Introduction

The MOST Delta printer is a RepRap derived from the Rostock printer with the following design goals:

  • Simple build process
  • Safe to operate
  • True to RepRap
  • Maximize value
  • Maximize rigidity
  • Aesthetically pleasing (or at least neutral)
  • All PLA printed parts
  • Excellent print performance

The design utilizes plywood linking boards cut to a length that yields a desired printer radius when attached to the printed vertices. This simplifies assembly while helping to assure that printer dimensions are fixed, stable and reasonably well known. It also improves flexibility as the print area in the x-y plane can be changed simply by replacing the boards with boards of a different length. The delta design is inherently simpler to assemble as compared to virtually all it's Cartesian counterparts; this design can easily be built within a day by one person having properly prepared parts.

The design uses a 12V 5/6A power brick instead of the popular 12V power supplies having mains connections relatively exposed, posing a potential safety issue, particularly when children are present. The power supply is roughly equivalent to those found with many inkjet printers.

As many printed parts are used in the design as are practical, including printed pulleys. This in large part drove the decision to use open T5 timing belts for the drive (some other printer designs use T2.5, for which printed pulleys can't be used), which also makes the design more flexible as the length of the guide rods doesn't need to be based upon the length of an off-the-shelf continuous belt.

Cost considerations drove decisions regarding everything from printer capabilities (as shown, prints PLA only*) to guide rod material and length (two six foot lengths of 8mm drill steel are required, producing no waste). A Melzi controller is used as it provides all the necessary features as well as SD card support and reasonable expansion options. The power supply is a fraction of the cost of that required for powering a heated bed.

Printed apexes are very robust, probably overkill, and along with the plywood components and ample fasteners produce a very rigid structure. The printer has proven to transport very well (and can even be seat belted) with no adjustment needed prior to printing at its destination.

The end effector is actively cooled allowing for a unitized effector/hot end mount printed in PLA. The hot end is recessed within the end effector, maximizing z-axis travel and also providing for some print cooling.

Printing performance has been very good as has been the experience of printing with this design. Much less user intervention has been required as compared to experience with Cartesian RepRaps.

Novice builders should be aware that while this design is fairly simple to assemble as compared to historical RepRaps, it is still not trivial. Review the MOST RepRap Primer and familiarize yourself with terminology and methods. The build process is relatively detailed and includes many images, and this is a living document so if a step is missing or difficult to understand, please make an attempt to correct it.

(* - The printer can print ABS but it does not have a heated bed. ABS can instead be printed by first laying down a PLA raft.)

Printer capabilities/statistics

  • Print media: PLA only (heated bed can be added, expanding media options)
  • Filament diameter: 1.75mm using a modified Airtripper's Bowden Extruder
  • Nozzle diameter: 0.5mm (can be changed)
  • Print volume: ~250mm radius (with 240mm long linking boards) 270mm high
  • Melzi print controller w/ integrated SD card reader

Files and Bill of Materials

Most of the files required for this design are located here: https://github.com/mtu-most/most-delta

Tools

  • 5.5mm nut driver and 5.5mm wrench or a pair of 5.5mm wrenches
  • 7mm wrench
  • 13mm wrench
  • Sharp x-acto-like knife
  • Small, flat bladed screwdriver
  • No.2 Phillips screwdriver (a power driver is best)
  • 1.5mm allen wrench
  • 2mm allen wrench
  • 2.5mm allen wrench
  • 3mm (1/8") drill bit
  • 8mm (5/16") drill bit
  • Sharp pencil
  • Sharp point marker
  • Tape measure (large calipers >300mm are better), preferably metric
  • Soldering iron
  • Wire strippers and cutters
  • Needle nose or other pliers

Consumables

  • Two-part epoxy (JB Weld plasticweld recommended)
  • JB Kwikweld
  • Thread locking compound (Loctite Blue)
  • Masking tape
  • Muffler cement
  • 1/4" kapton tape (recommended)
  • White lithium grease (spray or paste)
  • Solder
  • Flux
  • 3/32" diameter heat shrink tubing

Before You Begin

Software to download and install

Software from github.com should be downloaded as a zip file. The link to download the zip file is located in the lower, right corner of the screen when it first opens. It is a button with a cloud icon and the text 'Download ZIP' on it.

All zip files must be extracted prior to attempting to install the software. If unsure how to unzip files, do a web search that includes the name of the operating system you use. There is almost never a need to install additional software to unzip files since all modern operating systems natively include the ability.

Upon unzipping the mighty1284p folder, it may be that a folder-in-a-folder is created - copy the folder containing the README.md file (there are other things in the folder, besides just README.md). The correct location to copy the mighty1284p folder to depends upon operating system:

  • Windows: It's usually in C:\Program Files\Arduino\hardware
  • Mac OSX: TBD
  • Linux: /usr/share/arduino/hardware

Download and install the following software (in order):

Building

The build process is organized by functional group. The following guide is prepared for a tandem build. Solo builders complete the build traversing the table by row (i.e. complete all tasks in each row of the build process).

For those participating in workshops, some of the assembly is completed before the workshop. Only those parts of the process highlighted green are required. It's important to get the steps requiring epoxying of parts completed early as the epoxy should be well cured by the time final assembly takes place.

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