One Step Back, 2 Steps Forward

      So, I've been doing a lot of printing on my 3d UV DLP printer lately, making little tweaks here and there. A few months ago, my friend Tristram Budel http://3dprinterplans.info/tag/tristram-budel/ was kind enough to send me one of his high-quality machined build vats. The frame of it is machine from a solid piece of aluminum, and he uses (I believe) FEP sheets to coat the vat bottom. He also uses a thin piece of borosilicate glass http://en.wikipedia.org/wiki/Borosilicate_glass

      I've been printing increasingly larger models on my 3d printer, and I think I hit a limit. As some of you know, the amount of force required to 'peel' a slice of a model off of the bottom of a vat can require a tremendous amount of force. Unfortunately, it was too much for the vat, and the borosilicate glass bottom broke, showering resin all over my mirror, projector & electronics, ugh...

The Remains of the vat

      After a lengthy process of cleaning up spilled semi-hazardous resin, I began to plan on how to fix it. I located several EBay auction for borosilicate glass. Most of these auctions were selling panes of glass that act as a stable build surface for FDM printers.http://www.ebay.com/itm/Borosilicate-glass-for-RepRap-3D-printers-214mm-x-200mm-x-3-3mm-/321241665891?pt=LH_DefaultDomain_0&hash=item4acb7ed163

      Borosilicate glass is used for it's optical transmission properties. Shown here is a few comparisons between several types of glass http://www.sinclairmfg.com/datasheets/optical3.html . Ultimately, I decided to take a chance. Instead of shelling out 25$ for a pane of glass, i decided to use a 5mm thick piece of polycarbonate plastic (Lexan)  that I had laying around from another project.

Polycarbonate - aka - 'bulletproof glass' or 'Plexiglass' has fairly decent transmission properties. It does NOT transmit deep UV, but it looks like right around 390nm or so it starts.

Spectral transmission for polycarbonate

Polycarbonate pane 155x155mm x ~5mm

      I knew that I was going to need a vat coating, I went ahead and ordered a few samples of FEP sheeting from CS Hyde http://catalog.cshyde.com/viewitems/films/fep-pfa-clear-ptfe-film?&bc=100|1002 . I ordered 1 sheet that was self-adhesive and 1 sheet that was not.

Taking a picture of  sheet of plastic is difficult at best...

The aluminum frame and walls all cleaned off, ready for a replacement

      I replaced the broken borosilicate glass with the plexiglass pane. I decided to use the FEP sheet that had the self-adhesive and I immediately regretted the decision. As soon as I peeled the FEP from the backing, it curled up and stuck to itself. It took a little doing to get the FEP properly placed on the plexi, and even then I was plagued by bubbles. Of course AFTER the fact, I did a little research on how to properly put down adhesive-back sheets (stickers, window tinting, etc...), so maybe next time, I'll have a little better luck, or use the non-adhesive version.

      I added in a generous amount on silicone sealant, and remounted the vat back on my machine. I was initially concerned that the plexi might block more UV light than the original, but after a few test prints, I was fairly convinced that there was no significant difference to the optical UV transmission for the lamp I was using.

All back in working order

     One new feature I added to my printer was a peristaltic pump (http://en.wikipedia.org/wiki/Peristaltic_pump) that I ordered from China. It was originally intended as a small aquarium medication pump. At first I was wondering how I was going to control this feature through Creation Workshop. Should I add a motor driver section? Should I have the controls automated? What G-Code could control this? In the end, I realized that I was completely over-thinking this, and I added a simple DPDT (double pole - double throw) switch connected to a 5v power supply. This allows me to control the direction of the pump. 

      I drilled 2 holes in the cap for the resin. The tube went through one hole in the cap, and the other hole is used for venting. I used a small fuel-line hose that I bought from an auto-parts store to extend the short hose of the pump. I also used a few short segments of brass tubing to connect the various hose lengths together, and to act as weights for the end of the hoses.  I did a few tests with some water and a few glasses to verify that the pumping system was working properly. The flow rate was good, no leaks, everything looks like a go!

     I mounted the peristaltic pump system in my printer. I used the word 'mounted' a little loosely here. It's actually just wired into the power supply and placed in the area that I want it. I did a few tests pump resin in and out of the vat and back into the bottle. It looks like everything is working well. Now I don't have to detach my vat to drain it, or use a syringe or funnel to get the resin back in resin container. In the next day or so, I'll probably FDM print a mount plate for the switch and pump and zip-tie a few cables.
The only thing I would change about this set-up is using BLACK tubing. I'm concerned about light curing leftover resin in the tube. Instead of changing everything, I may either spray-paint the tube, or wrap some tape around it to block out light.

I can use the fill/drain tube to add/remove resin from the vat

I would HIGHLY recommend getting a cheap peristaltic pump, a length of tubing and a switch to make your own system.

More to come later.
-Steve

UV DLP Pico Projector Experiments Part 1

      I briefly mentioned in one of my last posts about ordering and receiving a pico projector to experiment with. I obtained a re-furbished  AAXA P2JR directly from their webite http://www.aaxatech.com/products/p2jr_pico_projector.html  . 

The victim

      It came with the usual accessories, power adapter, micro-VGA to VGA adapter, composite cables, etc... My intent in ordering this is to see if I can adapt it for use in a bottom-up (or top-down) UV DLP 3d printer. I was a little nervous for several reasons. Normally, I don't just purchase new pieces of technology for the sole purpose of ripping them apart, but I figured I needed to break a few eggs to make an omelet.

       I was hoping that this projector would 'just work' and be able to cure resin without any modifications, but I pretty much figured it was going to need some mods. After powering it up, connecting it to my computer, and projecting silly images across my walls, cats, and girlfriend, I decided to get down to business. I ran my latest development code of 'Creation Workshop', sliced up a model, and chose a nice slice to test with.

Initial resin test

      I put a few drops of UV resin in a plastic sandwich bag, laid it flat, and projected an image slice. It went pretty much how I figured. After about 30 seconds, I checked the bag, and to my disappoint (but not surprise) I saw that it had failed to cure the resin in the slightest. 

      Now, I have it on good source that at least one person in the community has been able to modify a pico-projector for UV DLP purposes, so I wasn't ready to give up yet. I began to prep the patient for surgery.

Back cover off

The green and blue cable goes to the DLP unit's LEDs

A flat ribbon cable connects the DLP to the main board

     I was kinda nervous taking this all apart. What if I break it? What if I nick off a resistor? Am I about to lose 169$ bucks? Well, I hit my stride, and decided to make some progress in the name of science. I was able to completely dis-assemble the projector into it's essential components, the case, the speaker, the battery, the main board, and the DLP unit which was attached to a hefty heat sink.

I gently lifted the little bar that held down the ribbon cable to remove the DLP. After freeing the DLP from the main board, I had a better chance to examine the actual DLP projector without fear of tearing the ribbon cable.

Note the blue/green wires, L-bracket and copper heatsink

Initially, I was a little puzzled by the 2 sets of 4 wires. 

A good view of the optic-path

At the bottom/left of the picture, you can see the L-Bracket, each side has a 4-wire lead. Light is being projected in from 2 sides - each at a 90 degree angle from each other. Notice the funny-looking bluish glass (it's important later).

I figured that the L-Bracket contained the LEDs, and that I was probably going to have to replace them with a better UV source. I carefully sliced through the black rubbery epoxy holding the LED L-Bracket to the side of the DLP Unit.

The removed Led bracket 

I examined the LED L-bracket and noted that 1 led was marked R/B and the second was marked G. Without getting TOO much in theory about how DLP projectors work, I wanted to make a few comparisons between Color-wheel types and LED types.

In a Color-wheel type of DLP projector, a light source is projected through a spinning color wheel. The wheel has an encoder mechanism that tells the control electronics which color the light is currently projecting through. The appropriate color mask is displayed on the DLP micro-mirror array.

In a LED-type projector, either 1, 2, or 3 LEDs are used. Since LEDs can quickly turn on/off, the control electronics will turn on a single color, the DLP chip will display the appropriate mask-image for that color, and the process is repeated for all colors.

An image I found that explains the optic path 

The above image is NOT a picture of my DLP device, but serves to show the portions of the optic path. My optic path is a little different, but has very similar elements. 

Light from LEDs shine through collumnating optics. Dichroic mirrors (http://en.wikipedia.org/wiki/Dichroic_filter) reflect a specific frequency of light through a fish-eye lens, reflect on a right angle, then pass through the DLP portion and out the projection lens.

I knew that the dichroic mirrors were going to be a problem. They only allows a very narrow bandwidth of light through. 

I went ahead and took out the dichroic mirror reflectors and replaced it with a single FSM (Front surface mirror). This essentially blocked off 1 light path, which was alright, because I'm only going to use 1 light path for a UV led.

I've got a bit more to say about this and a few more results, but I'm going to save it for part 2.

Stay tuned.

-Steve

More Pix

I took a few more pix and video of my machine in action. I was able to get a few more prints off the machine when it broke again.

My machine fell victim to UV resin-dissolving ABS-eater again. 

The 'before' pic

Some of the aftermath

I rebuilt the Z-Axis Build-Arm.

I used some 5mm aluminum plating I had laying around to re-build the z-axis build arm. I added some 5mm bolts with double nuts on the bottom to help adjust the build plate to parallel with the vat. Wingnuts tighten down the top.

Gender-bending required.

 I'm adding some basic serial control of the projector through an open serial port. I purchased a small F-F gender bender and started some programming. Instead of simply hard-coding some commands to control my projector, I took a more universal approach that allows the user to create new commands, give it a name, and assign a hex string to send to the projector.

The relocated power panel.

 I moved the power panel from the back of the machine to the side panel. I plan on adding another small panel for connection to the USB hub connected to the usb/serial connector to the serial port of the projector. I also have the Arduino connected to another port on the USB hub.

Goldberg Sphere. 50 micron accuracy Z, 100 micron X/Y, Dimensions are 15x15x15mm

I had a few more good prints out of my machine before it died again. I am very proud of the resolution attainable.

The rear bearing holder piece broke. I was sloppy with my dripping resin.

I really need to take more care and caution in dealing with chemicals. I've damaged several ABS printed parts to UV Resin. I printed another rear bracket. I just may soak it in UV resin and cure it to create a meta-material part.

The weird part about these parts dissolving is that they simply crumble into pieces. I've treated many ABS parts with acetone vapor, and parts simply 'Melt' a bit like cheese or butter, to smooth and harden parts. This UV Resin must be destroying the long CH bonds from the polymer molecules in the ABS. I think if I want to try a chemical UV bath and curing session for an ABS part, I should do it quickly before the ABS has a chance to break down.

 I'm already ordering parts for the next version of the printer. I'm going to name this version the "Mark I". The 'Mark II' version will have a much smaller projector that I recently ordered http://www.aaxatech.com/products/p2jr_pico_projector.html . My plan is to make a z-axis with a single linear rail and simplified build plate/vat design.

I also ordered a peristaltic pump. My plan is to have a simple forward/reverse switch connected to the pump to control the flow of resin in/out of the vat. 

We'll see what the next iteration of the machine will hold. For now, I'm going to fix my machine, keep printing, and improve my "Creation Workshop".

Creation Workshop Beta 10

Well, the time has finally come to release the next version of Creation Workshop. I keep saying this, but it's been too long since I made a release. Thanks to the help of dozens of users, I was able to make fixes and improvements to the slicing, generation of GCode, control of the printer, multiple profiles, and dozens of other items. Please see the ReleaseNotes.txt for a full list of improvements. The one things I really wanted to finish up - Automatic Support Generation is unfortunately not in this release. It will be coming soon, but I didn't want to delay this release any more.

I decided to move the software out of the Alpha stage and into Beta. It seems stable enough, and from what I've seen, dozens of users have been able to print some wonderful models with it.

I've taken the time to update the manual and add in a hardware guide to address many of the question I have about my setup.

You can get the latest Version 10 Beta from the usual spot here: https://github.com/Pacmanfan/UVDLPSlicerController/blob/master/UVDLP/Published/CreationWorkshop_beta_10.zip

Please take the time to play around with it and give some feedback. I look forward to hearing from you all.

-S

An update

So, I haven't made a blog posting for a while, but it's not because of lack of progress. Progress continues on my Slicing and building software https://github.com/Pacmanfan/UVDLPSlicerController .The main issue that I'm facing right now with my UV DLP Printer is the resin sticking to the bottom of the vat. The UV light cures the resin, and it adheres fairly well to the glass bottom of the build tray as well as the build arm platform. 

 The problem happens when the arm (and platform) try to lift the slice up. The printed resin slice is too firmly attached to the glass bottom of the vat, and the resin releases from the build arm platform instead of the vat platform. I've tried roughing up the bottom of the build arm platform for better adhesion, as well as greasing up the glass vat with silicone lubricant. No luck so far.

   Other designs I've seen use a mechanism for sliding and/or tilting the build vat. This allows the interface between the resin and the bottom of the vat to release suction before/during the lift sequence. 

One problem that I'm facing now is that my vat is fairly large, and I don't have room on the surface of my printer to add in a tilt/slide mechanism easily. The reason my vat is so large is because I didn't modify my projector optics for a shorter throw distance. I suppose the "ideal" throw distance would project the 1024x768 resolution of the projector onto a 102 x 77mm area on the bottom of the vat for a 10 pixels per mm resolution. My projector's minimum throw distance is a little longer, giving me a size of approximately 155 x 120 mm. This is fine by me, however; if I want to add in a tilt mechanism, I may have do one or more of several things:

 1) Adjust the projector throw distance to be shorter, so I can have a smaller vat, and more room for a slide/tilt mechanism on my existing machine.

2) Rebuild my machine with a larger top surface for additional space for the tilt/slide

3) Completely rebuild my machine - Now to be fair, I was thinking about doing this anyways. I want to have a smaller design that uses a horizontally mounted projector and a mirror to project the image to the surface of the bottom of the vat.

Well, I should just choose an option and stop stalling so I can get up and printing. 

On some good news, several people have reported to me that they've used my software along with their printers to successfully print!

I'm still in the process of adding more functionality to my application. Look for some good new features real soon.

-Steve

Resin tray rebuild and UV Resin testing.

Last week, I purchased some UV resin specifically designed for 3d printing from 3DInk http://buy3dink.com/p/59/uv-resin . It arrived yesterday and I immediately started conducting a few print tests. One of the first things I noticed is that the resin was much less viscous than the SolarEZ resin I tried before. The 3DInk resin flowed almost like water. Again, I put a few drops in a sandwich bag and placed it on my resin tray.

I fired up my software and picked a nice slice from the 'Goldberg Sphere'. The resin cured within seconds! Good progress so far. The next step was to test the adhesion (or hopefully lack of adhesion) to my polycarbonate resin build tray. I used a silicone spray and paper towel to grease up my build tray, and I place a small amount (few drops) of resin on the tray to be exposed.

The remains of my first build tray.

Unfortunately, The resin firmly adhered to the build tray. No amount of coaxing could remove it. I decided polycarbonate might not be the best choice, or I might have to use a thin film of Teflon coating on the polycarbonate. Either way, this build tray was toast. 

Shown here is the resin stuck to the tray.

I found a nice small pane of soda glass I had been saving, and re-tried with a few more drops on an un-coated pane. Even un-coated, the resin did not adhere very well to the glass. I was able to slide a few test prints off the pane.

Some test object slices of the 'Goldberg Sphere'

New build tray

I used some aluminum channel stock I had lying around along with the glass pane to construct a new build tray of the proper size. I used silicone sealant on all bottom edges and the corners to ensure a proper watertight seal.

I think this new build tray will do the trick. The last thing I need to do is finish the arm that connects to the ZAxis and dips into the resin. I've already added a leveling system to the bottom of the build tray on the printer. I may have to add a small leveling system (some screws) to the build arm.

Exposure Tests

I ran some exposure tests last night. I placed a small amount of UV resin into a plastic sandwich bag and laid it flat on the Resin tray. I went to a middle layer slice of a model slice and I let the resin expose for approximately 30 seconds.

Exposing the Resin to the projected image

As you can see, the resin set into the slice of the projected image. Exposure time took longer than I thought it would, and the resultant piece was still very soft and rubbery. I think I'm using a non-optimal UV resin for this printer. (I bought a quart over 2 years ago from www.solarez.com that was meant for surfboards). I need to bite the bullet and invest in a small quantity of of resin that is specifically designed for 3d printing.

The resultant created object.

If anyone knows of a site where I can purchase a small (quart or liter size) amount of UV resin specifically designed for 3D printing, please let me know.

Initial Alpha release of software

Well, I felt it's time to share the initial software release of my "Creation Workshop" UV DLP Slicing and control software. Any feedback would be greatly appreciated. You can download the initial release from GitHub here : https://github.com/Pacmanfan/UVDLPSlicerController/tree/master/UVDLP/Published

UV Printer getting closer to completion

I spent quite a few hours this past weekend working both on my 3D UV DLP printer, as well as the control software for it. I took the time to take a bunch of pictures. This is going to be a picture-heavy post, so please bare with me.

In this pic, I'm attaching the z-axis arm to the top of the printer. I've cut a hole to allow for the DLP projector to shine light on the bottom of the plastic build tray.

Here's a picture of how it's attacked. I used 4x 5mm bolts to secure the z-axis and prevent any wobble.

Shown here is the attached Z-Axis with the build tray in place.

I have the projector mounted at a fixed location on the interior of the printer cabinet.

I remembered that I had a 4 axis CNC stepper motor controller board along with an Arduino Mega 2650 that I had used in another project. I plan on recycling some of it as a controller.

After debating what I should use as a power supply, I settled on using a power supply from an Arcade Cabinet (Yes, that one...http://probjectblogs.blogspot.com/2009/04/heres-donor-tv.html). It's a 5v 11amp and 12 V 4amp power supply. More than enough to power an Arduino and NEMA 23 motor.

I wanted an integrated 1-push power system, so I dug through my spare parts box and found a 3 prong power receptacle as well as a push on/off mains switch.

I quickly designed and printed a plate for the rear of the machine to hold the switch and power receptacle.

Shown here is the mounted power supply wired to the back plate and the DLP Projector. Now, one push can turn on the entire system.

Some Progress this weekend

I didn't get as much done on my project this weekend as I had hoped. I did manage to print and attach some handles to the cabinet I built. I also put together the polycarbonate build tray with some plastic glue. Hopefully this will be a suitable tray for build. I still have a pane of glass that can be used if the UV resin sticks to the polycarbonate plastic too much. I also started the assembly of z-axis that I printed from my Thingiverse "Generic 23 printed axis" object http://www.thingiverse.com/thing:37123 .

The Z axis being assembled

The completed polycarbonate build tray

More DLP Printer progress.

I made a case for my DLP printer. 3/4 inch MDF. With a walnut top. Also shown are a bag of the printer parts for the z axis. Additionally, I cut some polycarbonate plastic for the UV resin tank. Tomorrow, I put it all together.  We'll see what happens.

3D UV DLP Printer progress

I've been working on a new 3d printer lately. It's a 3d UV DLP printer that uses a photosensitive UV resin to create high resolution models. I've made some good progress lately and I wanted to show some results. I made a posting earlier to Thingiverse, sharing my first alpha build of my slicing and control software. You can take a look at it here:  http://www.thingiverse.com/thing:40778 . I've also gone ahead and posted the source code on GitHub here: https://github.com/Pacmanfan/UVDLPSlicerController . I've very proud of the slicing and control application that I've created. Getting the slicing to work correctly and handle all the special cases was no easy task.