with the glove holes is split so it slides to each side for smaller items. It has a return funnel built into the base below the expanded metal work surface, and a 4" line going to a cyclone separator with suction/propulsion driven by 1(?) HP Baldor motor, and "fines" ejected out the back. It sounds like a turbine engine idling when it's running, very loud, and the fines are a problem for everything within 20 yards or more.

Between the fines problem and getting it out of my shop to run, I find I rarely use it even when it's the ideal tool. Since I live in Phoenix with nearly no rust problems, I wanted to store it out under my awning, and build a water bath on the ejection side to manage most of the fines. But a friend who had done that with a similar large cabinet advised against it. He said it was in good shape when put out there, but due to the perpetually raw steel surfaces generated by blasting, it developed terminal rust in only a few years.

With all that said, I'm interested in what you said about the rubber sheets used for granite etching. When I got it, the cyclone separator had abraded a hole in its case from the returned abrasive stream. I already was already on that path when I welded it up as I used a layer of silicone to provide a (hopeful) protective layer where the abrasive is hitting. But now I'm thinking maybe just clean it out and paint the inside to seal it up, and then line it with your rubber mask sheets. Same sheet also as an upgrade for the cyclone hopper repair. The turbine impeller also has severe erosion with a few perforations, which I suspect is part of why it's SO loud. Finding a replacement for that is much lower on priorities, and zero if I can't get it more generally useful.

No idea if that's practical, or will prevent decay, but storing it outside my shop would make it FAR more useful.

Question is, where do you get such sheets?
pete wrote:
Wed May 29, 2019 5:22 pm
What about painting the items with a rubberized truck bed liner product Russ? Or MSC, McMaster Carr etc sell a variety of rubber sheets and the easy to get contact adhesive would be more than enough to bond it in place. In mining the conveyor shute's and just about everything in the grinding and milling process involves huge volumes of highly abrasive rock. Even the big ball mills get rubber faced bolted in replaceable liners. Lot's of parts get sent out to specialty firms for rubber lining bonded in place as the rubber will still wear out over enough time, but that's way to expensive for home shop parts. Can you hook a shop vac up to your blast cabinet with the vac's exhaust run outside for the dust?
Harold_V wrote:
Thu May 30, 2019 3:13 am
BadDog wrote:
Wed May 29, 2019 4:04 pm
Question is, where do you get such sheets?
Hmmm. That's a good question. It would help if a guy knew the name of the product involved. I recall going to the maker of headstones to buy what I used, and that was many years ago, as I mentioned. With the proper name, it shouldn't be difficult to find and buy. Wish I knew more.

Here's a link that shows some being applied, and the results of blasting.

https://www.bing.com/videos/search?q=ho ... &FORM=VIRE

I may have found a source for the masking material. Give this a try:
https://www.hittmarking.com/category/sa ... -stencils/

H
RSG wrote:
Thu May 30, 2019 6:31 am
BadDog, you can buy sheet rubber from MMC with or without adhesives on the back. In many thicknesses. It's what I used to line my one vibratory finisher. Look under the "Abrasion-Resistant Polyurethane Rubber Sheets, Bars, and Strips" subtitle

https://www.mcmaster.com/rubber

Harold, Your setup sounds perfect for the type of blasting you require. As you mention my setup requires more control for texturing and surface finish so different medias and pressures. They tell me if I keep my pressures under 20 psi the beads will last for a very long time as you are doing more peening than abrading. Regardless of research I have a lot of testing to do to refine, or "dial in" the process for my application.
Russ
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BadDog
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Re: Blast cabinet liner

Post by BadDog » Thu May 30, 2019 3:25 pm

Thanks for the references. A brief look at each indicates that it may be price prohibitive. I'll investigate more when I have time to focus on it, and maybe see if I can find a local granite blaster so I can get just the quantity I need. I also need to get my exact dimensions so I can get a better idea on excessive waste volume vs smaller pieces tiled together.

Another question. The thicker options would obviously be ideal, but I'm wondering if the thinner wouldn't be ok for an infrequently used home shop blast cabinet. The 7.5 mil thick seems a bit on the shy side, but maybe not since it wouldn't be subject to sustained direct impact from the gun.
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RSG
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Re: Blast cabinet liner

Post by RSG » Thu May 30, 2019 3:52 pm

7.5 mil seems a bit thin to me. It might not take long to tare through it especially if you are using Garnet or Silicon Oxide as a media.
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BadDog
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Re: Blast cabinet liner

Post by BadDog » Thu May 30, 2019 4:07 pm

That's what I was thinking, but sometimes I overthink things. :oops:

I was thinking 1/16 would be a good minimum thickness, but have nothing to base that on but gut feeling.
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warmstrong1955
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Re: Blast cabinet liner

Post by warmstrong1955 » Thu May 30, 2019 4:18 pm

I'm confused.
I have a blast cabinet, and it's not lined. I have worked with many, on different jobs, and they weren't lined.
I also worked at a dealer, that sold Empire cabinets. None were lined.

Or am I missing something here???
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BadDog
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Re: Blast cabinet liner

Post by BadDog » Thu May 30, 2019 4:29 pm

Because it's such a mess (and takes up a lot of space), I want to store it outside under my shop awning. Liberates the space, and makes it MUCH more convenient to use without having to first remove from shop, get it all setup, and run it outside to allow the exhaust fines to disperse across the yard. When I mentioned this plan to a friend of mine (also here in Phoenix), he indicated that he had tried just that some years earlier with a similar cabinet, but that due to the perpetual raw sheet metal inside the blast cabinet, his rusted beyond use in a matter of a few years and was scrapped. He strongly advised I not pursue outside storage, and I've followed that advice.

But the net effect is that the vast majority of jobs for which it would be ideal, I find another way to accomplish just to avoid the (dig out stuff around and on it) move, setup, run, cleanup, re-store. The initial comment regarding linings got me thinking that maybe I could clean it up good, etch the metal, and provide a good sealing paint job to prevent the rust from storing outside. Of course paint won't last, so on top of that, to protect the paint, these soft sheets would protect the finish from direct impact of blast media.

And then there is the alternative idea of some sort of rubberized bed liner. I'm a bit less confident in that approach, but it's undoubtedly cheaper and easier, so might be inclined to try it depending on the economics of the sheet lining.
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warmstrong1955
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Re: Blast cabinet liner

Post by warmstrong1955 » Thu May 30, 2019 5:21 pm

Ahhhh....OK....I get what you are gettin' to....
:)

As far as bed liner....the stuff that comes in a spray can, won't live a long time. I use it on my old swamp cooler to stop the leaks. Works, but I have to respray it every couple of years. (I keep threatening to get a new cooler....and then end up spraying it again)
The real stuff, like Rhino Lining, or similar....I think would last forever. Been beating around my '03 pickup with all kinds of parts and junk for years, and it's still there....no holes. It's still a bit flexible, not hard, so that's a good thing. Like was said, flexible stuff....beads and sand bounce off. Seems to me that would be worth pricing out.
Problem with self adhesive stuff, is the places that don't 'self adhere', or with contact cement....the spots you miss. Not to mention the corners etc.

A friend of mine bought some stuff a couple years ago, to do the lower parts of his 4X4, rather than paint getting torn to shreds by the sand & rocks. I forget the name, but I'll ask him, and how it's looking since he put it on. Similar to Rhino & other polyurethane liners, but can be done without a kazillion dollars of equipment.

I'll letcha know.

Bill
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SteveHGraham
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Re: Blast cabinet liner

Post by SteveHGraham » Thu May 30, 2019 7:34 pm

Not to hijack the thread or anything, BUT...what kind of CFM do you need for little blasting jobs? Not car doors, but parts and so on. My small compressor has had some issues, and I am thinking of upgrading to a somewhat better small compressor.

I'm planning to put the big compressor in my garage, and I don't want a blasting cabinet in there.
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BadDog
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Re: Blast cabinet liner

Post by BadDog » Thu May 30, 2019 8:30 pm

Depends on the nozzle size, and related things (media specific, min pressure, desired finish, etc). But within the scope of achieving a particular goal, mainly nozzle size.

They make mini-blasters (soda mainly I think) about like an airbrush, and they don't need much air at all. But for real world cleaning of rusty and crusty paint parts, it takes quite a lot of CFM, so I don't think you'll be too happy running one from a small compressor. I've got a small hand held blaster (kind of like a gravity feed paint gun) that I use on small jobs, you can get one of those from HF, but of course you lose the media if you don't rig up a way to catch and reclaim it. Next step up is a portable hopper and siphon gun, typically more CFM. And pressure pots take less than the far more common venturi blasters, but that brings its own issues. So just how much CFM you need is going to be dependent on nozzle/gun size/design.

So, figure that out, and look that the manufacturer spec. But don't think "eh, it's close enough". In my experience, you do NOT want to scrimp of CFM running a blaster. It'll do little more than piss you off. It also works in cycles as your compressor cycles. Typically, at lower limits of acceptable pressure, just before it cuts on to refill, the media starts getting less and less efficient, and more and more troublesome in general. And if you keep going, and the compressor can't keep up, it just gets worse and worse. So don't plan to scrimp on CFM unless you like being aggravated. Unless that's your thing...
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Harold_V
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Re: Blast cabinet liner

Post by Harold_V » Fri May 31, 2019 1:42 am

In regards to air supply, I run a 5 horse Quincy, an old one, built in the late 60's. Bought it new, and have done nothing more than keep the intake filter clean, change the oil as required, and install one seal on the crank. It has been a wonderful piece of equipment. I leave it on all the time, as I have almost no air leaks, so it doesn't cycle much. It is rated @ 20 feet of air @ 175 pounds. I tend to blast @ 100 psi, and the compressor can keep up with me, even stop occasionally. My blast cabinet is not large--it's about 32" wide, a Trinco, the gun equipped with a 12 cfm air jet and a ¼" carbide nozzle.

I do not recommend a blast cabinet for a smaller compressor, not if you hope to use it for more than a few minutes. You'll deplete the air supply quickly, then you'll have to wait for the compressor to catch up. That process will go on endlessly, and you'll come to hate your blast cabinet.

Do not assume that a larger storage tank will eliminate the need for a larger compressor. While you'll extend the blast time, you also extend the recharge time. If a compressor can't produce at least as much air being used, it isn't large enough for the cabinet.

Blasting with bead at low pressure will do little damage to a cabinet, but if you blast with aluminum oxide, or any of the aggressive, sharp media available, you can expect holes to develop in the cabinet. All depends on how often you hit the same spot. Random blasting will be more forgiving than blasting a given item time and again, where one develops a routine.

Likewise, if you blast with bead, the nozzle will last indefinitely, assuming it's made of tungsten or boron carbide. The use of the aggressive media, especially at higher blast pressures, extracts a toll on the nozzle, the gun, and the air jet. That said, ceramic nozzles are nothing short of a joke. I strongly advise against buying a cabinet so equipped, as they simply are not suited to the task. It isn't unusual to have to replace the nozzle more than once daily, depending on how the cabinet is being used. I am now on my third carbide nozzle, having owned my blast cabinet, which I purchased used, way back in the late 60's.

H
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Re: Blast cabinet liner

Post by RSG » Fri May 31, 2019 6:40 am

BadDog - A thought for you, you could paint the inside of the cabinet (my preference is white) for the rust protection and then drape a piece of the rubber off the back wall so it is just hangs there to absorb the impact while the paint takes care of rust protection.

Steve - I have one of those hand held guns (Speed blaster) and it runs well at 90 psi/11cfm. As long as your tank is 60 gallons minimum it should be fine. It makes a hell of a mess of the backyard but worked in a pinch. That's why I bought the cabinet and am working on the negative pressure cabinet to avoid the dust issue. I also just bought a new compressor for my system with an output of 18cmf @ 100psi so I have lots, technically overkill for the type of blasting I do.
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Re: Blast cabinet liner

Post by Harold_V » Fri May 31, 2019 3:39 pm

RSG wrote:
Fri May 31, 2019 6:40 am
for the type of blasting I do.
Key words. How one uses their blasting equipment makes a huge difference in requirements.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

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