How do you prevent clogging your random orbital sand paper from cured resin?

Discussion in 'Boatbuilding' started by magentawave, Aug 25, 2013.

  1. oldsailor7
    Joined: May 2008
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    oldsailor7 Senior Member

    Just scrap the orbital sandpaper and buy some new.
    Next time you sand make sure the surface is fully cured before you use the orbital sander.
     
  2. magentawave
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    magentawave Senior Member

    I found that running the orbital or big sander/grinder/polisher with 40 grit at slow speed minimizes the clogging.

    Buy some new what? Sandpaper? Yeah sure but those big 40 grit discs are expensive man.
     
  3. SukiSolo
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    SukiSolo Senior Member

    I just keep a wire brush handy! When using 40,60, 80 grits on orbital 1/2 sheet sander, if it threatens to clog, just back off a bit keep it from overheating surface and frequent little quick wipes with the wire ensure clean cutting grit.
    Works on epoxy and polyester for me anyway. Very occasionally a small 'lump' needs removing with a knife or screwdriver tip.

    Mostly it is the initial cut, where there is either amine bloom or less than fully cured polyester. That is when to be constantly checking. Also make sure the dust is constantly cleaned away before it builds up (partly with heat) and becomes clogging 'putty'!.

    Others may have better ways, so I can only vouch for a mode I can work with.
    Also assumed is proper commercial grade sandpaper.
     
  4. PAR
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    PAR Yacht Designer/Builder

    Slow speed and very aggressive grit will slow clogging, but following established procedures is really the only true prevention. You can't sand goo, it has to be cured. If you have no choice but to work a gooey batch of whatever, a scraper maybe with some heat, is far better.
     
  5. boatbuilder41
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    boatbuilder41 Senior Member

    There is not going to be any easy way, in one case,I did use a sandblaster, a big commercial blaster. I save a lot of money by using diamond blades and flush mount arbours. It may not be practical for the one time builder to spend the extra money for expensive blades not knowing how to properly use them. Diamond cutting blades with a flush mount arbour can be used in sanding and for long periods of time. They do clog, but easily cleaned by cutting into a concrete block. These blades are typically used in granite fabrication.check out a tooling company call GRANQUARTZ. FOR LESS THAN $100.00 you can get a good 5 inch piranha blade and a flush mount arbour. You wwill be impressed.
     
  6. viking north
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    viking north VINLAND

    There are sandpapers specifically developed for fiberglass sanding that are less susceptible but not immune to clogging. I use SIA Abrasives out of Switzerland but I'm sure other big abrasive companies must market a similar product.(The latest are colour coded purple.) They are available in all formats, sheet, rolled strip,pre cut strips,and circular of 4, 5, 6, in. diameter with and without dust collection holes. Also plain, stick on and velcro backing. I have had good success with this product with what I estimate as 50% less susteptable to clogging and fantastic cutting characteristics. When i encounter gooey FRP surfaces I hand sand using a longboard equipped with 40 grit paper usually a cut up sanding belt just to skim off the surface until I get a good flow of clean FRP dust. This talc like dust also helps reduce the gooeyness of the area yet to be sanded. Once I have accumulated an initial supply I use my draftsman brush to spread it over the unsanded area to dilute the gooeyness of the new cuttings under the sandpaper. Much the same as using fine sawdust to clean up a resin or oil spill. The handsanding isn't as labour consuming and gumming up as you would suspect once you get a suppluy of the clean FRP dust to work with. When you have handsanded the area in this manner you can then use your electric ROS with very little to no gumming up of the paper. My chosen ROS tool bar none is the 6 in. Metabo. With it's great vacuum port,adjustable speed and orbital controls there is almost no job too tough to handle. I do however prefer the lighter Porter Cable ROS tools for finishing. In addition to the Metabo I have three Porter Cable's, One of the Grinder style and two different models of the the palm.(old and new) The difference between the two being the rotation. The old model had an aggressive rotation the new much less producing almost no swirl marks in the finish work. Anyhow these are the secrets of an old guy that operated a small shop for years. The key here being as a small shop I didn't always developed female molds( too costly) and male molds required ample sanding before application of gel coat or paint as the final finish. I'm presently into the male mold /sanding process as one can see from my posted build. Hope this helps somewhat ---- Geo.
     
    Last edited: Dec 26, 2013
  7. LCrosby
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    LCrosby Junior Member

    Glad I read all the posts before I told you to use a wire brush.
    This works the best.
    Also, never push down on the sander. Let the weight of the DA and the grit do the cutting.
    Try hooking up to a vacuum, I have found discs will last at least three times
    longer.
     
  8. midnitmike
    Joined: Apr 2012
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    midnitmike Senior Member

    There's some good advice here namely using lower speeds, lighter pressure, and a vacumn attachment to quickly remove the grinding dust before it clogs the disc. Once the disc starts to accumulate clumps a stiff wire brush (like a welding brush) can easily knock off the larger bits. If and when the disc has become completely saturated and unuseable I'll drop them in a sealed bucket with a few inches of acetone. Usually by the time I've clogged my next disc the previous one is ready to be removed from the "Tone" for it's next go around. You can recycle disc this way until the abrasive finally looses it's cutting edge and it's time for a new one anyway.

    MM
     
  9. missinginaction
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    missinginaction Senior Member

    All good advise. Be especially aware of cure times. Just because resin doesn't stick to you doesn't mean it's fully cured. Try to plan ahead so that you aren't trying to sand epoxy today that was applied yesterday afternoon.

    I also found that the propensity to clog varies greatly with the sandpapers manufacturer. I used to buy disks at the local big box store. A couple of years ago I switched to some disks I found online that had good reviews. The difference was startling. I was amazed. Much less likely to load up and the abrasive lasts much longer.

    I've had very good results with this company's abrasives. You can order this on line from places like Amazon if you cannot find it locally. I use the gold and soft gold lines.

    http://www.mirka.com/en-US/us/abrasives/abrasives/
     
  10. Ilan Voyager
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    Ilan Voyager Senior Member

    The presence of oxygen and humidity will inhibit the cure of a non waxed polyester resin. Inhibit means that the cure is stopped but it's not always irreversible: if you insulate the resin from the oxygen it will probably fully cure.

    I would try to coat the sticky resin surface with a light coat of the same resin but with a bit of cobalt naphtenate (often called violet) added plus wax (generally paraffin diluted with styrene). Add also lots (about 2 to 3% with most resins instead of the 1 to 1.5%) of catalyst (generally peroxide). Let it cure completely, probably the sticky resin will cure. I counsel to make a trial on a small place first, and the good or bad results without messing with an entire piece will tell you if it's a valuable solution.

    About sanding...orbital are for finishing not for sanding heavily, the sander will die if you use it in that way. Try another tool. My preference goes for a light belt sander and 60 to 80 grit used with a very light hand to sand the worst bumps, and after the orbital will get a smooth surface.

    If you find zinc stearate, use it to coat the sand paper, that helps greatly about sticking.

    If possible use water with a drop of dish soap applied lightly with a sponge on the surface when using the orbital, that helps a lot as the soaped water absorbs a lot of heat, lubricates and impedes the resin powder to agglomerate and to stick to the paper. Clean often the surface with the sponge and add a light coat of soapy water.
     
  11. Ilan Voyager
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    Ilan Voyager Senior Member

    I do agree. Thanks for the interesting link.
     
  12. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Sand papers come with different binders and coatings, some are well suited to high speed sanding (stearate or phosphate coatings for example) and also different cutting agents (aluminum oxide is common). Some of the coatings and to a lesser extent the cutting agents don't do well at high speed or with gooey stuff.

    One in particular is known as "FreCut" and it's mostly animal fats, used as a non-stick coating on and in between the cutting agent particulates. I've had a world of pain with this stuff and can't recommend it for anything, but it does stay "unclogged" quite well.

    The screen style of papers from Mirka work very well, compared to traditional papers and are easy to unclog if they gum up.

    I too use diamond blades, instead of traditional disks and wheels. They do take some getting used to, but are far superior to anything else.
     
  13. SukiSolo
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    SukiSolo Senior Member

    I would also second the Mirka abrasives, one of the best available. Excellent products and very good life from the grit. Used to be a bit more widely available in the UK. I note some manufacturers imitating the product with inferior stuff - do not be fooled get the real stuff. There are a few dark red papers (garnet) also worth using and I buy 50 meter rolls.
     

  14. fpjeepy05
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    fpjeepy05 Senior Member

    OP, three options.
    Peal-Ply, Poly Vinyl Alchol (PVA), or waste some sandpaper. Unwaxed polyester will clog paper even if you let it cure for months. Nothing will take the clogging off the paper, and nothing will stop it from happening.

    Of these options I like Peel-Ply the best, as it is the fastest method, but it is also the most expensive.
     
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