Vivtek DH913 Retrofit

rkundlarkundla Member, Moderator, Backers, Ultimate Backer
My Draken has been working well, so I bought another one from 3D Facture so I can do some experimentation with different configurations, etc. I was one of the ultimate backers, so I have the first revision of the Draken design. It was nice to get one of the new ones that has all of the enhancements made so far.

The first modification I made was to use a Vivitek DH913 projector. This projector comes from the same line up that is used in the B9Creator printers. It is known to have good light uniformity and its optics are better than the ones that are in the Acer H6510BD. I found a used one on eBay for $750 with reported little lamp use. Brand new these projectors are $950-$1000.

The DH913 manual had the measurements for the mounting holes on the bottom of the projector housing. Using some CAD software, I created a paper template and used that to mark on the existing projector mounting plate two holes to help secure the projector to the plate. These two holes along with the three rubber bumpers helped stabilize the projector. I purchased two aluminum standoffs ($1.34 each at McMaster-Carr) to provide more rigidity as well as some M4 screws ($9.63 for a bag of 100 at McMaster-Carr) (the Acer requires M3 screws).

The projector is larger than the Acer, so fitment is a concern. Luckily based on where I positioned everything, it cleared the side wall.


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I did not modify the lens at all in this projector, so when I mounted it into slot 3, I was not able to get the lens to focus onto the bottom of the vat. The only add-on solution I could come up with was the use of close up lens filters, typically used in photography to allow longer focal length lenses to act more like macro lenses for close up photography. While the actual lens diameter is smaller, the outer ring was very similar to a 77 mm diameter filter. I picked up a set of Tiffen close up lenses ($75.95 at Amazon) to try to reduce the focus area. The outer ring is not threaded, so I needed to use some painters tape to hold it on top of the ring so it wouldn't shift.


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I needed all three close up lenses (+7 total) in order to get the image to focus at slot 5. The build size is similar to what you'd get in slot 1 and after calibration, I was able to get a 30 micron XY print.


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The Vivitek pours out a lot of heat. So much that the metal shelf where the vat is installed was very hot to the touch. I added an exhaust fan to the right side to help get rid of some of the heat, but I think I need something larger. The 120 mm case fan I do have doesn't line up with the holes on the side of the chassis, so I will need to think of something else.


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Here is an example print that is used by the Reify Solus guys to test their printer (props to them!) at pre-calibrated settings. It is 50 micron Z with a reported XY value of 28 micron. ;-) I apologize for the photos, I used my Sony point and shoot camera instead of my nice DSLR.


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Ron

Comments

  • robjos1robjos1 Member, Backers
    Amazing work as always, will be interesting to see how it fares in the long run
  • Joseph_OsbornJoseph_Osborn Member, Backers
    It's good to know the Vivitek will fit inside the case, but the close-up lenses are not an ideal solution to the focus problem. B9Creations modifies these projectors to focus closer, and now we know why the bottom of the B9Creator isn't enclosed! Too much heat :) I'm still holding out for a cheaper HD UV projector to come along. The Moonray has started shipping and they can easily use the entire build plate in almost complete silence and little heat due to the UV DLP, although at rather coarse XY resolution.
  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    The only saving grace I have is that by using larger close up lenses for a smaller projection lens, I am more in the sweet spot. ;-) However, I think if I zoom it out I can see some distortion along one of the edges.

    I'll play with it some more and see what happens.
    Ron
  • GravelleGravelle Member, Backers
    Looks great.  I've been rolling around an idea in my head about how to address the heat production.  Thinking of doing a forced cool air method by using a peltier element, heatsink and fan underneath the projector and force cool air into the intake vent.  And also adding an exhaust fan like you have above.  I will probably use an arduino to control the peltier so it doesn't get too cold and create condensation.  We'll see, probably won't try anything for a bit for a little while, my work schedule has been pretty crazy.
    Check out my Youtube channel Garage Science for videos and tutorials about printing with the Draken.
  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    Hey @Gravelle there may be enough extra cycles on the STM32 Arduino-compatible chip on the controller board to handle some of that for you. :)

    I've been fine tuning the Vivitek so I will share some pictures this weekend.
    Ron
  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    Ran the Reify 3D Solus test print on the Vivitek at full size and a 50% scale reduction.

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    Under the scope, the detail on the reduction is still pretty amazing! Unfortunately I had a computer error while resulted in quite a few layers of full exposure prints, causing my self-built acrylic vat to have the PDMS pull up in one of the corners. The PDMS came out easy at that point so I will need to pour a new layer into my vat. :P
    Ron
  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    I haven't done too much with the Vivitek lately since I've been messing with the WaxCast on the Acer. However, I have some free time so I will go back to playing with the Vivitek.

    I did get tired of messing with those close up lenses and the blue painter tape, so I designed a little adapter ring in CAD and blew the dust off my old XYZ DaVinci FDM printer. Surprisingly enough, it worked after being idle for over a year and I was able to print out the ring. The scaling was off a little, but with the help of my micromotor and a sanding drum, I was able to thin the rings to get everything to fit!

    I didn't take a picture yet, but I will and post it for all to see. I can make the CAD files available for anyone that might be interested.

    Ron
  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    CAD drawing of the adapter:

    image

    Photo of the adapter on the projector:

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    Ron
  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    I decided to remove the filter from the front of the Vivitek bulb to try to decrease the exposure times.

    I had a lot of flashing from overexposure using my B9 red/cherry 2:1 resin mix, so I had to put the projector into Eco mode to reduce the light output. I also increased the contrast to 100, left the brightness at 50 and maxed out the sharpness. I have not had any temperature issues or smells of melting plastic or burnt circuitry. <knock on wood>

    Now things are starting to look better, but it appears that my stacked lens arrangement is leaving an light bleed artifact that is causing excess resin to cure. I've been able to mitigate the excess light with a sticky note on the bottom of my vat, but I will need to perform the lens mod or try a different lens. There is an Opteka 10x lens that has multiple elements. Hopefully that will do what I want it to do in lieu of the three lens set on there now. 

    More to report later.
    Ron
  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    I've been using that skivved PTFE film, which is somewhat translucent, instead of the FEP film because PTFE has a lower coefficient of friction than FEP, which means less adhesion to the film during cure.

    I started with 5 mil thick PTFE and while I was able to cure prints and the looked good, the fine detail wasn't there most likely due to the scattering effect of the light against the translucent material.

    I swapped for 2 mil thick PTFE and the fine detail looks better. Now I am dialing in my exposure settings and I am currently running a test at 2.8 seconds per layer, where I started at 5. Negative detail like holes are starting to show improvement, so I hope to find a good set point real soon.

    During all of this testing, I had a tilt servo failure. Started making funny noises, then stopped working. I could smell the burnt out electronics before I got to the printer. The servo arm was at a impossible angle, which probably accelerated its demise. I luckily had a spare, so after about an hour of mucking around, fine tuning the servo and replacing the PTFE film due to a pin hole and a tear along the side, I am back in business and printing again.

    I have plenty of print samples, so I will have to take some photographs once my testing is complete!

    Ron
  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    I finally took the time to disassemble the DH913 to extend the lens by 3 mm. Getting the projector apart wasn't too difficult, but after the modification I could no longer use the zoom ring and had to remove it. The focus ring is rubbing against the outer trim ring, so it is a little stiff.

    I found that wasn't enough distance to allow the projector to focus on the bottom of the vat without the use of the close up lenses. I was able to only use a single lens (the +4) versus all three combined. This has minimized the flaring that I was seeing that caused additional overcure.

    I ran a 20x20 resin calibration print, so I will do some measurements to see what my final resolution ended up being with the mod.

    Ron
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