The Plan

The Printer: Prusa Mendel RepRap

The Prusa is the latest design iteration of the Mendel series, it has a number of improvements, but essentially its built with less metal, parts making it a more efficient model of 3D printer. The Prusa also has an extra motor for the z-axis which ends up making it cheaper instead of compensating with more timing belts.

Components

There are a lot of components, but I have divided them into 7 primary components that need to be taken into consideration when building a printer.

1. Plastics
2. Metals (Vitamins)
3. Electronics
4. Motors
5. Printbed
6. Extruder
7. Extras that are optional but you will probably end up buying anyways....

Plastics (allow me to get on my soap box for a minute here...)

The most unique and attractive feature about the reprap printer is that it's designed with the intention of being a self replicating machine. In its current form the reprap can print the plastic parts needed to build another 3D printer and some very basic electronic circuit boards.

This is a critical feature because it means that the reprap is truly an open source device. Some toolbag manufacturer could sell you the plastic parts for a ridiculous mark up of about $300 because they have the molds or machines to make the parts that nobody else does.

However because of the nature of what 3D printing is as a technology, and what the reprap represents as an open source project, nobody can ever have an exclusive monopoly as a manufacturer of "hard to get" parts, they just don't exist as part of the printer's design.

You will notice that all the parts listed are hobbyist grade components readily available at a local shop or online, the metal parts are things you can get at a hardware store, and the plastics are sold on eBay by other people who operate their own 3D printer.

Current Methods

There are currently two methods of obtaining plastic parts, either with other 3D printers, or using molds. 

The first method is the most simple and just involves another printer to create the parts, most are ready to be assembled but can take up to a day to create with a reprap. It is common for people in 3D printing community with either repraps or makerbots to print plastic components other beginners need and sell them on eBay as a way of subsidizing the cost to build their own printer. The resolution/quality of plastic parts varies depending on the resolution of the print, i.e. the size of the filament and extruder nozzle. Sometimes parts need to be sanded or filed down so the rods have a smoother fit

The second method is referred to as a clonedel, it uses molds. First a set of plastic parts are printed, sanded, and filed down to eliminate any imperfections form printing. The plastics are then used as a cast to create a mold for which future parts are made. The process makes creating plastic parts almost trivial which the exception of holes needing to be drilled for the metal rods. Using molds, a set of plastics can be created very quickly and with greater consistency through a wider range of plastic materials that can be poured and mixed instead of printed through a spool.

My Decision

I think the resin material used in the Clonedel variant of the reprap is stronger and better quality, also its cheaper than what was available through most eBay retailers. I bought a set of metric drilled Clonedel molds for $75. The molds were created with clear resin and when they arrived I found the gear for wades extruder to be very fine and overall great quality.

Clonedel Molds and Resulting Parts

Metals ( Rods, nuts, bolts, washers)

The non-plastic parts used for the frame are often referred to as vitamins, don't ask why, I think its a European/British thing. As I started off I assumed I could buy the metal parts at a hardware store, but metric parts are harder to find in America and I turned to online distributors instead. 

McMaster-Car has a great online catalog and you could probably get everything you need there however I opted for a vitamin kit from Thingfarm North America T $81. This was a really good deal as I had previously specked out the metals on Amazon, and ran up to $85 before I even added the rods to my shopping cart. I imagine McMaster could match that price or do better but as I am just starting off it is very reassuring to get an all in one kit and not have to worry too much about measurements or having the right amount of parts. Being in America I would have liked to build the SAE variant of the Prusa Mendel but kits were hard to find or just more expensive, and for now most parts/measurements are in metric.

My Decision
I bought a kit from Thingfarm North America for $81, this included all the nuts, bolts, washers, smooth rods, threaded rods, and timing belts. Compared to the list that I priced out from Amazon for just the bolts, and the lengths of rods that I would have to cut to the right length if I got them form McMaster, this kit was the best price.

A complete vitamins kit from ThingFarm North America

Electronics
There are basically two choices, RAMPS or Sanguinololu. RAMPS is basically a shield that interfaces with an Arduino Mega and handles motors and other controls before passing data/commands/whatever off to the main board. I found this particularly unappealing because your are essentially paying an additional $50 for an Arduino board after the original $150 you spent on the RAMPS shield that goes on top of it.

There are also endstops which are small sensors that tell the computer when it reaches the end of its axis when moving the extruder or print bed. The two options are mechanical or optical endstops.

My Decision
I opted for a Sanguino build with Pololu stepper drivers, this combination is known as Sanguinololu. The Sanguio board was designed for the reprap in mind and consists of a Atmega 644p. It is overall cheaper to build and has a much more compact form factor.

A Sanguinololu 1.2 board

Motors
There wasn't much of a decision to look into here. Nema 17 is the standard motor form factor used, there is a list of motors that have been used and verified to work, the usual drive length is about 20mm.

Printbed
The printbed is an interesting component because there are two ways to build it, either heated or not. The simplest way is to buy acrylic sheets, layered with kapton thermal tape and then just print the plastic onto it. The other way is to have a special heated acrylic sheet that keeps the printbed hot, this way the plastics wont warp when they cool off too fast, and you can print bigger parts.

My Decision
I bought some acrylic printbed sheets that I will attach to a pcb-heatbed. I think having a heated printbed is the best method for printing and the heatbed sold by Utilimachine is the best one available.

Extruder
There are currently three extruders commonly used, Adrians, Wades, and Bowdens. Wades improves on Adrians extruder design and right now is the most common. Bowdens is different and offers a lot of promise, it moves the extruder motor off of the print head and attaches it to the frame, this makes the print head lighter. However there are some challenges, since the motor is what pushes the plastic filament through the hot end, there is a possibilit of jamming as the filament is now being fed through a giant plastic tube which needs to flexible so the print head can move.

Keep in mind the extruder is a lot of compnents, its composed of plastics, nuts, blots, springs, washers, copper/alluminum hot ends, and some kind of heating element such as nichrome wire with thermal tape to bind it. For the extruder it is usually best to buy a kit for its assembly.

Adrians Extruder

Bowden Extruder

My Decision
I bought a Wades extruder kit, keep in mind you need a hobbed bolt, but if you don't have the machinery available you can just buy this already done for you and not worry about it, that's what I did.

Wades Extruder

Extras
There are extra parts which you may add on or use to enhance your printer. Some people have extra acrylic boards to mount their electronics to the printer frame, people have upgraded mechanical endstops to optical, attached pc case fans to the printhead or electronics, even used thermocouples and SD card readers. These are all optional and can be added later on but have been known to enhance the operation of the printer.