Planning and preparing for a build

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Mendel Build Documentation

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So, you've decided you're going to build a Mendel. Fantastic. There's so much documentation, but after reading through it, you're still unsure on how to proceed. Let's try and ease that transition.

It is recommend that before you start getting into the materials procurement process that you briefly:

  • Familiarize yourself with the printer & Bill of Materials (BOM). Hopefully you've watched a handful of videos or seen some pictures so you have a very basic understanding of the parts you will be working with.
  • Scan over the Mendel Buyers Guide which has tons of great information listed for approved part suppliers.


To procure a Mendel, you can piece the whole machine together bit by bit, buy a completely functional printer "off the shelf," or anything & every combination in between. It can be overwhelming deciding on what path to take. As a general rule, you will save money ($$$) by purchasing various Mendel kits of sub-assembly material. Note: The below sections on procurement are subjective and based on the collaborative opinions of the author(s). How one decides to purchase the relevant parts is up to the consumer.

The three (3) major consumable groups are Vitamins, RP parts, & Electronics.


Vitamins? What are those? The bulk of the vitamins are:

  • Fasteners
  • Rods
  • Boards/sheets/mounting plates/etc
  • Drive belts

Decide what type of vitamins you want.

  • Most world users will seek all machined/metal parts in Metric. US users will have a bit more difficult time procuring metric parts locally at decent volumes from local hardware stores. SAE mendel does exist, although most active designs currently in the community are Metric-centric.
  • Stainless steel (SST) rods are common for your framework. Most individuals have no preference on fastener material. 'Cheap' is popular as Mendel doesn't weigh much--nothing is under significant load, except some motors when printing at high speeds! There are ways to compensate for that, not discussed here!
  • Most everyone uses the standard T5, synchroflex profile belts. Most RP pulleys are compatible with this profile, hence deviating from the standard belt will require new gears! New users are recommended to purchase belts and motors per recommendations in the Mendel Buyers Guide.
  • You can buy complete framing and fastener vitamin kits for the 'stock' version of Mendel, or break them down into sub kits. Your choice! Complete frame kits and hardware kits do make life easy.
    • If you have a hacksaw and grinding tools, it may be in your interest to purchase raw rods or bar stock and cut them to size yourself. Straight smooth rods are used for the printer to traverse back and forth, up and down. Wobbly or bent rods will lead you into great despair. Tread with caution!
  • There are many, many small components under the Vitamins umbrella! I'd recommend making a checklist of the BOM Bill of Materials (BOM) and marking those that you have plans to obtain and those that you have already purchased until are parts are accounted for. Pay close attention to quantities!

RP parts

RP parts are the most fun parts of your printer to procure. Why? Because there is great variety to choose from and they aren't terribly expensive! Materials. Colors. Suppliers. There is great diversity with what RP parts you select. You can buy full kits from shops, single parts from individuals on the reprap forum, ebay, or even have your neighbor print them for you. Cast/molded RP parts are coming onto the scene, as of recent.

Ask and read around before buying these--you may have the advantage of greater color and material selection, as well as newer designs that haven't rippled back up into the formal Mendel design. It is recommended while scanning through the BOM to jump on the IRC channel and chat with fellow RepRappers about the latest and greatest Mendel features.

  • For example, many different extruder types exist, and some can be easily argued as superior to the standard Mendel design found in the latest BOM. It may be worth your effort to pursue 'better' designs from the start, vs. starting with the status quo. [Wade%27s_Geared_Extruder|Wade's Geared Extruder]] was a very popular extruder design in 2010. Greg's Hinged Extruder has been very popular in 2011. These things often exist on, but not necessarily on the wiki.
    • is a popular site to share CAD & .stl files in all of the prototyping community (not only reprappers). Don't worry about this while planning, but know it exists!


Electronics are technically vitamins as well (because you can't print them), however, they are such a significant part of your build process that they deserve their own section. Here in the planning section, we will only talk about the high level options you have for Electronics. The most important part of your decision here is deciding on what control system to implement, and how much you want to be involved in the manufacture of your control system.

You need to know that:

  • Various input/output controller systems exist, and all of them can make a reprap print, but each does so differently
  • Some can be fabricated from the ground up (make your own PCBs with gen7 electronics)
  • Some are off the shelf solutions that essentially require you to only 'plug and play' (gen6 electronics)
  • Some solutions are expandable to accommodate for more future features or any custom features (RAMPS utilizes an off the shelf controller with various ports expandable to add new widgets & trinkets!)
  • Some are more easily serviceable
  • They all take up different physical space on the printer

The electronics page lists out all of the popularly accepted solutions. The requirements for procuring all of the relevant control systems components will be detailed in the Electronics section.

Non-Standard Popular Features

|heated bed is an incredibly popular feature which increases adhesion of the first layer of your print to the bed. At this point in time, there is not a 'standard' bed that is used across the community, nor a uniform way to mount & power it. Serious reprappers at this point in time rarely print without one. It is not required to get healthy prints, but is known increase quality via superior adhesion.


If you sourced all of your parts individually, it may be worth reviewing all of the parts and ensuring that they are compatible with each other. Look out for some obvious caveats:

  • Not mixing SAE & metric HW & RP parts together
  • [Stepper|Stepper] motors--do they have the right connections for your controllers? For example, the gen6 board is prepped & ready for BiPolar, 4 wire connections. A unipolar 6 wire motor is not immediately compatible!
  • Did you purchase a |heated bed? Is your power supply capable? Some beds can pull >10 amps @ 12 volts. Can you recycled old laptop power supply support the printer controls, motors, and bed simultaneously?
  • (please build more common "oop" newbie reprapper mistakes into this list)

Required Tools

You will need a "standard" toolbox to build a Mendel. That includes, but is not limited to:

  • Metric allen key / hex wrench set
  • Soldering iron and associated consumables (solder, sponge, wick, etc). This assumes that you will be wiring your own connections. Some 'out-of-the-box' electronics kits & motors still need some connections made. My motor wires came pre-cut, however I extended them for clean routing & strain relief.
  • Dikes/needle-nose pliers/small vice grips. A few different size 'grabbers' will make you a happy hobbyist
  • Measuring device, preferably a set of calipers [1], but a decent ruler will work
  • Scissors
  • Wire stripper

It is recommended to also have:

  • Small files &/or a dremel
  • Drill & common bit sizes
  • Loctite (I used 'red' on my frame to keep those big M8 nuts in place)
  • Diagonal pliers (side cutters [2])
  • Hacksaw (if you buy uncut smooth rods or support rods. Also may be useful if you need to modify your bolt for wades extruder--but you'll cover that later!)
  • Multimeter for checking connections if your electronics do not come pre-setup/configured