Adventures in 3d printing Or "I Finally Built a RepRap!"

I've wanted a 3d printer for quite some time. A few years ago I stared building one that, to say the least, was poorly engineered and under constructed. It never actually worked at all. Some of the designs could have worked, especially in a large CNC machine, but were just not a good fit for a small 3d printer. I've been eyeing the RepRap i3 models for a while now, last week I bought a kit (less electronics).

RepRap i3 with cooling fans and filament spool.
Note spool is on backwards to allow for the sloped ceiling in my lab.

Assembly was quite straightforward, there is a partial guide, though it skips (or I missed) some key steps.

A few tips:

• Final alignment of the XZ (vertical) frame should be done after assembly. Just line it up so the extruder will reach the front and back of the Y frame and is square.
• I printed thumbnuts to fine tune the bed leveling, it makes it really easy to get it spot on. I used these "Easy Heated Bed Leveling Thumbnuts"
• The Z axis endstop was a pain, part of it was I used the wrong mount, but I printed this "Adjustable Z-Axis Endstop Arm" to make it easier

Fire in the Hole!

Everything I (and probably everyone else) build has some "teething" issues. I had (and am still having) a few. After I got it set up fairly good I started a print and it seemed to be working nicely, then the Sanguinololou literally caught fire (there were flames). The bug list for the Sanguinololou says the traces for the heated bed are too small, so I had reinforced them with wires before this point, it was the wires that caught fire. Turns out the mosFET shorted and the bed just stayed on continuously drawing ~16A. I salvaged the board and put a new mosFET (all I had on hand was a 12A logic level one) put it back together, set it to pwm at 50% and it lasted about 30 seconds before shorting too (I was watching this time). I swapped it again, added a reverse diode and ran it through an automotive relay (so the mosFET turns the relay on and off). That works really good.

Electronics, complete with rats nest

Now that the fires were out It was time to try some real prints. The filament won't stick to the bed. No matter what I do it won't stick. I tried cleaning really well, nope. gluestick helped, allowed me to print the upgrades I mentioned, but was hit or miss. I researched, tweaked settings, spent the better part of a day on it. Finally my brother was over and (looking on his tablet) said "they say here that Reprapper brand glossy black PLA won't stick to glass, use blue tape". Yep, I had Reprapper brand glossy black PLA filament, and yes, it sticks really well to blue tape.

A Sheep! Here's the first print that I took a picture of.

A few remain

Now I can print, I've still got a few issues left, mostly "dialing in" problems.

• Overhangs and bridging don't work quite right. I've been lowering the extrusion temperature and it really helps. I started at 200C and am down to 180C for the first layer and 175C after that. A box fan after ~5 layers helps even more.
• I printed some large parts and they warped, pulling the blue tape off the glass. The cooling fan bracket printed really nice with the 182C/177C and bed at 35C settings. this might be licked, but can't say yet. 
• The first layer of big parts will bunch up a bit during infill, leaving stuff sticking up that can catch the extruder. If it gets 3 layers or so it will bury the problem and will complete fine. I might still be a touch close on my z-axis start point or it might be something else.

Future plans

• Upgrade to optical endstop for Z-axis. It should be considerably more repeatable than a mechanical endstop, so I think it would be a big improvement. The X and Y axis are not nearly as critical, so I don't see any need to change those endstops.
• Upgrade the electronics so I don't need a computer hooked to it and add cooling fan support. I've got several options: MosFET board and sd adapter, MosFET board and android tablet, Panelolou (includes Mosfets on the interface board and SD on the panel). I'm leaning toward the tablet option. The software looks really cool. I need to try it sometime.

UPDATE: I printed a bracket to mount some 40mm cooling fans, but all my small fans are 50mm, so I printed a 50mm bracket. Seems I chose one bad fan (rattles) so I'll have to replace that at some point. It makes a huge difference. I'll do another post on integrating it with the electronics.

Links

http://www.thingiverse.com/thing:208137 - thumbscrews
http://www.thingiverse.com/thing:267927 - Z-Axis Endstop Arm

My PCB Fabrication Process

Desulfator

My last desulfator design was Rev B. I decided it should be Rev A (even though Rev B is etched on the board), as it was the first desulfator board I actually built. For future reference I'm doing major revisions A, B, C, but minor (and or pre release) tweaks 001, 002, etc. So this should be Rev A 003, I think.

For more information on the desulfator see my previous post here.

Specs / Limitations

• When I do the layout I've found I can etch down to about 0.010"(50% success), but 0.020" is much more forgiving (80+% success). So I do most of my traces as 0.020". but they won't fit between some pins, so I run a 0.020" trace as close as I can, end it, put a 0.010-0.012 trace in the tight spot, end it, and continue with a 0.020 trace.
• I try to maintain 0.025" clearance around traces, since I don't use a solder mask it helps me avoid bridging traces.
• I flood-fill everything I can, the more copper I leave on the board the quicker it etches.
• So far I only do single-sided boards. Hasn't been a huge issue yet. I'd be tempted to just order 2 sided boards when I need them.

I use the toner transfer method for both the etch resist and the silkscreen. As far as prep it goes like this:

Copper Side First

1. Sand board with 400grit (wet sandpaper) wet with just a drop of dish soap
2. Dry board with a paper towel
3. Apply rubbing alcohol and dry with a paper towel.
4. Print resist on a piece of shiny paper, I have varing results with this, seems to depend on the paper I find. I read that the (glossy) whites of newspaper / magazine ads worked the best, but I find that some heavily colored ads have more of the wax / clay stuff on them and work better for me, with the exception of the silk screen side (more on that later)
5. Align board and paper, either fold the ends over to keep it in place or use a tiny piece of tape. Then run through laminator 5+ times.
6. Soak in cold water until paper starts to dissolve. Some times it peels off, other times I have to rub it until just the toner remains. sometimes I loose traces and stuff, if it's not too tight I continue, otherwise back to step 1.
7. Gently dry and examine carefully, touch up little holes in the flood fills and broken traces with a permanent sharpe(3 coats).

Etching
For etching I use cupric chloride, it works really good above 60F, somewhere around 40-50F and below it's really slow. It needs to work fairly fast, the majority of the problems I've had with it were when it's cold out and instead of 20-40 minutes it took 2-3 hours.

I keep it out in the garage, as I prefer not to risk spilling stuff like that in the house. (I don't want to spill it out there either, but I have better ventilation and access to a garden hose for emergency clean-up)

    8. Etch until traces are isolated.

    9. Rinse thoroughly, then Sand with 400 grit to remove toner, should look
        like this: (note the 2 is missing from the 2013? yep, didn't transfer perfect)

Bottom

Then the Front (silkscreen)
    10. Dry then drill two holes (for through-hole parts) as far apart as possible
          (either corner would be good) and use them to align your silk screen (do
          steps 3-6). I poke a wire right through the board and paper for alignment.
          (remove wire before running through laminator) Note: I try to use mostly
          white paper for this as the colors tend to stick.

Top

When it's all assembled and tested I spray the copper side with several thick coats of Rust-Oleum clear coat.