This ’ible really is about the Sharp XG-MB70X DLP projector, not just about how I found it and not about the 3D printer itself, but first I do want to mention a couple of things about those topics. The inspiration for my printer came from the excellent instructable “Chimera: $60 DLP High-Res 3D Printer” by matstermind - https://www.instructables.com/id/Chimera-60-DLP-re... If you are thinking of building a top-down SLA printer, then you really should check out that article.
The projector I am using is a Sharp XG-MB70X DLP projector. I think this is worth mentioning that I was able to purchase, used from a local university’s surplus sale for $40. It was sold as-is, and I was not certain that it was going to be up to the job, but for $40, only 187 hours on the lamp, and a money back guarantee that it was in fine working order I figured I’d at least have a decent projector for movies.
SIDE NOTE: Until recently I was completely unaware that most state schools have such surplus sales at regular intervals, some municipalities do this too. There are REAL bargains to be had on all sorts of stuff, from office furniture ($5 for near perfect condition office chairs for example) to computers ($100 laptops - $30 22” flat screens), to DLP projectors…the list goes on. But enough…let’s get to it…
As it turns out the Sharp XG-MB70X is a beautiful 1024x768 3000 lumen beamer and is perfect for building an SLA printer. Unmodified it can cure Maker Juice Sub G+ without modification, but it is a slow cure…30 to 60 seconds per slice. I’m not patient enough, so I decided to check in to removing the UV filter. It turns out to be fairly easy once you get over the quandary about whether or not you want to risk botching it and killing the projector. I’m writing this to make this decision easier for you…you can do it. I did it in about 30 minutes, and now, with the UV filter removed, it cures a layer in 8 seconds…3 if you have it on its brightest setting, but then it begins to shrink and curl before it can adhere to the previous layer…NOT GOOD. You will have to really spend some time in tuning the build process…I have it OK, but need to do more work.
Standard Disclaimer: I will assume no responsibility for any injury to you or others if you follow these steps. I assume no responsibility for damage to your projector. Removal of the UV filter WILL void the warranty on the projector. You will need to take protective precautions when using the projector after the UV filter is removed. I use a UV shield, and 99% UV protective sunglasses at all times while working with the projector…sunscreen may also be needed if you are very fair skinned and/or are in any way susceptible to sunburns or other sun related issues. NOTE: I HAVE burned the skin on the back of my hand. You have now been warned, so here we go.
I am going partially from memory here…I did this 3 weeks ago, and took pictures, but have not gotten back to do this write-up until now. If you find something different from what I describe, I do apologize…please leave a comment correcting any mistake that I might make, and I will eventually incorporate it into the main document.
First an overview of the basic steps.
1) Remove the Lamp assembly. This is a consumer maintenance task, and is well documented. http://www.projectorcentral.com/pdf/projector_man...
2) Remove all of the screws holding the case together. One for the Lamp cover. 3 screws along the front edge, one in the middle of the case, and two at the back corners, and one in the top center of the back side where the connectors are.
3) Remove the top cover of the projector.
4) Now that we are inside, remove all of the connectors to the motherboard.
5) Remove the screws holding the motherboard in place.
6) Remove the motherboard.
7) Identify the light path, and find the covers over various sections. We only need to open the one closest to the lamp.
8) Locate the UV filter bracket, and its one retaining screw.
9) Remove the screw, then gently and carefully pull out the filter assembly using a forceps or needle nose pliers.
Ok, those simple overview steps may be sufficient for some who have done this kind of thing a time or twelve, but if not I will provide some details and photos to help you out…I know it would have helped me out.
Step 1: Step 1: Removing the Lamp.
Turn the projector bottom side up and locate the lamp door. Unscrew the retaining screw. Slide the door to the side and lift it off. Now remove the 2 retaining screws from the lamp assembly…then stick them to a magnet of put them in a small bowl…take note of their type and size for re-assembly. Now grab the bail on the top and pull STRAIGHT up firmly…wiggling it a little is ok, just don’t pull it to the side too much. Set the lamp assembly aside in a very safe location.
Step 2: Remove Case Screws.
The pics indicate where all of the screws are located. Again make sure you note the type and size of the screws and put them aside in a safe place.
Step 3: Remove the Top Cover of the Projector.
Turn the projector right side up. The remainder of the work will be done from the top. Firmly press in on the black side panels and you should hear the top pop loose. There are no electrical connections to the top cover, so you can now just lift the top cover off.
Step 4: Disconnect All of the Wires...
Once you have the case open, all of the motherboard wire connectors are immediately visible, and must be disconnected so that we can remove the motherboard. The pics indicate the locations of all of the connectors. Most of the connectors must be pulled straight out wiggling as needed.
Step 5: Remove the Screws.
Now remove the screws holding the motherboard in place. The pics show the locations of all of the screws.
Carefully lift the front of the motherboard…if I missed any of the screws in my photos this is when you will know it. As you lift it, you will feel the main connection underneath the motherboard pop free. The second photo shows the connector...it will have to be realigned during re-assembly. After it pops free, you will need to pull forward slightly, it should come free and lift out easily. Put the motherboard in a safe place.
Step 7: Remove the Beam Path Cover.
Locate the initial beam path cover (see step photos below),
remove the 4 screws holding it in place and remove the cover. There are some wires taped to this cover. It is probably easiest to remove the taped on wires.
WARNING: This partially exposes the fragile glass color wheel. Be very careful not to damage it since your projector will not function if the color wheel is damaged.
Step 8: Locate the UV Filter Bracket.
With that cover removed, you will easily notice the color wheel on the side opposite the lamp. Just inside this compartment, nearest the lamp is the UV filter. It is in a bracket which is attached to the bottom of the compartment by one screw.
Remove the screw, and then lift the UV filter assembly out of the projector.
You may want to keep the UV filter in case you ever want to replace it. I taped it to the inside of the case during re-assembly.
Step 9: All Done.
Well almost. Reverse the disassembly steps to put the projector back together. You are ready to use the projector in your 3d printer.
Standard Disclaimer take 2:
The projector is now dangerous. I am adding a warning label to the outside of mine stating that the UV filter has been removed.
Again: I will assume no responsibility for any injury to you or others if you follow these steps. I assume no responsibility for damage to your projector. Removal of the UV filter will void the warranty on the projector. You will need to take protective precautions when using the projector after the UV filter is removed. I use a UV shield, and 99% UV protective sunglasses at all times while working with the projector…sunscreen may also be needed if you are very fair skinned and/or are in any way susceptible to sunburns or other sun related issues. NOTE: I HAVE burned the skin on the back of my hand.