Desktop Polymer Mixing System with Injection Molder

Sparx Engineering acquired the Mix-Molder(TM) system to evaluate polymer blends and determine optimum pigment loadings.  Having previously worked with expensive capital equipment such as the Process 11, we were particularly interested in the effectiveness of the mixing system for blending additives.  Experience driven effects observed from shear upon additives in reactive extrusion, presented a true evaluation of the Mix-Molder(TM) system to answer the fundamental question:  For modification of engineering grade resins with additives, would the Mix-Molder(TM) provide sufficient mixing and shear to prepare representative samples for optimization of new products?

Mix-Molder System - demo image-01

Several experiments presented the system with specific challenges.  First, an alloy polymer blend of polycarbonate and polyester was impregnated with black pigment.  Application of the Mix-Molder(TM) system generated samples that were indistinguishable from native resin, as measured by TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry).  Continue reading

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Multi-Tiered Linux Backup System – Part I

Backing up important data and memories is an important task that should not be neglected. Just as important as performing Linux backups is verifying that the backups made are good and can be used to recover from data disaster. The principle technologies typically considered for verifiable backups are Cloud Backups and saving the data to a system using ZFS. Apple’s Time Machine is not mentioned since it has no mechanism to detect data degradation and the database that it saves data to can itself become corrupt.

Cloud Backup

Cloud Backup services like Dropbox or Crashplan offer a very compelling price point with the promise that uploaded data is safe and that it is protected from corruption. As some customers have discovered, that is not true. Although these cases of cloud corruption are few and far between, the consequences for putting the responsibility of managing and protecting important data into someone else’s hands can be quite severe (total loss of backup).

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Better Living with Chemistry- Windshield Wipers

The recent deluge of rain in the Houston area has me considering trading my car for an airboat.  Except for February, each month of 2015 has exceeded the normal monthly rainfall average.  Several very heavy rains in the last week of  April, have been followed with several ‘monsoons‘ already here in early May.  In the interim, the annoying sound of my windshield wipers approached exceeding the functional limit of their purpose.  In other words, the sound was so distracting, I started manually turning them on and off repeatedly to avoid listening to the squeak.  As my mind often does, I started thinking about the chemistry of the rubber blades.  My car is only 2.5 years old, so what has changed in the blades to resulting in the distracting racket.  As the rain can only pour in Houston, so does the sun.  From the UV light to the cleaning agents in the wiper fluid, the blades changed.  Read below for the chemistry, keep reading for the solution.

Rain Rain Go Away
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Clojure: An improved workflow

ClojureLike many beginning Clojure programmers, I started off following Stuart Sierra’s “Reloaded” workflow guide. While it was a great starting point, there were a number of things that I wanted to change.

  1. If the project doesn’t compile then the REPL doesn’t even start (the “reloaded” guide mentions this toward the end of the post).
  2. There isn’t a good separation of “configuration” and “system”.  I wanted a way to specify various configurations, and launch running systems from those.
  3. I wanted a way, when re-launching a system, to choose to either maintain the current configuration, or specify a new configuration to launch.
  4. I wanted to be able to maintain REPL vars for e.g. db, without having to reinstantiate them individually each time I relaunched a new system var.

1. Starting the Clojure REPL

To fix the first problem, I essentially decimated the user namespace. Now it only contains the functions necessary to reload the source files, but nothing to actually use them.

(ns user
  (:require [] :refer :all))

I put the rest of the system-specific code in a new namespace called repl. Continue reading

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PCB Design Credentials: IPC Certified Interconnect Designer (CID)

Complex PCB DesignOther than years of experience, a polished resume, and the ability to design circuits on a white board with 3 hiring managers looking over your shoulder, what can an electrical engineer do to stack the deck in their favor when looking for a job? In our previous blogs, we’ve outlined the importance of a PE license. Being a professional engineer is the number one thing an electrical engineer can do to stand out, especially because it’s something most electrical engineers do not pursue. One of the next best things an electrical engineer can do is to become an IPC Certified Interconnect Designer (CID).

If you’ve designed a PCB, you probably find yourself wondering about the finer details of PCB design that you may be missing. Your design works, but are you sure it’ll have the reliability and performance that you need? Early in my career, I could design a schematic, use various pcb layout tool, and build a working board, but I knew there were many aspects of the design that I did not fully understand.

How do I select my board stackup, and what’s a pre-preg? What can I leave up to the manufacturer, and what choices are important that I make myself? How do I size annular rings, through-holes, and surface mount pads for optimum reliability? How do I size thermal relief to a pad? How do I appropriately select trace thickness for higher currents? What about spacing for high voltage?
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An Engineers Review of the Fitbit Charge HR

I purchased a Fitbit Charge HR to help keep me active.  I’m a bit of a tech geek and follow the fitness wearable industry very closely.  I’m also an engineer, so I like data.  At Sparx, we are very familiar with fitness wearables.  We are currently working on the design and fabrication of a unique fitness gadget for high-end athletes, the BSX Insight (

After a few weeks of use of the Fitbit Charge HR, here is my review.

Fitbit Charge HR

About Me

In the past I have used the Fitbit One, Fitbit Flex, and the Fitbit integration on my iPhone to track my activity.  I also routinely track all of my meals on MyFitnessPal and have utilize the MyFitnessPal/Fitbit integration for about 3 years now.  These two tools are a great way to control your diet and exercise routines.  Logging your food intake is a great way to make you think about your food choices.  Activity tracking is beneficial because you can get “credit” for all activities that you do during the day, not just intended exercise.  This “credit” is in the form of burned calories.   If you take the stairs at work, go on a long walk, run, bike, or play tag with your kid at the park, you get activity credit.  This credit can be a way to meet your personal activity goal or justify that extra scoop of ice cream.  It takes the guesswork out of the balance between eating and exercising.
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