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Re: [diy_3d_printing_and_fabrication] Re: Want to make 3d printer

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  • Mike Payson
    On Sat, Apr 30, 2011 at 9:37 AM, Michael Couch ... believe actually. Were these parts sanded after printing? I m betting ther were.
    Message 1 of 96 , Apr 30 12:29 PM
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      On Sat, Apr 30, 2011 at 9:37 AM, Michael Couch <cmichaelcouch@...> wrote:
      >
      > I must admit those BitsFromBytes results look very impressive. Hard to believe actually. Were these parts sanded after printing? I'm betting ther were. Makes me reconsider, still about 1/2 size I need.
      >
      > Michael Couch

      It is possible that some post processing has been done on some of those parts, but not much. It is hard to say since the photos are not particularly good They probaby were not sanded, as sanding ABS leaves a dull finish. Wiping the part with a bit of acetone will get rid of any print lines. At least some of those photos are of unaltered parts, you can see build lines in the black and yellow turbine assembly, and in the blue part in the photo that has several different colored parts. 

      As for the size, remember that to get a larger printer than that today (without modifying one of the other RepRap kits or designs) you would need to go to a $25,000 Stratasys Dimension (or possbly something from another competitor, but I doubt t will be much cheaper). To get the build area you really want you are probably looking at one of the Stratasys Fortus printers... And those are so expensive they don't post prices. That is never a good sign,
       
      On important thing I mentioned briefly, but never expanded upon is build speed. The Dimension uses a .254mm nozzle and a .254mm layer height (or an optional .33mm layer height on the more expensive versions). That makes a very pretty print, but also means that it takes a long time to build a part. Those layer heights and nozzle sizes are possible on the RepRap, but few people are using them, simply because of time. Most people use a .35 or .5mm nozzle, and a .3-,6mm layer height because builds are much, much faster, potentially 2-10x faster or more depending on the exact configuration. For my purposes, most of the parts I need do not need super high resolution, so I am happy to get a faster build time. On the Dimension, that is not even an option. 

      To see an extreme example of the possible print speeds, watch this: http://blog.ultimaker.com/2011/01/31/insane-speeds-with-pla-on-ultimaker/. To be clear, part quality suffered at that print speed, that was a proof-of-concept video. It is interesting to note that that was done using a firmware that did not support acceleration. The latest firmwares (finally!) do, so we are already seeing big improvements in speeds without a corresponding drop in quality, for example here is a standard "toy" Prusa Mendel feeding at 184mm/sec, roughly 2x as fast as a Dimension: http://www.youtube.com/watch?v=IsGtEQwLLPc

      Now compare that to this video of the $33,000 Dimension SST 1200es: http://www.youtube.com/watch?v=1Bc0Qdb4k1M. Not much comparison in terms of speed, even if it is still winning in terms of quality (and support material). Keep in mind that feed rate is only one part of the equation, your final build time is based on a combination of factors including feed rate, nozzle diameter, layer height, material used, etc., and in terms of print speed, the RepRap is ahead i every one of those categories.
    • JES_VFR
      ... You make some valid points, but since I have to play chinese takeout menu with the various reprap producers just to get pieces that might yield the
      Message 96 of 96 , May 7, 2011
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        At 04:56 PM 5/1/2011, you wrote:
        I agree... but you are missing my point. Safety is not either/or, safe or unsafe. It is a continuum between two extremes, and even something that is common in the household can be unsafe if used improperly.

        I did not mean to imply that they were dangerous, just that they were more dangerous than ABS or PLA (just as ABS is more dangerous than PLA), and as I noted, since they are liquid as opposed to solid, there are more possible exposure routes that you need to be aware of. At the very least, they are more dangerous to your carpets, since I suspect it would be tough to get any spilled resin out. Dropped filament is fairly easy to retrieve. ;-)

        You make some valid points, but since I have to play chinese takeout menu with the various reprap producers just to get pieces that might yield the resolution and might be repeatable, to get the parts I need, I have to look at something more certain. Juniors printer can make all but the largest series of parts I need right now at the resolutions that I need.

        JohnS
        A Dragon Ascending
        "Forging my body in the Fires of my Will"

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