The blog was a bit of an afterthought, so I should probably bring things up-to-date.
First: Rosie? Take a look at the About page for a complete explanation – the robot that will result from this project has been christened “Rosie” in honor of the Jetson’s mechanical marvel.
Exactly what I am building? The RepRap site lists two machines: the original, Darwin, and the updated version, Mendel. I am building a Mendel. I am also going to use the Generation 3 electronics.
In the interest of full disclosure, I have to admit I know almost nothing about electronics. Sure, I can talk about Ohm’s law and resistors and capacitors, and I can even describe the general workings of a microprocessor. But build anything practical? Nope, not really. So this is going to involve a lot of learning – from how the circuits operate to how to program the processors to how to solder teensy-weensy SMD (surface mount device) components to a circuit board. Oh, and making circuit boards (but more about that later).
The mechanical part of this project I’m pretty comfortable with – no stranger to nuts and bolts. Procurement may pose some issues as the RepRap project has its home at Bath University in the UK and all of the dimensions are in the metric system. Why the US has to be the only industrialized nation that uses English units (which even the English don’t use) is beyond me.
What have I done so far?
1) I’ve started trying to learn about electric circuits. This has taken the form of working my way through the book “Make: Electronics” by Charles Platt. Pretty simple stuff at the beginning, but soon moves into basic switching and digital circuits.
2) Started putting together the toolkit. I think I have all (or most, at least) of the mechanical tools I need, but the electronics tools are a different matter. So far I’ve purchased a number of basic items and am trying to choose a good soldering station. That said, much of the soldering is surface mount, so I need to decide if I am going to try and hand solder all the parts or use reflow soldering for the bulk of the work, which means procuring a hot plate, skillet, or toaster oven.
3) Started buying electronic parts. I purchased three Opto-Stop kits from MakerBot.com, as well as the bare motherboard. I also took advantage of the automated Bill-Of-Materials generator on the RepRap site, which saved me at least an hour (maybe more). Most of the parts came from Mouser.com, with a few from Digikey. As far as cost goes, about 1/4 of my outlay so far has been on postage. The overall cost has been pretty minimal, although I’ll keep a tally of the receipts as I go and post a summary from time to time. A couple items of note: I discovered that one of the capacitors listed on the website is obsolete, and had to figure out an alternative. Also, I discovered that the NEMA-17 stepper motor identified on the RepRap site is no longer made. It might be possible to find them somewhere, but I was unable and am trying to identify a good alternative. When I get it figured out I will post what I use.
4) I still need 4 additional boards – the three stepper motor controllers and the print head controller. These are supposed to be available from MakerBot, and I am on the email notification list, but from the info I’ve gleaned from the message boards I’m not encouraged that they will be available anytime soon. I’ll leave this for now and work with the electronics I have and do as much mechanical assembly as possible, then reevaluate the situation. I’d rather not go into etching my own circuit boards, but if that’s what it takes, that’s what it takes.
5) One of the very cool things about a RepRap machine is that it can make parts for other RepRap machines. There is a series of parts that can be machined, laser cut, or 3-D printed which provide much of the custom joinery, alignment, etc. Ideally, if you can find another person with a functioning RepRap, you can wheedle (or bribe) them into making a set on their machine (this takes several days – the printing, not the wheedling, which may take weeks). I have the very good fortune to work for a company that has a commercial 3-D printer that occasionally has some idle hours. They have graciously allowed me to make use of that printer with the help of my co-worker John. My thanks go to to both the owners of the company and to John for their assistance. (I don’t feel comfortable, unfortunately, saying who I work for because I don’t think they want potential RepRappers bugging them to build parts.)
I think that about brings things up-to-date. Tonight I’m going to order some soldering supplies on the internet (I spent an hour at Fry’s this weekend and couldn’t find what I wanted) and we will be off to the races. The printed parts are about 1/2 complete, so I’m hoping I can get serious about the procurement of the mechanical parts soon. Stay tuned.