Abrasive blasters

mickyd · Post by **mickyd** » Mon Oct 19, 2009 1:41 pm

A topic came up on the yahoo 10ERusers group that really caught me eye regarding a homemade abrasive blasting system that uses baking soda as the abrasive for CLEANING a painted surface. A quick google search also found that the method also works effectively at bringing an aluminum surfaces back to life AND even for paint removal.

Having spent 6 hours Saturday stripping all of my painted ER10 parts using paint stripper, I now wonder if this could have been accomplished with a similar system.

tom_k/mo · Post by **tom_k/mo** » Mon Oct 19, 2009 2:39 pm

Mike, as one that has an abrasive blasting setup (for Sandcarving) here's a couple tips. If you're going to get serious about doing any abrasive blasting, for oxidation removal, paint removal, etc... don't use a syphon system, use a pressure pot. Pressure pot abrasive units use much less air pressure (at the nozzle) than syphon systems and can do a much better job, removing rust/paint quicker. Instead of a large volume of air sucking media through a venturi, the media is actually pushed through the hose/nozzle from a pressurized container. You also have much better control over the media/air mixture. Most syphon systems run at about 90PSI. My pressure pot has 90-110PSI input and the output at the nozzle is regulated at 20-25PSI and I'm able to cut glass, marble and granite with Aluminum Oxide abrasive.

Harbor Freight makes a couple cheap blasting cabinets that are set up as syphon systems, and they also sell pressure pots.
Small Cabinet
Medium Cabinet
Large Cabinet
Small Pressure Pot
Large Pressure Pot
The cabinet can be modified easily to work with the pressure pot rather than a syphon blaster. Using a cabinet allows you to recycle your abrasive, which reduces blasting costs and allows you to operate with a smaller amount of abrasive overall. I have heard that the small and medium cabinets from HF are rather "leaky" and you might want to use some silicone caulking when assembling so that the media doesn't leak out of the joints in the cabinet.

I would also recommend that if you try media blasting, make sure you have adequate ventilation and use a respirator. Silicosis is a hazardous side effect of inadequate ventilation and protection with certain medias.

mickyd · Post by **mickyd** » Mon Oct 19, 2009 3:05 pm

Hi Tom,

I am missing something on this whole pressure pot concept.

Can you explain the purpose of the pressure pot? (or for that matter the whole system from compressor to the nozzle)

What CFM does the air compressor need to deliver?

Answers will lead to more questions.

Mike

JPG · Post by **JPG** » Mon Oct 19, 2009 3:14 pm

mickyd wrote:Hi Tom,

I am missing something on this whole pressure pot concept.

Can you explain the purpose of the pressure pot? (or for that matter the whole system from compressor to the nozzle)

What CFM does the air compressor need to deliver?

Answers will lead to more questions.

Mike

Methinks the pressure is input to the 'pot' above the media. The pressure forces the media and some air out the bottom into the hose. from there it travels through the tube to the nozzle. There is a pressure gradient through the media IN the pot. c'nest pa?;) The CFM will be less than a bernoulli(sp???) system.

tom_k/mo · Post by **tom_k/mo** » Mon Oct 19, 2009 3:36 pm

mickyd wrote:Hi Tom,

I am missing something on this whole pressure pot concept.

Can you explain the purpose of the pressure pot? (or for that matter the whole system from compressor to the nozzle)

What CFM does the air compressor need to deliver?

Answers will lead to more questions.

Mike

Mike, JPG answered some of the questions. A pressure pot system is a closed container in which you put your abrasive. It is pressurized to 90-110PSI (from your compressor). A regulator and dryer is recommended between the compressor and pressure pot. A hose comes out of the pressure pot and goes to the inside of the blasting cabinet. You can either have a deadman's valve on the end of the hose to shut off the air/media flow, or you can have a Richman foot switch that operates a solenoid to shut off the air/media flow. I use the foot switch because it is much easier to work with when working with sandcarving projects.

The purpose of a pressure pot is to provide more abrasive, at a lower air pressure/volume and more efficient use, AND to be able to more easily adjust the media/air mixture.

The CFM requirements of your compressor are dependent upon the pressure you want/need and the nozzle size you're using. Smaller nozzles will require much less air volume, but increase blast times. HERE'sa table that shows the relationships.

On another note... the latest technology in media blasting for cleaning, paint/oxidation removal is Dry Ice blasting. The machines make dry ice pellets as you blast, and after hitting the object being blasted they evaporate, no clean-up...

mickyd · Post by **mickyd** » Mon Oct 19, 2009 3:43 pm

[quote="JPG40504"]Methinks the pressure is input to the 'pot' above the media. The pressure forces the media and some air out the bottom into the hose. from there it travels through the tube to the nozzle. There is a pressure gradient through the media IN the pot. c'nest pa?]
Got it. I was missing the fact that the abrasive goes into the pot. (nothing like getting confused right out of the chute!!) This makes my question to Tom RE: describing the whole system mute......hopefully he's not typing away

. I have to digest a few things than I post again.

mickyd · Post by **mickyd** » Mon Oct 19, 2009 3:50 pm

tom_k/mo wrote:Mike, JPG answered some of the questions. A pressure pot system is a closed container in which you put your abrasive. It is ......

Got it!! I was missing the fact that the blasting media goes into the pot. My mind was stuck on a siphon type system. Nothing like getting lost right out of the chute!! The table is helpful for me to see what CFM I need vs. nozzle size. I assume this is a 100% duty cycle table and deviating away (large nozzle or less CFM) will only decrease duty cycle. Safe assumption?

tom_k/mo · Post by **tom_k/mo** » Mon Oct 19, 2009 5:05 pm

Yes Mike, safe assumption.

mickyd · Post by **mickyd** » Mon Oct 19, 2009 6:53 pm

If this youtube advertisement is supposed to make you want to jump in and spend a few hundred $$ on a soda blast system, I would think that they would have shown and example where the paintS being removed a little faster!!! I thought the video was stuck until I watched it a couple times. Maybe my 6 hour paint stripper method wasn't so bad after all.

Is this the best an abrasive blaster system can do at typical home compressor pressures / CFM or is it because they are using baking soda vs. other abrasive materials?

mickyd · Post by **mickyd** » Sun Oct 25, 2009 4:43 am

Well, I made up a quick and dirty prototype of the soda blast system that I referred to in post 1. I wanted to try it for paint removal. I followed the instructions as specified except I didn't have the correct 7/16" diameter clear vinyl tubing or the small OD air nozzle. Instead, the tubing was the larger 3/8" diameter tube and the nozzle...about twice the diameter as that shown.

Stuck the vinyl tubing into a small box of regular baking soda and did a test hit on the nozzle level. The soda BLASTED out of the tube in a cloud. Pretty impressive so I took one of the ER castings that still had a little bit of paint on it and blasted it. In about 15 seconds, I used up the entire box of baking soda!!:eek: It DID remove the paint. There was about a section the size of a fifty cent piece that was cleaned right down to to the base metal.

The hose and nozzle diameter were definitely too large so I picked up the right stuff at Home Depot for less than $10. Tomorrow (actually today since it's 1:45 am), I'll give it a try and let you know how it worked. Also decided that the only way to do this is to use an enclosure similar to a blast cabinet so that I can reuse the soda. I'll make an enclosure using a big cardboard box and some glass for a window.

Picked up a 50 lb. bag of blasting soda from Harbor Freight for $30. The blasting soda is a little more course than the household soda so it should work better.

Not a believer yet but it may just have promise. I'll find out later