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9103Re: [diy_3d_printing_and_fabrication] Digest Number 1258

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  • Graham Stabler
    Jan 5, 2014
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      Fooling a laser printer is a pointless exercise and you are very unlikely to get what you want, much "easier" is to drive the mirror and your own laser with a microcontroller or FPGA.

      I'm not convinced about heating a build chamber (vat) for a resin based printer. I would expect a lot of the warpage to be related to polymerisation and heating can actually cure the resin. 

      Regards,

      Graham


      On Sun, Jan 5, 2014 at 6:11 PM, Jon Watson <jon@...> wrote:
       

      Yes, very nice approach. I have thought of taking apart a laser printer, replacing the laser, and move the scanner assembly over or under a vat of resin.  The biggest obstacle would be tricking the printer into thinking it's still printing on paper.  I don't have the tech skills to mess with that.  You would need to fool the sensors and also create a moving carriage that moves the same speed and distance as if were printing on paper, similar to an inkjet powder type printer.

      No matter what you use as the "exposing" method, you still have to deal with a vat and what to use for non stick surface.  So far, tilting and PDMS are good enough for now and doesn't impact the quality of print.  I know it's a pain to replace the PDMS every couple of prints but it works.

      To me, in my opinion, after building and testing my DLP printer,  it's not the "exposure method" that is the weak link in current DIY resin printers.  It's the resin.  Shrinkage is the killer here.  Sure, If your going to print action figures and organic sculptures, available cheap resin will do just fine.  If you want to print mechanical parts or models that need to fit together or fit to something already existing in the real world, then we need a resin that has better shrinkage characteristics.

      It's easy enough to compensate for overall shrinkage in software but what's also happening is that parts are warping because of it.  Maybe a heated chamber would help.  I know the larger Envisiontec printers have heated build chambers.  See, that's the killer I think.  Just like in FFF printing, you have a part that is being pulled in different directions because of varying temps as it cures.  As the next layer is exposed and cured, it's going to pull on the previous layers that are now cooler and have already shrunk.  Keeping the temp higher helps this no matter what type of printing method.  I think even sintering printers have heated chambers.  This would allow an even, overall shrinkage that can be compensated for.

      There's nothing wrong with using a DLP for exposing layers, It's faster than anything out there. 
      Keep in mind,  there are no other 3d printers out there that can print a layer of an object in less than 10 seconds! 

      Also, very important:  You get what you pay for! 
      If you want super hi rez or larger parts, buy an HD or 4k projector.  Not cheap, but again, you get what you pay for.

      If the resin is as good as it gets, then heating the chamber is the next step.  Of course what I'm saying here is more relevant the larger you want to print.  If you're printing jewelry and very small objects, the shrinkage factor is really irrelevant at those sizes.

      Whew.....Just my thoughts.

      Jon

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