Thursday, September 9, 2010


I have decided to write this blog in order to write about my trials and tribulations of creating DIY machinery to help me create things in a somewhat automated way. This all began when I stumbled upon the RepRap project through an instructable about CNC laser cutters and mills. It took nearly a year before i decided to build a reprap and by the time I had returned to the reprap page version 2 "mendel" was now up and running, so this is where I decided to start.

I made up a bill of materials, bought boards, components, rod, and belts. I was able to assemble almost all the electronics within a week after learning how to do surface mount soldering with a hotplate. I figured with that kinda speed i should be able to knock out this project in a month. Little did i know the hard part had just begun...

I was short 3 driver boards, and found that makerbot didn't sell the bare pcbs for them anymore. No matter i didn't need them till all the mechanical stuff was done anyway. This is where all the trouble started. Almost all the structural parts were made on a reprap and i did not have access to one already so i had to find other options to get those structural pieces. I found a set of 2d parts that could be printed and used as guides to handcraft the 3d parts necessary. This seemed all well and good, but due to heat issues i was limited to the amount of time i could spend outside in our garage shop. This made making the parts very difficult as i lack the skill needed to make the parts within a tight enough tolerance needed. So i enlisted the help of my father. Being that our time available in the shop was limited the parts moved slowly. I then decided it was a better use of our time if i bought a prefab machine to make the rest of my parts and then i'd have two working models so i could experiment on the other. So i purchased a makerbot cupcake cnc.

This proved to be a pretty straightforward build except that i found the acrylic parts in the extruder broke very easily and i had to make new parts to fix the broken ones. This set me back perhaps a day to get it all sorted out and then i was printing. Then i found that my barrel was pushing out of the thermal barrier because in replacing the block i neglected to put something to attach the retainer ring which seemed unnecessary at the time. I fixed this problem only to have to make a new barrel and tip as i ruined them when the barrel pushed out and crashed into the bed. This proved to be a time consuming and annoying problem. I started out by trying to make a piece of brass rod lathed down to the proper size to thread and then drill out the proper hole. While attempting this i had problems with the rod bending, or the drill not being centered and coming out the side. Most of these problems may have been due to an uncentered part in the lathe. I finally decided to cut down my problems by purchasing brass bolts of proper thread and length, cutting the head off, and drilling down the middle. This worked well except some bolts have hard spots that cause the drill to deflect, so its a matter of finding a good bolt. To rebuild the tip i used a tip on the reprap site and i got brass acorn nuts and just drilled out the little hole needed after i rethreaded the inside to work on the new barrel. This started to work but then failure of my nichrome wire. Again i had to wait for new materials to arrive.

While i was waiting i also started to read other blogs about reprap and found nopheads blog which led me to try a heater core instead of the finicky nichrome. This lead me to my current predicament. I started using some 12ohm power resistors but was unable to make the working temperature i needed so i looked back at makerbot which had just released their new extruder. It also uses a heatercore but uses 5 ohm 10watt resistors, so i went and got the exact specified resistors. When i attached them and fired them up they exploded, after a little fiddling i could get them to near 200C before they exploded but still failure. So i got some 15watt rated resistors and those exploded faster, which doesn't make that much sense. So going back to nopheads blog i decided to try his other heatercore version of inserting a vitreous resistor into the block instead of attaching the aluminum clad resistors to the outside. So this is where i sit.

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