Open-source metal 3-D printer

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Contents

[edit] Source

Gerald C. Anzalone, Chenlong Zhang, Bas Wijnen, Paul G. Sanders and Joshua M. Pearce, “Low-Cost Open-Source 3-D Metal PrintingIEEE Access, 1, pp.803-810, (2013). doi: 10.1109/ACCESS.2013.2293018 open access preprint

See also:

Open-source 3D metal printer (short)
Open-source 3D metal printer (detail)


[edit] Abstract

Technical progress in the open-source self replicating rapid prototyper (RepRap) community has enabled a distributed form of additive manufacturing to expand rapidly using polymer-based materials. However, the lack of an open-source metal alternative and the high capital costs and slow throughput of proprietary commercialized metal 3-D printers has severely restricted their deployment. The applications of commercialized metal 3-D printers are limited to only rapid prototyping and expensive finished products. This severely restricts the access of the technology for small and medium enterprises, the developing world and for use in laboratories. This paper reports on the development of a <$2000 open-source metal 3-D printer. The metal 3-D printer is controlled with an open-source micro-controller and is a combination of a low-cost commercial gas-metal MIG welder and a derivative of the Rostock, a deltabot RepRap. The bill of materials, electrical and mechanical design schematics, and basic construction and operating procedures are provided. A preliminary technical analysis of the properties of the 3-D printer and the resultant steel products are performed. The results of printing customized functional metal parts are discussed and conclusions are drawn about the potential for the technology and the future work necessary for the mass distribution of this technology.

[edit] Bill of Materials

Item Number Cost(USD) Source
All 12 Printed Parts @ $40/kg $12.00 Local RepRap
All Fasteners $2.00 http://www.mcmaster.com/
M3 nut 90
M3x10 mm screw 12
M3x12mm screw 48
M3x20mm screw 12
M3x8mm set screw 6
M3washer 102
M8nut 6
M8set screw 3
152mm x 152mm ceramic insulation 1 $ 4.00
Rods,bearings and ties http://www.amazon.com/
300mm x 8mm smooth rod 6 $25.00
304.8mm carbon fiber rod 6 $6.00
608zz bearings 6 $2.40
LM8UUbearings 6 $6.00
Small wire ties 3 $0.50
Tie rod end 24 $ 8.00
600mm T5 belt 3 $ 5.90 http://www.polytechdesign.com/
241mm x 51mm x 4mm Aluminum plate 3 $114.00 Local machine shop
NEMA17 Stepper motor (1.8 deg.,5.5kg-cm holding torque, 750mm wire) 3 $39.00 http://www.kysanelectronics.com/
Mechanical limit switch 3 $3.33 http://www.digikey.com/
Melzi Microcontroller board 1 $120.00 http://matterfy.com/
Millermatic 140 Auto-set MIG Welder with Cart 1 $836.00 http://www.millerwelds.com/
Power supply 1 $8.00 (Recycled)/Internet
Wires 1 $ 2.00 (Recycled)/Internet

Total $1,194.13


[edit] Printed Parts

Metalp.png

Print these STL files on any flavor of RepRap. The red parts in the image on the right are the printed parts. The SCAD if you need it.

[edit] Construction

[edit] Note to Makers

If you have made a RepRap before this will be easy -- if you are not familiar with RepRaps or Deltabots like the Rostock - more detailed build instructions are available at the MOST Prusa RepRap build page and the Delta Build Overview:MOST. Those links will give details on how, for example, you can braid the wires or configure the Melzi/Arduino microcontroller.

This concept, however, is not limited to this specific design and should of course work for most RepRap printers -- you just need the fire proofing and a your welder...good luck! If you get it to work - please drop us a line.

[edit] Initial Prep

  1. Prepare all the materials listed in BOM
  2. Print all plastic components on a RepRap
  3. Ream the M3 screw holes in each plastic part and clean out nut traps with a sharp knife, make it fit for all M3 screws and nuts

[edit] Single pillar build

Detail of bottom inside, showing placement of limit switch
Detail of bottom outside
Detail top
  1. Attach the motor and the base plastic with M3 X 10mm screws with washers. Insert two M3 nuts into the set screw nut traps in the pulley, loosely insert two M3 X 8mm set screws into the pulley. Push the pulley through the motor rods and fasten all screws.
  2. Attach the limit switch to its holder on the base plastic using M2 X 10mm screws. Add some epoxy to make sure the switch doesn't move. Ensure that the screw in the carriage engages the switch arm. Adjust this screw to set the position where the carriage engages the limit switch.
  3. Use drill or knife to clean the rod openings, insert 2 parallel 300mm smooth rods into the holes in base plastic, use M3 X 12mm screw with washers to fasten all the rod to immobilize the both rods.
  4. Emerge the LM8UU bearings into oil for lubrication, insert 2 LM8UU bearings into the slots in the plastic shuttle, and firmly tighten each bearing with two small wire ties. Slide the LM8UU bearings with the plastic shuttles onto each rods.
  5. Fasten the top end of the parallel rods into the top plastics with M3 X 12mm screws with washers. Use the M8 set screw and M8 nut to fix two 608zz bearings into the center holes in the top plastic.
  6. Pass one end of the T5 belt through and around one belt terminator and pull the tail of the belt through other terminator. Loop the end of the belt around the pulley. Loop the other end of the belt around the 608zz bearings. Attach one terminator to the plastic shuttle with LM8UU bearings with an M3 X 10mm screw with washer. Firmly fasten the terminators with a small wire tie.

[edit] 3X

This ends the single pillar build. 3 pillars should be built in parallel. 241mm X 51mm aluminum plates are attached to both bottom and top plastics to make the frame a triangular prism shape.

[edit] Platform build

  1. Epoxy the tie wire ends to carbon fiber rods in both ends. M3 X 12mm screw and nut set is used to fasten the tie wire ends to the plastic shuttles. The other end is fastened to the plastic stage holder.
  2. Ensure the M3 screws are loosely thread through the hole in the tie wire ends so that it allows each carbon fiber arm to shift in all direction freely.
  3. 3 5cm long nails are thread into the plastic platform holder for supporting the 152mm X 152mm ceramic tray.

[edit] Electronics

Fig. 2 Wiring Diagram
  • For the wiring diagram see Fig. 2
  • Step motors and limit switches are wired to corresponding terminals on the microcontroller board, which is connected to Linux computer with a USB cable.
  • The board is powered with a recycled computer power supply.
  • To control the welder we use one of these relays attached to the RAMPS auxiliary i/o and power pins. Changing the state of the pins to which the board is attached changes the state of the relay assigned to the activated pin. The relay contacts are then wired in parallel with the trigger switch in the handle of the welding gun. Toggling the handle trigger or the relay will toggle the welder. This way the welder can still be used as it normally would when not attached to the printer...

[edit] Safety

  • Safety equipment is based off of standard MIG welding safety protocols [1]

[edit] Work Area

  • Use your metal 3D printer on a flat surface isolated from water and flammable materials.
  • Verify that you have proper grounding with a metal on metal connection to your substrate.
  • Ensure your gas cylinder is secured to an upright support or cart at all times and only use gas hoses designed for welding.
  • Eliminate clutter from the work area as you will be raining sparks everywhere. Minimize the number of cables underfoot to avoid tripping.
  • Examine hoses regularly for leaks, wear and loose connections and replace faulty lines. Spray with a soap and water mixture. Bubbles will show leaks.
  • Ensure proper ventilation of work area. Welding fumes are hazardous. In a home garage leave a door or window open and run a box fan as an exhaust to remove fumes from your breathing area. We have also used masks.

[edit] Safety gear

  • Wear safety glasses at all times while in the lab.
  • When printing and/looking at the printer while printing wear a welders mask/welding helmet (auto-darkening or flip-shade with current ANSI certification) or look at it using a webcam. Do not watch the printer with unprotected eyes!
  • Use pliers to pick up the substrate after printing or thick leather gloves
  • Always wear flame-resistant lab coat and heavy duty leather gloves when handling the printed parts
  • Wear leather shoes - high-tops (steel-toes are a bonus).

Metal 3D printing exposes you to welding for longer periods of time than is normal for routine welding. You should ensure that all of your skin is covered by something to avoid "sun burns".

[edit] Operation

The stage is controlled like a regular RepRap Delta 3-D printer. For a primer on the nomenclature try this. Download Repetier firmware and host software, use Arduino to upload the firmware to the stage, and set up Cura on the host. This will work on any type of computer but we recommend the free and open source Debian.

Models can be created and modified with any 3-D editor, such as OpenSCAD, Blender or a CAD application like FreeCAD (for a more detailed list of free open source CAD programs go here. The model should be exported as an STL file. That is loaded into Cura and sliced to a toolpath. It may take a few tries to get all the settings right. The GCode is saved to disk and opened with Repetier Host, which sends it to the stage. When the platform reaches the welding gun, switch on the welder by plugging in cable leading to the switch (which is to be held pressed with a wire tie).

While the print is going, pay attention to the distance between the gun and the object. This should start out at approximately 7 mm and remain the same. If it increases, either decrease the layer height, or slow down the movement (this can be done during the print with Repetier Host). If it decreases, do the opposite.

[edit] Experimental features

While the whole setup is still highly experimental, some parts are more experimental than others. Some features are listed here that are being tested with various levels of success.

Cura will attempt to adjust the "line width" of the deposited filament by changing its feedrate. Currently the welder does not support any such adjustment, so some parts get more material than they should, while others get less. To solve this, a plugin for Cura was developed which converts these feedrate changes into nozzle speed changes. The plugin can be found with the scad file on github.

This plugin also supports adding in custom commands when travel ends or starts. This can be used to activate a relay for switching the welder power.

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