Monthly Archives: November 2011

Another CNC-made Random Tree

CNC cut random tree over doorI first made a “Random Tree” model a few weeks ago using Inkscape Render and Gcodetools extension.  Since then, my wife thought that a scaled-up version of the original would look nice on the wall above a doorway in our house.  Although I have a 7×12 router, my “tree” ended up about 7″ tall and 6″ wide.  It could have been slightly larger, but given the proportions, this was close to the limit of my machine.  The scaling was done in Inkscape, with the proportions locked.  Gcode was then generated in the same way as the first post.

After it was cut, I unfortunately had to cut it out more with a Leatherman tool as I didn’t cut deeply enough.  I set it to cut a depth of .256 inches, so either the material was oversize, I didn’t zero correctly, or somehow the router was loosing it’s position on the Z-axis.  I would guess it was a combination of the first two – since the shaft of my spindle can be compressed slightly, this could have also contributed.  This happened on my little random tree as well using a Dremel tool, so I may need to start cutting deeper on 1/4 inch MDF.

After cutting, the MDF Read more »

The Chemistry Behind Bleach T-Shirts

white king bleachThe most common bleaches in use today, such as the chlorine-based Clorox and Purex, are aqueous solutions containing 4-6% sodium hypochlorite (NaOCl).  They are formed by dissolving chlorine gas in sodium hydroxide according to the following reaction.

Cl2(g) + 2NaOH (aq) –> NaOCl + NaCl + H2O

The chromophore is the part of a molecule which is responsible for its color.  Examples of chromophores include C=C and C=O (Carbon to Carbon and Carbon to Oxygen) bonds.  The chromophore of a dye molecule causes it to absorb certain wavelengths of light and transmit or reflect other wavelengths of light.  An oxidizing bleach such as Clorox breaks chemical bonds in the chromophore so that it can no longer absorb light (a dark t-shirt is absorbing instead of reflecting most light, whereas a light area reflects more light).

When the objective is to bleach a dark object white, problems often arise.  Typically, the new color is orange, not white.  This has happened to me – one day, I was at work and spilled some bleach on my black shorts.  They ended up with orange spots all over them and I had to buy some new shorts.  It may be possible for one to bleach a black object white if he is patient and allows the chromophore-busting reaction to proceed for an extended period of time (considerably longer than 15 minutes; it may take up to one day as the process requires multiples bleach/rinse cycles).  Therefore, I would recommend trying the following procedure to dye a white tiger paw onto a dark-colored shirt (or check out this article to see how it was bleached in orange).

Procedure for bleaching a dark-colored shirt: Read more »

A Free Monitor Stand from Your Engineering Catalogs

computer monitors supported by books

The correct way to utilize 2 monitors

As an engineer, I receive many catalogs each year.  Some get outdated, and some I didn’t want to begin with.  At 6’4, and with some back issues, the standard monitor stand just didn’t cut it for me height-wise.  I was having to look down all the time, whereas it would seem the proper ergonomic position would be for the monitor to be level with your natural eyeline.  The solution I came up with was to use these unused catalogs as monitor stand.

After installing this “book monitor stand”, my back feels much better.  I’ve also been doing some different exercises at home so that probably helped too.  Interestingly enough, one of the Industrial Engineers that I work with is 6’7″ and has his monitor at the standard height.  Apparently looking down on your monitor isn’t a problem for everyone. *Edit: he has a normal stand on his non-notebook monitor.*

On a side note Read more »