Hardware Store (HS) Extruder

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Hardware Store (HS) Extruder

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The Hardware Store (HS) Extruder is a tool head that, like some other RepRapToolHeads, is designed to mount on a Darwin RepRep, where it pulls in a cold thermoplastic raw material, melts it, and squirts the hot filament onto the "thick sheet" work area.

(Does this work with the Mendel, or has the Hardware Store (HS) Extruder been made obsolete by some other Extruder ?

This is a variation on the extruder design that can be made from elements found at a common hardware store (less the PTFE thermal break). Total cost for the extruder without the drive motor or any electronics is approximately $20. The great benefit of this extruder is that it can be made without exotic materials and with a minimum of tools; namely a drill press, a hack saw, a couple drills, and a #10-32 tap.

Here are the basic steps to construct this extruder:

  1. Fabricate the tension bearing bracket and guides.
  2. Fabricate the frame.
  3. Attach the drive bearings to the drive screw.
  4. Attach the drive assembly to the frame.
  5. Assemble the tension bearing bracket.
  6. Attach the tension bearing bracket.
  7. Fabricate heater flanges.
  8. Fabricate heater barrel.
  9. Fabricate thermal break.
  10. Assemble heater.
  11. Attach heater assembly to the frame.
  12. Fabricate drive coupler.
  13. Attach GM3 gear motor.

Of course, calibration follows each of these steps and the build as a whole so this simplistic view of the construction maybe isn't correct enough to give you an exact idea of the time required. From personal experience, I find that it takes me about 4 hours to construct and assemble one of these extruders.

Let's get to it!

Bill of Materials

You will need the follow items from the hardware store in order to construct the HS Extruder.

# Item Dimensions
1 Steel Bar Stock 1/8" x 1/2" x 8"
1 PTFE Rod 3/8 x 1"
1 Bolt 1/4-20 x 1/2"
1 Nut 1/4-20
1 Shoulder Bolt M6 x 5
3 Stainless Steel Bolt #6-32 x 1-1/2"
3 Hex nuts #6-32
2 Flat Washer 2" Dia.
2 U-Bolt 1-1/4" x 1"
2 Angle Bracket 2" x 2"
3 Skate Bearings 608
1 Vynil Aquarium Hose 1"

Fabricate the Tension Bearing Bracket and Guides

The tension bearing bracket is a small L-bracket that bolts onto the extruder frame to hold a bearing and guide slightly less than a filament width away from the drive screw. The filament feeds down the guide and gets pressed to the drive screw by the bearing. The tolerances on this piece of the extruder are the most critical. The more time you take here, the better your extruder will work though you can get a very rough model to work with a little extra effort.

The bracket is made up of several parts:

  • Two 2" L-bracket
  • One 608 Skate Bearing
  • One M6 Shoulder bolt (or equivalent)
  • A few Flat washers

The steps below outline the build process:

  1. Bend the 2" L-bracket into shape.
  2. Drill holes in L-bracket for shoulder bolt.
  3. Drill two holes in other L-bracket for guides.
  4. Cut two guide flanges off.
  5. Bend guide flanges to shape.
  6. File or grind guide flanges to final shape.

Fabricate the Frame

Fabricate Drive Screw

Attach the Drive Bearings to the Drive Screw

Attach the Drive Assembly to the Frame

Assemble the Tension Bearing Bracket

Attach the Tension Bearing Bracket

Fabricate Heater flanges

Fabricate Heater Barrel

Fabricate Thermal Break

Assemble Heater

Attach Heater Assembly to the Frame

Fabricate Drive Coupler

Attach GM3 Gear Motor

<More to come!>