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Windell H. Oskay &

Lenore M. Edman

Evil Mad Scientist Laboratorieswww.evilmadscientist.com

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It would be fun to have a 3D printer...

Motivation:

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Open-sourcefused-deposition fabber

-Extrudes melted plastic

http://www.reprap.org/

self-replicating(can make some of its

own parts)

(Bath University)

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http://fabathome.org/

Open-source fabber

-Extrudes e.g., silicone

Available as a kit

Fab@home

(Cornell)

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Existing fabricators are great if...

You want to build small, high-precisionplastic parts,

and/or

Your company has lots of money to

spend on a nifty machine!

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Design goals & principles

Ultra-low cost 3D Fabricator

Build size > resolution

Low media costs Open source design

Sidestep the patent minefield!

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One solution:

Build objects out of melted sugar

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Box with movable floor

(piston)

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The Process

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Sugar!

Hot air gun

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Move hot air gun,Selectively fuse sugar

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Lower Bed

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Add more sugar

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Selectively fuse sugarto layer below

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Lower Bed

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Add more sugar

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Selectively fuse sugarto layer below

Hot air gun

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Lower Bed(Etc.)

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Grow objects,layer by layer

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Selective Hot Air Sintering And Melting

Very low cost Low tech: easy and reliable Eye Safe No open flame

Works with a variety of media Good acronym

(SHASAM)

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Why Sugar?

Seriously cheap! Safe, non-toxic, biodegradable

Kid friendly. Tasty! Potentiallygood for casting

Remarkably rigid, despite low melting point Smellsgreatwhen it melts.

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Building the CandyFab 4000

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First victim: HP DraftPro pen plotter

(Future CandyFab X-axis)

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Next victim: HP 7550A pen plotter

(Future CandyFab Y-axis)

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3rd victim: 12 V Scissor Jack

(Future CandyFab Z-axis)

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Build volume: 23 x 13 x 9 (!)

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Electronic design

4-axis control: 3 motion + heater

Custom AVR-based servo motor controls Use original quadrature-encoded servomotors from HP plotters

Using Make Controller as computerinterface (overkill!)

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Control System: Big picture

Computer

Goto X1,Y1,Z1,Goto X2,Y2,Z2,

Goto...

Hardwareinterface

3D model

Locally-managedclosed-loop control

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Closed-loopservo control code

(C and/orassembly)

uint16_teepromWord__attribute__((section(".eeprom")));

int main( void ){unsignedint FontWord,m,n; ! ! ! //16-bitunsignedintegersunsignedchar hiByte;uint8_tstringNo,stringNoCopy,i,altset,NoOfStrings; ! //8-bitunsignedintegersuint8_tPA,PB,PD; ! ! ! !!PGM_Pp;char buf[100]; ! ! ! //Setnumberofcharactersperstring:thiseatsmostofthe SRAM!

!//Initializationroutine:Clearwatchdogtimer--thiscanpreventseveralthingsfromgoingwrong. !MCUSR&= 0xF7; ! //ClearWDRFFlagWDTCSR = 0x18; ! //Setstupidbitssowe cancleartimer...WDTCSR = 0x00;

DIDR= 3U; ! ! //Disableanalogcomparator--savepower.#ifdefcommonanode! PORTA= 255U;! PORTB= 255U;! PORTD= 255U;#endif

//Initroutine:Checktoseeif pinD4isconnectedto ground.Ifit is,thenwewill use//StringSet2insteadofStringSet1asour listofvalidstrings.//Inthe defaultfirmware,thisisusedtochoose whetherweshouldusethe holidayphrasesornot.//Howit'sdone: ConfigurepinD4asan input,withpull-upresistorturnedon.//Then,readinputvalue. Ifinputislow, D4hasbeenpulledlow byanexternalforce.

DDRD&=~_BV(PD4); ! //D4:InputPORTD|=_BV(PD4); ! //D4Highasm("nop"); ! ! ! //Waitonecyclefor inputtobeready --thisisimportant.

! altset= 0;! NoOfStrings=NoOfStrings1;//Datadirectionregister:DDRD//Setallportstooutput *EXCEPT*PA2(notused)! DDRA= 3U;! DDRB= 255U;! DDRD= 127U;//TurnallLEDsoffto beginwith:

#ifdefcommonanode! PORTA= 255U;! PORTB= 255U;! PORTD= 255U;#else! PORTA= 0;! PORTB= 0;! PORTD= 0;#endif!!!//ReadstringnumberfromEEPROM datamemory.Ifgood,incrementitand save//thenewvalue toEEPROM.This allowsustocyclethroughthe setofstringsinflash,//usingannew oneeachtimethat theunitisreset.

if (eeprom_read_word(&eepromWord)> (uint16_t)NoOfStrings)! stringNo= 0U;else! stringNo=(uint8_t)(eeprom_read_word(&eepromWord));!!s tr in gN oC op y = s tr in gN o;!if (++stringNo>=NoOfStrings)! stringNo= 0U;eeprom_write_word(&eepromWord,stringNo);

stringNo=stringNoCopy;

for (;;) //mainloop{

! memcpy_P(&p,&StringSet1[stringNo],sizeof(PGM_P));!! strcpy_P(buf,p); !!!/ / i f ( ( st r i n gN o C o py = = 0 ) & & ( + + s tr i n g No > = N o O f S tr i n g s) ) / / L oo p t h r o ug h s t r i ng s i n D e m o m o de !// stringNo =0U;

! if (stringNoCopy==0){! ! if (++stringNo>=NoOfStrings)! ! ! stringNo= 0U;! }!

i= 0;! while(buf[i]!= '\0' ) ! //i.e.,whilethestring hasnotended! {! !//Addashortdelay--an offperiod--betweencharacters://Defaultdelaytimevalue:2000U,butyou canchangethisvaluein therange(0,65535U).//Thisdelayisimportantbecauseitgives visualseparationbetweenrepeatingletters.//Withoutthedelay,theword"TREE"looks likeitjustsays"TRE"

! m= 0;! while (m> 8; ! //Wanttoworkwithone byteata time,here.!//Calculatemappingfromfontsontooutputpinports:! ! ! ! P B = ( 255U&FontWord);! ! ! ! PD=((hiByte& 15U)|((hiByte& 48U ) < > 6);

! m= 0;

.C

Linked Object Code

:100000000C9434000C9485000C944F000C944F0019

:100010000C944F000C944F000C944F000C944F0024:100020000C944F000C944F000C944F000C944F0014

:100030000C944F000C944F000C944F000C944F0004:100040000C944F000C944F000C944F000C944F00F4

:100050000C944F000C944F000C944F000C944F00E4:100060000C944F000C944F0011241FBECFEFD4E02E

:10007000DEBFCDBF11E0A0E0B1E0E0E1F6E002C0FC:1000800005900D92A030B107D9F711E0A0E0B1E0E2

:1000900001C01D92A430B107E1F70C94CC000C9480:1000A00000001092000110920101109202011092C2

:1000B000030152985A9A3D98459AE9E6F0E080810A:1000C0008160808380818D7F8083E89A7894089511

:1000D000E89A0895882329F060E070E080E090E0DD:1000E0000895609100017091010180910201909149

:1000F00003010895882341F44093000150930101C6:10010000609302017093030108951F920F920FB63E

:100110000F9211242F933F938F939F93AF93BF938D:1001200029B186B133273695279536952795992796

:10013000689414F8969587951694E1F7822793278B:1001400080FF0CC08091000190910101A0910201FB

:10015000B09103010196A11DB11D0BC0809100015A:1001600090910101A0910201B09103010197A109B1

:10017000B1098093000190930101A0930201B09313:100180000301BF91AF919F918F913F912F910F905C

:100190000FBE0F901F901895C9EED4E0DEBFCDBF03:1001A0000E94510083EA84BD81E085BD17BC18BC64

:1001B00080E68AB91092800081EC8093810088EEFD:1001C0009DEF909385008093840080ED9DE0AFEFDC

:1001D000BFEF8093000190930101A0930201B093BF:1001E00003018091000190910101A0910201B09161

:1001F0000301662477244301198A1A8A1B8A1C8A00:1002000013E2E12E1AEFF12E1FEF012F1FEF112F36

:10021000ED86FE860F87188B19861A861B861C862C:100220004424552400E61AEE1E8B0D8B18861F827F

:10023000222433242CED3FEF3E832D831C821B822E:100240001A821982809184009091850081569A4E7D

:1002500058F480918400909185008153954798F0DF:100260008B819C81892B79F41092850010928400F7

:1002700090E296BB81EC80938100ACEDBFEFBE8332:10028000AD831C821B82B59B5CC0EB81FC81EF2B94

:1002900089F4E0908600F0908700FE82ED8281E88C:1002A00080938100B0E2FB2EF6BA01E010E01C83DF

:1002B0000B8347C080918600909187002D813E81FD:1002C000821B930B9E838D836CE070E00E94F4028E

:1002D0009B018D819E816CE070E00E94F402069784:1002E00010F02F5F3F4F80E395E790938500809358

:1002F00084001C821B82C901875B93408B5494400D:1003000000F553E0283E350718F428EE33E006C028

:1003100087E0213D380710F020ED37E0285E3340BC:100320008FE190E0DC012A9FC0012B9F900D3A9F46

:10033000900D11247C0100271127E98AFA8A0B8B82:100340001C8B8091000190910101A0910201B0915C

.hex

Code stored inFlash memory

Simplified view:

GNU tools for AVR are excellent, extremely well supported

Easy GUI installers for Mac, Windows, full packages for Linux

Microcontroller choice: AVR + GCC toolchain

Compiler & Linker+ Libraries

Programmer

avrdude

avr-gccavr-libcbinutils

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Ugly--but functional-- prototypes!

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Operational testing

First step: Test 2D motion control system& air heater

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Worlds first CNC toaster!

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Next: 3D Modeling software

(Manygood options...)

Initial choice:POV-Ray

www.povray.org

Freeware with available source Cross-platform support Programming language for 3D graphics Makes slicing easy

http://www.povray.org/http://www.povray.org/

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Compatibility

Standard file type for 3D fabbingis .STL

Successfully converted, thus far:Blender, Rhino STL files

Others likely including sketchup

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Perform slicing operation in POV-Ray:

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Mass production!

Mass production!

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Mass production!

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Improving build quality

(or, You call thata dodecahedron?)

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Heating element for hot air rework station

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Heating element for hot-air rework station(desoldering tool)

Up to 500W (using ~50 W), $10

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Problems with the current heater

Airflow is too high: Blows around dry sugar,pushes melted sugar

Too large of an area is heated Inconsistent heating leads to variable color

Unknown heater construction...

Not food grade output!

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Too much air...

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C li li i

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Culinary applications

Initial tests were not consideredfood safe.

Need to treat sugar like food Need clean, audited air path

Not recycling sugar through system Easily cleaned inner liner

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First Edible CandyFab Output

Wh S ?

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Why Sugar?

Seriously cheap! Safe, non-toxic. Kid friendly.

Biodegradable, cleans up easily Tasty!

Potentiallygood for casting

Remarkably rigid, despite low melting point Smellsgreatwhen it melts.

O b d

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On beyond sugar....

If it bleeds, we can kill it.melts fab

O b d

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On beyond sugar....

Chocolate chips

Waxes Other sugars, sorbitol, ....

Many plastics (Thermoplastics)

Low melting point glasses (maybe?) Low melting point metals (Tin, bismuth....)

Media choices:whatever can melt in your oven

First durable CandyFabbed Object

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First durable CandyFabbed Object

Polypropylene pellets

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CandyFabMaking Rapid Prototypinga little sweeter!

www.candyfab.org

The CandyFab Project

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The CandyFab Project

Complete redesign of CandyFabby May 2008:

The CandyFab 5000S

Redesign will use off-the-shelf components(no old plotters!)

All hardware, mechanics, software, firmwarewill be open source & cross-platform

First Goal:

The CandyFab Project

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The CandyFab Project

CandyFab.org has been up one month(10% of time to May 2008)

60+ volunteers, with a wide range ofinterests and skills

Significant progress on newheater & nozzle reference designs

Status:

Early progress: New heater design by Brian ward

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y p g g y

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Early progress: CFD simulations by Brian ward

The CandyFab Project

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The CandyFab Project

Design of new XYZ motion control system Sort out control model & types of

feedback used

New architectural model of base Likely choice: CNC routed plywood

Begin hardware & firmware design of

new motor controllers

Design CNC control software Possibly branch an existing project

Next Steps (in order):

Control System: Big picture

Goto X1,Y1,Z1,

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y g p

Computer

Goto X1,Y1,Z1,Goto X2,Y2,Z2,

Goto...

Hardware

interface(Low-cost AVR)

3D model

.STL, POV-Rayor set of slices (JPEG)

Locally-managedclosed-loop control

Open-source electronics:

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p

Unusual approach to make design accessible:

Electronic design usingopen-source tools:the gEDA suite: gSchem + PCB

The future: open-source sculpture?

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p p

Sculpture Metatron, by Bathsheba Grossman,released as open source .STL file

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CandyFabMaking Rapid Prototypinga little sweeter!

www candyfab org