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Release status: Experimental

Gunstrap sketchup.jpg
A fully enclosed heated repstrap.
CAD Models
External Link

The Gunstrap is a plywood based repstrap that is constructible with only basic tools and can use parts obtainable from old domestic printers and scanners. It also uses a heated build chamber and heated build platform.


The Gunstrap is a plywood repstrap that is based on the Mantis CNC design. It has a build area of 200x200x100mm (comparable to the Mendel) and is employs a heated build platform and a heated build chamber. Unlike other wood based repstrap's, no ball bearings are required for its construction, excluding the extruder and all parts can be obtained from scrapped printers and scanners. In addition, its build chamber can be heated up to 100 degrees Celsius as most stepper motors are contained out side of the build chamber and no thermoplastic is used in its construction. The only stepper motor within the build chamber is the extruder stepper motor which is actively cooled using a peltier.

The Mantis compared to the Gunstrap

Advantages and disadvantages


  • Has a very low build cost (around $25USD) excluding the electronics.
  • Does not require any bearings apart from the extruder.
  • Can be constructed with only a hack saw, drill, screwdriver and epoxy resin adhesive.
  • Has a larger build area as compared to the Mantis 9.1
  • Due to its fold open construction it is easy to access for cleaning and changing tool heads.
  • Uses a heated build chamber which has been seen to improve the quality of prints for large objects.


  • Requires active thermal management in order to keep the extruder stepper motor at a safe operating temperature as its located in the heated build chamber.
  • Due to the use of stainless steel sleeves instead of ball bearings, this design will ware slightly with time.
  • Due to the design of the zaxis the gunstrap may not be able to achieve the same resolution as a Mendel.
  • This design requires more parts to be fabricated than the original [[Mantis 9.1] in order to accommodated the heated build chamber.
  • Requires the procurement of stainless steel shafts, stepper motors, belts, ect from old printers and scanners.
  • Can not currently print any of its own parts.

Fold Open Design

In order to accommodated access to the build platform the Gunstrap has been designed to fold open in two stages. The glass or perspex window folds up to expose the build chamber for access during a print or to make quick modifications.

The glass door folded up

For greater access the sides (with glass doors still in the folded up position) also fold down.

The sides folded down

Build process

The design is based around using 16mm thick plywood.

An exploded view of the Gunstrap

A full list of parts required will be added at a later date.

Changes that could be implemented

An alternative method for keeping the extruder stepper motor cool is to use a Bowden Extruder So that the stepper motor is located outside the heated build chamber. Examples include Ed's and Erik's| design.