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3D Printed Circuit Board

Because our own Mr. Steinson would not claim the credit for himself, I give to you the ‘Steinson Circuit Board’; a circuit board made with a 3D printer using ABS plastic.

A board is made with a 3D printer in white ABS plastic. The wires and electronic components are pushed into place. No glue, solder, or other material is required to secure components. Photo courtesy of M. Steinson. (c) 2013.

A board is made with a 3D printer in white ABS plastic. The wires and electronic components are pushed into place. No glue, solder, or other material is required to secure components. Photo courtesy of M. Steinson. (c) 2013.

 

For size reference, a U.S. quarter is just slightly smaller than the square.  To complete it a resistor, amplifier IC (placed on the opposite side of board), and connecting wires are inserted into slots and holes in the plastic board, making a perfectly working circuit.  While it may look particularly shiny, no glues, conductive paints, or other materials were used to fasten the wires and connectors.  The pins for the amplifier are simply bent, as are the leads for the resistor.  Wires are ‘hammered’ in place with a small awl.  Once put together, the wires and components are surprisingly secure.  In some ways the board offers more protection than a typically soldered PCB.  Not shown in the picture above is a small cover and clamp that prevents accidental shorts (such as by laying the board on a conductive surface) and further secures the wires and components.

It might seem that we used a new tool to do something that can be better accomplished with other approaches.  For the MMA weather station project, however, we dreaded the idea of designing and ordering custom PCBs, as this would undermine the whole idea of bypassing mass-production in favor of local fabrication and eventual customization.  A small CNC router could make PCBs, but small boards are  difficult to build, and it added another tool and level of complexity to the project.  Again, the point of the MMA is to move fabrication and eventual design of weather stations to developing countries.  Similarly, the thought of etching a PCB with chemicals was unattractive given the skills necessary, likely scarcity of the materials needed in our envisioned project locations, and some danger / hazard to the maker.  Of course solder boards are available, but then too we would need to supply boards externally, as well as introduce new skills and tools.

Most of the circuits on the weather station are very simple; typically consisting of a sensor, amplifier, resistor and then points for power and read out.  Few of the sensors the project has considered are ICs, and for now at least there are no SMD components.  The only chips in use are the amplifiers and clock timers.  Everything then hooks up to a micro-processor, such as an Arduino.  While the 3D printed plastic circuit is not for every application, the ability to do so makes the stations considerably more simple and inexpensive to fabricate.  It also makes the overall project simpler, by not necessitating additional tools and methods to address one specific component.

Using PLA for Long-Term Outdoor Applications

Eh….probably not….but maybe.

Some of the structural components we have designed for the weather station have been developed on a 3D printer that uses PLA.  PLA is great as the warping is less than with ABS.  This is particularly important for larger pieces or those with extremely thin walls, such as the Stevenson screen.  Typically corners are printed more sharply as well, and PLA is comparably more rigid than ABS.  All of this is good for the end ‘fit and finish’ of the station, or case components for something like a Chatty Beetle.

Unfortunately, PLA is not really intended for outdoor use.  One of the great environmentally friendly things about PLA is that it is biodegradable, but I am not so sure we will want this material property for a weather station.   Some of the research looking at the properties of PLA note that biodegradation will occur in a matter of months, but this is with powder or small fibers maintained at a high temperature and moisture in a controlled composter.  A larger piece undergoing natural temperature and humidity fluctuations, such as for the project weather station, might not biodegrade as quickly.

Despite many stating that PLA is not appropriate for outdoor use, which may be true for structurally critical components, the survivability may just be fine for light structural applications.  The components on our weather station, for instance, are largely to hold sensors and wiring that is feather weight.  In Biodegradable Poly (Lactic Acid): Synthesis, Modification, Processing, and Applications, author Jie Ren notes:

To biodegrade within 90 days, as described, the products have to reach 140 F for 10 consecutive days.  This requires a special facility, which few consumers have access to.  If your PLA products end up at the landfill, they will not degrade any faster than a petroleum-based product.

The above mentioned reference does, however, state that PLA will degrade in high humidity and temperatures above 110 F.  In all likelihood then, PLA does degrade when outside, but the rapid biodegradation often discussed requires a specific set of conditions, which are unlikely to naturally occur.   As a side note, PLA is referenced as considerably UV resistant.

So the question is will a weather station printed with PLA degrade considerably over a one year period, or will it be able to remain largely intact up to a three year period, when replacement of structural components makes sense in the normal life cycle of the station?  Based upon some of the references I have mentioned, I do not think PLA would rapidly deteoriate as shown in a composting situation, but it is not clear if some level of degradation would still occur, which would make a component unusable or affect the readings taken by a sensor.  Of course the durability will be affected by local environmental conditions, to which the PLA printed structures are exposed.

To attempt to figure this out, we are placing test blocks of ABS and PLA in various outside conditions, however, I suspect in the end, we will initially need to print in ABS, as we do not want to delay the project simply to test structural components over a multiple year period.

Small Scale 3D Printing Versus Injection Molding for Small Runs

Injection molding provides a number of advantages over most additive fabrication techniques, such as 3D extrusion printers.   Even with small, manually operated appliances, the parts produced on an injection mold machine will have a better finish and greater strength than those produced by a filament extrusion 3D printer.  Also, injection mold machines can typically support a wider variety of materials, such as various rubbers.

Of course the real advantage of injection mold processes is speed.   Once a mold is created, a part can be finished in minutes, if not seconds.  Consider a button.  These can be produced in seconds on even a manually operated injection mold machine.  On a 3D printer, you should expect 15-30 minutes; sometimes longer.  Printing six 1cm x 1cm x 1cm calibration cubes (at once) on our various printers takes anywhere from 2-3 hours.

Getting the speed advantage of an injection mold machine, however, requires an up front investment in designing, testing, and then finalizing a mold for the desired part.  This is not trivial.

For our weather station project, we do not foresee any country placing more than a hundred stations, and we would claim victory after a couple dozen fabricated, calibrated, fielded, and operating stations.  In our envisioned application, slow production of stations is okay, if not desirable.  The intent is not to deploy 100 stations at once, but rather to do so over months and even perhaps a couple years.  This has several advantages, but the most important benefit is not outstripping the absorptive capacity of a national weather service to place and maintain equipment.  Another advantage is an ability to slightly iterate and customize parts, as units are deployed, thereby integrating lessons learned in the middle of a project.

Having weighed options, an injection mold machine in the MMA project would likely only be used for highly detailed parts, or those that require special material.  Otherwise, the investment in a high quality mold outweighs the benefit.