Measure As Little As You Want With OpenQCM

The clever folks over at [Novaetech SRL] have unveiled openQCM, their open-source quartz crystal microbalance. A QCM measures very minute amounts of mass or mass variation using the piezoelectric properties of quartz crystal. When an object is placed on the surface of this sensor, the changes in the crystal’s resonant frequency can be detected and used to determine its mass in a variety of experimental conditions (air, vacuum, liquid). However, most QCM technology is proprietary and pricey – at least US$3000 for the microbalance itself. Any consumables, such as additional crystals, cost several hundred dollars more.

The openQCM has a sensitivity of 700 picograms. At its core is an Arduino Micro with a custom PCB. The board contains a 10K thermistor for temperature offset readings and the driver for a Pierce oscillator circuit. The quartz crystal frequency is determined by hacking the timer interrupts of the Arduino’s ATmega32u4. An external library called FreqCount uses the clock to count the number of pulses of the TTL signal in a 1 second time frame. This yields quartz crystal frequency resolution of 1Hz. The user interface is built in Java so that data can be read, plotted, and stored on your computer. The entire casing is 3D-printed, and it appears that the sensors are standard oscillator crystals without their cases.

Simplistic design makes assembly and maintenance a breeze. It only weighs 55 grams. Replacing the quartz crystal requires no special tools due to the clip system. The openQCM can be used as a single unit, or in multiples to form a network for all of your precise measurement needs. While they have kits available that will set you back US$500, all of the files and schematics for 3D-printing, assembly, and the PCB are available on the openQCM site for free.

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Fail Of The Week: Easy Cheese? Printer Says No

Well, this is timely. We saw a lot of things at Midwest RepRap Festival this year on both the printer and the material fronts. We told you about the delicious offerings made possible through remote extruder setups, strong and heavy filaments infused with copper and other metals, and a printer built out of K’NEX. No one was printing with canned cheese, though, and maybe for good reason.

[Andrew] here has created a 3D-printed arm that holds a can of aerosol cheese-like substance in place. A motor causes the holder to move the spout to the side, dispensing the goo. At first he squirts it in a coiled pile on to a cracker. That goes pretty well until it’s time to move away from the cracker. [Andrew]’s later attempt to build up four cheesy walls had us cheering. You can see what we mean after the break.

There are a couple of issues at play. Sometimes the add-on just plain falls off the end of the spout. Other times, air in the can interrupts the flow, just as it does during manual operation. And every once in a while, it just seems that the spout was too close to the substrate.

What do you think about the viability of cheese printing? Would it work better if the extrusion took place remotely, and the cheese was pushed through a thinner tip? Would a cooled print bed help? Let us know.

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