CNC

SLS 3D Printer using RAMP's and Marlin

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A simple Prototype.

My first SLS 3D printer using RAMPS and Marlin.

            So what is an SLS Printer, why would you want one, and how do you make one using some common household tools, local hardware, and common electronics?

The SLS Printer uses Powder opposed to Plastic Filament for material when building a 3D Part, the benefit to using Powder is quite simply the diverse selection of materials available, making options for applicable uses almost limitless.

Material can be anything from Ceramic, or Mild Steel and Titanium, all the way to Wax, each one offering one benefit from another, for example, Wax can be used to create a Plug (Mold).

Steel, Aluminium, or even Titanium, can be printed then sintered (melted together) using a Kiln, great for other detailed projects that require some strong parts.

Ceramics can be printed, sintered using a Kiln for decoration or to make very sensitive sensors (other steps required).

            For those who’ve seen or built any version of Rep-Rap 3D-Printer with a spare RAMP’s board laying around this maybe a pretty simple project for you, and if you’re new to all this welcome!

The concepts required to build a RepRap Filament 3D Printer are pretty much the same, this printer just needs some simple adjustments to get it working properly.

The parts used to build the machine are common, the tools used where simple and don’t produce much noise, I used a Hacksaw to chop threw all the wood and bar stock.

The Electronics/ Software isn’t much different from this printer to the filament style machine; no Post processor required to make it work properly, no tool change setup, just a tweak or two in Marlin and two added G-Code commands to the “Layer Change G-Code” section under printer settings in Slic3r for the powder deposition (you will need to enable advanced settings for this feature to work correctly).

This Image is of my (almost) finished SLS Printer prototype, it uses five Driver Boards so RAMP’s is required. The additional Driver is to move one of the Z axis Stepper Motor Print Beds, the E2 Axis on the RAMP’s board will need to be set in the Marlin Firmware to accomplish this.

How an SLS Printer Works:

Mechanics:

The 3D-Printer commonly constructed based on free online plans at http://reprap.org uses Filament to build a part, it does this by layering plastic, this kind of machine may use Two motors to move the Z axis and will only use one driver to do it (depending on model).

The reason why these versions can do this is because the Z-Axis moves in one direction, the SLS printer on the other hand moves two platforms in opposite directions.

One motor lifts a Powder Bed, and one lowers a Print Bed, these Beds are in a Cylinder so the powder is contained. The X and Y axis move as normal over the Print Bed but scrape Powder from the Powder Bed onto the Print bed between layers.

This extra step requires a Scraper and some custom settings, but nothing too crazy, the Scraper is connected to the Y-Axis, at Zero position it sits at the end of the Powder Bed and the Print Nozzle sits at the corner of the Print Bed.

By using Slic3r and the Layer Change G-Code option the printer will move to the max position on Y between each layer, and return to Zero before starting a new one, spreading the powder.

The extra G-Code spreads the Powder from the Powder Bed because the Layer Change G-Code does not start until the Z axis has moved.

By having the Print/ Glue head and the Scraper bar at Zero position when the last layer finishes (including the movement of the Z-Axis) the Layer Change takes place and the powder is pushed across the bed.

Inverting one set of Motor Wires the direction of one motor will be different from the other, causing one motor to push Powder up and the other to lower the part for the next layer, one driver alone cannot complete this task so two are used.

Electronics:

RAMP’s was chosen for this project because of how readily available, inexpensive, small, and popular the board is online, lots of support can be found and RAMP’s can be found on many trustworthy websites like E-Bay or Amazon. This board supports Marlin Firmware, and can support five motor drivers.

The power supply is 12VDC and was procured online, one Step down Transformer is being used for IR Sintering, this is not required for all builds, it just depends on the material (powder) being used.

Limit Stops are Mechanical, the switches chosen where momentary and procured from the local hardware store, they had to be inverted in the Firmware.

            Note: You can add a Camera and add Tool Change G-Code to snap a shot after each layer, Marlin Firmware also supports the use of Cameras (among a ton of other things).

Software:

·         Slic3R (Slicing Software/ G-Code Generation)

·         Pronterface (Machine Software, sends commands threw a Serial Port to the RAMP’s board via USB).

·         Marlin Firmware (The Firmware, processing software stored on the Arduino for RAMP’s).

Hardware/ Structure:

·         Frame: Cut from Pine Wood found at the local hardware store, glued together using Epoxy from the Dollar Store.

·         Pistons: Cut from Pine Wood left over from the Frame, holes were drilled on the underside to support bar stock and bearings, a Stepper motor (Nema 17) was epoxied to the underside.

·         Nuts/ Fasteners: used to hold some components not glued, also used for the Z Axis.

·         Stepper Motors: A Coupler was used to attach Threaded Bar Stock to the Motor.

·         Linear Slide Rails: were used for the X and Y axis.

·         Belt and Sprockets: Used to move the X and Y motor.

·         Power Supply: Provide RAMP’s Power.

·         RAMP’s: Motion Control Electronics.

 

Machine Details:

·         Resolution:

o   .05mm Nozzle

o   .09 Degree Step Angle / 12V 1.2A Motors (400 Steps per revolution).

o   T5 Belt.

o   “Past Extruder” from Thiniverse.com

·         Parameters:

o   Print Area:

§  Y-Axis = 80mm

§  X-Axis = 80mm

§  Z-Axis = 20mm

o   Overall:

§  Y-Axis = 287mm

§  X-Axis = 85mm

§  Z-Axis = 20mm

How to build a simple one time use Mold with Wax…  

  1.    Cover the Wax Printed Sculpture in Plaster Of Paris, make sure to get all the air out, vibrating or shaking the bowl all this stuff is in will do the job.

  2. Leave vent holes for air to escape, Toothpicks will work well for this step.

  3. Leave an entry location for pouring molten material in, and leave an exit location for the excess to escape, this can be done with a Drink Straw, or Pencil, even Tubing will work.

  4.  Once dry remove the Drink Straw/ Pencil, and Toothpicks.

  5. Pour molten material like Aluminum or Gold into the mold, this will melt the wax and replace it with the molten material, be careful! Water in the Mold or Water in the in the Wax may cause it to “Spit” a little, a face shield along with other Personal Protective Equipment should be used

  6. Break open the mold.

  7. Debur and clean the newly cast part.

How to Build a Multiple Use Mold using Wax…

1.      Cover the Wax in a Mold Release Agent, depending on complexity partition the mold using Wax Paper into sections.

2.      Pour the Plaster of Paris over the Printed Wax part (or) Cover in Enamel with or without carbon fiber (Fiberclass).

3.      Get the air out by gyration.

4.      Allow the material to set.

5.      Break apart and remove the wax armature.

6.      Reassemble and fasten together

7.      Pour in material of choice.

8.      Repeat parts 1-7

 

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