Distractions in electronics

It’s been a while since I last posted, and there’s been a massive amount of progress to report. I plan to release a series of updates in the coming weeks to recount the work that’s been done. 

Work over the summer took a turn as I attempted to craft electronics for the child printer with the help of its parent. I began initially with plans to make Traumflug’s laudable generation 7 electronics. PCB manufacture would be done through the etch resist method. I quickly realized that PLA plastic was not a suitable substitute for etch resist as it simply could not adhere to the smooth copper plate. With that, I switched to an ink based resist with the usual post-apocalyptic bent. In short, this means I stuck a magic marker on the printer and stood back:

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Not bad, not bad. A few tracks laid were sitting awfully close to one another, but that wasn’t anything that could be fixed with some alcohol and a q-tip.

Next came the etchant.

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Chemistry in the grim dark future might be a little tricky. The most common etchant used is ferric chloride, but many diy-ers today have used a combination of hydrogen peroxide and muriatic acid. Muriatic acid may be much more accessible without infrastructure since it can be made readily from dissolving chlorine gas in water. Chlorine can be produced easily enough via electrolysis, though handling it safely is, of course, another matter. At first the ease of producing muriatic acids seem to suggest the acid/peroxide approach is preferred in the context of my study, but we also have to consider the other ingredient, Hydrogen peroxide. To me, the production of hydrogen peroxide is prohibitively esoteric. It’s do-able, perhaps, but if you already have muriatic acid, ferric chloride is just a reaction away – a matter of mixing muriatic acid with a source of iron oxide, e.g. rusty nails. It was for this reason that I ultimately went with the ferric chloride method. While it would be an interesting endeavor to make the solution from scratch, I am in no way inclined to mess with chlorine gas, so we’ll settle for a bottle of ferric chloride we get from radio shack, okay?

 

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The resist is washed away with some alcohol
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and what remains are the circuits…

 

 

 

 

 

2013-08-11 14.54.44 all that’s left is drilling and soldering

 

 

 

 

 

 

aand done.  2013-08-11 14.56.10 

Well, I’m never doing that again. Why, you might ask?

 * chemical etchant is useful for mass production, but it isn’t going to last long if you have to produce your own chemicals. The dangers involved are so prohibitive I would never dare to attempt them in a real post-apocalyptic setting, let alone my current situation where I do it for fun.

 * Drilling through holes in a modest workshop is tedious and inaccurate. Honest, this thing is still lying in my workshop. I still have yet to test it! I don’t even want to bring myself to test it since I know there would have doubtlessly been issues incurred by this step of the process that render my efforts moot and unrecoverable.

Trying to escape the tedium of drilling only makes matters worse. Surface mount technology is an obvious solution to the problem, but then you have to work with scales much smaller than could be afforded by someone in this context.

For heavens sake, just look at it!2013-08-11 14.56.00

 

 

 

 

 

 

 

 

 

So with that, this is one part of my experiment where I have met with disappointment. Trying to manufacture a specialized PCB in a scavenging society is simply not feasible, if at the least not through the chemical etchant method that I attempted. Chemicals are quickly spent and can only be resupplied by methods that have no place in a nonindustrial setting. While it’s still theoretically possible in a post-apocalyptic environment where health and safety standards are relaxed, someone in this environment would be far more ready to etch pcbs by mechanical means, that is, by way of a CNC mill. A CNC mill shares many of the same principles as a 3d printer, and its reasonable to assume anyone capable of using the etch resist method would also have the knowledge needed to create a CNC mill. Once a CNC mill is created there is no need to rely on a dwindling supply of chemicals to manufacture electronics, no need to drill holes by hand, and most important of all, the utility of a CNC mill extends much farther beyond etching printed circuit boards. The experience I’ve accrued in chemical etching has clearly outlined the need for a CNC mill in the future of this project.

Barring the use of CNC mills, the only hope for the future would lie in devices made before the downfall of society – chiefly breadboards, stepper drivers, and DIY microcontrollers like the Arduino. It’s very reasonable to assume progress could be made for a time while these devices remain functional. The fact these devices are so versatile means they are very likely to be found lying around in workshops today, and the same versatility means they can be put to use in any number of ways after the collapse of society. Compare this with the electonics one could scavenge from pcbs: while certain components (e.g. resistors, transistors, capacitors) would be much more readily available than an Arduino board, a certain subset (e.g. integrated circuits) would be much harder to find, and these more likely than not are a sine qua non for technologies such as 3d printing. It’s possible that someone could find an IC that would suit his purpose to some extent, but unless that IC is a break out replacement for what he needs, he will likely have to redesign his entire board around it.

Now, I would go through the exercise of building the electronics through breadboard, but this is something I had already accomplished in order to create the parent printer. In the interest of time, I have gone ahead and procured an Arduino shield for the child, the ever popular RAMPS. Please forgive me if this comes as a cop-out, but as I continue to work on this project I maintain the peripherial goal of upgrading my modest carpenter’s workshop to a reliable maker’s laboratory. 

Clearly, it seems progress is still needed if 3d printing is to ever survive long term in a post-apocalyptic setting. We have certainly demonstrated it can exist for a time, but unless we find a way to manufacture the computers and microcontrollers that drive the 3d printers we will find it increasingly difficult to maintain them. Perhaps one day, 3d printers could be able to print entire circuit boards, components and all. This would require a great deal of progress to be made in the realm of materials science, but were it achievable it would ensure the continued existence of many of the things we come to associate with modern life.

 

Yet another metal hotend

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I mention in my previous post one of the few things I’d so far been unable to fabricate for the child printer has been extruder gears. Yes, attempting current generation extruder gears with a 0.8 mm nozzle diameter results in nothing short of a blobby mess. It was clear that a self reproducing filament deposition machine could not easily exist in a scavenging society unless its nozzle was of sufficient resolution to print its own gears. This placed the nozzle squarely in the place of a bottleneck. While I had previously tested the first iteration of my hot end with 0.6 mm diameter, this solution was found to clog soon after anything of legitimate size was printed. As a result, I would conclude the nozzle needed to be reworked, from scratch.

This was not the only reason to rework the nozzle, however. The nozzle as it then stood was finicky between prints, and required long bouts of troubleshooting where the toaster wire was repeatedly removed and reinstalled to access the rest of the nozzle. This no doubt placed stress on the insulation used to guard the toaster wire from short circuits. Once, after a long session of troubleshooting I restarted the printer to find the toaster wire I’d used as a heating element start to short out, glowing red hot before briefly combusting the kapton tape, then overloading the PSU’s fuse and effectively shutting itself down. The event lasted no more than a second or so and was over before I’d reached for the off switch. With the heating element toast, it was pretty clear a new nozzle was needed.

Before continuing, let me say: I know full well that pre-fabricated hot ends are readily available off the internet for the right price. Still, I remain a dogged post-apocalyptic cheap skate. Nothing on the market at present is completely outside the reach of the common man, at least in function, and at the very least the machines used to make the hot ends can themselves be machined. Concessions are necessarily to ensure failsafe operation, but overall these concessions could still be limited to purchased components which could still in theory be procured from scavenging old parts, e.g. heating elements.

With that in mind, I’ll start off by outlining the needs I considered in designing the new nozzle. First, it was clear a heat resistor would be used in place of toaster wire. A heat resistor is inherently immune to short outs and would always provide a reliable resistance and wattage density, making it far safer than any toaster wire ever could be. A heat resistor, however, is a bulky thing, and using one would require a custom made heat block to hold it. Barring this, it could be that the entire nozzle would have to be custom made. Still, having only a drill press in my carpenter’s work shop I wanted to make sure these components could be fabricated without the help of a lathe.

Secondarily, I ideally wanted an all metal design which could enable printouts from material with higher melting points such as ABS and polycarbonate. This is a demanding task, though, and if need be I was willing to suffice with a metal hot end bearing a thin teflon lining to lubricate the filament through the isolator, much like the successful J-head nozzle. Doing this would at least remove the need for ordering thick rods of PEEK or Teflon from the internet. In either event, an nozzle made almost entirely from metal would require some sort of heat sink to act as a thermal break, possibly even requiring a fan.

There were still a dizzying number of diy hot ends on the reprap wiki which could fulfill these objectives, however none did quite exactly what I needed. Many, I found, required drilling long, straight holes through solid stainless steel threaded rod or carriage bolts in order to make a steel isolator. The kettle hat nozzle is a good example of a nozzle I tried like this. I tried a few good days trying to get holes such as this. Some limited success was had, but in the end none of the holes I drilled got anywhere near the length needed to support an isolator, heating block, and acorn nut nozzle tip. Even if I were successful in drilling a hole this length, I was very uncertain the process could be repeated for other diy-ers with their own drill press and work shop.

That was when I started to rethink these designs. Previously, I was working off the assumption the nozzle tip would be the most difficult component to machine since it required drilling through a block just far enough to the other side that you could drill the remaining way with a flimsy bit less than a millimeter in diameter. If the remaining wall was too thick, the small drill bit would likely break before any progress was made. In my previous nozzle design this led me to create my nozzle as is frequently done from an acorn nut.

Nevertheless, after very little effort I was able to drill my own custom made nozzle tips from blocks of aluminum. Going this route also allowed me to couple the heater block with the nozzle, saving space as well as reducing a extra joint at which leaks could occur. At the same time, I was finding it much harder to drill long distances through threaded rod in order to make the isolator. Given these findings, I refocused my design to make the isolator as easy to fabricate as possible. On a chance visit to hobby lobby, I found a good collection of metal tubing which could act as a pre-fabricated isolator:

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Tubing was available for many diameters in aluminum, copper, and brass. The 2mm diameter tubing fit perfectly with the teflon lining I’d already purchased for my previous nozzle iteration. I also chose the brass tubing given it has the lowest thermal conductivity of my three options. If any are hoping to replicate this nozzle, steel would be an even better choice assuming its available in your area.

A second heat block/nozzle tip was crafted that resembled the ones I’d tried with threaded rod, however this time around I drilled a hole that matched the diameter of the tubing I’d gotten from hobby lobby. The fit was intentionally made snug enough such that I had to bash the brass tubing into the heat block/nozzle tip with a rubber mallet (careful not to use a regular hammer – I’m quite certain it would bend the tubing!).

The heat sink I attached to the nozzle was originally meant to cool a series of mosfets in a computer I’d taken apart. It serindipitously fit snugly with the 2mm isolator I went with, however just in case it should come loose I tightened it further in place with a screw whose diameter roughly matched the distance between the rills in the heatsink. The contraption holds very steady without requiring any holes to be drilled in the heatsink.

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I tested the contraption on a printout of a star trek commbadge (shown here). At a few points when calibrating z-axis offset, I set the nozzle too low and crashed it into the bed. I was worried in this event the metal tubing would be flexible enough to bend out of shape, however after a few times of this occurring I believe its safe to say this does not occur.

A bigger issue occurred as I scaled up print size – the heat sink would saturate with heat and cause the filament to melt too early, in turn jamming the nozzle. I had anticipated this problem, however, and it was quickly resolved by screwing a scavenged pc fan to the heatsink.

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Now the heatsink is just a few degrees above room temperature, and the only limit to size now is the build space!

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Shown below is the printer fabricating the chuck to a printable lathe, which will hopefully go on to further simplify hot end creation. In time, I hope to write up an article on the reprap wiki to document the design, with plenty of pictures to document the process. Switching out the drilled out threaded rods can definitely simply the construction of metal hot ends in the future.

What rough beast…

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What rough beast...

Work on the child printer (pictured above) begins in earnest. At the time the picture was taken only its y-axis drive train and base had been constructed. Nevertheless, with the benefit of an existing 3d printer, it becomes immediately obvious to me that construction of the child printer is far easier than its parent’s construction ever was. Overall, the greatest improvement has simply been the removal of mental overhead presented by the untested design of the parent printer. Questions I found myself constantly returning to on the parent printer (e.g. structural integrity, motor torque) are virtually eliminated now that there is the benefit of a design that has already been tested. Pre-designed printouts remove the need to think about the design and construction of a part to accomplish specific purposes. Printouts, while still crude when coming from the 0.8 mm nozzle, are still sturdy and capable of accomplishing their purposes. So far, I’ve found only the gears of the extruder are beyond the reach of the parent printer at this point, but plans are in the works to craft a better nozzle from scavenged parts that is capable of printing at the resolution needed for these finer pieces.

The child printer takes its design from the Prusa i3. The design is much less rigorously tested in comparison to the venerable Prusa Mendels before it, however uncertainty in design is not something I’m unfamiliar with. 🙂 More importantly, the Prusa i3 strips the number of printed parts to a minimum and shifts a significant portion of the frame to a wood or steel based construction. These two features make the Prusa i3 a no brainer given my current setup. Reducing the number of printed parts reduces the demand placed on an as-of-yet untested 3d printer, and a partial wood construction leverages the existing capability of my modest carpenter’s workshop.

The best part of waking up…

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The new nozzle has so far proven to be reliable enough to print some (relatively) large objects almost completely without supervision. Shown here is the hopper for a Lyman filament extruder. It started out on the night before a work day and went on through the night. The next morning I woke up to the image here.

There are kinks yet, yes. You might notice close to the end the printer missed a few steps. This makes it look like the top “teleported” a few millimeters to the left. Strangely enough, the printer still managed to span the rather impressive overhang and bridges that resulted. Besides the frame shift, the top part suffers no other defects. After the print I took a hacksaw and cut the piece where the frame shift occurred. I then welded the top piece back into the correct place with a soldering iron. The result still has a noticeable seam to it, but its air tight, sturdy, and functionally without flaw.

I highly suspect the ad hoc z axis played some role in the skipped that occurred. There’ll be more later on how I plan to address it. In brief, a post apocalyptic printer would be a short lived thing if it’s not able in the end to print out its own replacement parts. That feature by itself has the added benefit of printing out offspring, ensuring (with some caveats) that the technology not only survives but thrives. Its about time for my printer to have a baby…

Timelapse

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Yes, yet another timelapse video of a 3d printer on youtube. How original.

Here its printing out a cellphone stand. The stl file can be found, here, for those interested:

http://www.thingiverse.com/thing:38681

In case you’re wondering, my head shows up way more often than I normally would given I’m trying to embed the usb cable into the piece rather than insert it after the fact. The usb cable I had lying around was a little too thick for the port provided in the stl file – really more a problem with the usb cable than the model.

Hot end, version 2

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Hot end, version 2

From the start of the project, it was pretty apparent the scavenged z axis was not designed for vertical motion and would easily fall under the weight of is own extruder. A bowden cable was the ready made solution, and rather than investigating the potential for polyethylene tubing I opted for the standard teflon setup. Most likely this would not be used in a scavenger society, yes. It turned out the teflon tubing I ordered was much larger in diameter than those found in most printers, but as I discovered it never made much a difference. Whats more, friction with a tube this large has never yet been a problem. This finding gives me hope for the potential in the more common polyethylene tubing you can find in any hardware store, though it may be a while before I care to give it a shot.

But that’s an aside. Problems at this point were becoming apparent with the bakelite isolator and a replacement was needed. Since I was already putting the bowden cable to use, I figured I might use it to my advantage. My idea was to incorporate the bowden cable into the nozzle itself. The teflon tubing was not only self lubricating, but was also well suited to high temperature applications. The diameter of my setup would not be able to guide the filament much, but a second tube of teflon I had used for nozzle lining would work to that end.

With no need for an isolator, I would then only need the heat block and nozzle. Brass acorn nuts are already frequently used for the nozzle and would be available in any hardware store, so as far as I was concerned that part was taken care of. This would mean the only problem really was in affixing the acorn nut to the isolator using only common, ready made parts. A 1/8″ pipe fitting was well suited for that, and as I found it fit okay against a 5/16″ acorn nut. As with the previous hot end, a 1/32″ or ~0.8mm hole was drilled through the acorn nut. This was chosen as it was the smallest drill bit I could find in local hardware stores, and I imagine any smaller drill bit would likely get lost or broken in the event society wasn’t around to make new ones.

Shown here is the resulting hot end, at work printing a fan cover for the one I had scavenged from an old computer.