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This topic comprises 2 pages: 1 2
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Topic: Tin Man Lamphouse
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Mark Gulbrandsen
Resident Trollmaster
Posts: 16657
From: Music City
Registered: Jun 99
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posted 05-16-2003 10:45 PM
First off this is not meant to be a critique of someone elses work. I'm sure the rebuilds that alot of technicians out there do are absolutely first class, and that some are more than likely questionable. This is all only meant to draw attention to the problems associated with Sand Blasting alumnium castings of equipment used in our industry. Indeed many non-critical castings can safely be blasted if you like as they are not close tolerance castings!
I have yet to find a media that doesn't alter the metal surface at least somwehat. Medias that remove the paint are going to at very least frost the unfinished, and underlying surfaces...which is changing the precision surface that was done in machining! Plastic bead is useless....the only thing I have not tried as of yet is high pressure water jet paint removal as there are not many places that do this.
I've personally done ALOT of sandblasting in the past and consulted with countless companies and salesman that CLAIM to have the best stuff, but I can definately tell you that media that will remove paint and not alter the underlying surface simply does not exist. The media has to be harder than the paint you're removing to get any results. Also very frequent media changes are required with really soft media as it quickly turns to dust!!
Dave Mccauleys way will work to some extent, but makes the chore even more time consumming than the norm. I gave up blasting pretty much completely along time ago except for very minor bead blasting of small parts only on occasion, or if the surface finish calls for it. Tim: First off, the term Sand Blasting is really a generis term and does not necessarily mean that one uses actual sand. There are hundreds of different blasting medias available on the market today, and yes, some are actually sand, but most of them are actually sand derivitaves. DuPont Star-Blast is a good example of a very popluar sand derivitave blasting media. Solvent alone does not work to remove paint. It may soften it somewhat but baked enamel as is on these castings can be a pain to remove. There are many dip chemical methods that allow you to strip paint off castings yourself that work very well and are ALOT less time consumming, and most importantly safe for the person doing the rebuild, and for the enviroment. Many are available in 55 gallon drums. Most of this old paint, especially black wrinkle, contains a good deal of lead that only special dust collection systems are capable of removing and not re-exhausting back into the atmosphere that you and your employees are breathing.
A good place to start is a place called Redi-Strip..... http://www.redi-strip.com/index.htm I have used them to strip hundreds of sets of castings in past years with no problems....plus.....its cheaper to have them do it than it is PAY ANOTHER EMPLOYEE to perform the merciless task of sand blasting day in and day out. He can be performing more important tasks for whom ever he works for. Overall, on a large scale, or for just one projector dip striping is the far better route for everything involved and no changes to the metal occur at all. Just remember that you also have to legally dispose of those tired 55 gallon drums of chemical stripper!! Mark
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Tim Reed
Better Projection Pays
Posts: 5246
From: Northampton, PA
Registered: Sep 1999
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posted 05-17-2003 11:10 AM
Mark, you misunderstand. He's protecting the machined surfaces, he knows what he's doing - I don't know how else to say it. And, yes, the media turns to dust very quickly, it's designed to.
His shop is very well equipped and was installed for this applicaiton, you really have no idea. Everything, every step of the process, is in an enclosed, filtered booth - no one breathes anything. By the way, he does all the work himself, nothing is "sent out".
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