Budget Strapped

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Budget Strapped Documentation
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Release status: Experimental

A low cost RepStrap
CAD Models
External Link


This printer is intended to be a very low cost 3D printer that is still capable of printing useful items. The cost of filament is very significant for a printer in this price bracket. To reduce this cost, BudgetStrapped will print with HDPE filament, which can be created relatively easily from household plastic waste.

Design Goals

  • under ~$100 total cost.
  • ability to print will filament made from recycled household plastics. Specifically HDPE (#2 plastic).
  • ability to be constructed with minimal power tools
    • Powered hand drill/screwdriver
    • Hand Saw(s)

Remaining Work and Concerns

  • The hot end I currently have is a knock-off J-head nozzle. Based on some searching it seems likely it will not work very well.
  • SLOW print speed. The X & Y axis print speed of 6.23mm/s [4.5mm/s now] is slower than I have seen anyone mentioning printing. (I saw 15mm/s for a first layer.) will the printer still function if it is printing this slowly?
    • In an article by someone trying to print HDPE, it was mentioned that printing very slowly (as slow as 0.75mm/s) seemed to cause the HDPE to print better. This is very encuraging
  • My household plastic recycler needs to be completed. Until this is completed I have only a few feet of 3mm PLA to work with.
  • I still need to verify the spooled fishing line drive method will work as planned.
  • The simplified electronics used do not use stepper boards. I have written a functioning motor test arduino sketch for this setup, but I haven't yet verified that an existing firmware can work with this setup. (I may have to modify the firmware myself.)

Printer Details

Structure And Motion

  • Printhead will move on X and Y axes, printbed will move on Z axis
  • Frame will be made (primarally) out of 2"x4" lumber
  • X and Y axes will use drawer slides (like WolfStrap)
  • Positioning on the drawer slides will be done using 70lb test multistrand fishing line.
  • Z axis will move on four 10-24 threadded rods
  • Multiple 28BYJ-48 stepper motors will be used on each axis instead of NEMA 14 or 17 stepper motors


  • An Arduino Nano will be the core of the electronics.
  • A shift register will be used to increase the number of digital I/O pins
  • 1 darlington array driver chip per motor (These come with the motors)
  • A bottom-of-the-line PC power supply will be used to provide power.


  • The current hot end is a knock-off J-head. (hopefully it works...)
  • The cold end is a WoodScrew Extruder.

Print Bed

  • The print bed will moved by four 10-24 threaded rods.
  • The bed support will be made out of 1/4" plywood.
  • Initially the print bed will be unheated. If it looks like heating may prove beneficial, it may be added.
  • The print surface will be polypropylene.
  • If added, the heated print surface will be made from a piece of glass with NiChrome wire taped to the back of it.

Printer Specifications

  • Cost: ~$85 - $105
    • Printed Parts: None
    • Electronics: $12
    • Extruder: $38
    • Motors: $18
    • Wood: $6
    • Other: ~$10 - $30
  • Printing Size: ~ 7"x7"x9"
  • Printing Speed: (SLOW) X & Y axis 4.5mm/s, Z axis 0.265mm/s
  • Precision: ??? (position), ??? (printing)


April 28th 2014 Update:

  • Significant progress has been made on the HDPE Plastic Recycler.
  • All three heaters have been made.
  • Construction of the majority of the recycler has been completed.

April 15th 2014 Update:

April 9th 2014 Update:

  • The X-Axis drawer slides are installed and seem to work well with no perceivable wiggle.
  • The Y-Axis drawer slides are being installed.
  • Rough calculations indicate a speed of ~4.5mm/s can be expected if the sewing bobbins aren't used.
  • Examination of final structure indicates that Z-axis range will likely be closer to 9" to 9.5"

April 7th 2014 Update:

  • The majority of the frame has been constructed.
  • Several of the new motor mounts have been cut out. They are stiffer and easier to make.
  • The design of spooled fishing line drive has been adjusted. The fishing line will now be spooled directly onto the 10-24 rods. Preliminary testing indicates that it shouldn't even be nessisary to drill a hole through the rod. This change will likely result in a slowdown of the X and Y axis by some amount. But once the printer is working, spools can be printed to improve this.

March 27th 2014 Update:

  • SketchUp Model completed on the 24th.
  • Most of the wood has been cut out for the frame.
  • During the cutting out of the motor mounts, it became apparent that they are both difficult to cut out and possibly not stiff enough. A new motor mount design has been created that uses three short pieces of the 1 1/4" x 1/4" lumber. In addition to being stiffer, it should be cheaper and maybe a bit easier to fabricate.
  • The 625 bearing holders have also been re-designed. They are now to be made out of the same 1 1/4" x 1/4" lumber as the motor mounts, (instead of plywood) and will now be mounted with the same machine screws as the motors themselves. This will remove 2 machine screws and lock nuts per motor. The lumber is cheaper and should perform the task as good if not better.
  • The printbed support design has been tweaked. Instead of using one large peice of plywood (~9.5" x 17.25") a smaller peice of plywood will be used and two lengths of 1 1/4" x 1/4" lumber will be used to hold it. They will glued and/or screwed onto the plywood.

March 19th 2014 Update:

  • Progress is being made on completing the SketchUp model before much more mechanical contruction is completed.

March 13th 2014 Update:

  • An issue with using T-nuts was uncovered, they pull out of the wood very easily. Also on further examination of the cost of T-nuts, and the 30 odd ~3" machine screws that would be required to make all the axes adjustable (~$20), it was decided, at least for the majority of the upper structure, to move to plywood. Both the top frame and the X-carriage will now be plywood. This should hopefully remove most of the need to have adjustments at the axes connections. The drawer sliders can be mounted in slots if this seems benificial. (Or if someone else is building this, drawer slides with slotted mounting holes could be used.)
  • Progress has been made on the WoodScrew Extruder.
  • Further research indicates that printing with HDPE will likely prove very difficult. Since a heated bed is already planned, ABS may prove a better inital printing material. On a related note this link [1] seems to have demonstrated that a hair dryer (or hot air gun) may be able to be used to assist in printing HDPE.

March 10th 2014 Update:

  • A design for a wood screw based cold end has been developed. This alleviates one of the largest contributors to missing the cost goal. The extruder works by having a 28BYJ-48 stepper motor turn a wood screw with the filament fed along it. A wiki page WoodScrew Extruder has been started.
  • Some of the 2x4s have been cut out.
  • The new spooled drives should be able to move the X and Y axis at 6.23 mm/s
  • A HDPE plastic recycler is being simultaneously developed. It should (hopefully) cost less than $100 to build.

Status as of March 5th 2014:

  • Most of design is drawn out on paper (some has been modeled in SketchUp as well).
  • A motor testing sketch for an Ardruino Nano has been written and used to verify the ability of the 28BYJ-48 stepper motors to reliably rotate a 10-24 threaded rod through a T-Nut. The sketch makes use of a shift register chip. The rod can be turned at ~15 rpm. This results in an ability to move that axis at 0.625"/min [0.265mm/s] which seems painfully slow for anything other than the Z-Axis. As a result it was decided to switch to a tantillus-like spooled fishing line drive to increase the movement speed.
  • T-nuts and machine screws will be used to allow alignment to be adjusted.