Project BrundleFab

Electronics

Arduino

Seed Studio SD Card v3.1 Shield

Well, connecting to an Arduino Mega2560 doesn't just snap on and work. You need to route some pins:

MEGA Pin	SD Shield	Function
ICSP1	D12	MOSI
ICSP2	5v	5v
ICSP3	D13	SCK
ICSP4	D11	MISO
ICSP6	GND	Gnd
D53	D10	SS

Use the arduino SD library, with a 'const int chipSelect=SS;' and you are good to go.

HP F4480

I am using a pile of trashed HP F4480 DeskJet printers as a source of motors, gears, and encoders.

Here are some information I have discovered about the internals of this printer:

Rotary optical encoder board

This board monitors the 1200 DPI optical encoder disk attached to the main paper handling roller in the printer.

It uses quadrature encoding, and can monitor both forward and reverse direction.

I am using the 'Encoder' library from the [1] Arduino library collection.

Pin 1 is the kerf on the CPU board connection

Pin	Function
4	Output A
3	Vcc 3.3v
2	Output B
1	Gnd

Linear Encoder

The HP F4480 printhead carriage monitors a 1200 DPI optical encoder strip, which is the feedback to the carriage motor.

DC Motors

All three DC motors (printhead, paper handling, and scanner carriage) are driven at 30v, PWM at 10% for nominal operation.

The printhead and paper handling motors are larger driving gear motors, the scanner carriage motor is a small motor driving a worm gear.

Powderbed

Overall Design

From the front of the printer, the X axis is from left (negative X - the feed bin area) to right (positive X - the part bin area).

Past the part bin, there is a 'cleaning' chute area where excess powder will fall during the print cycle.

The conceptual design is for the powder roller to immediately follow the print head, and the print head never executes a negative X movement until the Z slice is complete.

The X axis is controlled by a DC motor + circular encoders from the paper feed of an HP4480 printer, which pull on braided (non-stretching) fishing line (weighted on both ends) attached to the X trolley.

The Y axis is controlled by a DC motor + linear encoder, mounted on the inkjet carriage of the HP4480 printer. As I have multiple HP4480s, I will use a mounting system that will allow me to easily interchange the inject carriage, so as to replace the Y axis movement in case of failure.

The Z-part and Z-feed axes will be constructed of 12VDC 1-ton electric scissor jacks - these should be able to handle any desired powder material. The positioning of the scissor jacks will use an optical encoder - rotary and linear are being considered.

Current Progress

Powder bed frame is 80% complete:

• 

  Powderbed Interior

• 

  Powderbed waste chute and electronics area blueprint

• 

  Powderbed 80% complete

TODO:

• Scissor jacks for Z-Part and Z-Feed axes
• Optical encoders for Z-Part and Z-Feed
• Center supports for X trolley rails
• Support frame for the powder bed (basically, a table with holes cut out for the scissor jacks)
• X trolley fishing line routing (wire nails, hooks, and weights)
• Sealing the powder bed MDF edges

Print Media

Granulated Sugar + Water

Process

1. Lay down 10mm of granulated sugar
2. Sift a layer of 1mm of granulated sugar
3. Apply 1mm droplets of (colored) water to the granulated sugar via a needle bottle (unknown tip size)
4. Go to 2. until part build volume is complete
5. Lay down 10mm of granulated sugar
6. Heat at 120C (250F) in oven for 1 hour
7. Let cool
8. Remove from build container, and remove excess sugar

Results

The resulting object was stiff, but easily crumbled. Water dispersion through the granulated sugar had an approx 5mm radius, and substantially filled in the interior of the part (wireframe cube).

Analysis

• Droplet size should be smaller
• Either a finer granularity or pressure packing of the media should reduce the spot size of the print head
• A food safe adhesive should be tried to increase bonding strength
  • In-powder adhesive (such as meringue powder) activated by water
  • In-suspension adhesive (such as egg whites)

Powdered Confectionery Sugar + Water

1. Lay down 10mm of granulated sugar
2. Sift a layer of 2mm of granulated sugar, and pack down to 1mm.
3. Apply 1mm droplets of (colored) water to the powdered sugar via a needle bottle (unknown tip size)
4. Go to 2. until part build volume is complete
5. Lay down 10mm of granulated sugar
6. Heat at 120C (250F) in oven for 1 hour
7. Let cool
8. Remove from build container, and remove excess sugar

Results

Sugar did not re-crystallize, I suspect the cornstarch at fault here.

Analysis

• Powdered Confectionery Sugar is not suitable for printing, due to the cornstarch content.

Powdered Sugar/Meringue Powder + Alcohol/Water

• Powder base is granulated sugar and meringue powder
• Adhesive is alcohol and water

Procedure

1. Lay down 10mm of powder
2. Sift a layer of 2mm of powder, and pack down to 1mm.
3. Apply 1mm droplets of (colored) adhesive to the powder via a needle bottle (unknown tip size)
4. Go to 2. until part build volume is complete
5. Lay down 10mm of granulated sugar
6. Heat at 120C (250F) in oven for 1 hour
7. Let cool
8. Remove from build container, and remove excess sugar

Results

• Sugar/Meringue powder is % by mass
• Alcohol/Water is % by volume

Sugar	Meringue Powder	Water	Alcohol	Results
90%	10%	50%	50%	Small droplet size (1mm), no capillary creep from the droplets; resulting object could be rinsed of excess powder

Analysis

• Should be a sufficient working material, need to experiment with different ratios.

• 

  90%/10%+50%/50% (dry)

• 

  90%/10%+50%/50% (wet)