The Letterville BullBoard: Sandblasting questions??

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Posted by Jack Davis (Member # 1408) on :

I have a friend with a nearly new 35 cfm 10hp commercial compressor. He has offered to let me use it to blast with, if it will work well. My questions are is it adequate for GOOD blasting with the proper blaster and nossel, and what size should the nozzle be. I have used several methods, and never seemed to have the right combo. I spent 2 hours the other day at a commercial sandblaster on something I saw accomplished in 30 seconds by another blaster a few years ago with one that you pull behind a truck for swimming pools. Unfortunately he had it going so furious, I could hardly get him to let up. I would like something in between. I will be blasting redwood and or cedar, and leave the HDU for carving. I would at least be able to accomplish a 4x4 in about 15 to 20 minutes, 1/2 to 5/8 inch deep Thanks, Bronzeo

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Jack Davis
1410 Main St
Joplin, MO 64801
www.imagemakerart.com
bronzeo@prodigy.net
http://www.imagemakerart.com

Posted by Glenn Taylor (Member # 162) on :

For me, I like to blast at 90psi with a 1/8" dia. nozzle. I prefer to use A-5 grade sand. Its about the consistancy of table salt. For me, it seems to cut pretty well and allows for very sharp detail. It doesn't beat the grain down like the larger grain sands do.

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**********
“During my service in the United States Congress, I took the initiative in creating the Internet.” (Al Gore, CNN’s “Late Edition with Wolf Blitzer,” March 9, 1999)
**********

Warning: A well designed sign may cause fatigue due to increased business.

:) Design is Everything! :)
Glenn Taylor
in beautiful North Carolina

http://members.tripod.com/taylor_graphics
walldog@geeksnet.com

Posted by Wayne Webb (Member # 1124) on :

Ditto Glenn,
With that many cfm's you shouldn't have any trouble sustaining 90 psi with a 1/8'' nozzle.
Your compressor will probably be able to cut in and out and take a breather.
Ours only produces 25 cfm and keeps up fine.

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Wayne Webb
Webb Sign Studio,Inc.
creators of "woodesigns"
"autograph your work with excellence"
webbsignstudio@digitalexp.com

Posted by Jack Davis (Member # 1408) on :

I suppose the air supply hose size makes a big difference also. Possibly that is part of the problem. The units that I have been using are wearing me slick, instead of the wood. Two hours on 3 square feet is pretty laughable. Is everybody using pressure pots or some using a draw feed unit?

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Jack Davis
1410 Main St
Joplin, MO 64801
www.imagemakerart.com
bronzeo@prodigy.net
http://www.imagemakerart.com

Posted by Wayne Webb (Member # 1124) on :

I use a pot and 1/2'' hose. Siphon fed ones are too slow. How big is your nozzle?

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Wayne Webb
Webb Sign Studio,Inc.
creators of "woodesigns"
"autograph your work with excellence"
webbsignstudio@digitalexp.com

Posted by Ricky Simpson (Member # 1318) on :

Jack,
I feel your pain. My first sandblasted sign(hdu) of any signifigance took me forever to blast. Blast a minute, unstop valve....blast a minute unstop valve....I think you get the picture. I think I am going to sub out the blasting in the future ,especially the larger ones.

Also I am fairly certain everyone uses a pressure pot, otherwise the process would be even slower I think, but then my advice with my lack of experience on the subject of blasting isnt worth alot.

I plan on trying a smaller tip on some samples to see if that will help me with my lack of compressor size (7 hp 60 gal., 11 cfms @ 90psi).

Moisture was my main culprit due to the compressor running so much.....hence my thoughts on the smaller tip. I used 1/8 I think before. I bought a .10 and plan to try that. Also I used glass beads which I have been told tend to absorb moisture more so than other mediums. Also I think I probably had too many coats of primer which made it more difficult to blast. Still undecided what medium to use especially with the health concerns of using silica sand.

Let us know when you hit on a good setup.

Ricky

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Ricky Simpson
Simpson Signs
South Central VA, USA
"railroader aspiring to be fulltime SignArtist."

[This message has been edited by Ricky Simpson (edited October 17, 2000).]

Posted by Rick Sacks (Member # 379) on :

Jack, if you're gonna be doing enough to invest in some equipment, perhaps you should go to some auctions. The tow behind compressors that drive jack hammers (pun intended) often run in the five or six bill range and the 200 pound pots another two bills. The next investment would be a GOOD filter for breathin air under the hood. I find an 1/8" nozzle to be a waste of time and also it concentrates the blast to such a small area that it takes work to blend. Look for 1/4" tip and a 125 cfm producer, and you'll be in the league of covering 10-12 square feet with a bag of sand in ten minutes. Oh, yes, the 10 hp unit will drive an 1/8" tip.

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The SignShop
Mendocino, California
"Where the Redwoods meet the Surf"

Posted by Henry Barker (Member # 174) on :

Rick is on the ball there!

I started with a TIP pot and small nozzles uneven coverage, too long a job blasting etc, that was driven by our workshop compressor which is 5.5hp (500litres per minute) sorry about the metric! A good air hood and filter will use that capacity alone, and then you need abit to blast with!

We have a diesel towable compressor and use 1/4" nozzle and blast HDU in minutes with fine sand, our pot with that nozzle requires 2000litres per minute, you have to figure that out yourself. We use Clemco equipment the same hood that's featured on the Anchor blast-lite ads in the sign mags, and their pressure pots, with remote control (deadman)

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Henry Barker #1924
akaKaftan
SignCraft AB
Stockholm, Sweden.
A little bit of England in a corner of Stockholm
www.signcraft.se
info@signcraft.se

Posted by Golden (Member # 164) on :

The answer you need to hear is not the one you want to hear. Rick Sacks said it about right. You need a 100 to 125 CFM minimum compressor and a 1/4" nozzle (new) and a 200 lb. pot or larger to do serious work. With that set up, you can expect to cover about 1 square foot per minute at normal depths with normal horizontal fine grained redwood.

When you look at compressors, make sure to look at the charts showing CFM in relation to 1/4" nozzles, because a small compressor can appear to create fairly high CFM with a tiny nozzle. For the most part, any electric motor version won't do the job. I checked with WWW Grainger and their largest compressor wouldn't consistently drive a 300 lb pot at 1/4" nozzle size...that was a 25 hp three phase compressor.

This is one case where there really isn't a middle ground. The small TIP pressure pots will blast wood and glass, but you eventually pay the price in time. Sandblasting a 4 x 12 panel is bad enough with proper industrial equipment, but doing it with little league equipment is no fun and not very profitable.

Lastly, never use a diesel or gasoline powered compressor to supply air to a hood, even with a filter. Carbon Monoxide fumes are not filtered out and can kill you. You must supply the air to your hood with an electric compressor, and even that takes a fairly good sized compressor if you have a built in air conditioner to the hood.

New compressor $10,000 to $16,000
New pressure pot $600
New hoses and connectors $150
Hood $100
Airconditioner and filter $300

You can get the compressor and pot used and save quite a bit of money. Rent the set up 10 or 12 times first so you know what you really need. You can blast $3000 to $10000 worth of signs for a $200 full day rental.

Mike Jackson

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Mike Jackson
Golden Era Studios
Jackson Hole, Wy
www.goldenstudios.com/

Posted by Jerry Mathel (Member # 526) on :

Rick and Mike are steering you in the right direction. I have a 105cfm Schramm gas powered compressor, and even that is a little small for any serious blasting. I have a 100 lb. pot and it is way too small.

I also have a small "TIP" blast pot with a media recovery system, but about all it is really good for is blasting small glass pieces.

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Jerry Mathel
Jerry Mathel Signs
Grants Pass, Oregon
signs@grantspass.com

Posted by Dave Sherby (Member # 698) on :

Rick and Mike are right on! 100 CFM compressor, 1/4 inch nozzle and 200 lb. pressure pot are the minimums for efficient blasting.

Mike, where do you find a new pressurized hood for $100??? My Bullard was $300 and used filter case (new filter) another $100.

Also, according to my sandblast equipment supplier, the gas air compressors that are a V8 engine reconfigured as a 4 cylinder engine and 4 cylinder compressor are a definate no no for breathing air. But a rotary vane or rotary screw compressor set up with the exhaust well away from the air intake can be used for breathing air if the proper filter is used. I'd love an electric breathing air compressor, but at $1200 it'll have to wait.

By the way, steer clear of those V8 compressors. Rotary screw compressors are the ultimate. Rotary vane is next choice. Either one will outlast those V8 conversions big time. And when it comes to electric, 35 HP 3 phase is the bare minimum as even that size will run continuous.

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Dave Sherby
"Sandman"
SherWood Sign & Graphic Design
Crystal Falls, MI 49920
906-875-6201
ICQ: 21604027
sherwood@up.net

Posted by Glenn Taylor (Member # 162) on :

Rick Sacks learns the hard way not to use a diesel powered air-compressor for a fresh air supply while blasting.....

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Warning: A well designed sign may cause fatigue due to increased business.

Design is Everything!
Glenn Taylor
in beautiful North Carolina

http://members.tripod.com/taylor_graphics
walldog@geeksnet.com

[This message has been edited by Glenn Taylor (edited October 18, 2000).]

Posted by Henry Barker (Member # 174) on :

HI Mike,

I am abit confused by your comments on air filters

I talked to my supplier today, he recommends changing the "active" filter at least once a year if not twice, as it breaks down after a time regardless of how much use.

As I mentioned earlier we have a Clemco system here and our air hood was around $350 dollars and the filter about the same, with replacement cartridges running about $100 a piece, we have a trailer mounted Atlas-Copco diesel compressor, this is one of the worlds largest compressor makers, and there are hundreds thousands using similar set ups in day to day abrasive cleaning.

Maybe the air intakes or the regulations are different in the US, but I can't see commercial companies on bridges, boats etc working with separate electric breathing apparatus.....you got me worried! Anyhow my local dealer are sending over some info they had on breathing filters etc from Clemco in the US.

I think the main point here is buy the right gear for the job and maintain it to a high standard to ensure a long and healthy life!

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Henry Barker #1924
akaKaftan
SignCraft AB
Stockholm, Sweden.
A little bit of England in a corner of Stockholm
www.signcraft.se
info@signcraft.se

Posted by Jack Davis (Member # 1408) on :

Henry and all blasters, The very serious and seldom thought of problem with an air supply from a gas or diesel powered compressor is the air supply intake on the compressor itself drags in the fumes from the exhaust from the motor very nearby, and tranfers it to the output line. You don't want this kind of air in your helmet......I have experienced 2 such incidents in the last years, (one last year) where 3 friends were sleeping on a houseboat at the Lake of the Ozarks and had powered their air conditioner with a gas powered generator on the deck about 10 feet from the A/C..The A/C pulled the fumes right through the windows..They never knew what hit them. They weren't found for over 3 days .. ..Another incident about 20 years ago where 13 divers from my neighborhood dive club went into a large deep lake and only 5 returned. They had air tanks filled with air that had been compressed with a gas powered portable compressor. Fumes into the intake of the compressor head Again this same problem. If you will notice on the dive boats, the compressor motor exhaust is usually 8 to 12 feet tall so this dosen't happen. Even in the old movies, you will see this. I don't think that the filter on either the compressor or any mask is going to detour these fumes. Not one that I am going to trust after my experiences.....This is something that people rarely consider...Get your air from a clean outside source. A smaller electric compressor with filters for the oil in the air is a reasonable choice say most......Bronzeo

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Jack Davis
1410 Main St
Joplin, MO 64801
www.imagemakerart.com
bronzeo@prodigy.net
http://www.imagemakerart.com

Posted by Golden (Member # 164) on :

To follow up on my comments:
My compressor was a Schram 125cfm gasoline powered v-6 (it might have been a v-8), with half the cylinders running the engine and half creating air. It was an old used rental compressor and is still in use to this day, 14 years after we moved here and I had it close to 6 years in Oklahoma.

The newer rotary screw compressors might handle the air system a little differently but I was told to never trust the air coming from a gasoline or diesel powered engine. I was also told, over and over, that NO CARBON AIR FILTER will remove carbon monoxide from the air...only oil and gunk. I believed them and took it seriously. We always just used the air supply from my 3 horse 3 cylinder Dayton Electric 240v compressor. It had to run hard, especially when the air contitioner unit was on and working.

Dave, I made the list with prices from memory of my purchase over 20 years ago. It seemed like the Empire hood was reasonably priced but the Air Conditioner add-on was quite expensive. For the most part, my list was just to give someone a basic idea that you need to budget some serious money to get the industrial stuff, and when you see a complete sandblasting unit (minus the compressor) in a TIP catalog for less than $500, you aren't getting what you need for blasting wood.

20 years ago, I paid $750 for the equipment forward from the compressor. I later added the OSHA required automatic shutoff for the nozzle which cost something like $350. It wasn't required at the time I bought the set up but was well worth the extra money. People can adjust the current prices with what I paid 20 years ago but I don't think that part has gone up drastically.

As one other side note, TIP sells a goofy little hood for people to use when blasting. That thing really looks unsafe to me since you are breathing in the air around you while blasting which is probably full of silica dust and redwood or foam dust. None of them are good for you and probably all of them can kill you. With the airfed hoods, the air supply is brought in to you by pressure and the excess air is blowing the good air out, keeping the contaminated air from entering the hood area. This is one area of the industry where you absolutely don't want to try to cut corners and save a few bucks. That option could kill you.

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Mike Jackson
Golden Era Studios
Jackson Hole, Wy
www.goldenstudios.com/

Posted by Wayne Webb (Member # 1124) on :

Jack,
This is what I use.
Set me back about $700 bucks or so.
You can get a 100' hose to go with it so you can keep it at a good distance from that CO source. http://www.bullard.com/products/Resp/airClimate/edp10.cfm

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Wayne Webb
Webb Sign Studio,Inc.
creators of "woodesigns"
"autograph your work with excellence"
webbsignstudio@digitalexp.com

Posted by Henry Barker (Member # 174) on :

I'd be interested in making some more enquiries, about the risks from carbon monoxide, we have a later model rotary screw compressor, and I had never thought before today about those effects, always assumed that as the exhaust and air intakes where at opposite ends and that the machine was revving hard that the exhaust was forced away behind you. I still wonder how much more you inhale than say walking down a busy city street in summer, if you are wearing a real air hood? We have the very same hood that Anchor feature in their SignCraft ad. Glad that you brought the matter up Mike its always good to find out anything new that we might just take for granted.

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Henry Barker #1924
akaKaftan
SignCraft AB
Stockholm, Sweden.
A little bit of England in a corner of Stockholm
www.signcraft.se
info@signcraft.se

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