RepRap build

I am building a second RepRap printer now that I know what I'm doing, and will sell my original once this one is operational.

This will be a really huge post detailing everything about building a reprap printer and it will take a couple of weeks to finish. I will make additional posts pointing back to it when I add new sections, it's a work in progress and will be behind a cut because it's going to be pages of photos and videos.

My hope is that those of you who are thinking about doing this (I know you're out there) will have a specific example and walkthrough of the required steps so you can decide whether this is something you want to do. I'm happy to answer questions.

SAE Prusa Mendel main page
Prusa Mendel assembly page

Step one: gathering materials

There are a lot of options when building a RepRap printer. Pretty much every single part from the electronics to the screws involves a choice and a decision based on availability of parts where you live. I live in Michigan and even though I would prefer to build everything in metric, it's not very practical here. "Metric" is a weird word that makes eyes glaze over here and the hardware available in metric is limited to a few drawers of screws and nuts in a corner of the hardware store.

There are many options here but I opted to go for the standard Arduino Mega 2560 with a RAMPS board attached, partially because that's what I am familiar with. I found an Arduino on eBay from a Chinese supplier for $36 shipped, and had a RAMPS 1.2 board for sale for $35 - The current version is RAMPS 1.4, but it's functionally pretty much the same thing as RAMPS 1.2 if you're only running one extruder, which is the vast majority of cases.

I ordered a Prusa heated print bed PC board from for $30. There are cheaper ways to go but not really better ones and this is worth every penny if your time is worth anything to you. You can save $15 or so, maybe, if you're willing to put several hours into it., and your results will probably not be as good.

I got thermistors coming from Ultimachine. They're the standard high temp glass bead ones for $2.95. Two are needed, one for the hotend, one for the print bed. Shipping can be a killer here so I got six just to have some on hand.

In addition I purchased my Pololu stepper driver carrier boards directly from Pololu electronics. $12.95 each plus shipping, 4 required. I got 5 because it's so easy to fry drivers.

For power supply I strongly suggest a separate 18 volt 15 amp supply and a 12v 5 amp supply. I ordered a 24v/15A supply and a 12v/12A supply from eBay. The 24v can be turned down to 18v which is way easier on the MOSFET on the RAMPS board but still heats very fast. The 12v supply is overpowered at 12A but it was only about $2 more than the 5A one that would have been running at its limits.

You'll also need some zip cord and whatever connectors you like, and it'd be really nice to make a case for the power supplies since they're industrial and the mains circuit is hanging right there open. I made a sheet metal case out of a hunk of metal from an old junked PC. The standard for power to a RepRap is a 3 pin XLR.

  • Arduino Mega 2560 (eBay): $36
  • RAMPS 1.2 board (Lulzbot): $35
  • Prusa heated print bed PC board (Lulzbot) $30
  • Thermistors (2) ( $7
  • XLR connectors, 1 male and 1 female each of chassis and inline types ($12)
  • some CAT5 cable for wiring motors and other low voltage stuff within the printer
  • Some heavier gauge wire for the cable to the heated print bed, must be able to carry 15 amps at 24 volts - I used 16 gauge lamp cord.
  • Some heavy wire for the power supply input - a few feet salvaged from an old 14 gauge extension cord would be great.
  • power supplies (ebay) 24v/15A ($40), 12v/12A ($25)
  • Pololu 4988 stepper drivers (4): $56

Printed parts
This took some time because of some of the options that you have to decide on. I will omit the indecision here and say that I opted to go with an SAE Prusa Mendel kit with the following changes:
  • Z motor mounts with integrated smooth rod clamps from here
  • Prusajr's LM8UU press fit X ends currently in the felt branch but will be promoted to the main branch soon.
  • Jolijar's Y axis LM8UU holders
  • Nophead's Z motor couplings which use a little bit of small tubing over the motor shaft.

  • Printed parts set - probably $50 if you have to buy one

The larger nuts and washers come from Tractor Supply - they sell standard hardware for $1.75 per pound so about $3 buys all you need for this thing.
  • 5/16 x 6 foot threaded rod from Lowes, $3.80 per 6 foot length x 3 = $11.40
  • 5/16 nuts and washers: a pound of them from Tractor Supply = $1.90.See if the 1/4" washers will fit over 5/16 bolts - usually they do and they're a better fit. 5/16 washers are too big and will bind the 608 bearing races.
  • 608 Bearings - 5 are about $3 - I bought 50 608 (skateboard) bearings for $25 from an eBay supplier, because I have a ton of things bouncing around in my head that I need bearings for.
  • Linear bearings - 12 LM8UU for $20 (eBay). The options that I chose require 11 of them.
  • Belt - XL (0.2") - (ebay) $17.49

Assembling the frame:
Threaded rod: comes in 6 foot lengths, which is 1828mm. We need:
  • Six 370mm pieces for the two triangular sides. 370 x 6
  • Four 294mm pieces for the front and rear cross pieces 294 x 4
  • Three 440mm pieces for the top and bottom (Z axis smooth rod support on bottom, gantry on top) 440 x 3
  • Two 210mm pieces for the Z axis drive 210 x 2

The SAE Prusa Mendel page has the optimum cut strategy for getting those out of three six-foot rods, repeated here.
  • 6' Rod1: 440mm,440mm,440mm,370mm,50mm 18",18",18",15",2+"
  • 6' Rod2: 370mm,370mm,370mm,370mm,294mm 15",15",15",15",12"
  • 6' Rod3: 370mm,294mm,294mm,294mm,210mm,210mm 15",12",12",12",9",9" + extra

Build the frame per the instructions here.
My photos:

Be sure to spend extra time jigging the frame so that it is exactly spaced and is tight. A small error here will cause big trouble later.

Side triangles assembled

Front and rear rods assembled

Basic framework assembled, tightened and jigged.

Y axis - I'm using LM8UU linear bearings so that will be different than the standard. Take four LM8UU carriers and insert the LM8UU bearings. Get a hunk of plywood or MDF or whatever the Y carriage will be and cut it to 140x225mm. The smooth rod will be spaced 148mm on center (140mm inside spacing) - It would be best to use a straightedge to put the two LM8UU carriers on one side in line, then drill the plywood with them in place. Mount them and line up the second set on a straightedge (jig the straightedge off the first two so they are exactly parallel), drill and mount those.

Put the two Y axis smooth rods through those mounts and install the whole carriage on the bottom bar clamps. Pick one side and make the smooth rod on that side precisely parallel to the frame (measure/jig to the vertex on that side). Get that parallel and tight. Now spend some time getting the other rod tight and perfectly spaced so that the Y carriage moves totally smoothly along the entire run.
Re: Smooth rods
I just went to ebay and found a vendor selling a full set for $25 shipped. They arrived today and are very clean, smooth, well packed and dead flat. They came from Missouri.

search for reprap smooth rod.