The document discusses selective laser sintering (SLS) 3D printing. SLS uses a laser to fuse powdered material into solid 3D objects through successive layers. It describes developing an affordable SLS 3D printer for small businesses and hobbyists. Several potential designs and components are presented, including the frame, powder beds, laser positioning system, and more. Tradeoffs between cost, safety, speed and other criteria are evaluated to select the optimal design.

1. Group 2 | SLS 3D Printer Introduction
Additive Manufacturing Selective Laser Sintering
- Rapid CAD to 3D Object
- Made of successive 2D layers
- Prototyping benefits to many industries
http://news.noahraford.com/?p=1495
Methods http://www.arptech.com.au/slshelp.htm
- Stereolithography (SLA) >$5000
- Fused Deposition Moulding (FDM) >$500
- Selective Laser Sintering (SLS) >$10000
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

2. Group 2 | SLS 3D Printer Problem
Formulation
Problem Statement:
Develop an SLS 3D printer with comparable cost and performance to small-business FDM 3D
printers currently on the market
There Exists a Need for an Economic SLS 3D Printer
for:
- Additive manufacturing research
- Material scientists
- Education institutions Ease of
Criteria Safety Constructi Cost Accuracy Speed Weight Total Rank
- Small businesses
on
- Hobbyists
Design Criteria: Safety 1 1 1 1 1 5 1
- Completely safe
Ease of
- Ease of Construction [hrs] Constructio 0 1 1 1 1 4 2
- Cost [$] n
- Accuracy of +/- 0.5 [mm]
- Print Speed [min/part] Cost 0 0 1 1 1 3 3
- Weight [kg]
Accuracy 0 0 0 1 1 2 4
Print Material:
- Chocolate Speed 0 0 0 0 1 1 5
Weight 0 0 0 0 0 0 6
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

3. Group 2 | SLS 3D Printer Potential Solutions
Subtractions Solutions
Frame Material Aluminum Plastic Wood
Safety Enclosure Fully Enclosed Laser-safe Plexiglass
Laser Type CO2 Laser Laser Diode
Stationary
Laser
Laser Positioning XY Gantry Pan/Tilt Mirror
Translating
Powder Box
Cylindrical Wedge Radial
Powder Transferring
Roller Slider Dispensing
Optical Lens Vertical
Laser Diameter Adjustment Adjustment
Adjustment
Thermo Electric Cooler
Temperature Control (TEC)
Fan
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

4. Group 2 | SLS 3D Printer Alternative
Designs
Design 1 Design 2 Design 3
Wood Plastic Aluminum
Full Enclosure Plexiglass Enclosure Full Enclosure
Laser Diode Laser Diode Laser Diode
Pan & Tilt XY Gantry XY Gantry
Cylindrical Roller Wedge Slider Radial Wiper
TEC TEC Fan
Decision Matrix
Criteria Safety Ease Cost Acc. Speed Weight Total
Weighting
100 90 70 60 50 40
Factor
4x100 = 5x90 5x70 5x60 8x50 4x40
Design 1 2060
400 = 450 = 350 = 300 = 400 = 160
6x100 = 7x90 6x70 6x70 7x50 6x40
Design 2 2660
600 = 630 = 420 = 420 = 350 = 240
9x100 = 8x90 = 8x90 = 8x60 = 6x50 = 7x40 =
Design 3 3240
900 720 720 480 300 280
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

5. Group 2 | SLS 3D Printer Mechanical
Systems
1. Frame
2. Electrical
Enclosure
3. Powder Beds
4. Radial Wiper
5. Laser Gantry
6. Screws/Bolts
7. Walls
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

6. Group 2 | SLS 3D Printer Powder Beds
Top View
Two linear stepper motors
Oversized feed bed
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Seal around moving box
base
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

7. Group 2 | SLS 3D Printer Radial Wiper
Top View
One servo motor
Radial slot guideway
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Access powder wiped into
drawer
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

8. Group 2 | SLS 3D Printer Laser Gantry
Top View
Capstan Roller Mechanism
Laser
Laser Translator QuickTime™ and a
Microsoft Video 1 decompressor
Two stepper motors
are needed to see this picture.
8mm diameter rods
4 linear bearings in laser mount
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

9. Group 2 | SLS 3D Printer Laser Gantry
Resolution
Stepper Motor Step Resolution = 1.8o or PI/10 [rad]
Roller radius = 4 [mm]
x=r*θ
x = 0.126 [mm/step]
θ
X
XY resolution of 0.126 [mm]
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

10. Group 2 | SLS 3D Printer Electronic
Enclosure
Top View
Power Supply
Arduino
Motor Drivers
Cooling Fan
Vent
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

11. Group 2 | SLS 3D Printer Frame and Walls
Top View
Fully enclosed for laser safety
Hinge lid
LCD screen (debugging and process
1/8” aluminum sheet walls
status)
8020 aluminum T-slot beams
Drawer to collect access powder
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

12. Group 2 |Transfer 3D Printer Laser Heat Transfer
Radiation Heat
SLS
Rate of heat transfer to powder directly determines
print
times
Chocolate crystal structures melt at 45oC
Spectral absorption and emission of chocolate with
diffuse grey assumption
α = ε = 0.85 http://www.ebay.com/itm/2W-445nm-M140-Blue-Laser-Diode-in-C
Incident radiation G involves chocolate absorptivity
and
laser output power [W/m2]
Differential volume is heated by:
Q”rad = m * Cd * dTemp
Heating chocolate from 20oC to 45oC
Can calculate Time vs Q” (laser power) to heat a http://www.engineeringtoolbox.com/radiation-heat-transfer-d_431.htm
given
volume of chocolate
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

13. Group 2 | SLS 3D Printer Print Time
Print area of 10,000mm2 was considered
2 Watt laser considered due to availability
10,000 [mm2] layer area * 1 [mm] thickness / 200[s] = 50 mm3/s
(estimated)
Example
Using a 2W laser, find time to print a solid hockey
puck:
Volume = 113,411.5 [mm3]
113,411.5 [mm3] / 50 [mm3/s] = 2,268 [s], or 38 minutes
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

14. Group 2 | SLS 3D Printer Power Flow
Chart
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

15. Group 2 | SLS 3D Printer Power Flow
Chart
Part Qty Voltage [V] Current [A] Power [W]
Laser Diode 1 12 1.1 13.2
Gantry
Stepper 2 12 0.48 11.52
Motor
Powder Bed
Stepper 2 12 0.48 11.52
Motor
Arduino
MEGA ADK
1 12 1 12
12VDC
Supply
1 12 3.06 48.24 Total
SUN Power Supply
12VDC
1 12 40.2 48.24
Output Voltage: 12V DC
Supply
Max Current: 15.0A
Cooling Fan 1 120 0.14 16.8
Max Power: 180W
120VAC
Outlet Supply
65.04 Total
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

16. Group 2 | SLS 3D Printer Software
System Overview
Main Loop
Pull instruction from USB
On G1 code:
- Calculate X,Y step
frequency
Main Read - Call XY gantry step function.
Loop Function
On Plane change
Gantry Step Z Step
Powder
Swiper
Laser
Control
- Turn off Laser
- Call Z-Step function
- Call Powder Swiper function
- Turn on Laser
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

17. Group 2 | SLS 3D Printer SkeinForge
STL Model G-Code
http://www.thingiverse.com/thing:3930
SkeinForge
http://www.thingiverse.com/thing:3930
facet normal ni nj nk
outer loop
vertex v1x v1y v1z
vertex v2x v2y v2z
vertex v3x v3y v3z
endloop
endfacet
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

18. Group 2 | SLS 3D Printer Stepper Functions
Stepper Logic Timer and Interrupt Libraries
TimerOne.h and Interrupt.h are available for
Goal is to maintain a diagonal constant speed,
use
so x
and y movement follow the path.
Arduino Mega has 4 timers available for
general programming
Speed is limited by melting requirement of laser
2 allocated to XY Gantry
1 allocated to Z Stepper
Achieve constant speed with discrete steps of
frequency x and y for respective directions
Modulate frequency using SetPeriod()
function
Call Xstep ISR every pulse from timer
vstep = vmelt / res
freqx = vstepcosθ
freqy = vstepsin θ
t = vmeltd
θ = atan2(y1 - y0, x1 - x0)
d = (x2 + y2)1/2
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

19. Group 2 | SLS 3D Printer Data Transfer
Communication: Serial vs USB
Need a method to transmit g-code data to Arduino Board
Serial
Requires constant connection to computer, communication
overhead to ensure data transfer
Requires application on computer to feed arduino code line by
line
Allows for feedback from printer by passing data back
USB
Arduino 2560 Mega ADK (Android Development Kit) has USB
port for communicating with external devices as a master
Less communication overhead as only 1 application will access
data
USB Host Shield github repository provides library max3421e.h
for Mega to read/write to USB port
USB is preferred to minimize data transfer delays and lack of
external PC requirement.
Serial will be used during debugging for feedback from printer
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

20. Group 2 | SLS 3D Printer Patents
Gantry: 1. Cable Drive
US Patent # 4957014, April 10, 1989
Edward F. Burke
2. Ilan Moyer
http://web.mit.edu/imoyer/www/portfolio/foamcore/
SLS Printing: Method For Producing 3D Object
US Patent # 8187522, May 29, 2012
Yoshikazu Higashi, et al.
Radial Wiper: No Patents
Youtube video: “quadraturencoder”
http://www.youtube.com/watch?v=YBqUOP-MA1Q&feature=plcp
Software
Skeinforge is copyrighted under GNU Affero General Public Licence, allowing it to be freely distributed
No other significant software in design is worth patenting or has been patented
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar

21. Group 2 | SLS 3D Printer References
ARPTECH - Rapid Prototyping Services, http://www.arptech.com.au/slshelp.htm, Oct 13th, 2012
Burke, Edward. Cable drive geometry. http://www.google.com/patents/US49570
14?pg=PA3&dq=4957014&hl=en&sa=X&ei=vaqpUMQ0icTbBbmugKgO&ved=0CDcQ6AEwAA#v=onepage
Nov 18th, 2012
Engineering Toolbox, http://www.engineeringtoolbox.com/radiation-heat-transfer-d_431.html, Nov
18th, 2012
Higashi, Yoshikazu. Method and apparatus for producing a three-dimensional object, and
three-dimensional shaped object. http://www.google.com/patents/US8187522?
pg=PA10&dq=8187522&hl=en&sa=X&ei=RZipULPDIejhygH27ICQBw&ved=0CDQQ6AEwAA#v=one
page&q=8187522&f=false, Nov 18th, 2012
Ilan Moyer, http://web.mit.edu/imoyer/www/portfolio/foamcore/, Nov 18th, 2012
Introduction to Thermal Systems Engineering,
http://ca.wiley.com/WileyCDA/WileyTitle/productCd-0471204900.html, Nov 18th, 2012
M140 Blue Laser Diode, http://www.ebay.com/itm/2W-445nm-M140-Blue-Laser-Diode-in-Copper-
Module-W-Leads-Three-Element-Glass-/170892986250?ssPageName=ADME:X:RTQ:US:1123
, Nov 18th 2012
Noah Raford, 21st Century Strategy, Policy and Design, http://news.noahraford.com/?p=1495, Nov
18th, 2012
Thingiverse, 120 Film Advance Crank http://www.thingiverse.com/thing:3930, Nov 17th, 2012
Andy Vopni Benjamin Cousins Brian Luptak Nima Majidifar