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Technology at Work Feature Making Prototypes By Laser Story and Photos by Julian Edgar Apart from the "flip top" cranium, this is an absolutely perfect replica of the skull of a real, live person ­– down to the tiniest detail and blemish. No moulds, no artists and, as the magicians say, 10  S C it's all done with mirrors! ilicon hip The skull opposite was crafted by lasers, using information derived from a medical “CAT” scan. It is an example of the amazing work carried on by the South Australian Centre for Manufacturing. What they can produce borders on fantastic – in the truest sense of the word! A key requirement of manufacturing industry is the development of working prototypes, before expensive investment is made in the final machine tools and metal moulds. The South Australia Centre for Manufacturing uses two laser-based machines to develop prototypes in either plastic or laminated paper. Both use carbon dioxide (CO2) lasers and sophisticated drive mechanisms to form the objects, layer by layer. Companies employed in activities as diverse as manufacturing power tools, cars and white goods use the processes, while the Royal Adelaide Hospital Cranio-Facial Unit has also developed skull models using the techniques. The Sinterstation 2000 With a process called Selective Laser Sintering (SLS) the Sinterstation produces prototypes using the heat generated by a CO2 laser to fuse powdered material together, layer by layer. Fig.1 shows a diagram of the SLS process. The object is formed in a chamber heated to approximately 180-190 degrees Celsius - just below the melting The Sinterstation 2000 uses the action of a laser on Nylon powder to produce functional plastic prototypes. point of the Nylon powder usually employed. A thin layer of heat-fusible powder is distributed across the Fig.1: The Selective Laser Sintering process develops 3-dimensional objects by using a laser to fuse powder, one cross-sectional layer at a time. workspace by the action of a roller, with the layer of powder generally 0.1mm thick. The system’s software uses CAD drawings to produce a series of a cross-sectional slices of the component to be built and the heat-generating laser traces these slices, one by one, on successive layers of the powder. The Laminated Object Manufacturing can also be used to produce small parts. This adjustable spanner was formed by the machine, including the adjustment thread formed in situ! September 1996  11 The Selective Laser Sintering process can produce very complex shapes. This is the base of the relay box from the yet-to-be-released Holden VT Commodore. Four of these parts were produced simultaneously, actually standing on their ends. This whistle – incredibly, complete with internal ball ­–­was produced on the SLS machine. movement of the laser is controlled by scanning mirrors, which in turn are controlled by the system’s dedicated PC. The powder on which of the laser falls is heated to the point of sintering, fusing the powder particles and forming a solid mass. The unfused powder remains in place. The working surface then drops by about 0.1mm and the roller distributes another layer of powder across it. The laser traces out the next cross-section of the object, with this sintered layer fusing to the one beneath. And so it goes on with layer after layer being formed. The object is produced at a vertical rate of about 10mm per hour, with the exact rate dependent on the cross-sectional area of the object being formed. When the process is complete the chamber is allowed to cool, the workspace container is removed and the unsintered powder is then brushed away to reveal the part(s). Because of the way in which the part is formed, extremely complex shapes with thin walls can be developed. For example, a referee’s whistle –complete with internal ball – can be made, with the ball developed in situ! As long as there is an opening through which the unsintered powder can be removed, parts can be formed inside other objects. In addition to various grades of Nylon, materials such as poly­carbonate and proprietary casting compounds can be used. The quality of the object’s surface finish is dependent on the thickness of powder layers used and the material used but it is generally slightly rough to the touch. Post-production sanding and waxing can be used to give an extremely smooth finish if required. In addition to the speed of production, the greatest advantage of the process is that the prototypes can be functional. Flexible Nylon hinges and click joins can be incorporated and components with sufficient strength to be tested in actual operating conditions can be produced. Fan blades produced by this technique, for example, can be assessed for flow properties, noise and vibration. The data input required is a 3-dimensional CAD drawing of the object in the form of an industry standard binary STL or IGES 5.1 text file, or Computervision CADDS 5 part database. Factors such as scaling, feed rates of the powder, temperature and so on are adjusted to suit the individual parts being produced. The Sinterstation 2000 cost $600,000 when purchased in 1993 and it has been working almost continuously since then. The manufacturer of the The capability of the SLS process to produce functional prototypes can be seen here. This fan was assessed for flow properties, noise and vibration after it was produced. Part of a rear view mirror adjustment mechanism, produced for a manufacturer of automotive rear vision systems. From this, the moulds for castings can be directly made. 12  Silicon Chip Fig. 2: The Laminated Object Manufacturing uses adhesive-coated paper. The laser cuts out the cross-sectional slices of the object, with a heated roller fusing the paper layers together. machine is DTM Corporation, based in Austin, Texas. The company was formed specifically to commercialise Selective Laser Sintering, with the patent for the SLS process held by the University of Texas. Laminated Object Manufacturing The other prototype manufacturing machine used by the Centre produces objects larger than those made in the Sinterstation 2000. Laminated Object Manufacturing (LOM) can also rapidly produce complex shaped parts by the action of a computer-controlled laser but instead of using plastic powder, adhesive-backed paper is used as the raw material. Fig.2 shows the LOM system. The adhesive-backed paper is fed from a continuous roll across the working surface. A heated roller then passes across the paper, melting the adhesive and bonding the paper to the layer below. In much the same way as the SLS system, the laser then traces that particular cross-section of the object onto the paper - however in this system the laser cuts the paper rather than fusing it. Where there is excess paper the laser crosshatches it, allowing later removal. The build platform then descends and the process is repeated, with the object again being formed layer by layer. Once all the layers have been laminated and cut, the cubes of crosshatched material are removed and the finished object is revealed. The end result has the appearance and characteristics of laminated wood. One of the advantages of the LOM process over other prototype development approaches is that the LOM object can be used in investment casting. Investment casting - once called “lost wax” casting - uses the LOM object as the plug in a mould. There are seven processes in turning a LOM object into a metal casting. Once the LOM object has been made, wax channels to feed molten metal to various parts of the casting are attached to the object. The assembly is then dipped in alternating layers of ceramic slurry and fine sand, until a thick coating has been added. The coated object is fired in a furnace, hardening the ceramic and at the same time burning away the LOM plug, which after all, is made only of paper! The residual ash is removed and then metal is poured into what has now become a mould. The ceramic coating is removed, excess metal from the feed channels cut off and the newly-created metal object is ready for final finishing. The cast object can then be pressed into prototype service, Laminated Object Manufacturing uses the action of a laser to cut out the cross-sectional shape of the part in a sheet of special paper, here cutting out the shape of a transmission bellhousing. Note the smoke released when the laser cuts the paper. Areas of material which will later be removed are crosshatched. Removing the laminated object from its ‘block’ is done by hand, with crosshatched surplus material pulled out. The end result: automotive transmission manufacturer BTR Engineering is using the LOM process to form one-off bellhousing adaptors, allowing the attachment of their transmissions to a variety of engines for testing and evaluation purposes. The bellhousing on the right of the above photo is one cast from the LOM processed prototype on the left. Another example of investment moulding using the LOM process, where LOM objects become the plug for investment casting moulds. The LOM form is burnt away after it is has been coated with a hard ceramic layer. The casting of metals into the resulting mould can then be easily carried out. A close-up of the LOM bellhousing shows the ‘laminated wood’ appearance of the finished prototype. An object like this costs around $8000 and takes 40 hours to produce. September 1996  13 VISIT OUR WEB SITE OUR COMPLETE CATALOGUE IS ON OUR SITE. A “STOP PRESS” SECTION LISTS NEW AND LIMITED PRODUCTS AND SPECIALS. VISIT: https://www.oatleyelectronics.com/ SWITCHED MODE POWER SUPPLY:Compact (50X360X380mm), enclosed in a perforated metal case, 240V AC in, 12V DC/2A and 5VDC/5A out: $17 ...HP POWER SUPPLIES: Compact (120X70X30mm) HP switched mode, power in plastic case, 100-240V AC input, 10.6V/1.32A DC output, slightly soiled: $14 ...LASER MODULE: Very bright (650nM/5mW) focusable module, suit many industrial applications, bright enough for a disco laser light show, good results with the Automatic Laser Light Show: $75 ...AUTOMATIC LASER LIGHT SHOW KIT: 3 motors, mirrors plus PCB and comp. kit, has laser diode reg. cct, could be powered by the above 12V switched mode power supply, produces many different patterns, can be used with the laser module: $70 ...LASER POINTER: Our new metal laser pointer (With keychain) is very bright, with 650nM/5mW diode: $65 ... LEDS SUPER PRICES, INCLUDING A SUPER BRIGHT BLUE!: All the following LEDS are in a 5mm housing ...By far THE BRIGHTEST BLUE EVER OFFERED, superbright at 400mCd: $1.50Ea. or 10 for $10 ... 1C red: 10 for $4 ...300mC green: $1.10Ea. or 10 for $7 .. MAKE WHITE LIGHT BY MIXING THE OUTPUT OF THE PREVIOUS 3 LEDS? ..3Cd Red: $1.10Ea. or 10 for $7 ... 3Cd yellow (Small torch!) also available in 3mm: 10 for $9 ... Superbright flashing LEDS: $1.50 Ea. or 10 for $10 ... PHOTOTRANSISTORS: Enclosed in clear 5mm housing similar to the 5mm LEDS, 30V/3uS/<100nA dark current: $1.30 or 10 for $9 ...CONSTANT VOLTAGE DIODES: 1.52-1.66V <at> 10uA: 10 for $7 ...MASTHEAD AMPLIFIER PLUS PLUGPACK SPECIAL: Our famous MAR-6 based masthead amplifier plus a suitable plupack to power it: $20, Waterproof box: $2.50, bottom box:$2.50 ...17mm MAGNIFIERS: Made in JAPAN by Micro Design these eyepiece style metal enclosed magnifiers will see the grain of most papers, used, limited qty.: $4 Ea. ...HF BALLASTS: Single tube 36W Dimmable high frequency ballasts: $18 Ea. ...12V SLA BATTERY CHARGERS: INTELLIGENT “PLUGPACK” 240V-12V GEL BATTERY CHARGERS, 13.8V / 650mA, proper “switching” design with LED status indicator: $8.80 ...LASER POINTER KIT: A special purchase of some 660nM/5mW laser diode means that we can reduce the price of our Laser Pointer kit, includes everything except the batteries: $29 ...SPECIAL BATTERY AND CHARGER OFFER: When our 7AHr/12V SLA battery ($30) is bought with the SLA battery charger the total price for both is: $33 ...USED BRUSHLESS DC FANS: 4"/12V/0.25A: $8, 24V/6"/17W: $12 ...100,000uF ELECTROLYTIC CAPACITORS: 30V/40Vsurge, used but in exc. cond.:$10 ...12Hr. MECHANICAL TIMERS: 55X48X40mm, 5mm shaft (Knob not supplied), two hours timing per 45deg. rotation, two 25V/16A SPST switches which close at the end of the timing period: $5 ...USED IEC LEADS: Used Australian IEC leads: $2.50 ...STANDARD PIEZO TWEETERS: Square, 85X85mm, 4-40KHz, 35V RMS: $8, Wide dispersion, 67X143mm, 3-30KHz, 35V RMS: $9 ...COMPUTER POWER SUPPLY: Standard large supply as used in large computer towers, +5V/22A, +12V/8.5A, -5V/0.5A, -12V/0.5A, used but in excellent condition, guaranteed: $30 ...MAGNIFIERS: Small eyepiece: $3, 30mm Loupe: $8, 75mm Loupe: $12, 110mm Loupe: $15, a set of one of each of these magnifiers (4): $30 ... NEW NICAD BATTERY BARGAIN: 6 PACK (7.2V) OF 1.2V / 800 mAHr. AA NICAD BATT’s plus 1 X thermal switch, easy to seperate: $4 per pack or 5 packs for $16, FLAT RECTANGULAR 1.2V, 400mAh NI-CAD BATTERIES with thermal switch, easy to seperate, (Each batt: 48x17x6 mm): $4 per pack or 5 packs for $16 ...UV MONEY DETECTOR: Small complete unit with cold cathode UV tube, works from 2 X AA batteries ( Not supplied), Inverter used can dimly light a 4W white fluoro tube: $5Ea. or 5 for $19 ...MISCELLANEOUS USED LENS ASSEMBLIES: Unusual lens assemblies out of industrial equipment: 3 for $22 ...USED PIR MOVEMENT DETECTORS: Commercial quality 10-15M range, used but tested and guaranteed, have O/C transistor (BD139) output and a tamper switch, 12V operation, circuit provided: $10 Ea. or 4 for $32 ...CCD CAMERA WITH BONUS: Tiny (32X32X27mm) CCD camera, 0.1lux, IR responsive (Works in total dark with IR illumination), connects to any standard video input (Eg VCR) or via a modulator to aerial input: $125, BONUS: With each camera you can buy the following at reduced prices: COMMERCIAL UHF TRANSMITTER for $15 (Normally $25), IR ILLUMINATOR KIT with 42 X 880nM LED’s for $25 (Normally $35), REGULATED 10.4V PLUGPACK for $10 (Normally $25) ...PIR CASE FOR CCD CAMERA: Used PIR cases of normal appearance, use to hide the CCD camera, plenty of room inside: $2.50 Ea. or 4 for $8 ...CAMERA-TIME LAPSE VCR RECORDING SYSTEM: Includes PIR movement detector and interface control kit, plus a learning remote control, combination can trigger any VCR to start recording with movement and stop recording a few minutes after the last movement has stops: $90 ...GEIGER COUNTER KIT: Based on a Russian tube, has traditional “click” to indicate each count. Kit includes PCB, all on-board components, a speaker and Yes, the geiger counter tube is included: $30 ...RARE EARTH MAGNETS: Very strong! 7X3mm $2, 10X3mm $4, Torroidal 50mm outer, 35mm inner, 5mm thick: $10 ...IR TESTER: Kit includes a blemished IR converter tube as used in night vision and an EHT power supply kit, excellent for seeing IR sources, price depends on blemishes: $30 / $40 ...ARGON-ION HEADS: Used Argon-Ion heads with 30-100mW output in the blue-green spectrum, power supply circuit provided, size: 350X160X160mm, weight 6Kg, needs 1KW transformer available elsewhere for about $170, head only for: $350 ...DIGITAL RECORDING MODULES: Small digital voice recording modules as used in greeting cards, microphone and a speaker included, 6 sec. recording time: $9 ...WIRED IR REPEATER KIT: Extend the range of existing IR remote controls by up to 15M and/or control equipment in other rooms: $18 ...12V-2.5W SOLAR PANEL KIT: US amorphous glass solar panels, 305X228mm, Vo-c 18-20V, Is/c 200mA: $22 Ea. or 4 for $70 ...MIDI KEYBOARDS: Quality midi keyboard with 49 keys, 2 digit LED display, MIDI out jack, Size: 655115X35mm, computer software included, see review in Feb. 97 EA: $80, 9V DC plugpack: $10, also available is a larger model which has mor features and has touch sensitive response keys: $200 ...STEREO FM TRANSMITTER KIT: 88-108MHz, 6-12V DC supply, 8mA <at> 9V, 25X65mm PCB size, PCB plus all on-board comp’s, plus battery connector and 2 electret mic’s: $25, plastic case to suit: $4 ...WOOFER STOPPER KIT: Stop that dog bark, also works on most animals, refer SC Feb. 96, Kit includes PCB and all on board comp’s, wound transformer, electret mic., and a horn piezo tweeter: $39, extra horn piezo tweeters (drives up to 4) $6 Ea. ...ALCOHOL BREATH TESTER KIT: Based on a thick film alcohol sensor. The kit includes a PCB, all on board comp’s and a meter : $30 ...CENTRAL LOCKING KIT (NEW): A complete central locking kit for a vehicle. The kit is of good quality and actuators are well made, the kit includes 4 actuators, electronic control box, wiring harness, screws, nuts, and other mechanical parts: $60, The actuators only: $9 Ea. ...CODE HOPPING UHF CENTRAL LOCKING KIT PLUS A ONE CHANNEL UHF REMOTE CONTROL: Similar to above but this one is wireless, includes code hoping Tx’s with two buttons (Lock-unlock), an extra relay in the receiver can be used to immobilise the engine, etc., kit includes 4 actuators, control box, two Tx’s, wiring harness, screws, nuts, and other mechanical parts: $109 ...ELECTROCARDIOGRAM PCB + DISK: The software disk and a silk screened and solder masked PCB (PCB size: 105 x 53mm) for the ECG kit published in EA July 95. No further components supplied: $10 ...SECURE IR SWITCH: IR remote controlled switch, both Rx and Tx have Dip switches for coding, kit includes commercial 1 Tx, Rx PCB and parts to operate a relay (not supplied): $22 8A/4KV relay $3 ...FLUORESCENT TAPE: High quality Mitsubishi brand all weather 50mm wide Red reflective tape with self adhesive backing: 3 meters for $5 ...LOW COST IR ILLUMINATOR: Illuminates night viewers or CCD cameras using 42 of our 880nm / 30mW / 12 degrees IR LEDs. Power output is varied using a trimpot., operates from 10 to 15V, current is 5-600mA ...IR LASER DIODE KIT: Barely visible 780nM/5mW (Sharp LT026) laser diode plus constant current driver kit plus collimator lens plus housing plus a suitable detector Pin diode, for medical use, perimeter protection, data transmission, experimentation: $32 ...WIRELESS IR EXTENDER: Converts the output from any IR remote control into a UHF transmission, Tx is self contained and attaches with Velcro strap under the IR transmitter, receiver has 2 IR Led’s and is place near the appliance being controlled, kit includes two PCB’s all components, two plastic boxes, Velcro strap, 9V transmitter battery is not supplied: $35, suitable plugpack for the receiver: $10 ...NEW - LOW COST 2 CHANNEL UHF REMOTE CONTROL: Two channel encoded UHF remote control has a small keyring style assembled transmitter, kit receiver has 5A relay contact output, can be arranged for toggle or momentary operation: $35 for one Tx and one Rx, additional Tx’s $12 Ea. OATLEY ELECTRONICS PO Box 89 Oatley NSW 2223 Phone (02) 9584 3563 Fax (02) 9584 3561 orders by e-mail: branko<at>oatleyelectronics.com major cards with phone and fax orders, P&P typically $6. with any required changes easily made before final tooling is prepared. An example of this approach has been taken by automotive parts manufacturer BTR Engineering, who has used the LOM investment casting process to make unique bell housings so that their transmissions can be test-fitted to various cars. LOM objects can also be used in other casting techniques, involving not just metals but also plastics and silicone rubber. The Laminated Object Manufacturing machine is produced by Helisys, Inc, a Torrance, California-based company. Three-Dimensional Scanning Both the SLS and LOM systems require the input of precise CAD data before development of an object can occur. However, in the case of a prototype developed from modelling clay, for example, no such drawings will exist. A device called a Digibot II scanner is used to develop this data. The Centre’s Digibot II acquires the x, y, z coordinates of complex shaped objects by shining a point of laser light at the object and detecting the reflection of the light with traversing sensors. Trigonometrical calculations are then carried out within the Digibot software to determine the distance from the light source to the point on the object’s surface. Objects containing undercuts, concavities and split contours do not cause the system any problems and because of the non-contact sensing system, even soft objects can be reliably scanned. In addition to the industrial applications of the machine, other uses include the scanning of internal ear models for the custom fitting of hearing aids and the scanning of fragile artefacts or fossils to enable the production of durable replacements for display. The system can produce quite large objects, limited only by the available workspace; up to 460mm in diameter sc and 460mm high. Contact: Jeff Groves, Manager, Advance Manufacturing Facility, South Australian Centre for Manufacturing. Phone: 08 300 1500 Fax: 08 347 1033 Are you frustrated using DOS or non-compliant Windows software? If so then you may be interested in the following schematic design software trade-in offer from OrCAD. Here are 7 good reasons to trade-in your old schematic software tool to OrCAD Capture for Windows… ❶ De-facto standard schematic capture software. OrCAD is the best-selling package with over 180,000 licensed users worldwide. ❷ Easy to use and learn. Capture has an online tutorial and hypertext ‘Help’. ❸ Works on Windows 3.x, Windows 95 and Windows NT. Support for all platforms provided in one box. ❹ True 32-bit application. Faster processing on 32-bit platforms. ❺ Cut, copy and paste between Capture and other Windows compliant software. Developed to comply with Microsoft Foundation Class. ❻ Supports hierarchical designs. Create complex designs in modular form. ❼ Only $799 (Trade-in offer to all registered owners of Protel schematics and selected other schematic capture software tools. Normally $2195). ✄ Please send me more information on OrCAD Capture for Windows. My details are: Name: Company: Address: Phone: Fax: I am using the following brands of software: Schematic Entry: Simulation: PCB Design: (Fax this form to EDA Solutions on 02-9413 4622 or ring and ask for Richard on 02-9413 4611) SC11/96 The Digibot II scanner is used to acquire the 3-dimensional coordinates of complex shaped objects. This data can then be fed into the rapid prototyping machines, allowing copies to be made. Level 3, South Tower 1-5 Railway Street CHATSWOOD NSW 2067 Australia Ph: +61-2-9413 4611 fax: +61-2-9413 4622 email: info<at>eda.com.au Offer for a limited time only. September 1996  15